1 /*
   2  * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/metadataOnStackMark.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "classfile/symbolTable.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc/g1/g1Allocator.inline.hpp"
  32 #include "gc/g1/g1BarrierSet.hpp"
  33 #include "gc/g1/g1CollectedHeap.inline.hpp"
  34 #include "gc/g1/g1CollectionSet.hpp"
  35 #include "gc/g1/g1CollectorPolicy.hpp"
  36 #include "gc/g1/g1CollectorState.hpp"
  37 #include "gc/g1/g1ConcurrentRefine.hpp"
  38 #include "gc/g1/g1ConcurrentRefineThread.hpp"
  39 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  40 #include "gc/g1/g1EvacStats.inline.hpp"
  41 #include "gc/g1/g1FullCollector.hpp"
  42 #include "gc/g1/g1GCPhaseTimes.hpp"
  43 #include "gc/g1/g1HeapSizingPolicy.hpp"
  44 #include "gc/g1/g1HeapTransition.hpp"
  45 #include "gc/g1/g1HeapVerifier.hpp"
  46 #include "gc/g1/g1HotCardCache.hpp"
  47 #include "gc/g1/g1MemoryPool.hpp"
  48 #include "gc/g1/g1OopClosures.inline.hpp"
  49 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  50 #include "gc/g1/g1Policy.hpp"
  51 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  52 #include "gc/g1/g1RemSet.hpp"
  53 #include "gc/g1/g1RootClosures.hpp"
  54 #include "gc/g1/g1RootProcessor.hpp"
  55 #include "gc/g1/g1StringDedup.hpp"
  56 #include "gc/g1/g1ThreadLocalData.hpp"
  57 #include "gc/g1/g1YCTypes.hpp"
  58 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
  59 #include "gc/g1/heapRegion.inline.hpp"
  60 #include "gc/g1/heapRegionRemSet.hpp"
  61 #include "gc/g1/heapRegionSet.inline.hpp"
  62 #include "gc/g1/vm_operations_g1.hpp"
  63 #include "gc/shared/adaptiveSizePolicy.hpp"
  64 #include "gc/shared/gcHeapSummary.hpp"
  65 #include "gc/shared/gcId.hpp"
  66 #include "gc/shared/gcLocker.hpp"
  67 #include "gc/shared/gcTimer.hpp"
  68 #include "gc/shared/gcTrace.hpp"
  69 #include "gc/shared/gcTraceTime.inline.hpp"
  70 #include "gc/shared/generationSpec.hpp"
  71 #include "gc/shared/isGCActiveMark.hpp"
  72 #include "gc/shared/oopStorageParState.hpp"
  73 #include "gc/shared/preservedMarks.inline.hpp"
  74 #include "gc/shared/suspendibleThreadSet.hpp"
  75 #include "gc/shared/referenceProcessor.inline.hpp"
  76 #include "gc/shared/taskqueue.inline.hpp"
  77 #include "gc/shared/weakProcessor.hpp"
  78 #include "logging/log.hpp"
  79 #include "memory/allocation.hpp"
  80 #include "memory/iterator.hpp"
  81 #include "memory/resourceArea.hpp"
  82 #include "oops/access.inline.hpp"
  83 #include "oops/compressedOops.inline.hpp"
  84 #include "oops/oop.inline.hpp"
  85 #include "prims/resolvedMethodTable.hpp"
  86 #include "runtime/atomic.hpp"
  87 #include "runtime/flags/flagSetting.hpp"
  88 #include "runtime/handles.inline.hpp"
  89 #include "runtime/init.hpp"
  90 #include "runtime/orderAccess.inline.hpp"
  91 #include "runtime/threadSMR.hpp"
  92 #include "runtime/vmThread.hpp"
  93 #include "utilities/align.hpp"
  94 #include "utilities/globalDefinitions.hpp"
  95 #include "utilities/stack.inline.hpp"
  96 
  97 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  98 
  99 // INVARIANTS/NOTES
 100 //
 101 // All allocation activity covered by the G1CollectedHeap interface is
 102 // serialized by acquiring the HeapLock.  This happens in mem_allocate
 103 // and allocate_new_tlab, which are the "entry" points to the
 104 // allocation code from the rest of the JVM.  (Note that this does not
 105 // apply to TLAB allocation, which is not part of this interface: it
 106 // is done by clients of this interface.)
 107 
 108 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 109  private:
 110   size_t _num_dirtied;
 111   G1CollectedHeap* _g1h;
 112   G1CardTable* _g1_ct;
 113 
 114   HeapRegion* region_for_card(jbyte* card_ptr) const {
 115     return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr));
 116   }
 117 
 118   bool will_become_free(HeapRegion* hr) const {
 119     // A region will be freed by free_collection_set if the region is in the
 120     // collection set and has not had an evacuation failure.
 121     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 122   }
 123 
 124  public:
 125   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
 126     _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { }
 127 
 128   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 129     HeapRegion* hr = region_for_card(card_ptr);
 130 
 131     // Should only dirty cards in regions that won't be freed.
 132     if (!will_become_free(hr)) {
 133       *card_ptr = G1CardTable::dirty_card_val();
 134       _num_dirtied++;
 135     }
 136 
 137     return true;
 138   }
 139 
 140   size_t num_dirtied()   const { return _num_dirtied; }
 141 };
 142 
 143 
 144 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 145   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 146 }
 147 
 148 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 149   // The from card cache is not the memory that is actually committed. So we cannot
 150   // take advantage of the zero_filled parameter.
 151   reset_from_card_cache(start_idx, num_regions);
 152 }
 153 
 154 
 155 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
 156                                              MemRegion mr) {
 157   return new HeapRegion(hrs_index, bot(), mr);
 158 }
 159 
 160 // Private methods.
 161 
 162 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 163   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 164          "the only time we use this to allocate a humongous region is "
 165          "when we are allocating a single humongous region");
 166 
 167   HeapRegion* res = _hrm.allocate_free_region(is_old);
 168 
 169   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 170     // Currently, only attempts to allocate GC alloc regions set
 171     // do_expand to true. So, we should only reach here during a
 172     // safepoint. If this assumption changes we might have to
 173     // reconsider the use of _expand_heap_after_alloc_failure.
 174     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 175 
 176     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 177                               word_size * HeapWordSize);
 178 
 179     if (expand(word_size * HeapWordSize)) {
 180       // Given that expand() succeeded in expanding the heap, and we
 181       // always expand the heap by an amount aligned to the heap
 182       // region size, the free list should in theory not be empty.
 183       // In either case allocate_free_region() will check for NULL.
 184       res = _hrm.allocate_free_region(is_old);
 185     } else {
 186       _expand_heap_after_alloc_failure = false;
 187     }
 188   }
 189   return res;
 190 }
 191 
 192 HeapWord*
 193 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 194                                                            uint num_regions,
 195                                                            size_t word_size) {
 196   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 197   assert(is_humongous(word_size), "word_size should be humongous");
 198   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 199 
 200   // Index of last region in the series.
 201   uint last = first + num_regions - 1;
 202 
 203   // We need to initialize the region(s) we just discovered. This is
 204   // a bit tricky given that it can happen concurrently with
 205   // refinement threads refining cards on these regions and
 206   // potentially wanting to refine the BOT as they are scanning
 207   // those cards (this can happen shortly after a cleanup; see CR
 208   // 6991377). So we have to set up the region(s) carefully and in
 209   // a specific order.
 210 
 211   // The word size sum of all the regions we will allocate.
 212   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 213   assert(word_size <= word_size_sum, "sanity");
 214 
 215   // This will be the "starts humongous" region.
 216   HeapRegion* first_hr = region_at(first);
 217   // The header of the new object will be placed at the bottom of
 218   // the first region.
 219   HeapWord* new_obj = first_hr->bottom();
 220   // This will be the new top of the new object.
 221   HeapWord* obj_top = new_obj + word_size;
 222 
 223   // First, we need to zero the header of the space that we will be
 224   // allocating. When we update top further down, some refinement
 225   // threads might try to scan the region. By zeroing the header we
 226   // ensure that any thread that will try to scan the region will
 227   // come across the zero klass word and bail out.
 228   //
 229   // NOTE: It would not have been correct to have used
 230   // CollectedHeap::fill_with_object() and make the space look like
 231   // an int array. The thread that is doing the allocation will
 232   // later update the object header to a potentially different array
 233   // type and, for a very short period of time, the klass and length
 234   // fields will be inconsistent. This could cause a refinement
 235   // thread to calculate the object size incorrectly.
 236   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 237 
 238   // Next, pad out the unused tail of the last region with filler
 239   // objects, for improved usage accounting.
 240   // How many words we use for filler objects.
 241   size_t word_fill_size = word_size_sum - word_size;
 242 
 243   // How many words memory we "waste" which cannot hold a filler object.
 244   size_t words_not_fillable = 0;
 245 
 246   if (word_fill_size >= min_fill_size()) {
 247     fill_with_objects(obj_top, word_fill_size);
 248   } else if (word_fill_size > 0) {
 249     // We have space to fill, but we cannot fit an object there.
 250     words_not_fillable = word_fill_size;
 251     word_fill_size = 0;
 252   }
 253 
 254   // We will set up the first region as "starts humongous". This
 255   // will also update the BOT covering all the regions to reflect
 256   // that there is a single object that starts at the bottom of the
 257   // first region.
 258   first_hr->set_starts_humongous(obj_top, word_fill_size);
 259   _g1_policy->remset_tracker()->update_at_allocate(first_hr);
 260   // Then, if there are any, we will set up the "continues
 261   // humongous" regions.
 262   HeapRegion* hr = NULL;
 263   for (uint i = first + 1; i <= last; ++i) {
 264     hr = region_at(i);
 265     hr->set_continues_humongous(first_hr);
 266     _g1_policy->remset_tracker()->update_at_allocate(hr);
 267   }
 268 
 269   // Up to this point no concurrent thread would have been able to
 270   // do any scanning on any region in this series. All the top
 271   // fields still point to bottom, so the intersection between
 272   // [bottom,top] and [card_start,card_end] will be empty. Before we
 273   // update the top fields, we'll do a storestore to make sure that
 274   // no thread sees the update to top before the zeroing of the
 275   // object header and the BOT initialization.
 276   OrderAccess::storestore();
 277 
 278   // Now, we will update the top fields of the "continues humongous"
 279   // regions except the last one.
 280   for (uint i = first; i < last; ++i) {
 281     hr = region_at(i);
 282     hr->set_top(hr->end());
 283   }
 284 
 285   hr = region_at(last);
 286   // If we cannot fit a filler object, we must set top to the end
 287   // of the humongous object, otherwise we cannot iterate the heap
 288   // and the BOT will not be complete.
 289   hr->set_top(hr->end() - words_not_fillable);
 290 
 291   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 292          "obj_top should be in last region");
 293 
 294   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 295 
 296   assert(words_not_fillable == 0 ||
 297          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 298          "Miscalculation in humongous allocation");
 299 
 300   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 301 
 302   for (uint i = first; i <= last; ++i) {
 303     hr = region_at(i);
 304     _humongous_set.add(hr);
 305     _hr_printer.alloc(hr);
 306   }
 307 
 308   return new_obj;
 309 }
 310 
 311 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 312   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 313   return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 314 }
 315 
 316 // If could fit into free regions w/o expansion, try.
 317 // Otherwise, if can expand, do so.
 318 // Otherwise, if using ex regions might help, try with ex given back.
 319 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 320   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 321 
 322   _verifier->verify_region_sets_optional();
 323 
 324   uint first = G1_NO_HRM_INDEX;
 325   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 326 
 327   if (obj_regions == 1) {
 328     // Only one region to allocate, try to use a fast path by directly allocating
 329     // from the free lists. Do not try to expand here, we will potentially do that
 330     // later.
 331     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 332     if (hr != NULL) {
 333       first = hr->hrm_index();
 334     }
 335   } else {
 336     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 337     // are lucky enough to find some.
 338     first = _hrm.find_contiguous_only_empty(obj_regions);
 339     if (first != G1_NO_HRM_INDEX) {
 340       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 341     }
 342   }
 343 
 344   if (first == G1_NO_HRM_INDEX) {
 345     // Policy: We could not find enough regions for the humongous object in the
 346     // free list. Look through the heap to find a mix of free and uncommitted regions.
 347     // If so, try expansion.
 348     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 349     if (first != G1_NO_HRM_INDEX) {
 350       // We found something. Make sure these regions are committed, i.e. expand
 351       // the heap. Alternatively we could do a defragmentation GC.
 352       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 353                                     word_size * HeapWordSize);
 354 
 355       _hrm.expand_at(first, obj_regions, workers());
 356       g1_policy()->record_new_heap_size(num_regions());
 357 
 358 #ifdef ASSERT
 359       for (uint i = first; i < first + obj_regions; ++i) {
 360         HeapRegion* hr = region_at(i);
 361         assert(hr->is_free(), "sanity");
 362         assert(hr->is_empty(), "sanity");
 363         assert(is_on_master_free_list(hr), "sanity");
 364       }
 365 #endif
 366       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 367     } else {
 368       // Policy: Potentially trigger a defragmentation GC.
 369     }
 370   }
 371 
 372   HeapWord* result = NULL;
 373   if (first != G1_NO_HRM_INDEX) {
 374     result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size);
 375     assert(result != NULL, "it should always return a valid result");
 376 
 377     // A successful humongous object allocation changes the used space
 378     // information of the old generation so we need to recalculate the
 379     // sizes and update the jstat counters here.
 380     g1mm()->update_sizes();
 381   }
 382 
 383   _verifier->verify_region_sets_optional();
 384 
 385   return result;
 386 }
 387 
 388 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size,
 389                                              size_t requested_size,
 390                                              size_t* actual_size) {
 391   assert_heap_not_locked_and_not_at_safepoint();
 392   assert(!is_humongous(requested_size), "we do not allow humongous TLABs");
 393 
 394   return attempt_allocation(min_size, requested_size, actual_size);
 395 }
 396 
 397 HeapWord*
 398 G1CollectedHeap::mem_allocate(size_t word_size,
 399                               bool*  gc_overhead_limit_was_exceeded) {
 400   assert_heap_not_locked_and_not_at_safepoint();
 401 
 402   if (is_humongous(word_size)) {
 403     return attempt_allocation_humongous(word_size);
 404   }
 405   size_t dummy = 0;
 406   return attempt_allocation(word_size, word_size, &dummy);
 407 }
 408 
 409 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
 410   ResourceMark rm; // For retrieving the thread names in log messages.
 411 
 412   // Make sure you read the note in attempt_allocation_humongous().
 413 
 414   assert_heap_not_locked_and_not_at_safepoint();
 415   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 416          "be called for humongous allocation requests");
 417 
 418   // We should only get here after the first-level allocation attempt
 419   // (attempt_allocation()) failed to allocate.
 420 
 421   // We will loop until a) we manage to successfully perform the
 422   // allocation or b) we successfully schedule a collection which
 423   // fails to perform the allocation. b) is the only case when we'll
 424   // return NULL.
 425   HeapWord* result = NULL;
 426   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 427     bool should_try_gc;
 428     uint gc_count_before;
 429 
 430     {
 431       MutexLockerEx x(Heap_lock);
 432       result = _allocator->attempt_allocation_locked(word_size);
 433       if (result != NULL) {
 434         return result;
 435       }
 436 
 437       // If the GCLocker is active and we are bound for a GC, try expanding young gen.
 438       // This is different to when only GCLocker::needs_gc() is set: try to avoid
 439       // waiting because the GCLocker is active to not wait too long.
 440       if (GCLocker::is_active_and_needs_gc() && g1_policy()->can_expand_young_list()) {
 441         // No need for an ergo message here, can_expand_young_list() does this when
 442         // it returns true.
 443         result = _allocator->attempt_allocation_force(word_size);
 444         if (result != NULL) {
 445           return result;
 446         }
 447       }
 448       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 449       // the GCLocker initiated GC has been performed and then retry. This includes
 450       // the case when the GC Locker is not active but has not been performed.
 451       should_try_gc = !GCLocker::needs_gc();
 452       // Read the GC count while still holding the Heap_lock.
 453       gc_count_before = total_collections();
 454     }
 455 
 456     if (should_try_gc) {
 457       bool succeeded;
 458       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 459                                    GCCause::_g1_inc_collection_pause);
 460       if (result != NULL) {
 461         assert(succeeded, "only way to get back a non-NULL result");
 462         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 463                              Thread::current()->name(), p2i(result));
 464         return result;
 465       }
 466 
 467       if (succeeded) {
 468         // We successfully scheduled a collection which failed to allocate. No
 469         // point in trying to allocate further. We'll just return NULL.
 470         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 471                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 472         return NULL;
 473       }
 474       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
 475                            Thread::current()->name(), word_size);
 476     } else {
 477       // Failed to schedule a collection.
 478       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 479         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 480                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 481         return NULL;
 482       }
 483       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 484       // The GCLocker is either active or the GCLocker initiated
 485       // GC has not yet been performed. Stall until it is and
 486       // then retry the allocation.
 487       GCLocker::stall_until_clear();
 488       gclocker_retry_count += 1;
 489     }
 490 
 491     // We can reach here if we were unsuccessful in scheduling a
 492     // collection (because another thread beat us to it) or if we were
 493     // stalled due to the GC locker. In either can we should retry the
 494     // allocation attempt in case another thread successfully
 495     // performed a collection and reclaimed enough space. We do the
 496     // first attempt (without holding the Heap_lock) here and the
 497     // follow-on attempt will be at the start of the next loop
 498     // iteration (after taking the Heap_lock).
 499     size_t dummy = 0;
 500     result = _allocator->attempt_allocation(word_size, word_size, &dummy);
 501     if (result != NULL) {
 502       return result;
 503     }
 504 
 505     // Give a warning if we seem to be looping forever.
 506     if ((QueuedAllocationWarningCount > 0) &&
 507         (try_count % QueuedAllocationWarningCount == 0)) {
 508       log_warning(gc, alloc)("%s:  Retried allocation %u times for " SIZE_FORMAT " words",
 509                              Thread::current()->name(), try_count, word_size);
 510     }
 511   }
 512 
 513   ShouldNotReachHere();
 514   return NULL;
 515 }
 516 
 517 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
 518   assert_at_safepoint_on_vm_thread();
 519   if (_archive_allocator == NULL) {
 520     _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
 521   }
 522 }
 523 
 524 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 525   // Allocations in archive regions cannot be of a size that would be considered
 526   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 527   // may be different at archive-restore time.
 528   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 529 }
 530 
 531 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 532   assert_at_safepoint_on_vm_thread();
 533   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 534   if (is_archive_alloc_too_large(word_size)) {
 535     return NULL;
 536   }
 537   return _archive_allocator->archive_mem_allocate(word_size);
 538 }
 539 
 540 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 541                                               size_t end_alignment_in_bytes) {
 542   assert_at_safepoint_on_vm_thread();
 543   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 544 
 545   // Call complete_archive to do the real work, filling in the MemRegion
 546   // array with the archive regions.
 547   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 548   delete _archive_allocator;
 549   _archive_allocator = NULL;
 550 }
 551 
 552 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 553   assert(ranges != NULL, "MemRegion array NULL");
 554   assert(count != 0, "No MemRegions provided");
 555   MemRegion reserved = _hrm.reserved();
 556   for (size_t i = 0; i < count; i++) {
 557     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 558       return false;
 559     }
 560   }
 561   return true;
 562 }
 563 
 564 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
 565                                             size_t count,
 566                                             bool open) {
 567   assert(!is_init_completed(), "Expect to be called at JVM init time");
 568   assert(ranges != NULL, "MemRegion array NULL");
 569   assert(count != 0, "No MemRegions provided");
 570   MutexLockerEx x(Heap_lock);
 571 
 572   MemRegion reserved = _hrm.reserved();
 573   HeapWord* prev_last_addr = NULL;
 574   HeapRegion* prev_last_region = NULL;
 575 
 576   // Temporarily disable pretouching of heap pages. This interface is used
 577   // when mmap'ing archived heap data in, so pre-touching is wasted.
 578   FlagSetting fs(AlwaysPreTouch, false);
 579 
 580   // Enable archive object checking used by G1MarkSweep. We have to let it know
 581   // about each archive range, so that objects in those ranges aren't marked.
 582   G1ArchiveAllocator::enable_archive_object_check();
 583 
 584   // For each specified MemRegion range, allocate the corresponding G1
 585   // regions and mark them as archive regions. We expect the ranges
 586   // in ascending starting address order, without overlap.
