1 /*
   2  * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/metadataOnStackMark.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "classfile/symbolTable.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc/g1/bufferingOopClosure.hpp"
  32 #include "gc/g1/g1Allocator.inline.hpp"
  33 #include "gc/g1/g1BarrierSet.hpp"
  34 #include "gc/g1/g1CollectedHeap.inline.hpp"
  35 #include "gc/g1/g1CollectionSet.hpp"
  36 #include "gc/g1/g1CollectorPolicy.hpp"
  37 #include "gc/g1/g1CollectorState.hpp"
  38 #include "gc/g1/g1ConcurrentRefine.hpp"
  39 #include "gc/g1/g1ConcurrentRefineThread.hpp"
  40 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  41 #include "gc/g1/g1EvacStats.inline.hpp"
  42 #include "gc/g1/g1FullCollector.hpp"
  43 #include "gc/g1/g1GCPhaseTimes.hpp"
  44 #include "gc/g1/g1HeapSizingPolicy.hpp"
  45 #include "gc/g1/g1HeapTransition.hpp"
  46 #include "gc/g1/g1HeapVerifier.hpp"
  47 #include "gc/g1/g1HotCardCache.hpp"
  48 #include "gc/g1/g1MemoryPool.hpp"
  49 #include "gc/g1/g1OopClosures.inline.hpp"
  50 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  51 #include "gc/g1/g1Policy.hpp"
  52 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  53 #include "gc/g1/g1RemSet.hpp"
  54 #include "gc/g1/g1RootClosures.hpp"
  55 #include "gc/g1/g1RootProcessor.hpp"
  56 #include "gc/g1/g1StringDedup.hpp"
  57 #include "gc/g1/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/preservedMarks.inline.hpp"
  73 #include "gc/shared/suspendibleThreadSet.hpp"
  74 #include "gc/shared/referenceProcessor.inline.hpp"
  75 #include "gc/shared/taskqueue.inline.hpp"
  76 #include "gc/shared/weakProcessor.hpp"
  77 #include "logging/log.hpp"
  78 #include "memory/allocation.hpp"
  79 #include "memory/iterator.hpp"
  80 #include "memory/resourceArea.hpp"
  81 #include "oops/access.inline.hpp"
  82 #include "oops/compressedOops.inline.hpp"
  83 #include "oops/oop.inline.hpp"
  84 #include "prims/resolvedMethodTable.hpp"
  85 #include "runtime/atomic.hpp"
  86 #include "runtime/handles.inline.hpp"
  87 #include "runtime/init.hpp"
  88 #include "runtime/orderAccess.inline.hpp"
  89 #include "runtime/threadSMR.hpp"
  90 #include "runtime/vmThread.hpp"
  91 #include "utilities/align.hpp"
  92 #include "utilities/globalDefinitions.hpp"
  93 #include "utilities/stack.inline.hpp"
  94 
  95 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  96 
  97 // INVARIANTS/NOTES
  98 //
  99 // All allocation activity covered by the G1CollectedHeap interface is
 100 // serialized by acquiring the HeapLock.  This happens in mem_allocate
 101 // and allocate_new_tlab, which are the "entry" points to the
 102 // allocation code from the rest of the JVM.  (Note that this does not
 103 // apply to TLAB allocation, which is not part of this interface: it
 104 // is done by clients of this interface.)
 105 
 106 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 107  private:
 108   size_t _num_dirtied;
 109   G1CollectedHeap* _g1h;
 110   G1CardTable* _g1_ct;
 111 
 112   HeapRegion* region_for_card(jbyte* card_ptr) const {
 113     return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr));
 114   }
 115 
 116   bool will_become_free(HeapRegion* hr) const {
 117     // A region will be freed by free_collection_set if the region is in the
 118     // collection set and has not had an evacuation failure.
 119     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 120   }
 121 
 122  public:
 123   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
 124     _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { }
 125 
 126   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 127     HeapRegion* hr = region_for_card(card_ptr);
 128 
 129     // Should only dirty cards in regions that won't be freed.
 130     if (!will_become_free(hr)) {
 131       *card_ptr = G1CardTable::dirty_card_val();
 132       _num_dirtied++;
 133     }
 134 
 135     return true;
 136   }
 137 
 138   size_t num_dirtied()   const { return _num_dirtied; }
 139 };
 140 
 141 
 142 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 143   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 144 }
 145 
 146 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 147   // The from card cache is not the memory that is actually committed. So we cannot
 148   // take advantage of the zero_filled parameter.
 149   reset_from_card_cache(start_idx, num_regions);
 150 }
 151 
 152 
 153 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
 154                                              MemRegion mr) {
 155   return new HeapRegion(hrs_index, bot(), mr);
 156 }
 157 
 158 // Private methods.