 587   for (size_t i = 0; i < count; i++) {
 588     MemRegion curr_range = ranges[i];
 589     HeapWord* start_address = curr_range.start();
 590     size_t word_size = curr_range.word_size();
 591     HeapWord* last_address = curr_range.last();
 592     size_t commits = 0;
 593 
 594     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 595               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 596               p2i(start_address), p2i(last_address));
 597     guarantee(start_address > prev_last_addr,
 598               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 599               p2i(start_address), p2i(prev_last_addr));
 600     prev_last_addr = last_address;
 601 
 602     // Check for ranges that start in the same G1 region in which the previous
 603     // range ended, and adjust the start address so we don't try to allocate
 604     // the same region again. If the current range is entirely within that
 605     // region, skip it, just adjusting the recorded top.
 606     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 607     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 608       start_address = start_region->end();
 609       if (start_address > last_address) {
 610         increase_used(word_size * HeapWordSize);
 611         start_region->set_top(last_address + 1);
 612         continue;
 613       }
 614       start_region->set_top(start_address);
 615       curr_range = MemRegion(start_address, last_address + 1);
 616       start_region = _hrm.addr_to_region(start_address);
 617     }
 618 
 619     // Perform the actual region allocation, exiting if it fails.
 620     // Then note how much new space we have allocated.
 621     if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
 622       return false;
 623     }
 624     increase_used(word_size * HeapWordSize);
 625     if (commits != 0) {
 626       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 627                                 HeapRegion::GrainWords * HeapWordSize * commits);
 628 
 629     }
 630 
 631     // Mark each G1 region touched by the range as archive, add it to
 632     // the old set, and set top.
 633     HeapRegion* curr_region = _hrm.addr_to_region(start_address);
 634     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 635     prev_last_region = last_region;
 636 
 637     while (curr_region != NULL) {
 638       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 639              "Region already in use (index %u)", curr_region->hrm_index());
 640       if (open) {
 641         curr_region->set_open_archive();
 642       } else {
 643         curr_region->set_closed_archive();
 644       }
 645       _hr_printer.alloc(curr_region);
 646       _old_set.add(curr_region);
 647       HeapWord* top;
 648       HeapRegion* next_region;
 649       if (curr_region != last_region) {
 650         top = curr_region->end();
 651         next_region = _hrm.next_region_in_heap(curr_region);
 652       } else {
 653         top = last_address + 1;
 654         next_region = NULL;
 655       }
 656       curr_region->set_top(top);
 657       curr_region->set_first_dead(top);
 658       curr_region->set_end_of_live(top);
 659       curr_region = next_region;
 660     }
 661 
 662     // Notify mark-sweep of the archive
 663     G1ArchiveAllocator::set_range_archive(curr_range, open);
 664   }
 665   return true;
 666 }
 667 
 668 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 669   assert(!is_init_completed(), "Expect to be called at JVM init time");
 670   assert(ranges != NULL, "MemRegion array NULL");
 671   assert(count != 0, "No MemRegions provided");
 672   MemRegion reserved = _hrm.reserved();
 673   HeapWord *prev_last_addr = NULL;
 674   HeapRegion* prev_last_region = NULL;
 675 
 676   // For each MemRegion, create filler objects, if needed, in the G1 regions
 677   // that contain the address range. The address range actually within the
 678   // MemRegion will not be modified. That is assumed to have been initialized
 679   // elsewhere, probably via an mmap of archived heap data.
 680   MutexLockerEx x(Heap_lock);
 681   for (size_t i = 0; i < count; i++) {
 682     HeapWord* start_address = ranges[i].start();
 683     HeapWord* last_address = ranges[i].last();
 684 
 685     assert(reserved.contains(start_address) && reserved.contains(last_address),
 686            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 687            p2i(start_address), p2i(last_address));
 688     assert(start_address > prev_last_addr,
 689            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 690            p2i(start_address), p2i(prev_last_addr));
 691 
 692     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 693     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 694     HeapWord* bottom_address = start_region->bottom();
 695 
 696     // Check for a range beginning in the same region in which the
 697     // previous one ended.
 698     if (start_region == prev_last_region) {
 699       bottom_address = prev_last_addr + 1;
 700     }
 701 
 702     // Verify that the regions were all marked as archive regions by
 703     // alloc_archive_regions.
 704     HeapRegion* curr_region = start_region;
 705     while (curr_region != NULL) {
 706       guarantee(curr_region->is_archive(),
 707                 "Expected archive region at index %u", curr_region->hrm_index());
 708       if (curr_region != last_region) {
 709         curr_region = _hrm.next_region_in_heap(curr_region);
 710       } else {
 711         curr_region = NULL;
 712       }
 713     }
 714 
 715     prev_last_addr = last_address;
 716     prev_last_region = last_region;
 717 
 718     // Fill the memory below the allocated range with dummy object(s),
 719     // if the region bottom does not match the range start, or if the previous
 720     // range ended within the same G1 region, and there is a gap.
 721     if (start_address != bottom_address) {
 722       size_t fill_size = pointer_delta(start_address, bottom_address);
 723       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 724       increase_used(fill_size * HeapWordSize);
 725     }
 726   }
 727 }
 728 
 729 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size,
 730                                                      size_t desired_word_size,
 731                                                      size_t* actual_word_size) {
 732   assert_heap_not_locked_and_not_at_safepoint();
 733   assert(!is_humongous(desired_word_size), "attempt_allocation() should not "
 734          "be called for humongous allocation requests");
 735 
 736   HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size);
 737 
 738   if (result == NULL) {
 739     *actual_word_size = desired_word_size;
 740     result = attempt_allocation_slow(desired_word_size);
 741   }
 742 
 743   assert_heap_not_locked();
 744   if (result != NULL) {
 745     assert(*actual_word_size != 0, "Actual size must have been set here");
 746     dirty_young_block(result, *actual_word_size);
 747   } else {
 748     *actual_word_size = 0;
 749   }
 750 
 751   return result;
 752 }
 753 
 754 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
 755   assert(!is_init_completed(), "Expect to be called at JVM init time");
 756   assert(ranges != NULL, "MemRegion array NULL");
 757   assert(count != 0, "No MemRegions provided");
 758   MemRegion reserved = _hrm.reserved();
 759   HeapWord* prev_last_addr = NULL;
 760   HeapRegion* prev_last_region = NULL;
 761   size_t size_used = 0;
 762   size_t uncommitted_regions = 0;
 763 
 764   // For each Memregion, free the G1 regions that constitute it, and
 765   // notify mark-sweep that the range is no longer to be considered 'archive.'
 766   MutexLockerEx x(Heap_lock);
 767   for (size_t i = 0; i < count; i++) {
 768     HeapWord* start_address = ranges[i].start();
 769     HeapWord* last_address = ranges[i].last();
 770 
 771     assert(reserved.contains(start_address) && reserved.contains(last_address),
 772            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 773            p2i(start_address), p2i(last_address));
 774     assert(start_address > prev_last_addr,
 775            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 776            p2i(start_address), p2i(prev_last_addr));
 777     size_used += ranges[i].byte_size();
 778     prev_last_addr = last_address;
 779 
 780     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 781     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 782 
 783     // Check for ranges that start in the same G1 region in which the previous
 784     // range ended, and adjust the start address so we don't try to free
 785     // the same region again. If the current range is entirely within that
 786     // region, skip it.
 787     if (start_region == prev_last_region) {
 788       start_address = start_region->end();
 789       if (start_address > last_address) {
 790         continue;
 791       }
 792       start_region = _hrm.addr_to_region(start_address);
 793     }
 794     prev_last_region = last_region;
 795 
 796     // After verifying that each region was marked as an archive region by
 797     // alloc_archive_regions, set it free and empty and uncommit it.
 798     HeapRegion* curr_region = start_region;
 799     while (curr_region != NULL) {
 800       guarantee(curr_region->is_archive(),
 801                 "Expected archive region at index %u", curr_region->hrm_index());
 802       uint curr_index = curr_region->hrm_index();
 803       _old_set.remove(curr_region);
 804       curr_region->set_free();
 805       curr_region->set_top(curr_region->bottom());
 806       if (curr_region != last_region) {
 807         curr_region = _hrm.next_region_in_heap(curr_region);
 808       } else {
 809         curr_region = NULL;
 810       }
 811       _hrm.shrink_at(curr_index, 1);
 812       uncommitted_regions++;
 813     }
 814 
 815     // Notify mark-sweep that this is no longer an archive range.
 816     G1ArchiveAllocator::set_range_archive(ranges[i], false);
 817   }
 818 
 819   if (uncommitted_regions != 0) {
 820     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 821                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 822   }
 823   decrease_used(size_used);
 824 }
 825 
 826 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
 827   ResourceMark rm; // For retrieving the thread names in log messages.
 828 
 829   // The structure of this method has a lot of similarities to
 830   // attempt_allocation_slow(). The reason these two were not merged
 831   // into a single one is that such a method would require several "if
 832   // allocation is not humongous do this, otherwise do that"
 833   // conditional paths which would obscure its flow. In fact, an early
 834   // version of this code did use a unified method which was harder to
 835   // follow and, as a result, it had subtle bugs that were hard to
 836   // track down. So keeping these two methods separate allows each to
 837   // be more readable. It will be good to keep these two in sync as
 838   // much as possible.
 839 
 840   assert_heap_not_locked_and_not_at_safepoint();
 841   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 842          "should only be called for humongous allocations");
 843 
 844   // Humongous objects can exhaust the heap quickly, so we should check if we
 845   // need to start a marking cycle at each humongous object allocation. We do
 846   // the check before we do the actual allocation. The reason for doing it
 847   // before the allocation is that we avoid having to keep track of the newly
 848   // allocated memory while we do a GC.
 849   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
 850                                            word_size)) {
 851     collect(GCCause::_g1_humongous_allocation);
 852   }
 853 
 854   // We will loop until a) we manage to successfully perform the
 855   // allocation or b) we successfully schedule a collection which
 856   // fails to perform the allocation. b) is the only case when we'll
 857   // return NULL.
 858   HeapWord* result = NULL;
 859   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 860     bool should_try_gc;
 861     uint gc_count_before;
 862 
 863 
 864     {
 865       MutexLockerEx x(Heap_lock);
 866 
 867       // Given that humongous objects are not allocated in young
 868       // regions, we'll first try to do the allocation without doing a
 869       // collection hoping that there's enough space in the heap.
 870       result = humongous_obj_allocate(word_size);
 871       if (result != NULL) {
 872         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 873         g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 874         return result;
 875       }
 876 
 877       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 878       // the GCLocker initiated GC has been performed and then retry. This includes
 879       // the case when the GC Locker is not active but has not been performed.
 880       should_try_gc = !GCLocker::needs_gc();
 881       // Read the GC count while still holding the Heap_lock.
 882       gc_count_before = total_collections();
 883     }
 884 
 885     if (should_try_gc) {
 886       bool succeeded;
 887       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 888                                    GCCause::_g1_humongous_allocation);
 889       if (result != NULL) {
 890         assert(succeeded, "only way to get back a non-NULL result");
 891         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 892                              Thread::current()->name(), p2i(result));
 893         return result;
 894       }
 895 
 896       if (succeeded) {
 897         // We successfully scheduled a collection which failed to allocate. No
 898         // point in trying to allocate further. We'll just return NULL.
 899         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 900                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 901         return NULL;
 902       }
 903       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
 904                            Thread::current()->name(), word_size);
 905     } else {
 906       // Failed to schedule a collection.
 907       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 908         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 909                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 910         return NULL;
 911       }
 912       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 913       // The GCLocker is either active or the GCLocker initiated
 914       // GC has not yet been performed. Stall until it is and
 915       // then retry the allocation.
 916       GCLocker::stall_until_clear();
 917       gclocker_retry_count += 1;
 918     }
 919 
 920 
 921     // We can reach here if we were unsuccessful in scheduling a
 922     // collection (because another thread beat us to it) or if we were
 923     // stalled due to the GC locker. In either can we should retry the
 924     // allocation attempt in case another thread successfully
 925     // performed a collection and reclaimed enough space.
 926     // Humongous object allocation always needs a lock, so we wait for the retry
 927     // in the next iteration of the loop, unlike for the regular iteration case.
 928     // Give a warning if we seem to be looping forever.
 929 
 930     if ((QueuedAllocationWarningCount > 0) &&
 931         (try_count % QueuedAllocationWarningCount == 0)) {
 932       log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
 933                              Thread::current()->name(), try_count, word_size);
 934     }
 935   }
 936 
 937   ShouldNotReachHere();
 938   return NULL;
 939 }
 940 
 941 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
 942                                                            bool expect_null_mutator_alloc_region) {
 943   assert_at_safepoint_on_vm_thread();
 944   assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
 945          "the current alloc region was unexpectedly found to be non-NULL");
 946 
 947   if (!is_humongous(word_size)) {
 948     return _allocator->attempt_allocation_locked(word_size);
 949   } else {
 950     HeapWord* result = humongous_obj_allocate(word_size);
 951     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
 952       collector_state()->set_initiate_conc_mark_if_possible(true);
 953     }
 954     return result;
 955   }
 956 
 957   ShouldNotReachHere();
 958 }
 959 
 960 class PostCompactionPrinterClosure: public HeapRegionClosure {
 961 private:
 962   G1HRPrinter* _hr_printer;
 963 public:
 964   bool do_heap_region(HeapRegion* hr) {
 965     assert(!hr->is_young(), "not expecting to find young regions");
 966     _hr_printer->post_compaction(hr);
 967     return false;
 968   }
 969 
 970   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
 971     : _hr_printer(hr_printer) { }
 972 };
 973 
 974 void G1CollectedHeap::print_hrm_post_compaction() {
 975   if (_hr_printer.is_active()) {
 976     PostCompactionPrinterClosure cl(hr_printer());
 977     heap_region_iterate(&cl);
 978   }
 979 }
 980 
 981 void G1CollectedHeap::abort_concurrent_cycle() {
 982   // If we start the compaction before the CM threads finish
 983   // scanning the root regions we might trip them over as we'll
 984   // be moving objects / updating references. So let's wait until
 985   // they are done. By telling them to abort, they should complete
 986   // early.
 987   _cm->root_regions()->abort();
 988   _cm->root_regions()->wait_until_scan_finished();
 989 
 990   // Disable discovery and empty the discovered lists
 991   // for the CM ref processor.
 992   _ref_processor_cm->disable_discovery();
 993   _ref_processor_cm->abandon_partial_discovery();
 994   _ref_processor_cm->verify_no_references_recorded();
 995 
 996   // Abandon current iterations of concurrent marking and concurrent
 997   // refinement, if any are in progress.
 998   concurrent_mark()->concurrent_cycle_abort();
 999 }
1000 
1001 void G1CollectedHeap::prepare_heap_for_full_collection() {
1002   // Make sure we'll choose a new allocation region afterwards.
1003   _allocator->release_mutator_alloc_region();
1004   _allocator->abandon_gc_alloc_regions();
1005   g1_rem_set()->cleanupHRRS();
1006 
1007   // We may have added regions to the current incremental collection
1008   // set between the last GC or pause and now. We need to clear the
1009   // incremental collection set and then start rebuilding it afresh
1010   // after this full GC.
1011   abandon_collection_set(collection_set());
1012 
1013   tear_down_region_sets(false /* free_list_only */);
1014 }
1015 
1016 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1017   assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1018   assert(used() == recalculate_used(), "Should be equal");
1019   _verifier->verify_region_sets_optional();
1020   _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
1021   _verifier->check_bitmaps("Full GC Start");
1022 }
1023 
1024 void G1CollectedHeap::prepare_heap_for_mutators() {
1025   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1026   ClassLoaderDataGraph::purge();
1027   MetaspaceUtils::verify_metrics();
1028 
1029   // Prepare heap for normal collections.
1030   assert(num_free_regions() == 0, "we should not have added any free regions");
1031   rebuild_region_sets(false /* free_list_only */);
1032   abort_refinement();
1033   resize_if_necessary_after_full_collection();
1034 
1035   // Rebuild the strong code root lists for each region
1036   rebuild_strong_code_roots();
1037 
1038   // Start a new incremental collection set for the next pause
1039   start_new_collection_set();
1040 
1041   _allocator->init_mutator_alloc_region();
1042 
1043   // Post collection state updates.
1044   MetaspaceGC::compute_new_size();
1045 }
1046 
1047 void G1CollectedHeap::abort_refinement() {
1048   if (_hot_card_cache->use_cache()) {
1049     _hot_card_cache->reset_hot_cache();
1050   }
1051 
1052   // Discard all remembered set updates.
1053   G1BarrierSet::dirty_card_queue_set().abandon_logs();
1054   assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1055 }
1056 
1057 void G1CollectedHeap::verify_after_full_collection() {
1058   _hrm.verify_optional();
1059   _verifier->verify_region_sets_optional();
1060   _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);
1061   // Clear the previous marking bitmap, if needed for bitmap verification.
1062   // Note we cannot do this when we clear the next marking bitmap in
1063   // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1064   // objects marked during a full GC against the previous bitmap.
1065   // But we need to clear it before calling check_bitmaps below since
1066   // the full GC has compacted objects and updated TAMS but not updated
1067   // the prev bitmap.
1068   if (G1VerifyBitmaps) {
1069     GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1070     _cm->clear_prev_bitmap(workers());
1071   }
1072   _verifier->check_bitmaps("Full GC End");
1073 
1074   // At this point there should be no regions in the
1075   // entire heap tagged as young.
1076   assert(check_young_list_empty(), "young list should be empty at this point");
1077 
1078   // Note: since we've just done a full GC, concurrent
1079   // marking is no longer active. Therefore we need not
1080   // re-enable reference discovery for the CM ref processor.
1081   // That will be done at the start of the next marking cycle.
1082   // We also know that the STW processor should no longer
1083   // discover any new references.
1084   assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
1085   assert(!_ref_processor_cm->discovery_enabled(), "Postcondition");
1086   _ref_processor_stw->verify_no_references_recorded();
1087   _ref_processor_cm->verify_no_references_recorded();
1088 }
1089 
1090 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1091   // Post collection logging.
1092   // We should do this after we potentially resize the heap so
1093   // that all the COMMIT / UNCOMMIT events are generated before
1094   // the compaction events.
1095   print_hrm_post_compaction();
1096   heap_transition->print();
1097   print_heap_after_gc();
1098   print_heap_regions();
1099 #ifdef TRACESPINNING
1100   ParallelTaskTerminator::print_termination_counts();
1101 #endif
1102 }
1103 
1104 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1105                                          bool clear_all_soft_refs) {
1106   assert_at_safepoint_on_vm_thread();
1107 
1108   if (GCLocker::check_active_before_gc()) {
1109     // Full GC was not completed.
1110     return false;
1111   }
1112 
1113   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1114       soft_ref_policy()->should_clear_all_soft_refs();
1115 
1116   G1FullCollector collector(this, &_full_gc_memory_manager, explicit_gc, do_clear_all_soft_refs);
1117   GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1118 
1119   collector.prepare_collection();
1120   collector.collect();
1121   collector.complete_collection();
1122 
1123   // Full collection was successfully completed.
1124   return true;
1125 }
1126 
1127 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1128   // Currently, there is no facility in the do_full_collection(bool) API to notify
1129   // the caller that the collection did not succeed (e.g., because it was locked
1130   // out by the GC locker). So, right now, we'll ignore the return value.
1131   bool dummy = do_full_collection(true,                /* explicit_gc */
1132                                   clear_all_soft_refs);
1133 }
1134 
1135 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1136   // Capacity, free and used after the GC counted as full regions to
1137   // include the waste in the following calculations.
1138   const size_t capacity_after_gc = capacity();
1139   const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1140 
1141   // This is enforced in arguments.cpp.
1142   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1143          "otherwise the code below doesn't make sense");
1144 
1145   // We don't have floating point command-line arguments
1146   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1147   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1148   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1149   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1150 
1151   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1152   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1153 
1154   // We have to be careful here as these two calculations can overflow
1155   // 32-bit size_t's.
1156   double used_after_gc_d = (double) used_after_gc;
1157   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1158   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1159 
1160   // Let's make sure that they are both under the max heap size, which
1161   // by default will make them fit into a size_t.
1162   double desired_capacity_upper_bound = (double) max_heap_size;
1163   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1164                                     desired_capacity_upper_bound);
1165   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1166                                     desired_capacity_upper_bound);
1167 
1168   // We can now safely turn them into size_t's.