 159 
 160 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 161   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 162          "the only time we use this to allocate a humongous region is "
 163          "when we are allocating a single humongous region");
 164 
 165   HeapRegion* res = _hrm.allocate_free_region(is_old);
 166 
 167   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 168     // Currently, only attempts to allocate GC alloc regions set
 169     // do_expand to true. So, we should only reach here during a
 170     // safepoint. If this assumption changes we might have to
 171     // reconsider the use of _expand_heap_after_alloc_failure.
 172     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 173 
 174     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 175                               word_size * HeapWordSize);
 176 
 177     if (expand(word_size * HeapWordSize)) {
 178       // Given that expand() succeeded in expanding the heap, and we
 179       // always expand the heap by an amount aligned to the heap
 180       // region size, the free list should in theory not be empty.
 181       // In either case allocate_free_region() will check for NULL.
 182       res = _hrm.allocate_free_region(is_old);
 183     } else {
 184       _expand_heap_after_alloc_failure = false;
 185     }
 186   }
 187   return res;
 188 }
 189 
 190 HeapWord*
 191 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 192                                                            uint num_regions,
 193                                                            size_t word_size) {
 194   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 195   assert(is_humongous(word_size), "word_size should be humongous");
 196   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 197 
 198   // Index of last region in the series.
 199   uint last = first + num_regions - 1;
 200 
 201   // We need to initialize the region(s) we just discovered. This is
 202   // a bit tricky given that it can happen concurrently with
 203   // refinement threads refining cards on these regions and
 204   // potentially wanting to refine the BOT as they are scanning
 205   // those cards (this can happen shortly after a cleanup; see CR
 206   // 6991377). So we have to set up the region(s) carefully and in
 207   // a specific order.
 208 
 209   // The word size sum of all the regions we will allocate.
 210   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 211   assert(word_size <= word_size_sum, "sanity");
 212 
 213   // This will be the "starts humongous" region.
 214   HeapRegion* first_hr = region_at(first);
 215   // The header of the new object will be placed at the bottom of
 216   // the first region.
 217   HeapWord* new_obj = first_hr->bottom();
 218   // This will be the new top of the new object.
 219   HeapWord* obj_top = new_obj + word_size;
 220 
 221   // First, we need to zero the header of the space that we will be
 222   // allocating. When we update top further down, some refinement
 223   // threads might try to scan the region. By zeroing the header we
 224   // ensure that any thread that will try to scan the region will
 225   // come across the zero klass word and bail out.
 226   //
 227   // NOTE: It would not have been correct to have used
 228   // CollectedHeap::fill_with_object() and make the space look like
 229   // an int array. The thread that is doing the allocation will
 230   // later update the object header to a potentially different array
 231   // type and, for a very short period of time, the klass and length
 232   // fields will be inconsistent. This could cause a refinement
 233   // thread to calculate the object size incorrectly.
 234   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 235 
 236   // Next, pad out the unused tail of the last region with filler
 237   // objects, for improved usage accounting.
 238   // How many words we use for filler objects.
 239   size_t word_fill_size = word_size_sum - word_size;
 240 
 241   // How many words memory we "waste" which cannot hold a filler object.
 242   size_t words_not_fillable = 0;
 243 
 244   if (word_fill_size >= min_fill_size()) {
 245     fill_with_objects(obj_top, word_fill_size);
 246   } else if (word_fill_size > 0) {
 247     // We have space to fill, but we cannot fit an object there.
 248     words_not_fillable = word_fill_size;
 249     word_fill_size = 0;
 250   }
 251 
 252   // We will set up the first region as "starts humongous". This
 253   // will also update the BOT covering all the regions to reflect
 254   // that there is a single object that starts at the bottom of the
 255   // first region.
 256   first_hr->set_starts_humongous(obj_top, word_fill_size);
 257   _g1_policy->remset_tracker()->update_at_allocate(first_hr);
 258   // Then, if there are any, we will set up the "continues
 259   // humongous" regions.
 260   HeapRegion* hr = NULL;
 261   for (uint i = first + 1; i <= last; ++i) {
 262     hr = region_at(i);
 263     hr->set_continues_humongous(first_hr);
 264     _g1_policy->remset_tracker()->update_at_allocate(hr);
 265   }
 266 
 267   // Up to this point no concurrent thread would have been able to
 268   // do any scanning on any region in this series. All the top
 269   // fields still point to bottom, so the intersection between
 270   // [bottom,top] and [card_start,card_end] will be empty. Before we
 271   // update the top fields, we'll do a storestore to make sure that
 272   // no thread sees the update to top before the zeroing of the
 273   // object header and the BOT initialization.
 274   OrderAccess::storestore();
 275 
 276   // Now, we will update the top fields of the "continues humongous"
 277   // regions except the last one.
 278   for (uint i = first; i < last; ++i) {
 279     hr = region_at(i);
 280     hr->set_top(hr->end());
 281   }
 282 
 283   hr = region_at(last);
 284   // If we cannot fit a filler object, we must set top to the end
 285   // of the humongous object, otherwise we cannot iterate the heap
 286   // and the BOT will not be complete.