1169   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1170   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1171 
1172   // This assert only makes sense here, before we adjust them
1173   // with respect to the min and max heap size.
1174   assert(minimum_desired_capacity <= maximum_desired_capacity,
1175          "minimum_desired_capacity = " SIZE_FORMAT ", "
1176          "maximum_desired_capacity = " SIZE_FORMAT,
1177          minimum_desired_capacity, maximum_desired_capacity);
1178 
1179   // Should not be greater than the heap max size. No need to adjust
1180   // it with respect to the heap min size as it's a lower bound (i.e.,
1181   // we'll try to make the capacity larger than it, not smaller).
1182   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1183   // Should not be less than the heap min size. No need to adjust it
1184   // with respect to the heap max size as it's an upper bound (i.e.,
1185   // we'll try to make the capacity smaller than it, not greater).
1186   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1187 
1188   if (capacity_after_gc < minimum_desired_capacity) {
1189     // Don't expand unless it's significant
1190     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1191 
1192     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1193                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1194                               "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1195                               capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1196 
1197     expand(expand_bytes, _workers);
1198 
1199     // No expansion, now see if we want to shrink
1200   } else if (capacity_after_gc > maximum_desired_capacity) {
1201     // Capacity too large, compute shrinking size
1202     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1203 
1204     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1205                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1206                               "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1207                               capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1208 
1209     shrink(shrink_bytes);
1210   }
1211 }
1212 
1213 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1214                                                             bool do_gc,
1215                                                             bool clear_all_soft_refs,
1216                                                             bool expect_null_mutator_alloc_region,
1217                                                             bool* gc_succeeded) {
1218   *gc_succeeded = true;
1219   // Let's attempt the allocation first.
1220   HeapWord* result =
1221     attempt_allocation_at_safepoint(word_size,
1222                                     expect_null_mutator_alloc_region);
1223   if (result != NULL) {
1224     return result;
1225   }
1226 
1227   // In a G1 heap, we're supposed to keep allocation from failing by
1228   // incremental pauses.  Therefore, at least for now, we'll favor
1229   // expansion over collection.  (This might change in the future if we can
1230   // do something smarter than full collection to satisfy a failed alloc.)
1231   result = expand_and_allocate(word_size);
1232   if (result != NULL) {
1233     return result;
1234   }
1235 
1236   if (do_gc) {
1237     // Expansion didn't work, we'll try to do a Full GC.
1238     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1239                                        clear_all_soft_refs);
1240   }
1241 
1242   return NULL;
1243 }
1244 
1245 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1246                                                      bool* succeeded) {
1247   assert_at_safepoint_on_vm_thread();
1248 
1249   // Attempts to allocate followed by Full GC.
1250   HeapWord* result =
1251     satisfy_failed_allocation_helper(word_size,
1252                                      true,  /* do_gc */
1253                                      false, /* clear_all_soft_refs */
1254                                      false, /* expect_null_mutator_alloc_region */
1255                                      succeeded);
1256 
1257   if (result != NULL || !*succeeded) {
1258     return result;
1259   }
1260 
1261   // Attempts to allocate followed by Full GC that will collect all soft references.
1262   result = satisfy_failed_allocation_helper(word_size,
1263                                             true, /* do_gc */
1264                                             true, /* clear_all_soft_refs */
1265                                             true, /* expect_null_mutator_alloc_region */
1266                                             succeeded);
1267 
1268   if (result != NULL || !*succeeded) {
1269     return result;
1270   }
1271 
1272   // Attempts to allocate, no GC
1273   result = satisfy_failed_allocation_helper(word_size,
1274                                             false, /* do_gc */
1275                                             false, /* clear_all_soft_refs */
1276                                             true,  /* expect_null_mutator_alloc_region */
1277                                             succeeded);
1278 
1279   if (result != NULL) {
1280     return result;
1281   }
1282 
1283   assert(!soft_ref_policy()->should_clear_all_soft_refs(),
1284          "Flag should have been handled and cleared prior to this point");
1285 
1286   // What else?  We might try synchronous finalization later.  If the total
1287   // space available is large enough for the allocation, then a more
1288   // complete compaction phase than we've tried so far might be
1289   // appropriate.
1290   return NULL;
1291 }
1292 
1293 // Attempting to expand the heap sufficiently
1294 // to support an allocation of the given "word_size".  If
1295 // successful, perform the allocation and return the address of the
1296 // allocated block, or else "NULL".
1297 
1298 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1299   assert_at_safepoint_on_vm_thread();
1300 
1301   _verifier->verify_region_sets_optional();
1302 
1303   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1304   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1305                             word_size * HeapWordSize);
1306 
1307 
1308   if (expand(expand_bytes, _workers)) {
1309     _hrm.verify_optional();
1310     _verifier->verify_region_sets_optional();
1311     return attempt_allocation_at_safepoint(word_size,
1312                                            false /* expect_null_mutator_alloc_region */);
1313   }
1314   return NULL;
1315 }
1316 
1317 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1318   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1319   aligned_expand_bytes = align_up(aligned_expand_bytes,
1320                                        HeapRegion::GrainBytes);
1321 
1322   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1323                             expand_bytes, aligned_expand_bytes);
1324 
1325   if (is_maximal_no_gc()) {
1326     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1327     return false;
1328   }
1329 
1330   double expand_heap_start_time_sec = os::elapsedTime();
1331   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1332   assert(regions_to_expand > 0, "Must expand by at least one region");
1333 
1334   uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1335   if (expand_time_ms != NULL) {
1336     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1337   }
1338 
1339   if (expanded_by > 0) {
1340     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1341     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1342     g1_policy()->record_new_heap_size(num_regions());
1343   } else {
1344     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1345 
1346     // The expansion of the virtual storage space was unsuccessful.
1347     // Let's see if it was because we ran out of swap.
1348     if (G1ExitOnExpansionFailure &&
1349         _hrm.available() >= regions_to_expand) {
1350       // We had head room...
1351       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1352     }
1353   }
1354   return regions_to_expand > 0;
1355 }
1356 
1357 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1358   size_t aligned_shrink_bytes =
1359     ReservedSpace::page_align_size_down(shrink_bytes);
1360   aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1361                                          HeapRegion::GrainBytes);
1362   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1363 
1364   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1365   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1366 
1367 
1368   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",
1369                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1370   if (num_regions_removed > 0) {
1371     g1_policy()->record_new_heap_size(num_regions());
1372   } else {
1373     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1374   }
1375 }
1376 
1377 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1378   _verifier->verify_region_sets_optional();
1379 
1380   // We should only reach here at the end of a Full GC which means we
1381   // should not not be holding to any GC alloc regions. The method
1382   // below will make sure of that and do any remaining clean up.
1383   _allocator->abandon_gc_alloc_regions();
1384 
1385   // Instead of tearing down / rebuilding the free lists here, we
1386   // could instead use the remove_all_pending() method on free_list to
1387   // remove only the ones that we need to remove.
1388   tear_down_region_sets(true /* free_list_only */);
1389   shrink_helper(shrink_bytes);
1390   rebuild_region_sets(true /* free_list_only */);
1391 
1392   _hrm.verify_optional();
1393   _verifier->verify_region_sets_optional();
1394 }
1395 
1396 // Public methods.
1397 
1398 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1399   CollectedHeap(),
1400   _young_gen_sampling_thread(NULL),
1401   _collector_policy(collector_policy),
1402   _soft_ref_policy(),
1403   _card_table(NULL),
1404   _memory_manager("G1 Young Generation", "end of minor GC"),
1405   _full_gc_memory_manager("G1 Old Generation", "end of major GC"),
1406   _eden_pool(NULL),
1407   _survivor_pool(NULL),
1408   _old_pool(NULL),
1409   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1410   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1411   _g1_policy(new G1Policy(_gc_timer_stw)),
1412   _collection_set(this, _g1_policy),
1413   _dirty_card_queue_set(false),
1414   _ref_processor_stw(NULL),
1415   _is_alive_closure_stw(this),
1416   _is_subject_to_discovery_stw(this),
1417   _ref_processor_cm(NULL),
1418   _is_alive_closure_cm(this),
1419   _is_subject_to_discovery_cm(this),
1420   _bot(NULL),
1421   _hot_card_cache(NULL),
1422   _g1_rem_set(NULL),
1423   _cr(NULL),
1424   _g1mm(NULL),
1425   _preserved_marks_set(true /* in_c_heap */),
1426   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1427   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1428   _humongous_reclaim_candidates(),
1429   _has_humongous_reclaim_candidates(false),
1430   _archive_allocator(NULL),
1431   _summary_bytes_used(0),
1432   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1433   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1434   _expand_heap_after_alloc_failure(true),
1435   _old_marking_cycles_started(0),
1436   _old_marking_cycles_completed(0),
1437   _in_cset_fast_test() {
1438 
1439   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1440                           /* are_GC_task_threads */true,
1441                           /* are_ConcurrentGC_threads */false);
1442   _workers->initialize_workers();
1443   _verifier = new G1HeapVerifier(this);
1444 
1445   _allocator = new G1Allocator(this);
1446 
1447   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1448 
1449   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1450 
1451   // Override the default _filler_array_max_size so that no humongous filler
1452   // objects are created.
1453   _filler_array_max_size = _humongous_object_threshold_in_words;
1454 
1455   uint n_queues = ParallelGCThreads;
1456   _task_queues = new RefToScanQueueSet(n_queues);
1457 
1458   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1459 
1460   for (uint i = 0; i < n_queues; i++) {
1461     RefToScanQueue* q = new RefToScanQueue();
1462     q->initialize();
1463     _task_queues->register_queue(i, q);
1464     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1465   }
1466 
1467   // Initialize the G1EvacuationFailureALot counters and flags.
1468   NOT_PRODUCT(reset_evacuation_should_fail();)
1469 
1470   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1471 }
1472 
1473 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1474                                                                  size_t size,
1475                                                                  size_t translation_factor) {
1476   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1477   // Allocate a new reserved space, preferring to use large pages.
1478   ReservedSpace rs(size, preferred_page_size);
1479   G1RegionToSpaceMapper* result  =
1480     G1RegionToSpaceMapper::create_mapper(rs,
1481                                          size,
1482                                          rs.alignment(),
1483                                          HeapRegion::GrainBytes,
1484                                          translation_factor,
1485                                          mtGC);
1486 
1487   os::trace_page_sizes_for_requested_size(description,
1488                                           size,
1489                                           preferred_page_size,
1490                                           rs.alignment(),
1491                                           rs.base(),
1492                                           rs.size());
1493 
1494   return result;
1495 }
1496 
1497 jint G1CollectedHeap::initialize_concurrent_refinement() {
1498   jint ecode = JNI_OK;
1499   _cr = G1ConcurrentRefine::create(&ecode);
1500   return ecode;
1501 }
1502 
1503 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1504   _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1505   if (_young_gen_sampling_thread->osthread() == NULL) {
1506     vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1507     return JNI_ENOMEM;
1508   }
1509   return JNI_OK;
1510 }
1511 
1512 jint G1CollectedHeap::initialize() {
1513   os::enable_vtime();
1514 
1515   // Necessary to satisfy locking discipline assertions.
1516 
1517   MutexLocker x(Heap_lock);
1518 
1519   // While there are no constraints in the GC code that HeapWordSize
1520   // be any particular value, there are multiple other areas in the
1521   // system which believe this to be true (e.g. oop->object_size in some
1522   // cases incorrectly returns the size in wordSize units rather than
1523   // HeapWordSize).
1524   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1525 
1526   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1527   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1528   size_t heap_alignment = collector_policy()->heap_alignment();
1529 
1530   // Ensure that the sizes are properly aligned.
1531   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1532   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1533   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1534 
1535   // Reserve the maximum.
1536 
1537   // When compressed oops are enabled, the preferred heap base
1538   // is calculated by subtracting the requested size from the
1539   // 32Gb boundary and using the result as the base address for
1540   // heap reservation. If the requested size is not aligned to
1541   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1542   // into the ReservedHeapSpace constructor) then the actual
1543   // base of the reserved heap may end up differing from the
1544   // address that was requested (i.e. the preferred heap base).
1545   // If this happens then we could end up using a non-optimal
1546   // compressed oops mode.
1547 
1548   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1549                                                  heap_alignment);
1550 
1551   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1552 
1553   // Create the barrier set for the entire reserved region.
1554   G1CardTable* ct = new G1CardTable(reserved_region());
1555   ct->initialize();
1556   G1BarrierSet* bs = new G1BarrierSet(ct);
1557   bs->initialize();
1558   assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1559   BarrierSet::set_barrier_set(bs);
1560   _card_table = ct;
1561 
1562   // Create the hot card cache.
1563   _hot_card_cache = new G1HotCardCache(this);
1564 
1565   // Carve out the G1 part of the heap.
1566   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1567   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1568   G1RegionToSpaceMapper* heap_storage =
1569     G1RegionToSpaceMapper::create_mapper(g1_rs,
1570                                          g1_rs.size(),
1571                                          page_size,
1572                                          HeapRegion::GrainBytes,
1573                                          1,
1574                                          mtJavaHeap);
1575   os::trace_page_sizes("Heap",
1576                        collector_policy()->min_heap_byte_size(),
1577                        max_byte_size,
1578                        page_size,
1579                        heap_rs.base(),
1580                        heap_rs.size());
1581   heap_storage->set_mapping_changed_listener(&_listener);
1582 
1583   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1584   G1RegionToSpaceMapper* bot_storage =
1585     create_aux_memory_mapper("Block Offset Table",
1586                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1587                              G1BlockOffsetTable::heap_map_factor());
1588 
1589   G1RegionToSpaceMapper* cardtable_storage =
1590     create_aux_memory_mapper("Card Table",
1591                              G1CardTable::compute_size(g1_rs.size() / HeapWordSize),
1592                              G1CardTable::heap_map_factor());
1593 
1594   G1RegionToSpaceMapper* card_counts_storage =
1595     create_aux_memory_mapper("Card Counts Table",
1596                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1597                              G1CardCounts::heap_map_factor());
1598 
1599   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1600   G1RegionToSpaceMapper* prev_bitmap_storage =
1601     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1602   G1RegionToSpaceMapper* next_bitmap_storage =
1603     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1604 
1605   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1606   _card_table->initialize(cardtable_storage);
1607   // Do later initialization work for concurrent refinement.
1608   _hot_card_cache->initialize(card_counts_storage);
1609 
1610   // 6843694 - ensure that the maximum region index can fit
1611   // in the remembered set structures.
1612   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1613   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1614 
1615   // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
1616   // start within the first card.
1617   guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card.");
1618   // Also create a G1 rem set.
1619   _g1_rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
1620   _g1_rem_set->initialize(max_capacity(), max_regions());
1621 
1622   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1623   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1624   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1625             "too many cards per region");
1626 
1627   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1628 
1629   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1630 
1631   {
1632     HeapWord* start = _hrm.reserved().start();
1633     HeapWord* end = _hrm.reserved().end();
1634     size_t granularity = HeapRegion::GrainBytes;
1635 
1636     _in_cset_fast_test.initialize(start, end, granularity);
1637     _humongous_reclaim_candidates.initialize(start, end, granularity);
1638   }
1639 
1640   // Create the G1ConcurrentMark data structure and thread.
1641   // (Must do this late, so that "max_regions" is defined.)
1642   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1643   if (_cm == NULL || !_cm->completed_initialization()) {
1644     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1645     return JNI_ENOMEM;
1646   }
1647   _cm_thread = _cm->cm_thread();
1648 
1649   // Now expand into the initial heap size.
1650   if (!expand(init_byte_size, _workers)) {
1651     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1652     return JNI_ENOMEM;
1653   }
1654 
1655   // Perform any initialization actions delegated to the policy.
1656   g1_policy()->init(this, &_collection_set);
1657 
1658   G1BarrierSet::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1659                                                  SATB_Q_FL_lock,
1660                                                  G1SATBProcessCompletedThreshold,
1661                                                  Shared_SATB_Q_lock);
1662 
1663   jint ecode = initialize_concurrent_refinement();
1664   if (ecode != JNI_OK) {
1665     return ecode;
1666   }
1667 
1668   ecode = initialize_young_gen_sampling_thread();
1669   if (ecode != JNI_OK) {
1670     return ecode;
1671   }
1672 
1673   G1BarrierSet::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1674                                                   DirtyCardQ_FL_lock,
1675                                                   (int)concurrent_refine()->yellow_zone(),
1676                                                   (int)concurrent_refine()->red_zone(),
1677                                                   Shared_DirtyCardQ_lock,
1678                                                   NULL,  // fl_owner
1679                                                   true); // init_free_ids
1680 
1681   dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1682                                     DirtyCardQ_FL_lock,
1683                                     -1, // never trigger processing
1684                                     -1, // no limit on length
1685                                     Shared_DirtyCardQ_lock,
1686                                     &G1BarrierSet::dirty_card_queue_set());
1687 
1688   // Here we allocate the dummy HeapRegion that is required by the
1689   // G1AllocRegion class.
1690   HeapRegion* dummy_region = _hrm.get_dummy_region();
1691 
1692   // We'll re-use the same region whether the alloc region will
1693   // require BOT updates or not and, if it doesn't, then a non-young
1694   // region will complain that it cannot support allocations without
1695   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1696   dummy_region->set_eden();
1697   // Make sure it's full.
1698   dummy_region->set_top(dummy_region->end());
1699   G1AllocRegion::setup(this, dummy_region);
1700 
1701   _allocator->init_mutator_alloc_region();
1702 
1703   // Do create of the monitoring and management support so that
1704   // values in the heap have been properly initialized.
1705   _g1mm = new G1MonitoringSupport(this);
1706 
1707   G1StringDedup::initialize();
1708 
1709   _preserved_marks_set.init(ParallelGCThreads);
1710 
1711   _collection_set.initialize(max_regions());
1712 
1713   return JNI_OK;
1714 }
1715 
1716 void G1CollectedHeap::initialize_serviceability() {
1717   _eden_pool = new G1EdenPool(this);
1718   _survivor_pool = new G1SurvivorPool(this);
1719   _old_pool = new G1OldGenPool(this);
1720 
1721   _full_gc_memory_manager.add_pool(_eden_pool);
1722   _full_gc_memory_manager.add_pool(_survivor_pool);
1723   _full_gc_memory_manager.add_pool(_old_pool);
1724 
1725   _memory_manager.add_pool(_eden_pool);
1726   _memory_manager.add_pool(_survivor_pool);
1727 
1728 }
1729 
1730 void G1CollectedHeap::stop() {
1731   // Stop all concurrent threads. We do this to make sure these threads
1732   // do not continue to execute and access resources (e.g. logging)
1733   // that are destroyed during shutdown.
1734   _cr->stop();
1735   _young_gen_sampling_thread->stop();
1736   _cm_thread->stop();
1737   if (G1StringDedup::is_enabled()) {
1738     G1StringDedup::stop();
1739   }
1740 }
1741 
1742 void G1CollectedHeap::safepoint_synchronize_begin() {
1743   SuspendibleThreadSet::synchronize();
1744 }
1745 
1746 void G1CollectedHeap::safepoint_synchronize_end() {
1747   SuspendibleThreadSet::desynchronize();
1748 }
1749 
1750 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1751   return HeapRegion::max_region_size();
1752 }
1753 
1754 void G1CollectedHeap::post_initialize() {
1755   CollectedHeap::post_initialize();
1756   ref_processing_init();
1757 }
1758 
1759 void G1CollectedHeap::ref_processing_init() {
1760   // Reference processing in G1 currently works as follows:
1761   //
1762   // * There are two reference processor instances. One is
1763   //   used to record and process discovered references
1764   //   during concurrent marking; the other is used to
1765   //   record and process references during STW pauses
1766   //   (both full and incremental).
1767   // * Both ref processors need to 'span' the entire heap as
1768   //   the regions in the collection set may be dotted around.
1769   //
1770   // * For the concurrent marking ref processor:
1771   //   * Reference discovery is enabled at initial marking.
1772   //   * Reference discovery is disabled and the discovered
1773   //     references processed etc during remarking.
1774   //   * Reference discovery is MT (see below).
1775   //   * Reference discovery requires a barrier (see below).
1776   //   * Reference processing may or may not be MT
1777   //     (depending on the value of ParallelRefProcEnabled
1778   //     and ParallelGCThreads).
1779   //   * A full GC disables reference discovery by the CM
1780   //     ref processor and abandons any entries on it's
1781   //     discovered lists.
1782   //
1783   // * For the STW processor:
1784   //   * Non MT discovery is enabled at the start of a full GC.
1785   //   * Processing and enqueueing during a full GC is non-MT.
1786   //   * During a full GC, references are processed after marking.
1787   //
1788   //   * Discovery (may or may not be MT) is enabled at the start
1789   //     of an incremental evacuation pause.
1790   //   * References are processed near the end of a STW evacuation pause.
1791   //   * For both types of GC:
1792   //     * Discovery is atomic - i.e. not concurrent.
1793   //     * Reference discovery will not need a barrier.
1794 
1795   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1796 
1797   // Concurrent Mark ref processor
1798   _ref_processor_cm =
1799     new ReferenceProcessor(&_is_subject_to_discovery_cm,
1800                            mt_processing,                                  // mt processing
1801                            ParallelGCThreads,                              // degree of mt processing
1802                            (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery
1803                            MAX2(ParallelGCThreads, ConcGCThreads),         // degree of mt discovery
1804                            false,                                          // Reference discovery is not atomic
1805                            &_is_alive_closure_cm);                         // is alive closure
1806 
1807   // STW ref processor
1808   _ref_processor_stw =
1809     new ReferenceProcessor(&_is_subject_to_discovery_stw,
1810                            mt_processing,                        // mt processing
1811                            ParallelGCThreads,                    // degree of mt processing
1812                            (ParallelGCThreads > 1),              // mt discovery
1813                            ParallelGCThreads,                    // degree of mt discovery
1814                            true,                                 // Reference discovery is atomic
1815                            &_is_alive_closure_stw);              // is alive closure
1816 }
1817 
1818 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1819   return _collector_policy;
1820 }
1821 
1822 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
1823   return &_soft_ref_policy;
1824 }
1825 
1826 size_t G1CollectedHeap::capacity() const {
1827   return _hrm.length() * HeapRegion::GrainBytes;
1828 }
1829 
1830 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1831   return _hrm.total_free_bytes();
1832 }
1833 
1834 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
1835   _hot_card_cache->drain(cl, worker_i);
1836 }
1837 
1838 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
1839   DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1840   size_t n_completed_buffers = 0;
1841   while (dcqs.apply_closure_during_gc(cl, worker_i)) {
1842     n_completed_buffers++;
1843   }
1844   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers, G1GCPhaseTimes::UpdateRSProcessedBuffers);
1845   dcqs.clear_n_completed_buffers();
1846   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
1847 }
1848 
1849 // Computes the sum of the storage used by the various regions.
1850 size_t G1CollectedHeap::used() const {
1851   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1852   if (_archive_allocator != NULL) {
1853     result += _archive_allocator->used();
1854   }
1855   return result;
1856 }
1857 
1858 size_t G1CollectedHeap::used_unlocked() const {
1859   return _summary_bytes_used;
1860 }
1861 
1862 class SumUsedClosure: public HeapRegionClosure {
1863   size_t _used;
1864 public:
1865   SumUsedClosure() : _used(0) {}
1866   bool do_heap_region(HeapRegion* r) {
1867     _used += r->used();
1868     return false;
1869   }
1870   size_t result() { return _used; }
1871 };
1872 
1873 size_t G1CollectedHeap::recalculate_used() const {
1874   double recalculate_used_start = os::elapsedTime();
1875 
1876   SumUsedClosure blk;
1877   heap_region_iterate(&blk);
1878 
1879   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
1880   return blk.result();
1881 }
1882 
1883 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
1884   switch (cause) {
1885     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
1886     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
1887     case GCCause::_wb_conc_mark:                        return true;
1888     default :                                           return false;
1889   }
1890 }
1891 
1892 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
1893   switch (cause) {
1894     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
1895     case GCCause::_g1_humongous_allocation: return true;
1896     default:                                return is_user_requested_concurrent_full_gc(cause);
1897   }
1898 }
1899 
1900 #ifndef PRODUCT
1901 void G1CollectedHeap::allocate_dummy_regions() {
1902   // Let's fill up most of the region
1903   size_t word_size = HeapRegion::GrainWords - 1024;
1904   // And as a result the region we'll allocate will be humongous.
1905   guarantee(is_humongous(word_size), "sanity");
1906 
1907   // _filler_array_max_size is set to humongous object threshold
1908   // but temporarily change it to use CollectedHeap::fill_with_object().
1909   SizeTFlagSetting fs(_filler_array_max_size, word_size);
1910 
1911   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
1912     // Let's use the existing mechanism for the allocation
1913     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
1914     if (dummy_obj != NULL) {
1915       MemRegion mr(dummy_obj, word_size);
1916       CollectedHeap::fill_with_object(mr);
1917     } else {
1918       // If we can't allocate once, we probably cannot allocate
1919       // again. Let's get out of the loop.
1920       break;
1921     }
1922   }
1923 }
1924 #endif // !PRODUCT
1925 
1926 void G1CollectedHeap::increment_old_marking_cycles_started() {
1927   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
1928          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
1929          "Wrong marking cycle count (started: %d, completed: %d)",
1930          _old_marking_cycles_started, _old_marking_cycles_completed);
1931 
1932   _old_marking_cycles_started++;
1933 }
1934 
1935 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
1936   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
1937 
1938   // We assume that if concurrent == true, then the caller is a
1939   // concurrent thread that was joined the Suspendible Thread
1940   // Set. If there's ever a cheap way to check this, we should add an
1941   // assert here.
1942 
1943   // Given that this method is called at the end of a Full GC or of a
1944   // concurrent cycle, and those can be nested (i.e., a Full GC can
1945   // interrupt a concurrent cycle), the number of full collections
1946   // completed should be either one (in the case where there was no
1947   // nesting) or two (when a Full GC interrupted a concurrent cycle)
1948   // behind the number of full collections started.
1949 
1950   // This is the case for the inner caller, i.e. a Full GC.
1951   assert(concurrent ||
1952          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
1953          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
1954          "for inner caller (Full GC): _old_marking_cycles_started = %u "
1955          "is inconsistent with _old_marking_cycles_completed = %u",
1956          _old_marking_cycles_started, _old_marking_cycles_completed);
1957 
1958   // This is the case for the outer caller, i.e. the concurrent cycle.
1959   assert(!concurrent ||
1960          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
1961          "for outer caller (concurrent cycle): "
1962          "_old_marking_cycles_started = %u "
1963          "is inconsistent with _old_marking_cycles_completed = %u",
1964          _old_marking_cycles_started, _old_marking_cycles_completed);
1965 
1966   _old_marking_cycles_completed += 1;
1967 
1968   // We need to clear the "in_progress" flag in the CM thread before
1969   // we wake up any waiters (especially when ExplicitInvokesConcurrent
1970   // is set) so that if a waiter requests another System.gc() it doesn't
1971   // incorrectly see that a marking cycle is still in progress.
1972   if (concurrent) {
1973     _cm_thread->set_idle();
1974   }
1975 
1976   // This notify_all() will ensure that a thread that called
1977   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
1978   // and it's waiting for a full GC to finish will be woken up. It is
1979   // waiting in VM_G1CollectForAllocation::doit_epilogue().
1980   FullGCCount_lock->notify_all();
1981 }
1982 
1983 void G1CollectedHeap::collect(GCCause::Cause cause) {
1984   assert_heap_not_locked();
1985 
1986   uint gc_count_before;
1987   uint old_marking_count_before;
1988   uint full_gc_count_before;
1989   bool retry_gc;
1990 
1991   do {
1992     retry_gc = false;
1993 
1994     {
1995       MutexLocker ml(Heap_lock);
1996 
1997       // Read the GC count while holding the Heap_lock
1998       gc_count_before = total_collections();
1999       full_gc_count_before = total_full_collections();
2000       old_marking_count_before = _old_marking_cycles_started;
2001     }
2002 
2003     if (should_do_concurrent_full_gc(cause)) {
2004       // Schedule an initial-mark evacuation pause that will start a
2005       // concurrent cycle. We're setting word_size to 0 which means that
2006       // we are not requesting a post-GC allocation.
2007       VM_G1CollectForAllocation op(0,     /* word_size */
2008                                    gc_count_before,
2009                                    cause,
2010                                    true,  /* should_initiate_conc_mark */
2011                                    g1_policy()->max_pause_time_ms());
2012       VMThread::execute(&op);
2013       if (!op.pause_succeeded()) {
2014         if (old_marking_count_before == _old_marking_cycles_started) {
2015           retry_gc = op.should_retry_gc();
2016         } else {
2017           // A Full GC happened while we were trying to schedule the
2018           // initial-mark GC. No point in starting a new cycle given
2019           // that the whole heap was collected anyway.
2020         }
2021 
2022         if (retry_gc) {
2023           if (GCLocker::is_active_and_needs_gc()) {
2024             GCLocker::stall_until_clear();
2025           }
2026         }
2027       }
2028     } else {
2029       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2030           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2031 
2032         // Schedule a standard evacuation pause. We're setting word_size
2033         // to 0 which means that we are not requesting a post-GC allocation.
2034         VM_G1CollectForAllocation op(0,     /* word_size */
2035                                      gc_count_before,
2036                                      cause,
2037                                      false, /* should_initiate_conc_mark */
2038                                      g1_policy()->max_pause_time_ms());
2039         VMThread::execute(&op);
2040       } else {
2041         // Schedule a Full GC.
2042         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2043         VMThread::execute(&op);
2044       }
2045     }
2046   } while (retry_gc);
2047 }
2048 
2049 bool G1CollectedHeap::is_in(const void* p) const {
2050   if (_hrm.reserved().contains(p)) {
2051     // Given that we know that p is in the reserved space,
2052     // heap_region_containing() should successfully
2053     // return the containing region.
2054     HeapRegion* hr = heap_region_containing(p);
2055     return hr->is_in(p);
2056   } else {
2057     return false;
2058   }
2059 }
2060 
2061 #ifdef ASSERT
2062 bool G1CollectedHeap::is_in_exact(const void* p) const {
2063   bool contains = reserved_region().contains(p);
2064   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2065   if (contains && available) {
2066     return true;
2067   } else {
2068     return false;
2069   }
2070 }
2071 #endif
2072 
2073 // Iteration functions.
2074 
2075 // Iterates an ObjectClosure over all objects within a HeapRegion.
2076 
2077 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2078   ObjectClosure* _cl;
2079 public:
2080   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2081   bool do_heap_region(HeapRegion* r) {
2082     if (!r->is_continues_humongous()) {
2083       r->object_iterate(_cl);
2084     }
2085     return false;
2086   }
2087 };
2088 
2089 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2090   IterateObjectClosureRegionClosure blk(cl);
2091   heap_region_iterate(&blk);
2092 }
2093 
2094 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2095   _hrm.iterate(cl);
2096 }
2097 
2098 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2099                                                                  HeapRegionClaimer *hrclaimer,
2100                                                                  uint worker_id) const {
2101   _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2102 }
2103 
2104 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2105                                                          HeapRegionClaimer *hrclaimer) const {
2106   _hrm.par_iterate(cl, hrclaimer, 0);
2107 }
2108 
2109 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2110   _collection_set.iterate(cl);
2111 }
2112 
2113 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2114   _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2115 }
2116 
2117 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2118   HeapRegion* hr = heap_region_containing(addr);
2119   return hr->block_start(addr);
2120 }
2121 
2122 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2123   HeapRegion* hr = heap_region_containing(addr);
2124   return hr->block_size(addr);
2125 }
2126 
2127 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2128   HeapRegion* hr = heap_region_containing(addr);
2129   return hr->block_is_obj(addr);
2130 }
2131 
2132 bool G1CollectedHeap::supports_tlab_allocation() const {
2133   return true;
2134 }
2135 
2136 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2137   return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2138 }
2139 
2140 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2141   return _eden.length() * HeapRegion::GrainBytes;
2142 }
2143 
2144 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2145 // must be equal to the humongous object limit.
2146 size_t G1CollectedHeap::max_tlab_size() const {
2147   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2148 }
2149 
2150 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2151   return _allocator->unsafe_max_tlab_alloc();
2152 }
2153 
2154 size_t G1CollectedHeap::max_capacity() const {
2155   return _hrm.reserved().byte_size();
2156 }
2157 
2158 jlong G1CollectedHeap::millis_since_last_gc() {
2159   // See the notes in GenCollectedHeap::millis_since_last_gc()
2160   // for more information about the implementation.
2161   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2162     _g1_policy->collection_pause_end_millis();
2163   if (ret_val < 0) {
2164     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2165       ". returning zero instead.", ret_val);
2166     return 0;
2167   }
2168   return ret_val;
2169 }
2170 
2171 void G1CollectedHeap::deduplicate_string(oop str) {
2172   assert(java_lang_String::is_instance(str), "invariant");
2173 
2174   if (G1StringDedup::is_enabled()) {
2175     G1StringDedup::deduplicate(str);
2176   }
2177 }
2178 
2179 void G1CollectedHeap::prepare_for_verify() {
2180   _verifier->prepare_for_verify();
2181 }
2182 
2183 void G1CollectedHeap::verify(VerifyOption vo) {
2184   _verifier->verify(vo);
2185 }
2186 
2187 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2188   return true;
2189 }
2190 
2191 const char* const* G1CollectedHeap::concurrent_phases() const {
2192   return _cm_thread->concurrent_phases();
2193 }
2194 
2195 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2196   return _cm_thread->request_concurrent_phase(phase);
2197 }
2198 
2199 class PrintRegionClosure: public HeapRegionClosure {
2200   outputStream* _st;
2201 public:
2202   PrintRegionClosure(outputStream* st) : _st(st) {}
2203   bool do_heap_region(HeapRegion* r) {
2204     r->print_on(_st);
2205     return false;
2206   }
2207 };
2208 
2209 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2210                                        const HeapRegion* hr,
2211                                        const VerifyOption vo) const {
2212   switch (vo) {
2213   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2214   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2215   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2216   default:                            ShouldNotReachHere();
2217   }
2218   return false; // keep some compilers happy
2219 }
2220 
2221 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2222                                        const VerifyOption vo) const {
2223   switch (vo) {
2224   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2225   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2226   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2227   default:                            ShouldNotReachHere();
2228   }
2229   return false; // keep some compilers happy
2230 }
2231 
2232 void G1CollectedHeap::print_heap_regions() const {
2233   LogTarget(Trace, gc, heap, region) lt;
2234   if (lt.is_enabled()) {
2235     LogStream ls(lt);
2236     print_regions_on(&ls);
2237   }
2238 }
2239 
2240 void G1CollectedHeap::print_on(outputStream* st) const {
2241   st->print(" %-20s", "garbage-first heap");
2242   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2243             capacity()/K, used_unlocked()/K);
2244   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2245             p2i(_hrm.reserved().start()),
2246             p2i(_hrm.reserved().end()));
2247   st->cr();
2248   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2249   uint young_regions = young_regions_count();
2250   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2251             (size_t) young_regions * HeapRegion::GrainBytes / K);
2252   uint survivor_regions = survivor_regions_count();
2253   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2254             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2255   st->cr();
2256   MetaspaceUtils::print_on(st);
2257 }
2258 
2259 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2260   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2261                "HS=humongous(starts), HC=humongous(continues), "
2262                "CS=collection set, F=free, A=archive, "
2263                "TAMS=top-at-mark-start (previous, next)");
2264   PrintRegionClosure blk(st);
2265   heap_region_iterate(&blk);
2266 }
2267 
2268 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2269   print_on(st);
2270 
2271   // Print the per-region information.
2272   print_regions_on(st);
2273 }
2274 
2275 void G1CollectedHeap::print_on_error(outputStream* st) const {
2276   this->CollectedHeap::print_on_error(st);
2277 
2278   if (_cm != NULL) {
2279     st->cr();
2280     _cm->print_on_error(st);
2281   }
2282 }
2283 
2284 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2285   workers()->print_worker_threads_on(st);
2286   _cm_thread->print_on(st);
2287   st->cr();
2288   _cm->print_worker_threads_on(st);
2289   _cr->print_threads_on(st);
2290   _young_gen_sampling_thread->print_on(st);
2291   if (G1StringDedup::is_enabled()) {
2292     G1StringDedup::print_worker_threads_on(st);
2293   }
2294 }
2295 
2296 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2297   workers()->threads_do(tc);
2298   tc->do_thread(_cm_thread);
2299   _cm->threads_do(tc);
2300   _cr->threads_do(tc);
2301   tc->do_thread(_young_gen_sampling_thread);
2302   if (G1StringDedup::is_enabled()) {
2303     G1StringDedup::threads_do(tc);
2304   }
2305 }
2306 
2307 void G1CollectedHeap::print_tracing_info() const {
2308   g1_rem_set()->print_summary_info();
2309   concurrent_mark()->print_summary_info();
2310 }
2311 
2312 #ifndef PRODUCT
2313 // Helpful for debugging RSet issues.
2314 
2315 class PrintRSetsClosure : public HeapRegionClosure {
2316 private:
2317   const char* _msg;
2318   size_t _occupied_sum;
2319 
2320 public:
2321   bool do_heap_region(HeapRegion* r) {
2322     HeapRegionRemSet* hrrs = r->rem_set();
2323     size_t occupied = hrrs->occupied();
2324     _occupied_sum += occupied;
2325 
2326     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2327     if (occupied == 0) {
2328       tty->print_cr("  RSet is empty");
2329     } else {
2330       hrrs->print();
2331     }
2332     tty->print_cr("----------");
2333     return false;
2334   }
2335 
2336   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2337     tty->cr();
2338     tty->print_cr("========================================");
2339     tty->print_cr("%s", msg);
2340     tty->cr();
2341   }
2342 
2343   ~PrintRSetsClosure() {
2344     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2345     tty->print_cr("========================================");
2346     tty->cr();
2347   }
2348 };
2349 
2350 void G1CollectedHeap::print_cset_rsets() {
2351   PrintRSetsClosure cl("Printing CSet RSets");
2352   collection_set_iterate(&cl);
2353 }
2354 
2355 void G1CollectedHeap::print_all_rsets() {
2356   PrintRSetsClosure cl("Printing All RSets");;
2357   heap_region_iterate(&cl);
2358 }
2359 #endif // PRODUCT
2360 
2361 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2362 
2363   size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2364   size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2365   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2366 
2367   size_t eden_capacity_bytes =
2368     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2369 
2370   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2371   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2372                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2373 }
2374 
2375 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2376   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2377                        stats->unused(), stats->used(), stats->region_end_waste(),
2378                        stats->regions_filled(), stats->direct_allocated(),
2379                        stats->failure_used(), stats->failure_waste());
2380 }
2381 
2382 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2383   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2384   gc_tracer->report_gc_heap_summary(when, heap_summary);
2385 
2386   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2387   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2388 }
2389 
2390 G1CollectedHeap* G1CollectedHeap::heap() {
2391   CollectedHeap* heap = Universe::heap();
2392   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2393   assert(heap->kind() == CollectedHeap::G1, "Invalid name");
2394   return (G1CollectedHeap*)heap;
2395 }
2396 
2397 void G1CollectedHeap::gc_prologue(bool full) {
2398   // always_do_update_barrier = false;
2399   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2400 
2401   // This summary needs to be printed before incrementing total collections.
2402   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2403 
2404   // Update common counters.
2405   increment_total_collections(full /* full gc */);
2406   if (full) {
2407     increment_old_marking_cycles_started();
2408   }
2409 
2410   // Fill TLAB's and such
2411   double start = os::elapsedTime();
2412   accumulate_statistics_all_tlabs();
2413   ensure_parsability(true);
2414   g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2415 }
2416 
2417 void G1CollectedHeap::gc_epilogue(bool full) {
2418   // Update common counters.
2419   if (full) {
2420     // Update the number of full collections that have been completed.
2421     increment_old_marking_cycles_completed(false /* concurrent */);
2422   }
2423 
2424   // We are at the end of the GC. Total collections has already been increased.
2425   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2426 
2427   // FIXME: what is this about?
2428   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2429   // is set.
2430 #if COMPILER2_OR_JVMCI
2431   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2432 #endif
2433   // always_do_update_barrier = true;
2434 
2435   double start = os::elapsedTime();
2436   resize_all_tlabs();
2437   g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2438 
2439   MemoryService::track_memory_usage();
2440   // We have just completed a GC. Update the soft reference
2441   // policy with the new heap occupancy
2442   Universe::update_heap_info_at_gc();
2443 }
2444 
2445 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2446                                                uint gc_count_before,
2447                                                bool* succeeded,
2448                                                GCCause::Cause gc_cause) {
2449   assert_heap_not_locked_and_not_at_safepoint();
2450   VM_G1CollectForAllocation op(word_size,
2451                                gc_count_before,
2452                                gc_cause,
2453                                false, /* should_initiate_conc_mark */
2454                                g1_policy()->max_pause_time_ms());
2455   VMThread::execute(&op);
2456 
2457   HeapWord* result = op.result();
2458   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2459   assert(result == NULL || ret_succeeded,
2460          "the result should be NULL if the VM did not succeed");
2461   *succeeded = ret_succeeded;
2462 
2463   assert_heap_not_locked();
2464   return result;
2465 }
2466 
2467 void G1CollectedHeap::do_concurrent_mark() {
2468   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2469   if (!_cm_thread->in_progress()) {
2470     _cm_thread->set_started();
2471     CGC_lock->notify();
2472   }
2473 }
2474 
2475 size_t G1CollectedHeap::pending_card_num() {
2476   size_t extra_cards = 0;
2477   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) {
2478     DirtyCardQueue& dcq = G1ThreadLocalData::dirty_card_queue(curr);
2479     extra_cards += dcq.size();
2480   }
2481   DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
2482   size_t buffer_size = dcqs.buffer_size();
2483   size_t buffer_num = dcqs.completed_buffers_num();
2484 
2485   return buffer_size * buffer_num + extra_cards;
2486 }
2487 
2488 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
2489   // We don't nominate objects with many remembered set entries, on
2490   // the assumption that such objects are likely still live.
2491   HeapRegionRemSet* rem_set = r->rem_set();
2492 
2493   return G1EagerReclaimHumongousObjectsWithStaleRefs ?
2494          rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) :
2495          G1EagerReclaimHumongousObjects && rem_set->is_empty();
2496 }
2497 
2498 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2499  private:
2500   size_t _total_humongous;
2501   size_t _candidate_humongous;
2502 
2503   DirtyCardQueue _dcq;
2504 
2505   bool humongous_region_is_candidate(G1CollectedHeap* g1h, HeapRegion* region) const {
2506     assert(region->is_starts_humongous(), "Must start a humongous object");
2507 
2508     oop obj = oop(region->bottom());
2509 
2510     // Dead objects cannot be eager reclaim candidates. Due to class
2511     // unloading it is unsafe to query their classes so we return early.
2512     if (g1h->is_obj_dead(obj, region)) {
2513       return false;
2514     }
2515 
2516     // If we do not have a complete remembered set for the region, then we can
2517     // not be sure that we have all references to it.
2518     if (!region->rem_set()->is_complete()) {
2519       return false;
2520     }
2521     // Candidate selection must satisfy the following constraints
2522     // while concurrent marking is in progress:
2523     //
2524     // * In order to maintain SATB invariants, an object must not be
2525     // reclaimed if it was allocated before the start of marking and
2526     // has not had its references scanned.  Such an object must have
2527     // its references (including type metadata) scanned to ensure no
2528     // live objects are missed by the marking process.  Objects
2529     // allocated after the start of concurrent marking don't need to
2530     // be scanned.
2531     //
2532     // * An object must not be reclaimed if it is on the concurrent
2533     // mark stack.  Objects allocated after the start of concurrent
2534     // marking are never pushed on the mark stack.
2535     //
2536     // Nominating only objects allocated after the start of concurrent
2537     // marking is sufficient to meet both constraints.  This may miss
2538     // some objects that satisfy the constraints, but the marking data
2539     // structures don't support efficiently performing the needed
2540     // additional tests or scrubbing of the mark stack.
2541     //
2542     // However, we presently only nominate is_typeArray() objects.
2543     // A humongous object containing references induces remembered
2544     // set entries on other regions.  In order to reclaim such an
2545     // object, those remembered sets would need to be cleaned up.
2546     //
2547     // We also treat is_typeArray() objects specially, allowing them
2548     // to be reclaimed even if allocated before the start of
2549     // concurrent mark.  For this we rely on mark stack insertion to
2550     // exclude is_typeArray() objects, preventing reclaiming an object
2551     // that is in the mark stack.  We also rely on the metadata for
2552     // such objects to be built-in and so ensured to be kept live.
2553     // Frequent allocation and drop of large binary blobs is an
2554     // important use case for eager reclaim, and this special handling
2555     // may reduce needed headroom.
2556 
2557     return obj->is_typeArray() &&
2558            g1h->is_potential_eager_reclaim_candidate(region);
2559   }
2560 
2561  public:
2562   RegisterHumongousWithInCSetFastTestClosure()
2563   : _total_humongous(0),
2564     _candidate_humongous(0),
2565     _dcq(&G1BarrierSet::dirty_card_queue_set()) {
2566   }
2567 
2568   virtual bool do_heap_region(HeapRegion* r) {
2569     if (!r->is_starts_humongous()) {
2570       return false;
2571     }
2572     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2573 
2574     bool is_candidate = humongous_region_is_candidate(g1h, r);
2575     uint rindex = r->hrm_index();
2576     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2577     if (is_candidate) {
2578       _candidate_humongous++;
2579       g1h->register_humongous_region_with_cset(rindex);
2580       // Is_candidate already filters out humongous object with large remembered sets.
2581       // If we have a humongous object with a few remembered sets, we simply flush these
2582       // remembered set entries into the DCQS. That will result in automatic
2583       // re-evaluation of their remembered set entries during the following evacuation
2584       // phase.
2585       if (!r->rem_set()->is_empty()) {
2586         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2587                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2588         G1CardTable* ct = g1h->card_table();
2589         HeapRegionRemSetIterator hrrs(r->rem_set());
2590         size_t card_index;
2591         while (hrrs.has_next(card_index)) {
2592           jbyte* card_ptr = (jbyte*)ct->byte_for_index(card_index);
2593           // The remembered set might contain references to already freed
2594           // regions. Filter out such entries to avoid failing card table
2595           // verification.
2596           if (g1h->is_in_closed_subset(ct->addr_for(card_ptr))) {
2597             if (*card_ptr != G1CardTable::dirty_card_val()) {
2598               *card_ptr = G1CardTable::dirty_card_val();
2599               _dcq.enqueue(card_ptr);
2600             }
2601           }
2602         }
2603         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2604                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2605                hrrs.n_yielded(), r->rem_set()->occupied());
2606         // We should only clear the card based remembered set here as we will not
2607         // implicitly rebuild anything else during eager reclaim. Note that at the moment
2608         // (and probably never) we do not enter this path if there are other kind of
2609         // remembered sets for this region.
2610         r->rem_set()->clear_locked(true /* only_cardset */);
2611         // Clear_locked() above sets the state to Empty. However we want to continue
2612         // collecting remembered set entries for humongous regions that were not
2613         // reclaimed.
2614         r->rem_set()->set_state_complete();
2615       }
2616       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2617     }
2618     _total_humongous++;
2619 
2620     return false;
2621   }
2622 
2623   size_t total_humongous() const { return _total_humongous; }
2624   size_t candidate_humongous() const { return _candidate_humongous; }
2625 
2626   void flush_rem_set_entries() { _dcq.flush(); }
2627 };
2628 
2629 void G1CollectedHeap::register_humongous_regions_with_cset() {
2630   if (!G1EagerReclaimHumongousObjects) {
2631     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2632     return;
2633   }
2634   double time = os::elapsed_counter();
2635 
2636   // Collect reclaim candidate information and register candidates with cset.
2637   RegisterHumongousWithInCSetFastTestClosure cl;
2638   heap_region_iterate(&cl);
2639 
2640   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2641   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2642                                                                   cl.total_humongous(),
2643                                                                   cl.candidate_humongous());
2644   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2645 
2646   // Finally flush all remembered set entries to re-check into the global DCQS.
2647   cl.flush_rem_set_entries();
2648 }
2649 
2650 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2651   public:
2652     bool do_heap_region(HeapRegion* hr) {
2653       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2654         hr->verify_rem_set();
2655       }
2656       return false;
2657     }
2658 };
2659 
2660 uint G1CollectedHeap::num_task_queues() const {
2661   return _task_queues->size();
2662 }
2663 
2664 #if TASKQUEUE_STATS
2665 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2666   st->print_raw_cr("GC Task Stats");
2667   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2668   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2669 }
2670 
2671 void G1CollectedHeap::print_taskqueue_stats() const {
2672   if (!log_is_enabled(Trace, gc, task, stats)) {
2673     return;
2674   }
2675   Log(gc, task, stats) log;
2676   ResourceMark rm;
2677   LogStream ls(log.trace());
2678   outputStream* st = &ls;
2679 
2680   print_taskqueue_stats_hdr(st);
2681 
2682   TaskQueueStats totals;
2683   const uint n = num_task_queues();
2684   for (uint i = 0; i < n; ++i) {
2685     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2686     totals += task_queue(i)->stats;
2687   }
2688   st->print_raw("tot "); totals.print(st); st->cr();
2689 
2690   DEBUG_ONLY(totals.verify());
2691 }
2692 
2693 void G1CollectedHeap::reset_taskqueue_stats() {
2694   const uint n = num_task_queues();
2695   for (uint i = 0; i < n; ++i) {
2696     task_queue(i)->stats.reset();
2697   }
2698 }
2699 #endif // TASKQUEUE_STATS
2700 
2701 void G1CollectedHeap::wait_for_root_region_scanning() {
2702   double scan_wait_start = os::elapsedTime();
2703   // We have to wait until the CM threads finish scanning the
2704   // root regions as it's the only way to ensure that all the
2705   // objects on them have been correctly scanned before we start
2706   // moving them during the GC.
2707   bool waited = _cm->root_regions()->wait_until_scan_finished();
2708   double wait_time_ms = 0.0;
2709   if (waited) {
2710     double scan_wait_end = os::elapsedTime();
2711     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2712   }
2713   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2714 }
2715 
2716 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2717 private:
2718   G1HRPrinter* _hr_printer;
2719 public:
2720   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2721 
2722   virtual bool do_heap_region(HeapRegion* r) {
2723     _hr_printer->cset(r);
2724     return false;
2725   }
2726 };
2727 
2728 void G1CollectedHeap::start_new_collection_set() {
2729   collection_set()->start_incremental_building();
2730 
2731   clear_cset_fast_test();
2732 
2733   guarantee(_eden.length() == 0, "eden should have been cleared");
2734   g1_policy()->transfer_survivors_to_cset(survivor());
2735 }
2736 
2737 bool
2738 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2739   assert_at_safepoint_on_vm_thread();
2740   guarantee(!is_gc_active(), "collection is not reentrant");
2741 
2742   if (GCLocker::check_active_before_gc()) {
2743     return false;
2744   }
2745 
2746   _gc_timer_stw->register_gc_start();
2747 
2748   GCIdMark gc_id_mark;
2749   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2750 
2751   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2752   ResourceMark rm;
2753 
2754   g1_policy()->note_gc_start();
2755 
2756   wait_for_root_region_scanning();
2757 
2758   print_heap_before_gc();
2759   print_heap_regions();
2760   trace_heap_before_gc(_gc_tracer_stw);
2761 
2762   _verifier->verify_region_sets_optional();
2763   _verifier->verify_dirty_young_regions();
2764 
2765   // We should not be doing initial mark unless the conc mark thread is running
2766   if (!_cm_thread->should_terminate()) {
2767     // This call will decide whether this pause is an initial-mark
2768     // pause. If it is, in_initial_mark_gc() will return true
2769     // for the duration of this pause.
2770     g1_policy()->decide_on_conc_mark_initiation();
2771   }
2772 
2773   // We do not allow initial-mark to be piggy-backed on a mixed GC.
2774   assert(!collector_state()->in_initial_mark_gc() ||
2775           collector_state()->in_young_only_phase(), "sanity");
2776 
2777   // We also do not allow mixed GCs during marking.
2778   assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity");
2779 
2780   // Record whether this pause is an initial mark. When the current
2781   // thread has completed its logging output and it's safe to signal
2782   // the CM thread, the flag's value in the policy has been reset.
2783   bool should_start_conc_mark = collector_state()->in_initial_mark_gc();
2784 
2785   // Inner scope for scope based logging, timers, and stats collection
2786   {
2787     EvacuationInfo evacuation_info;
2788 
2789     if (collector_state()->in_initial_mark_gc()) {
2790       // We are about to start a marking cycle, so we increment the
2791       // full collection counter.
2792       increment_old_marking_cycles_started();
2793       _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2794     }
2795 
2796     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2797 
2798     GCTraceCPUTime tcpu;
2799 
2800     G1HeapVerifier::G1VerifyType verify_type;
2801     FormatBuffer<> gc_string("Pause ");
2802     if (collector_state()->in_initial_mark_gc()) {
2803       gc_string.append("Initial Mark");
2804       verify_type = G1HeapVerifier::G1VerifyInitialMark;
2805     } else if (collector_state()->in_young_only_phase()) {
2806       gc_string.append("Young");
2807       verify_type = G1HeapVerifier::G1VerifyYoungOnly;
2808     } else {
2809       gc_string.append("Mixed");
2810       verify_type = G1HeapVerifier::G1VerifyMixed;
2811     }
2812     GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2813 
2814     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2815                                                                   workers()->active_workers(),
2816                                                                   Threads::number_of_non_daemon_threads());
2817     active_workers = workers()->update_active_workers(active_workers);
2818     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2819 
2820     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2821     TraceMemoryManagerStats tms(&_memory_manager, gc_cause());
2822 
2823     G1HeapTransition heap_transition(this);
2824     size_t heap_used_bytes_before_gc = used();
2825 
2826     // Don't dynamically change the number of GC threads this early.  A value of
2827     // 0 is used to indicate serial work.  When parallel work is done,
2828     // it will be set.
2829 
2830     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2831       IsGCActiveMark x;
2832 
2833       gc_prologue(false);
2834 
2835       if (VerifyRememberedSets) {
2836         log_info(gc, verify)("[Verifying RemSets before GC]");
2837         VerifyRegionRemSetClosure v_cl;
2838         heap_region_iterate(&v_cl);
2839       }
2840 
2841       _verifier->verify_before_gc(verify_type);
2842 
2843       _verifier->check_bitmaps("GC Start");
2844 
2845 #if COMPILER2_OR_JVMCI
2846       DerivedPointerTable::clear();
2847 #endif
2848 
2849       // Please see comment in g1CollectedHeap.hpp and
2850       // G1CollectedHeap::ref_processing_init() to see how
2851       // reference processing currently works in G1.
2852 
2853       // Enable discovery in the STW reference processor
2854       _ref_processor_stw->enable_discovery();
2855 
2856       {
2857         // We want to temporarily turn off discovery by the
2858         // CM ref processor, if necessary, and turn it back on
2859         // on again later if we do. Using a scoped
2860         // NoRefDiscovery object will do this.
2861         NoRefDiscovery no_cm_discovery(_ref_processor_cm);
2862 
2863         // Forget the current alloc region (we might even choose it to be part
2864         // of the collection set!).
2865         _allocator->release_mutator_alloc_region();
2866 
2867         // This timing is only used by the ergonomics to handle our pause target.
2868         // It is unclear why this should not include the full pause. We will
2869         // investigate this in CR 7178365.
2870         //
2871         // Preserving the old comment here if that helps the investigation:
2872         //
2873         // The elapsed time induced by the start time below deliberately elides
2874         // the possible verification above.
2875         double sample_start_time_sec = os::elapsedTime();
2876 
2877         g1_policy()->record_collection_pause_start(sample_start_time_sec);
2878 
2879         if (collector_state()->in_initial_mark_gc()) {
2880           concurrent_mark()->pre_initial_mark();
2881         }
2882 
2883         g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
2884 
2885         evacuation_info.set_collectionset_regions(collection_set()->region_length());
2886 
2887         // Make sure the remembered sets are up to date. This needs to be
2888         // done before register_humongous_regions_with_cset(), because the
2889         // remembered sets are used there to choose eager reclaim candidates.
2890         // If the remembered sets are not up to date we might miss some
2891         // entries that need to be handled.
2892         g1_rem_set()->cleanupHRRS();
2893 
2894         register_humongous_regions_with_cset();
2895 
2896         assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
2897 
2898         // We call this after finalize_cset() to
2899         // ensure that the CSet has been finalized.
2900         _cm->verify_no_cset_oops();
2901 
2902         if (_hr_printer.is_active()) {
2903           G1PrintCollectionSetClosure cl(&_hr_printer);
2904           _collection_set.iterate(&cl);
2905         }
2906 
2907         // Initialize the GC alloc regions.
2908         _allocator->init_gc_alloc_regions(evacuation_info);
2909 
2910         G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
2911         pre_evacuate_collection_set();
2912 
2913         // Actually do the work...
2914         evacuate_collection_set(&per_thread_states);
2915 
2916         post_evacuate_collection_set(evacuation_info, &per_thread_states);
2917 
2918         const size_t* surviving_young_words = per_thread_states.surviving_young_words();
2919         free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
2920 
2921         eagerly_reclaim_humongous_regions();
2922 
2923         record_obj_copy_mem_stats();
2924         _survivor_evac_stats.adjust_desired_plab_sz();
2925         _old_evac_stats.adjust_desired_plab_sz();
2926 
2927         double start = os::elapsedTime();
2928         start_new_collection_set();
2929         g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
2930 
2931         if (evacuation_failed()) {
2932           set_used(recalculate_used());
2933           if (_archive_allocator != NULL) {
2934             _archive_allocator->clear_used();
2935           }
2936           for (uint i = 0; i < ParallelGCThreads; i++) {
2937             if (_evacuation_failed_info_array[i].has_failed()) {
2938               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
2939             }
2940           }
2941         } else {
2942           // The "used" of the the collection set have already been subtracted
2943           // when they were freed.  Add in the bytes evacuated.
2944           increase_used(g1_policy()->bytes_copied_during_gc());
2945         }
2946 
2947         if (collector_state()->in_initial_mark_gc()) {
2948           // We have to do this before we notify the CM threads that
2949           // they can start working to make sure that all the
2950           // appropriate initialization is done on the CM object.
2951           concurrent_mark()->post_initial_mark();
2952           // Note that we don't actually trigger the CM thread at
2953           // this point. We do that later when we're sure that
2954           // the current thread has completed its logging output.
2955         }
2956 
2957         allocate_dummy_regions();
2958 
2959         _allocator->init_mutator_alloc_region();
2960 
2961         {
2962           size_t expand_bytes = _heap_sizing_policy->expansion_amount();
2963           if (expand_bytes > 0) {
2964             size_t bytes_before = capacity();
2965             // No need for an ergo logging here,
2966             // expansion_amount() does this when it returns a value > 0.
2967             double expand_ms;
2968             if (!expand(expand_bytes, _workers, &expand_ms)) {
2969               // We failed to expand the heap. Cannot do anything about it.
2970             }
2971             g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
2972           }
2973         }
2974 
2975         // We redo the verification but now wrt to the new CSet which
2976         // has just got initialized after the previous CSet was freed.
2977         _cm->verify_no_cset_oops();
2978 
2979         // This timing is only used by the ergonomics to handle our pause target.
2980         // It is unclear why this should not include the full pause. We will
2981         // investigate this in CR 7178365.
2982         double sample_end_time_sec = os::elapsedTime();
2983         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
2984         size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
2985         g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
2986 
2987         evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
2988         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
2989 
2990         if (VerifyRememberedSets) {
2991           log_info(gc, verify)("[Verifying RemSets after GC]");
2992           VerifyRegionRemSetClosure v_cl;
2993           heap_region_iterate(&v_cl);
2994         }
2995 
2996         _verifier->verify_after_gc(verify_type);
2997         _verifier->check_bitmaps("GC End");
2998 
2999         assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
3000         _ref_processor_stw->verify_no_references_recorded();
3001 
3002         // CM reference discovery will be re-enabled if necessary.
3003       }
3004 
3005 #ifdef TRACESPINNING
3006       ParallelTaskTerminator::print_termination_counts();
3007 #endif
3008 
3009       gc_epilogue(false);
3010     }
3011 
3012     // Print the remainder of the GC log output.
3013     if (evacuation_failed()) {
3014       log_info(gc)("To-space exhausted");
3015     }
3016 
3017     g1_policy()->print_phases();
3018     heap_transition.print();
3019 
3020     // It is not yet to safe to tell the concurrent mark to
3021     // start as we have some optional output below. We don't want the
3022     // output from the concurrent mark thread interfering with this
3023     // logging output either.
3024 
3025     _hrm.verify_optional();
3026     _verifier->verify_region_sets_optional();
3027 
3028     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3029     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3030 
3031     print_heap_after_gc();
3032     print_heap_regions();
3033     trace_heap_after_gc(_gc_tracer_stw);
3034 
3035     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3036     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3037     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3038     // before any GC notifications are raised.
3039     g1mm()->update_sizes();
3040 
3041     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3042     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3043     _gc_timer_stw->register_gc_end();
3044     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3045   }
3046   // It should now be safe to tell the concurrent mark thread to start
3047   // without its logging output interfering with the logging output
3048   // that came from the pause.
3049 
3050   if (should_start_conc_mark) {
3051     // CAUTION: after the doConcurrentMark() call below,
3052     // the concurrent marking thread(s) could be running
3053     // concurrently with us. Make sure that anything after
3054     // this point does not assume that we are the only GC thread
3055     // running. Note: of course, the actual marking work will
3056     // not start until the safepoint itself is released in
3057     // SuspendibleThreadSet::desynchronize().
3058     do_concurrent_mark();
3059   }
3060 
3061   return true;
3062 }
3063 
3064 void G1CollectedHeap::remove_self_forwarding_pointers() {
3065   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3066   workers()->run_task(&rsfp_task);
3067 }
3068 
3069 void G1CollectedHeap::restore_after_evac_failure() {
3070   double remove_self_forwards_start = os::elapsedTime();
3071 
3072   remove_self_forwarding_pointers();
3073   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3074   _preserved_marks_set.restore(&task_executor);
3075 
3076   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3077 }
3078 
3079 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3080   if (!_evacuation_failed) {
3081     _evacuation_failed = true;
3082   }
3083 
3084   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3085   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3086 }
3087 
3088 bool G1ParEvacuateFollowersClosure::offer_termination() {
3089   G1ParScanThreadState* const pss = par_scan_state();
3090   start_term_time();
3091   const bool res = terminator()->offer_termination();
3092   end_term_time();
3093   return res;
3094 }
3095 
3096 void G1ParEvacuateFollowersClosure::do_void() {
3097   G1ParScanThreadState* const pss = par_scan_state();
3098   pss->trim_queue();
3099   do {
3100     pss->steal_and_trim_queue(queues());
3101   } while (!offer_termination());
3102 }
3103 
3104 class G1ParTask : public AbstractGangTask {
3105 protected:
3106   G1CollectedHeap*         _g1h;
3107   G1ParScanThreadStateSet* _pss;
3108   RefToScanQueueSet*       _queues;
3109   G1RootProcessor*         _root_processor;
3110   ParallelTaskTerminator   _terminator;
3111   uint                     _n_workers;
3112 
3113 public:
3114   G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3115     : AbstractGangTask("G1 collection"),
3116       _g1h(g1h),
3117       _pss(per_thread_states),
3118       _queues(task_queues),
3119       _root_processor(root_processor),
3120       _terminator(n_workers, _queues),
3121       _n_workers(n_workers)
3122   {}
3123 
3124   void work(uint worker_id) {
3125     if (worker_id >= _n_workers) return;  // no work needed this round
3126 
3127     double start_sec = os::elapsedTime();
3128     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3129 
3130     {
3131       ResourceMark rm;
3132       HandleMark   hm;
3133 
3134       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
3135 
3136       G1ParScanThreadState*           pss = _pss->state_for_worker(worker_id);
3137       pss->set_ref_discoverer(rp);
3138 
3139       double start_strong_roots_sec = os::elapsedTime();
3140 
3141       _root_processor->evacuate_roots(pss, worker_id);
3142 
3143       // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3144       // treating the nmethods visited to act as roots for concurrent marking.
3145       // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3146       // objects copied by the current evacuation.
3147       _g1h->g1_rem_set()->oops_into_collection_set_do(pss, worker_id);
3148 
3149       double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3150 
3151       double term_sec = 0.0;
3152       size_t evac_term_attempts = 0;
3153       {
3154         double start = os::elapsedTime();
3155         G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3156         evac.do_void();
3157 
3158         evac_term_attempts = evac.term_attempts();
3159         term_sec = evac.term_time();
3160         double elapsed_sec = os::elapsedTime() - start;
3161 
3162         G1GCPhaseTimes* p = _g1h->g1_policy()->phase_times();
3163         p->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3164         p->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3165         p->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3166       }
3167 
3168       assert(pss->queue_is_empty(), "should be empty");
3169 
3170       if (log_is_enabled(Debug, gc, task, stats)) {
3171         MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3172         size_t lab_waste;
3173         size_t lab_undo_waste;
3174         pss->waste(lab_waste, lab_undo_waste);
3175         _g1h->print_termination_stats(worker_id,
3176                                       (os::elapsedTime() - start_sec) * 1000.0,   /* elapsed time */
3177                                       strong_roots_sec * 1000.0,                  /* strong roots time */
3178                                       term_sec * 1000.0,                          /* evac term time */
3179                                       evac_term_attempts,                         /* evac term attempts */
3180                                       lab_waste,                                  /* alloc buffer waste */
3181                                       lab_undo_waste                              /* undo waste */
3182                                       );
3183       }
3184 
3185       // Close the inner scope so that the ResourceMark and HandleMark
3186       // destructors are executed here and are included as part of the
3187       // "GC Worker Time".
3188     }
3189     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3190   }
3191 };
3192 
3193 void G1CollectedHeap::print_termination_stats_hdr() {
3194   log_debug(gc, task, stats)("GC Termination Stats");
3195   log_debug(gc, task, stats)("     elapsed  --strong roots-- -------termination------- ------waste (KiB)------");
3196   log_debug(gc, task, stats)("thr     ms        ms      %%        ms      %%    attempts  total   alloc    undo");
3197   log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3198 }
3199 
3200 void G1CollectedHeap::print_termination_stats(uint worker_id,
3201                                               double elapsed_ms,
3202                                               double strong_roots_ms,
3203                                               double term_ms,
3204                                               size_t term_attempts,
3205                                               size_t alloc_buffer_waste,
3206                                               size_t undo_waste) const {
3207   log_debug(gc, task, stats)
3208               ("%3d %9.2f %9.2f %6.2f "
3209                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3210                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3211                worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3212                term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3213                (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3214                alloc_buffer_waste * HeapWordSize / K,
3215                undo_waste * HeapWordSize / K);
3216 }
3217 
3218 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3219 private:
3220   BoolObjectClosure* _is_alive;
3221   G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3222   OopStorage::ParState<false /* concurrent */, false /* const */> _par_state_string;
3223 
3224   int _initial_string_table_size;
3225   int _initial_symbol_table_size;
3226 
3227   bool  _process_strings;
3228   int _strings_processed;
3229   int _strings_removed;
3230 
3231   bool  _process_symbols;
3232   int _symbols_processed;
3233   int _symbols_removed;
3234 
3235   bool _process_string_dedup;
3236 
3237 public:
3238   G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3239     AbstractGangTask("String/Symbol Unlinking"),
3240     _is_alive(is_alive),
3241     _dedup_closure(is_alive, NULL, false),
3242     _par_state_string(StringTable::weak_storage()),
3243     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3244     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3245     _process_string_dedup(process_string_dedup) {
3246 
3247     _initial_string_table_size = (int) StringTable::the_table()->table_size();
3248     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3249     if (process_symbols) {
3250       SymbolTable::clear_parallel_claimed_index();
3251     }
3252   }
3253 
3254   ~G1StringAndSymbolCleaningTask() {
3255     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3256               "claim value %d after unlink less than initial symbol table size %d",
3257               SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3258 
3259     log_info(gc, stringtable)(
3260         "Cleaned string and symbol table, "
3261         "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3262         "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3263         strings_processed(), strings_removed(),
3264         symbols_processed(), symbols_removed());
3265   }
3266 
3267   void work(uint worker_id) {
3268     int strings_processed = 0;
3269     int strings_removed = 0;
3270     int symbols_processed = 0;
3271     int symbols_removed = 0;
3272     if (_process_strings) {
3273       StringTable::possibly_parallel_unlink(&_par_state_string, _is_alive, &strings_processed, &strings_removed);
3274       Atomic::add(strings_processed, &_strings_processed);
3275       Atomic::add(strings_removed, &_strings_removed);
3276     }
3277     if (_process_symbols) {
3278       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3279       Atomic::add(symbols_processed, &_symbols_processed);
3280       Atomic::add(symbols_removed, &_symbols_removed);
3281     }
3282     if (_process_string_dedup) {
3283       G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3284     }
3285   }
3286 
3287   size_t strings_processed() const { return (size_t)_strings_processed; }
3288   size_t strings_removed()   const { return (size_t)_strings_removed; }
3289 
3290   size_t symbols_processed() const { return (size_t)_symbols_processed; }
3291   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
3292 };
3293 
3294 class G1CodeCacheUnloadingTask {
3295 private:
3296   static Monitor* _lock;
3297 
3298   BoolObjectClosure* const _is_alive;
3299   const bool               _unloading_occurred;
3300   const uint               _num_workers;
3301 
3302   // Variables used to claim nmethods.
3303   CompiledMethod* _first_nmethod;
3304   CompiledMethod* volatile _claimed_nmethod;
3305 
3306   // The list of nmethods that need to be processed by the second pass.
3307   CompiledMethod* volatile _postponed_list;
3308   volatile uint            _num_entered_barrier;
3309 
3310  public:
3311   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3312       _is_alive(is_alive),
3313       _unloading_occurred(unloading_occurred),
3314       _num_workers(num_workers),
3315       _first_nmethod(NULL),
3316       _claimed_nmethod(NULL),
3317       _postponed_list(NULL),
3318       _num_entered_barrier(0)
3319   {
3320     CompiledMethod::increase_unloading_clock();
3321     // Get first alive nmethod
3322     CompiledMethodIterator iter = CompiledMethodIterator();
3323     if(iter.next_alive()) {
3324       _first_nmethod = iter.method();
3325     }
3326     _claimed_nmethod = _first_nmethod;
3327   }
3328 
3329   ~G1CodeCacheUnloadingTask() {
3330     CodeCache::verify_clean_inline_caches();
3331 
3332     CodeCache::set_needs_cache_clean(false);
3333     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3334 
3335     CodeCache::verify_icholder_relocations();
3336   }
3337 
3338  private:
3339   void add_to_postponed_list(CompiledMethod* nm) {
3340       CompiledMethod* old;
3341       do {
3342         old = _postponed_list;
3343         nm->set_unloading_next(old);
3344       } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
3345   }
3346 
3347   void clean_nmethod(CompiledMethod* nm) {
3348     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3349 
3350     if (postponed) {
3351       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3352       add_to_postponed_list(nm);
3353     }
3354 
3355     // Mark that this thread has been cleaned/unloaded.
3356     // After this call, it will be safe to ask if this nmethod was unloaded or not.
3357     nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3358   }
3359 
3360   void clean_nmethod_postponed(CompiledMethod* nm) {
3361     nm->do_unloading_parallel_postponed();
3362   }
3363 
3364   static const int MaxClaimNmethods = 16;
3365 
3366   void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3367     CompiledMethod* first;
3368     CompiledMethodIterator last;
3369 
3370     do {
3371       *num_claimed_nmethods = 0;
3372 
3373       first = _claimed_nmethod;
3374       last = CompiledMethodIterator(first);
3375 
3376       if (first != NULL) {
3377 
3378         for (int i = 0; i < MaxClaimNmethods; i++) {
3379           if (!last.next_alive()) {
3380             break;
3381           }
3382           claimed_nmethods[i] = last.method();
3383           (*num_claimed_nmethods)++;
3384         }
3385       }
3386 
3387     } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
3388   }
3389 
3390   CompiledMethod* claim_postponed_nmethod() {
3391     CompiledMethod* claim;
3392     CompiledMethod* next;
3393 
3394     do {
3395       claim = _postponed_list;
3396       if (claim == NULL) {
3397         return NULL;
3398       }
3399 
3400       next = claim->unloading_next();
3401 
3402     } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
3403 
3404     return claim;
3405   }
3406 
3407  public:
3408   // Mark that we're done with the first pass of nmethod cleaning.
3409   void barrier_mark(uint worker_id) {
3410     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3411     _num_entered_barrier++;
3412     if (_num_entered_barrier == _num_workers) {
3413       ml.notify_all();
3414     }
3415   }
3416 
3417   // See if we have to wait for the other workers to
3418   // finish their first-pass nmethod cleaning work.
3419   void barrier_wait(uint worker_id) {
3420     if (_num_entered_barrier < _num_workers) {
3421       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3422       while (_num_entered_barrier < _num_workers) {
3423           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3424       }
3425     }
3426   }
3427 
3428   // Cleaning and unloading of nmethods. Some work has to be postponed
3429   // to the second pass, when we know which nmethods survive.
3430   void work_first_pass(uint worker_id) {
3431     // The first nmethods is claimed by the first worker.
3432     if (worker_id == 0 && _first_nmethod != NULL) {
3433       clean_nmethod(_first_nmethod);
3434       _first_nmethod = NULL;
3435     }
3436 
3437     int num_claimed_nmethods;
3438     CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3439 
3440     while (true) {
3441       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3442 
3443       if (num_claimed_nmethods == 0) {
3444         break;
3445       }
3446 
3447       for (int i = 0; i < num_claimed_nmethods; i++) {
3448         clean_nmethod(claimed_nmethods[i]);
3449       }
3450     }
3451   }
3452 
3453   void work_second_pass(uint worker_id) {
3454     CompiledMethod* nm;
3455     // Take care of postponed nmethods.
3456     while ((nm = claim_postponed_nmethod()) != NULL) {
3457       clean_nmethod_postponed(nm);
3458     }
3459   }
3460 };
3461 
3462 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3463 
3464 class G1KlassCleaningTask : public StackObj {
3465   volatile int                            _clean_klass_tree_claimed;
3466   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3467 
3468  public:
3469   G1KlassCleaningTask() :
3470       _clean_klass_tree_claimed(0),
3471       _klass_iterator() {
3472   }
3473 
3474  private:
3475   bool claim_clean_klass_tree_task() {
3476     if (_clean_klass_tree_claimed) {
3477       return false;
3478     }
3479 
3480     return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0;
3481   }
3482 
3483   InstanceKlass* claim_next_klass() {
3484     Klass* klass;
3485     do {
3486       klass =_klass_iterator.next_klass();
3487     } while (klass != NULL && !klass->is_instance_klass());
3488 
3489     // this can be null so don't call InstanceKlass::cast
3490     return static_cast<InstanceKlass*>(klass);
3491   }
3492 
3493 public:
3494 
3495   void clean_klass(InstanceKlass* ik) {
3496     ik->clean_weak_instanceklass_links();
3497   }
3498 
3499   void work() {
3500     ResourceMark rm;
3501 
3502     // One worker will clean the subklass/sibling klass tree.
3503     if (claim_clean_klass_tree_task()) {
3504       Klass::clean_subklass_tree();
3505     }
3506 
3507     // All workers will help cleaning the classes,
3508     InstanceKlass* klass;
3509     while ((klass = claim_next_klass()) != NULL) {
3510       clean_klass(klass);
3511     }
3512   }
3513 };
3514 
3515 class G1ResolvedMethodCleaningTask : public StackObj {
3516   volatile int       _resolved_method_task_claimed;
3517 public:
3518   G1ResolvedMethodCleaningTask() :
3519       _resolved_method_task_claimed(0) {}
3520 
3521   bool claim_resolved_method_task() {
3522     if (_resolved_method_task_claimed) {
3523       return false;
3524     }
3525     return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0;
3526   }
3527 
3528   // These aren't big, one thread can do it all.
3529   void work() {
3530     if (claim_resolved_method_task()) {
3531       ResolvedMethodTable::unlink();
3532     }
3533   }
3534 };
3535 
3536 
3537 // To minimize the remark pause times, the tasks below are done in parallel.
3538 class G1ParallelCleaningTask : public AbstractGangTask {
3539 private:
3540   bool                          _unloading_occurred;
3541   G1StringAndSymbolCleaningTask _string_symbol_task;
3542   G1CodeCacheUnloadingTask      _code_cache_task;
3543   G1KlassCleaningTask           _klass_cleaning_task;
3544   G1ResolvedMethodCleaningTask  _resolved_method_cleaning_task;
3545 
3546 public:
3547   // The constructor is run in the VMThread.
3548   G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3549       AbstractGangTask("Parallel Cleaning"),
3550       _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3551       _code_cache_task(num_workers, is_alive, unloading_occurred),
3552       _klass_cleaning_task(),
3553       _unloading_occurred(unloading_occurred),
3554       _resolved_method_cleaning_task() {
3555   }
3556 
3557   // The parallel work done by all worker threads.
3558   void work(uint worker_id) {
3559     // Do first pass of code cache cleaning.
3560     _code_cache_task.work_first_pass(worker_id);
3561 
3562     // Let the threads mark that the first pass is done.
3563     _code_cache_task.barrier_mark(worker_id);
3564 
3565     // Clean the Strings and Symbols.
3566     _string_symbol_task.work(worker_id);
3567 
3568     // Clean unreferenced things in the ResolvedMethodTable
3569     _resolved_method_cleaning_task.work();
3570 
3571     // Wait for all workers to finish the first code cache cleaning pass.
3572     _code_cache_task.barrier_wait(worker_id);
3573 
3574     // Do the second code cache cleaning work, which realize on
3575     // the liveness information gathered during the first pass.
3576     _code_cache_task.work_second_pass(worker_id);
3577 
3578     // Clean all klasses that were not unloaded.
3579     // The weak metadata in klass doesn't need to be
3580     // processed if there was no unloading.
3581     if (_unloading_occurred) {
3582       _klass_cleaning_task.work();
3583     }
3584   }
3585 };
3586 
3587 
3588 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3589                                         bool class_unloading_occurred) {
3590   uint n_workers = workers()->active_workers();
3591 
3592   G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3593   workers()->run_task(&g1_unlink_task);
3594 }
3595 
3596 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3597                                        bool process_strings,
3598                                        bool process_symbols,
3599                                        bool process_string_dedup) {
3600   if (!process_strings && !process_symbols && !process_string_dedup) {
3601     // Nothing to clean.
3602     return;
3603   }
3604 
3605   G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3606   workers()->run_task(&g1_unlink_task);
3607 
3608 }
3609 
3610 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3611  private:
3612   DirtyCardQueueSet* _queue;
3613   G1CollectedHeap* _g1h;
3614  public:
3615   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3616     _queue(queue), _g1h(g1h) { }
3617 
3618   virtual void work(uint worker_id) {
3619     G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3620     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3621 
3622     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3623     _queue->par_apply_closure_to_all_completed_buffers(&cl);
3624 
3625     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3626   }
3627 };
3628 
3629 void G1CollectedHeap::redirty_logged_cards() {
3630   double redirty_logged_cards_start = os::elapsedTime();
3631 
3632   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3633   dirty_card_queue_set().reset_for_par_iteration();
3634   workers()->run_task(&redirty_task);
3635 
3636   DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set();
3637   dcq.merge_bufferlists(&dirty_card_queue_set());
3638   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3639 
3640   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3641 }
3642 
3643 // Weak Reference Processing support
3644 
3645 bool G1STWIsAliveClosure::do_object_b(oop p) {
3646   // An object is reachable if it is outside the collection set,
3647   // or is inside and copied.
3648   return !_g1h->is_in_cset(p) || p->is_forwarded();
3649 }
3650 
3651 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) {
3652   assert(obj != NULL, "must not be NULL");
3653   assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj));
3654   // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below
3655   // may falsely indicate that this is not the case here: however the collection set only
3656   // contains old regions when concurrent mark is not running.
3657   return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor();
3658 }
3659 
3660 // Non Copying Keep Alive closure
3661 class G1KeepAliveClosure: public OopClosure {
3662   G1CollectedHeap*_g1h;
3663 public:
3664   G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {}
3665   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3666   void do_oop(oop* p) {
3667     oop obj = *p;
3668     assert(obj != NULL, "the caller should have filtered out NULL values");
3669 
3670     const InCSetState cset_state =_g1h->in_cset_state(obj);
3671     if (!cset_state.is_in_cset_or_humongous()) {
3672       return;
3673     }
3674     if (cset_state.is_in_cset()) {
3675       assert( obj->is_forwarded(), "invariant" );
3676       *p = obj->forwardee();
3677     } else {
3678       assert(!obj->is_forwarded(), "invariant" );
3679       assert(cset_state.is_humongous(),
3680              "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3681      _g1h->set_humongous_is_live(obj);
3682     }
3683   }
3684 };
3685 
3686 // Copying Keep Alive closure - can be called from both
3687 // serial and parallel code as long as different worker
3688 // threads utilize different G1ParScanThreadState instances
3689 // and different queues.
3690 
3691 class G1CopyingKeepAliveClosure: public OopClosure {
3692   G1CollectedHeap*         _g1h;
3693   OopClosure*              _copy_non_heap_obj_cl;
3694   G1ParScanThreadState*    _par_scan_state;
3695 
3696 public:
3697   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3698                             OopClosure* non_heap_obj_cl,
3699                             G1ParScanThreadState* pss):
3700     _g1h(g1h),
3701     _copy_non_heap_obj_cl(non_heap_obj_cl),
3702     _par_scan_state(pss)
3703   {}
3704 
3705   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3706   virtual void do_oop(      oop* p) { do_oop_work(p); }
3707 
3708   template <class T> void do_oop_work(T* p) {
3709     oop obj = RawAccess<>::oop_load(p);
3710 
3711     if (_g1h->is_in_cset_or_humongous(obj)) {
3712       // If the referent object has been forwarded (either copied
3713       // to a new location or to itself in the event of an
3714       // evacuation failure) then we need to update the reference
3715       // field and, if both reference and referent are in the G1
3716       // heap, update the RSet for the referent.
3717       //
3718       // If the referent has not been forwarded then we have to keep
3719       // it alive by policy. Therefore we have copy the referent.
3720       //
3721       // If the reference field is in the G1 heap then we can push
3722       // on the PSS queue. When the queue is drained (after each
3723       // phase of reference processing) the object and it's followers
3724       // will be copied, the reference field set to point to the
3725       // new location, and the RSet updated. Otherwise we need to
3726       // use the the non-heap or metadata closures directly to copy
3727       // the referent object and update the pointer, while avoiding
3728       // updating the RSet.
3729 
3730       if (_g1h->is_in_g1_reserved(p)) {
3731         _par_scan_state->push_on_queue(p);
3732       } else {
3733         assert(!Metaspace::contains((const void*)p),
3734                "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3735         _copy_non_heap_obj_cl->do_oop(p);
3736       }
3737     }
3738   }
3739 };
3740 
3741 // Serial drain queue closure. Called as the 'complete_gc'
3742 // closure for each discovered list in some of the
3743 // reference processing phases.
3744 
3745 class G1STWDrainQueueClosure: public VoidClosure {
3746 protected:
3747   G1CollectedHeap* _g1h;
3748   G1ParScanThreadState* _par_scan_state;
3749 
3750   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3751 
3752 public:
3753   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3754     _g1h(g1h),
3755     _par_scan_state(pss)
3756   { }
3757 
3758   void do_void() {
3759     G1ParScanThreadState* const pss = par_scan_state();
3760     pss->trim_queue();
3761   }
3762 };
3763 
3764 // Parallel Reference Processing closures
3765 
3766 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3767 // processing during G1 evacuation pauses.
3768 
3769 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3770 private:
3771   G1CollectedHeap*          _g1h;
3772   G1ParScanThreadStateSet*  _pss;
3773   RefToScanQueueSet*        _queues;
3774   WorkGang*                 _workers;
3775   uint                      _active_workers;
3776 
3777 public:
3778   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3779                            G1ParScanThreadStateSet* per_thread_states,
3780                            WorkGang* workers,
3781                            RefToScanQueueSet *task_queues,
3782                            uint n_workers) :
3783     _g1h(g1h),
3784     _pss(per_thread_states),
3785     _queues(task_queues),
3786     _workers(workers),
3787     _active_workers(n_workers)
3788   {
3789     g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
3790   }
3791 
3792   // Executes the given task using concurrent marking worker threads.
3793   virtual void execute(ProcessTask& task);
3794 };
3795 
3796 // Gang task for possibly parallel reference processing
3797 
3798 class G1STWRefProcTaskProxy: public AbstractGangTask {
3799   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3800   ProcessTask&     _proc_task;
3801   G1CollectedHeap* _g1h;
3802   G1ParScanThreadStateSet* _pss;
3803   RefToScanQueueSet* _task_queues;
3804   ParallelTaskTerminator* _terminator;
3805 
3806 public:
3807   G1STWRefProcTaskProxy(ProcessTask& proc_task,
3808                         G1CollectedHeap* g1h,
3809                         G1ParScanThreadStateSet* per_thread_states,
3810                         RefToScanQueueSet *task_queues,
3811                         ParallelTaskTerminator* terminator) :
3812     AbstractGangTask("Process reference objects in parallel"),
3813     _proc_task(proc_task),
3814     _g1h(g1h),
3815     _pss(per_thread_states),
3816     _task_queues(task_queues),
3817     _terminator(terminator)
3818   {}
3819 
3820   virtual void work(uint worker_id) {
3821     // The reference processing task executed by a single worker.
3822     ResourceMark rm;
3823     HandleMark   hm;
3824 
3825     G1STWIsAliveClosure is_alive(_g1h);
3826 
3827     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
3828     pss->set_ref_discoverer(NULL);
3829 
3830     // Keep alive closure.
3831     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
3832 
3833     // Complete GC closure
3834     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
3835 
3836     // Call the reference processing task's work routine.
3837     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3838 
3839     // Note we cannot assert that the refs array is empty here as not all
3840     // of the processing tasks (specifically phase2 - pp2_work) execute
3841     // the complete_gc closure (which ordinarily would drain the queue) so
3842     // the queue may not be empty.
3843   }
3844 };
3845 
3846 // Driver routine for parallel reference processing.
3847 // Creates an instance of the ref processing gang
3848 // task and has the worker threads execute it.
3849 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
3850   assert(_workers != NULL, "Need parallel worker threads.");
3851 
3852   ParallelTaskTerminator terminator(_active_workers, _queues);
3853   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
3854 
3855   _workers->run_task(&proc_task_proxy);
3856 }
3857 
3858 // End of weak reference support closures
3859 
3860 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
3861   double ref_proc_start = os::elapsedTime();
3862 
3863   ReferenceProcessor* rp = _ref_processor_stw;
3864   assert(rp->discovery_enabled(), "should have been enabled");
3865 
3866   // Closure to test whether a referent is alive.
3867   G1STWIsAliveClosure is_alive(this);
3868 
3869   // Even when parallel reference processing is enabled, the processing
3870   // of JNI refs is serial and performed serially by the current thread
3871   // rather than by a worker. The following PSS will be used for processing
3872   // JNI refs.
3873 
3874   // Use only a single queue for this PSS.
3875   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
3876   pss->set_ref_discoverer(NULL);
3877   assert(pss->queue_is_empty(), "pre-condition");
3878 
3879   // Keep alive closure.
3880   G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
3881 
3882   // Serial Complete GC closure
3883   G1STWDrainQueueClosure drain_queue(this, pss);
3884 
3885   // Setup the soft refs policy...
3886   rp->setup_policy(false);
3887 
3888   ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
3889 
3890   ReferenceProcessorStats stats;
3891   if (!rp->processing_is_mt()) {
3892     // Serial reference processing...
3893     stats = rp->process_discovered_references(&is_alive,
3894                                               &keep_alive,
3895                                               &drain_queue,
3896                                               NULL,
3897                                               pt);
3898   } else {
3899     uint no_of_gc_workers = workers()->active_workers();
3900 
3901     // Parallel reference processing
3902     assert(no_of_gc_workers <= rp->max_num_queues(),
3903            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
3904            no_of_gc_workers,  rp->max_num_queues());
3905 
3906     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
3907     stats = rp->process_discovered_references(&is_alive,
3908                                               &keep_alive,
3909                                               &drain_queue,
3910                                               &par_task_executor,
3911                                               pt);
3912   }
3913 
3914   _gc_tracer_stw->report_gc_reference_stats(stats);
3915 
3916   // We have completed copying any necessary live referent objects.
3917   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
3918 
3919   make_pending_list_reachable();
3920 
3921   rp->verify_no_references_recorded();
3922 
3923   double ref_proc_time = os::elapsedTime() - ref_proc_start;
3924   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
3925 }
3926 
3927 void G1CollectedHeap::make_pending_list_reachable() {
3928   if (collector_state()->in_initial_mark_gc()) {
3929     oop pll_head = Universe::reference_pending_list();
3930     if (pll_head != NULL) {
3931       // Any valid worker id is fine here as we are in the VM thread and single-threaded.
3932       _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head);
3933     }
3934   }
3935 }
3936 
3937 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
3938   double merge_pss_time_start = os::elapsedTime();
3939   per_thread_states->flush();
3940   g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
3941 }
3942 
3943 void G1CollectedHeap::pre_evacuate_collection_set() {
3944   _expand_heap_after_alloc_failure = true;
3945   _evacuation_failed = false;
3946 
3947   // Disable the hot card cache.
3948   _hot_card_cache->reset_hot_cache_claimed_index();
3949   _hot_card_cache->set_use_cache(false);
3950 
3951   g1_rem_set()->prepare_for_oops_into_collection_set_do();
3952   _preserved_marks_set.assert_empty();
3953 
3954   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
3955 
3956   // InitialMark needs claim bits to keep track of the marked-through CLDs.
3957   if (collector_state()->in_initial_mark_gc()) {
3958     double start_clear_claimed_marks = os::elapsedTime();
3959 
3960     ClassLoaderDataGraph::clear_claimed_marks();
3961 
3962     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
3963     phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
3964   }
3965 }
3966 
3967 void G1CollectedHeap::evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3968   // Should G1EvacuationFailureALot be in effect for this GC?
3969   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
3970 
3971   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
3972 
3973   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
3974 
3975   double start_par_time_sec = os::elapsedTime();
3976   double end_par_time_sec;
3977 
3978   {
3979     const uint n_workers = workers()->active_workers();
3980     G1RootProcessor root_processor(this, n_workers);
3981     G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
3982 
3983     print_termination_stats_hdr();
3984 
3985     workers()->run_task(&g1_par_task);
3986     end_par_time_sec = os::elapsedTime();
3987 
3988     // Closing the inner scope will execute the destructor
3989     // for the G1RootProcessor object. We record the current
3990     // elapsed time before closing the scope so that time
3991     // taken for the destructor is NOT included in the
3992     // reported parallel time.
3993   }
3994 
3995   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
3996   phase_times->record_par_time(par_time_ms);
3997 
3998   double code_root_fixup_time_ms =
3999         (os::elapsedTime() - end_par_time_sec) * 1000.0;
4000   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4001 }
4002 
4003 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4004   // Also cleans the card table from temporary duplicate detection information used
4005   // during UpdateRS/ScanRS.
4006   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4007 
4008   // Process any discovered reference objects - we have
4009   // to do this _before_ we retire the GC alloc regions
4010   // as we may have to copy some 'reachable' referent
4011   // objects (and their reachable sub-graphs) that were
4012   // not copied during the pause.
4013   process_discovered_references(per_thread_states);
4014 
4015   // FIXME
4016   // CM's reference processing also cleans up the string and symbol tables.
4017   // Should we do that here also? We could, but it is a serial operation
4018   // and could significantly increase the pause time.
4019 
4020   G1STWIsAliveClosure is_alive(this);
4021   G1KeepAliveClosure keep_alive(this);
4022 
4023   {
4024     double start = os::elapsedTime();
4025 
4026     WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
4027 
4028     double time_ms = (os::elapsedTime() - start) * 1000.0;
4029     g1_policy()->phase_times()->record_weak_ref_proc_time(time_ms);
4030   }
4031 
4032   if (G1StringDedup::is_enabled()) {
4033     double fixup_start = os::elapsedTime();
4034 
4035     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4036 
4037     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4038     g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4039   }
4040 
4041   if (evacuation_failed()) {
4042     restore_after_evac_failure();
4043 
4044     // Reset the G1EvacuationFailureALot counters and flags
4045     // Note: the values are reset only when an actual
4046     // evacuation failure occurs.
4047     NOT_PRODUCT(reset_evacuation_should_fail();)
4048   }
4049 
4050   _preserved_marks_set.assert_empty();
4051 
4052   _allocator->release_gc_alloc_regions(evacuation_info);
4053 
4054   merge_per_thread_state_info(per_thread_states);
4055 
4056   // Reset and re-enable the hot card cache.
4057   // Note the counts for the cards in the regions in the
4058   // collection set are reset when the collection set is freed.
4059   _hot_card_cache->reset_hot_cache();
4060   _hot_card_cache->set_use_cache(true);
4061 
4062   purge_code_root_memory();
4063 
4064   redirty_logged_cards();
4065 #if COMPILER2_OR_JVMCI
4066   double start = os::elapsedTime();
4067   DerivedPointerTable::update_pointers();
4068   g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4069 #endif
4070   g1_policy()->print_age_table();
4071 }
4072 
4073 void G1CollectedHeap::record_obj_copy_mem_stats() {
4074   g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4075 
4076   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4077                                                create_g1_evac_summary(&_old_evac_stats));
4078 }
4079 
4080 void G1CollectedHeap::free_region(HeapRegion* hr,
4081                                   FreeRegionList* free_list,
4082                                   bool skip_remset,
4083                                   bool skip_hot_card_cache,
4084                                   bool locked) {
4085   assert(!hr->is_free(), "the region should not be free");
4086   assert(!hr->is_empty(), "the region should not be empty");
4087   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4088   assert(free_list != NULL, "pre-condition");
4089 
4090   if (G1VerifyBitmaps) {
4091     MemRegion mr(hr->bottom(), hr->end());
4092     concurrent_mark()->clear_range_in_prev_bitmap(mr);
4093   }
4094 
4095   // Clear the card counts for this region.
4096   // Note: we only need to do this if the region is not young
4097   // (since we don't refine cards in young regions).
4098   if (!skip_hot_card_cache && !hr->is_young()) {
4099     _hot_card_cache->reset_card_counts(hr);
4100   }
4101   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4102   _g1_policy->remset_tracker()->update_at_free(hr);
4103   free_list->add_ordered(hr);
4104 }
4105 
4106 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4107                                             FreeRegionList* free_list) {
4108   assert(hr->is_humongous(), "this is only for humongous regions");
4109   assert(free_list != NULL, "pre-condition");
4110   hr->clear_humongous();
4111   free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */);
4112 }
4113 
4114 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4115                                            const uint humongous_regions_removed) {
4116   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4117     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4118     _old_set.bulk_remove(old_regions_removed);
4119     _humongous_set.bulk_remove(humongous_regions_removed);
4120   }
4121 
4122 }
4123 
4124 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4125   assert(list != NULL, "list can't be null");
4126   if (!list->is_empty()) {
4127     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4128     _hrm.insert_list_into_free_list(list);
4129   }
4130 }
4131 
4132 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4133   decrease_used(bytes);
4134 }
4135 
4136 class G1FreeCollectionSetTask : public AbstractGangTask {
4137 private:
4138 
4139   // Closure applied to all regions in the collection set to do work that needs to
4140   // be done serially in a single thread.
4141   class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4142   private:
4143     EvacuationInfo* _evacuation_info;
4144     const size_t* _surviving_young_words;
4145 
4146     // Bytes used in successfully evacuated regions before the evacuation.
4147     size_t _before_used_bytes;
4148     // Bytes used in unsucessfully evacuated regions before the evacuation
4149     size_t _after_used_bytes;
4150 
4151     size_t _bytes_allocated_in_old_since_last_gc;
4152 
4153     size_t _failure_used_words;
4154     size_t _failure_waste_words;
4155 
4156     FreeRegionList _local_free_list;
4157   public:
4158     G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4159       HeapRegionClosure(),
4160       _evacuation_info(evacuation_info),
4161       _surviving_young_words(surviving_young_words),
4162       _before_used_bytes(0),
4163       _after_used_bytes(0),
4164       _bytes_allocated_in_old_since_last_gc(0),
4165       _failure_used_words(0),
4166       _failure_waste_words(0),
4167       _local_free_list("Local Region List for CSet Freeing") {
4168     }
4169 
4170     virtual bool do_heap_region(HeapRegion* r) {
4171       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4172 
4173       assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4174       g1h->clear_in_cset(r);
4175 
4176       if (r->is_young()) {
4177         assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4178                "Young index %d is wrong for region %u of type %s with %u young regions",
4179                r->young_index_in_cset(),
4180                r->hrm_index(),
4181                r->get_type_str(),
4182                g1h->collection_set()->young_region_length());
4183         size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4184         r->record_surv_words_in_group(words_survived);
4185       }
4186 
4187       if (!r->evacuation_failed()) {
4188         assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4189         _before_used_bytes += r->used();
4190         g1h->free_region(r,
4191                          &_local_free_list,
4192                          true, /* skip_remset */
4193                          true, /* skip_hot_card_cache */
4194                          true  /* locked */);
4195       } else {
4196         r->uninstall_surv_rate_group();
4197         r->set_young_index_in_cset(-1);
4198         r->set_evacuation_failed(false);
4199         // When moving a young gen region to old gen, we "allocate" that whole region
4200         // there. This is in addition to any already evacuated objects. Notify the
4201         // policy about that.
4202         // Old gen regions do not cause an additional allocation: both the objects
4203         // still in the region and the ones already moved are accounted for elsewhere.
4204         if (r->is_young()) {
4205           _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4206         }
4207         // The region is now considered to be old.
4208         r->set_old();
4209         // Do some allocation statistics accounting. Regions that failed evacuation
4210         // are always made old, so there is no need to update anything in the young
4211         // gen statistics, but we need to update old gen statistics.
4212         size_t used_words = r->marked_bytes() / HeapWordSize;
4213 
4214         _failure_used_words += used_words;
4215         _failure_waste_words += HeapRegion::GrainWords - used_words;
4216 
4217         g1h->old_set_add(r);
4218         _after_used_bytes += r->used();
4219       }
4220       return false;
4221     }
4222 
4223     void complete_work() {
4224       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4225 
4226       _evacuation_info->set_regions_freed(_local_free_list.length());
4227       _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4228 
4229       g1h->prepend_to_freelist(&_local_free_list);
4230       g1h->decrement_summary_bytes(_before_used_bytes);
4231 
4232       G1Policy* policy = g1h->g1_policy();
4233       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4234 
4235       g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4236     }
4237   };
4238 
4239   G1CollectionSet* _collection_set;
4240   G1SerialFreeCollectionSetClosure _cl;
4241   const size_t* _surviving_young_words;
4242 
4243   size_t _rs_lengths;
4244 
4245   volatile jint _serial_work_claim;
4246 
4247   struct WorkItem {
4248     uint region_idx;
4249     bool is_young;
4250     bool evacuation_failed;
4251 
4252     WorkItem(HeapRegion* r) {
4253       region_idx = r->hrm_index();
4254       is_young = r->is_young();
4255       evacuation_failed = r->evacuation_failed();
4256     }
4257   };
4258 
4259   volatile size_t _parallel_work_claim;
4260   size_t _num_work_items;
4261   WorkItem* _work_items;
4262 
4263   void do_serial_work() {
4264     // Need to grab the lock to be allowed to modify the old region list.
4265     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4266     _collection_set->iterate(&_cl);
4267   }
4268 
4269   void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4270     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4271 
4272     HeapRegion* r = g1h->region_at(region_idx);
4273     assert(!g1h->is_on_master_free_list(r), "sanity");
4274 
4275     Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4276 
4277     if (!is_young) {
4278       g1h->_hot_card_cache->reset_card_counts(r);
4279     }
4280 
4281     if (!evacuation_failed) {
4282       r->rem_set()->clear_locked();
4283     }
4284   }
4285 
4286   class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4287   private:
4288     size_t _cur_idx;
4289     WorkItem* _work_items;
4290   public:
4291     G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4292 
4293     virtual bool do_heap_region(HeapRegion* r) {
4294       _work_items[_cur_idx++] = WorkItem(r);
4295       return false;
4296     }
4297   };
4298 
4299   void prepare_work() {
4300     G1PrepareFreeCollectionSetClosure cl(_work_items);
4301     _collection_set->iterate(&cl);
4302   }
4303 
4304   void complete_work() {
4305     _cl.complete_work();
4306 
4307     G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4308     policy->record_max_rs_lengths(_rs_lengths);
4309     policy->cset_regions_freed();
4310   }
4311 public:
4312   G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4313     AbstractGangTask("G1 Free Collection Set"),
4314     _cl(evacuation_info, surviving_young_words),
4315     _collection_set(collection_set),
4316     _surviving_young_words(surviving_young_words),
4317     _serial_work_claim(0),
4318     _rs_lengths(0),
4319     _parallel_work_claim(0),
4320     _num_work_items(collection_set->region_length()),
4321     _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4322     prepare_work();
4323   }
4324 
4325   ~G1FreeCollectionSetTask() {
4326     complete_work();
4327     FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4328   }
4329 
4330   // Chunk size for work distribution. The chosen value has been determined experimentally
4331   // to be a good tradeoff between overhead and achievable parallelism.
4332   static uint chunk_size() { return 32; }
4333 
4334   virtual void work(uint worker_id) {
4335     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4336 
4337     // Claim serial work.
4338     if (_serial_work_claim == 0) {
4339       jint value = Atomic::add(1, &_serial_work_claim) - 1;
4340       if (value == 0) {
4341         double serial_time = os::elapsedTime();
4342         do_serial_work();
4343         timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4344       }
4345     }
4346 
4347     // Start parallel work.
4348     double young_time = 0.0;
4349     bool has_young_time = false;
4350     double non_young_time = 0.0;
4351     bool has_non_young_time = false;
4352 
4353     while (true) {
4354       size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4355       size_t cur = end - chunk_size();
4356 
4357       if (cur >= _num_work_items) {
4358         break;
4359       }
4360 
4361       double start_time = os::elapsedTime();
4362 
4363       end = MIN2(end, _num_work_items);
4364 
4365       for (; cur < end; cur++) {
4366         bool is_young = _work_items[cur].is_young;
4367 
4368         do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4369 
4370         double end_time = os::elapsedTime();
4371         double time_taken = end_time - start_time;
4372         if (is_young) {
4373           young_time += time_taken;
4374           has_young_time = true;
4375         } else {
4376           non_young_time += time_taken;
4377           has_non_young_time = true;
4378         }
4379         start_time = end_time;
4380       }
4381     }
4382 
4383     if (has_young_time) {
4384       timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4385     }
4386     if (has_non_young_time) {
4387       timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, non_young_time);
4388     }
4389   }
4390 };
4391 
4392 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4393   _eden.clear();
4394 
4395   double free_cset_start_time = os::elapsedTime();
4396 
4397   {
4398     uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4399     uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4400 
4401     G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4402 
4403     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4404                         cl.name(),
4405                         num_workers,
4406                         _collection_set.region_length());
4407     workers()->run_task(&cl, num_workers);
4408   }
4409   g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4410 
4411   collection_set->clear();
4412 }
4413 
4414 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4415  private:
4416   FreeRegionList* _free_region_list;
4417   HeapRegionSet* _proxy_set;
4418   uint _humongous_objects_reclaimed;
4419   uint _humongous_regions_reclaimed;
4420   size_t _freed_bytes;
4421  public:
4422 
4423   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4424     _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4425   }
4426 
4427   virtual bool do_heap_region(HeapRegion* r) {
4428     if (!r->is_starts_humongous()) {
4429       return false;
4430     }
4431 
4432     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4433 
4434     oop obj = (oop)r->bottom();
4435     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4436 
4437     // The following checks whether the humongous object is live are sufficient.
4438     // The main additional check (in addition to having a reference from the roots
4439     // or the young gen) is whether the humongous object has a remembered set entry.
4440     //
4441     // A humongous object cannot be live if there is no remembered set for it
4442     // because:
4443     // - there can be no references from within humongous starts regions referencing
4444     // the object because we never allocate other objects into them.
4445     // (I.e. there are no intra-region references that may be missed by the
4446     // remembered set)
4447     // - as soon there is a remembered set entry to the humongous starts region
4448     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4449     // until the end of a concurrent mark.
4450     //
4451     // It is not required to check whether the object has been found dead by marking
4452     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4453     // all objects allocated during that time are considered live.
4454     // SATB marking is even more conservative than the remembered set.
4455     // So if at this point in the collection there is no remembered set entry,
4456     // nobody has a reference to it.
4457     // At the start of collection we flush all refinement logs, and remembered sets
4458     // are completely up-to-date wrt to references to the humongous object.
4459     //
4460     // Other implementation considerations:
4461     // - never consider object arrays at this time because they would pose
4462     // considerable effort for cleaning up the the remembered sets. This is
4463     // required because stale remembered sets might reference locations that
4464     // are currently allocated into.
4465     uint region_idx = r->hrm_index();
4466     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4467         !r->rem_set()->is_empty()) {
4468       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",
4469                                region_idx,
4470                                (size_t)obj->size() * HeapWordSize,
4471                                p2i(r->bottom()),
4472                                r->rem_set()->occupied(),
4473                                r->rem_set()->strong_code_roots_list_length(),
4474                                next_bitmap->is_marked(r->bottom()),
4475                                g1h->is_humongous_reclaim_candidate(region_idx),
4476                                obj->is_typeArray()
4477                               );
4478       return false;
4479     }
4480 
4481     guarantee(obj->is_typeArray(),
4482               "Only eagerly reclaiming type arrays is supported, but the object "
4483               PTR_FORMAT " is not.", p2i(r->bottom()));
4484 
4485     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",
4486                              region_idx,
4487                              (size_t)obj->size() * HeapWordSize,
4488                              p2i(r->bottom()),
4489                              r->rem_set()->occupied(),
4490                              r->rem_set()->strong_code_roots_list_length(),
4491                              next_bitmap->is_marked(r->bottom()),
4492                              g1h->is_humongous_reclaim_candidate(region_idx),
4493                              obj->is_typeArray()
4494                             );
4495 
4496     G1ConcurrentMark* const cm = g1h->concurrent_mark();
4497     cm->humongous_object_eagerly_reclaimed(r);
4498     assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj),
4499            "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s",
4500            region_idx,
4501            BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)),
4502            BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj)));
4503     _humongous_objects_reclaimed++;
4504     do {
4505       HeapRegion* next = g1h->next_region_in_humongous(r);
4506       _freed_bytes += r->used();
4507       r->set_containing_set(NULL);
4508       _humongous_regions_reclaimed++;
4509       g1h->free_humongous_region(r, _free_region_list);
4510       r = next;
4511     } while (r != NULL);
4512 
4513     return false;
4514   }
4515 
4516   uint humongous_objects_reclaimed() {
4517     return _humongous_objects_reclaimed;
4518   }
4519 
4520   uint humongous_regions_reclaimed() {
4521     return _humongous_regions_reclaimed;
4522   }
4523 
4524   size_t bytes_freed() const {
4525     return _freed_bytes;
4526   }
4527 };
4528 
4529 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4530   assert_at_safepoint_on_vm_thread();
4531 
4532   if (!G1EagerReclaimHumongousObjects ||
4533       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4534     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4535     return;
4536   }
4537 
4538   double start_time = os::elapsedTime();
4539 
4540   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4541 
4542   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4543   heap_region_iterate(&cl);
4544 
4545   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4546 
4547   G1HRPrinter* hrp = hr_printer();
4548   if (hrp->is_active()) {
4549     FreeRegionListIterator iter(&local_cleanup_list);
4550     while (iter.more_available()) {
4551       HeapRegion* hr = iter.get_next();
4552       hrp->cleanup(hr);
4553     }
4554   }
4555 
4556   prepend_to_freelist(&local_cleanup_list);
4557   decrement_summary_bytes(cl.bytes_freed());
4558 
4559   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4560                                                                     cl.humongous_objects_reclaimed());
4561 }
4562 
4563 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4564 public:
4565   virtual bool do_heap_region(HeapRegion* r) {
4566     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4567     G1CollectedHeap::heap()->clear_in_cset(r);
4568     r->set_young_index_in_cset(-1);
4569     return false;
4570   }
4571 };
4572 
4573 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4574   G1AbandonCollectionSetClosure cl;
4575   collection_set->iterate(&cl);
4576 
4577   collection_set->clear();
4578   collection_set->stop_incremental_building();
4579 }
4580 
4581 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4582   return _allocator->is_retained_old_region(hr);
4583 }
4584 
4585 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4586   _eden.add(hr);
4587   _g1_policy->set_region_eden(hr);
4588 }
4589 
4590 #ifdef ASSERT
4591 
4592 class NoYoungRegionsClosure: public HeapRegionClosure {
4593 private:
4594   bool _success;
4595 public:
4596   NoYoungRegionsClosure() : _success(true) { }
4597   bool do_heap_region(HeapRegion* r) {
4598     if (r->is_young()) {
4599       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4600                             p2i(r->bottom()), p2i(r->end()));
4601       _success = false;
4602     }
4603     return false;
4604   }
4605   bool success() { return _success; }
4606 };
4607 
4608 bool G1CollectedHeap::check_young_list_empty() {
4609   bool ret = (young_regions_count() == 0);
4610 
4611   NoYoungRegionsClosure closure;
4612   heap_region_iterate(&closure);
4613   ret = ret && closure.success();
4614 
4615   return ret;
4616 }
4617 
4618 #endif // ASSERT
4619 
4620 class TearDownRegionSetsClosure : public HeapRegionClosure {
4621 private:
4622   HeapRegionSet *_old_set;
4623 
4624 public:
4625   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
4626 
4627   bool do_heap_region(HeapRegion* r) {
4628     if (r->is_old()) {
4629       _old_set->remove(r);
4630     } else if(r->is_young()) {
4631       r->uninstall_surv_rate_group();
4632     } else {
4633       // We ignore free regions, we'll empty the free list afterwards.
4634       // We ignore humongous regions, we're not tearing down the
4635       // humongous regions set.
4636       assert(r->is_free() || r->is_humongous(),
4637              "it cannot be another type");
4638     }
4639     return false;
4640   }
4641 
4642   ~TearDownRegionSetsClosure() {
4643     assert(_old_set->is_empty(), "post-condition");
4644   }
4645 };
4646 
4647 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
4648   assert_at_safepoint_on_vm_thread();
4649 
4650   if (!free_list_only) {
4651     TearDownRegionSetsClosure cl(&_old_set);
4652     heap_region_iterate(&cl);
4653 
4654     // Note that emptying the _young_list is postponed and instead done as
4655     // the first step when rebuilding the regions sets again. The reason for
4656     // this is that during a full GC string deduplication needs to know if
4657     // a collected region was young or old when the full GC was initiated.
4658   }
4659   _hrm.remove_all_free_regions();
4660 }
4661 
4662 void G1CollectedHeap::increase_used(size_t bytes) {
4663   _summary_bytes_used += bytes;
4664 }
4665 
4666 void G1CollectedHeap::decrease_used(size_t bytes) {
4667   assert(_summary_bytes_used >= bytes,
4668          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
4669          _summary_bytes_used, bytes);
4670   _summary_bytes_used -= bytes;
4671 }
4672 
4673 void G1CollectedHeap::set_used(size_t bytes) {
4674   _summary_bytes_used = bytes;
4675 }
4676 
4677 class RebuildRegionSetsClosure : public HeapRegionClosure {
4678 private:
4679   bool            _free_list_only;
4680   HeapRegionSet*   _old_set;
4681   HeapRegionManager*   _hrm;
4682   size_t          _total_used;
4683 
4684 public:
4685   RebuildRegionSetsClosure(bool free_list_only,
4686                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
4687     _free_list_only(free_list_only),
4688     _old_set(old_set), _hrm(hrm), _total_used(0) {
4689     assert(_hrm->num_free_regions() == 0, "pre-condition");
4690     if (!free_list_only) {
4691       assert(_old_set->is_empty(), "pre-condition");
4692     }
4693   }
4694 
4695   bool do_heap_region(HeapRegion* r) {
4696     // After full GC, no region should have a remembered set.
4697     r->rem_set()->clear(true);
4698     if (r->is_empty()) {
4699       // Add free regions to the free list
4700       r->set_free();
4701       _hrm->insert_into_free_list(r);
4702     } else if (!_free_list_only) {
4703 
4704       if (r->is_humongous()) {
4705         // We ignore humongous regions. We left the humongous set unchanged.
4706       } else {
4707         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
4708         // We now move all (non-humongous, non-old) regions to old gen, and register them as such.
4709         r->move_to_old();
4710         _old_set->add(r);
4711       }
4712       _total_used += r->used();
4713     }
4714 
4715     return false;
4716   }
4717 
4718   size_t total_used() {
4719     return _total_used;
4720   }
4721 };
4722 
4723 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
4724   assert_at_safepoint_on_vm_thread();
4725 
4726   if (!free_list_only) {
4727     _eden.clear();
4728     _survivor.clear();
4729   }
4730 
4731   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
4732   heap_region_iterate(&cl);
4733 
4734   if (!free_list_only) {
4735     set_used(cl.total_used());
4736     if (_archive_allocator != NULL) {
4737       _archive_allocator->clear_used();
4738     }
4739   }
4740   assert(used_unlocked() == recalculate_used(),
4741          "inconsistent used_unlocked(), "
4742          "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
4743          used_unlocked(), recalculate_used());
4744 }
4745 
4746 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
4747   HeapRegion* hr = heap_region_containing(p);
4748   return hr->is_in(p);
4749 }
4750 
4751 // Methods for the mutator alloc region
4752 
4753 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
4754                                                       bool force) {
4755   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4756   bool should_allocate = g1_policy()->should_allocate_mutator_region();
4757   if (force || should_allocate) {
4758     HeapRegion* new_alloc_region = new_region(word_size,
4759                                               false /* is_old */,
4760                                               false /* do_expand */);
4761     if (new_alloc_region != NULL) {
4762       set_region_short_lived_locked(new_alloc_region);
4763       _hr_printer.alloc(new_alloc_region, !should_allocate);
4764       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
4765       _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region);
4766       return new_alloc_region;
4767     }
4768   }
4769   return NULL;
4770 }
4771 
4772 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
4773                                                   size_t allocated_bytes) {
4774   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4775   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
4776 
4777   collection_set()->add_eden_region(alloc_region);
4778   increase_used(allocated_bytes);
4779   _hr_printer.retire(alloc_region);
4780   // We update the eden sizes here, when the region is retired,
4781   // instead of when it's allocated, since this is the point that its
4782   // used space has been recored in _summary_bytes_used.
4783   g1mm()->update_eden_size();
4784 }
4785 
4786 // Methods for the GC alloc regions
4787 
4788 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
4789   if (dest.is_old()) {
4790     return true;
4791   } else {
4792     return survivor_regions_count() < g1_policy()->max_survivor_regions();
4793   }
4794 }
4795 
4796 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
4797   assert(FreeList_lock->owned_by_self(), "pre-condition");
4798 
4799   if (!has_more_regions(dest)) {
4800     return NULL;
4801   }
4802 
4803   const bool is_survivor = dest.is_young();
4804 
4805   HeapRegion* new_alloc_region = new_region(word_size,
4806                                             !is_survivor,
4807                                             true /* do_expand */);
4808   if (new_alloc_region != NULL) {
4809     if (is_survivor) {
4810       new_alloc_region->set_survivor();
4811       _survivor.add(new_alloc_region);
4812       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
4813     } else {
4814       new_alloc_region->set_old();
4815       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
4816     }
4817     _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region);
4818     _hr_printer.alloc(new_alloc_region);
4819     bool during_im = collector_state()->in_initial_mark_gc();
4820     new_alloc_region->note_start_of_copying(during_im);
4821     return new_alloc_region;
4822   }
4823   return NULL;
4824 }
4825 
4826 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
4827                                              size_t allocated_bytes,
4828                                              InCSetState dest) {
4829   bool during_im = collector_state()->in_initial_mark_gc();
4830   alloc_region->note_end_of_copying(during_im);
4831   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
4832   if (dest.is_old()) {
4833     _old_set.add(alloc_region);
4834   }
4835   _hr_printer.retire(alloc_region);
4836 }
4837 
4838 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
4839   bool expanded = false;
4840   uint index = _hrm.find_highest_free(&expanded);
4841 
4842   if (index != G1_NO_HRM_INDEX) {
4843     if (expanded) {
4844       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
4845                                 HeapRegion::GrainWords * HeapWordSize);
4846     }
4847     _hrm.allocate_free_regions_starting_at(index, 1);
4848     return region_at(index);
4849   }
4850   return NULL;
4851 }
4852 
4853 // Optimized nmethod scanning
4854 
4855 class RegisterNMethodOopClosure: public OopClosure {
4856   G1CollectedHeap* _g1h;
4857   nmethod* _nm;
4858 
4859   template <class T> void do_oop_work(T* p) {
4860     T heap_oop = RawAccess<>::oop_load(p);
4861     if (!CompressedOops::is_null(heap_oop)) {
4862       oop obj = CompressedOops::decode_not_null(heap_oop);
4863       HeapRegion* hr = _g1h->heap_region_containing(obj);
4864       assert(!hr->is_continues_humongous(),
4865              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4866              " starting at " HR_FORMAT,
4867              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4868 
4869       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
4870       hr->add_strong_code_root_locked(_nm);
4871     }
4872   }
4873 
4874 public:
4875   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4876     _g1h(g1h), _nm(nm) {}
4877 
4878   void do_oop(oop* p)       { do_oop_work(p); }
4879   void do_oop(narrowOop* p) { do_oop_work(p); }
4880 };
4881 
4882 class UnregisterNMethodOopClosure: public OopClosure {
4883   G1CollectedHeap* _g1h;
4884   nmethod* _nm;
4885 
4886   template <class T> void do_oop_work(T* p) {
4887     T heap_oop = RawAccess<>::oop_load(p);
4888     if (!CompressedOops::is_null(heap_oop)) {
4889       oop obj = CompressedOops::decode_not_null(heap_oop);
4890       HeapRegion* hr = _g1h->heap_region_containing(obj);
4891       assert(!hr->is_continues_humongous(),
4892              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4893              " starting at " HR_FORMAT,
4894              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4895 
4896       hr->remove_strong_code_root(_nm);
4897     }
4898   }
4899 
4900 public:
4901   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4902     _g1h(g1h), _nm(nm) {}
4903 
4904   void do_oop(oop* p)       { do_oop_work(p); }
4905   void do_oop(narrowOop* p) { do_oop_work(p); }
4906 };
4907 
4908 // Returns true if the reference points to an object that
4909 // can move in an incremental collection.
4910 bool G1CollectedHeap::is_scavengable(oop obj) {
4911   HeapRegion* hr = heap_region_containing(obj);
4912   return !hr->is_pinned();
4913 }
4914 
4915 void G1CollectedHeap::register_nmethod(nmethod* nm) {
4916   guarantee(nm != NULL, "sanity");
4917   RegisterNMethodOopClosure reg_cl(this, nm);
4918   nm->oops_do(&reg_cl);
4919 }
4920 
4921 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
4922   guarantee(nm != NULL, "sanity");
4923   UnregisterNMethodOopClosure reg_cl(this, nm);
4924   nm->oops_do(&reg_cl, true);
4925 }
4926 
4927 void G1CollectedHeap::purge_code_root_memory() {
4928   double purge_start = os::elapsedTime();
4929   G1CodeRootSet::purge();
4930   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
4931   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
4932 }
4933 
4934 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
4935   G1CollectedHeap* _g1h;
4936 
4937 public:
4938   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
4939     _g1h(g1h) {}
4940 
4941   void do_code_blob(CodeBlob* cb) {
4942     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
4943     if (nm == NULL) {
4944       return;
4945     }
4946 
4947     if (ScavengeRootsInCode) {
4948       _g1h->register_nmethod(nm);
4949     }
4950   }
4951 };
4952 
4953 void G1CollectedHeap::rebuild_strong_code_roots() {
4954   RebuildStrongCodeRootClosure blob_cl(this);
4955   CodeCache::blobs_do(&blob_cl);
4956 }
4957 
4958 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
4959   GrowableArray<GCMemoryManager*> memory_managers(2);
4960   memory_managers.append(&_memory_manager);
4961   memory_managers.append(&_full_gc_memory_manager);
4962   return memory_managers;
4963 }
4964 
4965 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
4966   GrowableArray<MemoryPool*> memory_pools(3);
4967   memory_pools.append(_eden_pool);
4968   memory_pools.append(_survivor_pool);
4969   memory_pools.append(_old_pool);
4970   return memory_pools;
4971 }