 287   hr->set_top(hr->end() - words_not_fillable);
 288 
 289   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 290          "obj_top should be in last region");
 291 
 292   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 293 
 294   assert(words_not_fillable == 0 ||
 295          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 296          "Miscalculation in humongous allocation");
 297 
 298   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 299 
 300   for (uint i = first; i <= last; ++i) {
 301     hr = region_at(i);
 302     _humongous_set.add(hr);
 303     _hr_printer.alloc(hr);
 304   }
 305 
 306   return new_obj;
 307 }
 308 
 309 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 310   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 311   return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 312 }
 313 
 314 // If could fit into free regions w/o expansion, try.
 315 // Otherwise, if can expand, do so.
 316 // Otherwise, if using ex regions might help, try with ex given back.
 317 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 318   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 319 
 320   _verifier->verify_region_sets_optional();
 321 
 322   uint first = G1_NO_HRM_INDEX;
 323   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 324 
 325   if (obj_regions == 1) {
 326     // Only one region to allocate, try to use a fast path by directly allocating
 327     // from the free lists. Do not try to expand here, we will potentially do that
 328     // later.
 329     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 330     if (hr != NULL) {
 331       first = hr->hrm_index();
 332     }
 333   } else {
 334     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 335     // are lucky enough to find some.
 336     first = _hrm.find_contiguous_only_empty(obj_regions);
 337     if (first != G1_NO_HRM_INDEX) {
 338       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 339     }
 340   }
 341 
 342   if (first == G1_NO_HRM_INDEX) {
 343     // Policy: We could not find enough regions for the humongous object in the
 344     // free list. Look through the heap to find a mix of free and uncommitted regions.
 345     // If so, try expansion.
 346     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 347     if (first != G1_NO_HRM_INDEX) {
 348       // We found something. Make sure these regions are committed, i.e. expand
 349       // the heap. Alternatively we could do a defragmentation GC.
 350       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 351                                     word_size * HeapWordSize);
 352 
 353       _hrm.expand_at(first, obj_regions, workers());
 354       g1_policy()->record_new_heap_size(num_regions());
 355 
 356 #ifdef ASSERT
 357       for (uint i = first; i < first + obj_regions; ++i) {
 358         HeapRegion* hr = region_at(i);
 359         assert(hr->is_free(), "sanity");
 360         assert(hr->is_empty(), "sanity");
 361         assert(is_on_master_free_list(hr), "sanity");
 362       }
 363 #endif
 364       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 365     } else {
 366       // Policy: Potentially trigger a defragmentation GC.
 367     }
 368   }
 369 
 370   HeapWord* result = NULL;
 371   if (first != G1_NO_HRM_INDEX) {
 372     result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size);
 373     assert(result != NULL, "it should always return a valid result");
 374 
 375     // A successful humongous object allocation changes the used space
 376     // information of the old generation so we need to recalculate the
 377     // sizes and update the jstat counters here.
 378     g1mm()->update_sizes();
 379   }
 380 
 381   _verifier->verify_region_sets_optional();
 382 
 383   return result;
 384 }
 385 
 386 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 387   assert_heap_not_locked_and_not_at_safepoint();
 388   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 389 
 390   return attempt_allocation(word_size);
 391 }
 392 
 393 HeapWord*
 394 G1CollectedHeap::mem_allocate(size_t word_size,
 395                               bool*  gc_overhead_limit_was_exceeded) {
 396   assert_heap_not_locked_and_not_at_safepoint();
 397 
 398   if (is_humongous(word_size)) {
 399     return attempt_allocation_humongous(word_size);
 400   }
 401   return attempt_allocation(word_size);
 402 }
 403 
 404 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
 405   ResourceMark rm; // For retrieving the thread names in log messages.
 406 
 407   // Make sure you read the note in attempt_allocation_humongous().
 408 
 409   assert_heap_not_locked_and_not_at_safepoint();
 410   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 411          "be called for humongous allocation requests");
 412 
 413   // We should only get here after the first-level allocation attempt
 414   // (attempt_allocation()) failed to allocate.
 415 
 416   // We will loop until a) we manage to successfully perform the
 417   // allocation or b) we successfully schedule a collection which
 418   // fails to perform the allocation. b) is the only case when we'll
 419   // return NULL.
 420   HeapWord* result = NULL;
 421   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 422     bool should_try_gc;
 423     uint gc_count_before;
 424 
 425     {
 426       MutexLockerEx x(Heap_lock);
 427       result = _allocator->attempt_allocation_locked(word_size);
 428       if (result != NULL) {
 429         return result;
 430       }
 431 
 432       // If the GCLocker is active and we are bound for a GC, try expanding young gen.
 433       // This is different to when only GCLocker::needs_gc() is set: try to avoid
 434       // waiting because the GCLocker is active to not wait too long.
 435       if (GCLocker::is_active_and_needs_gc() && g1_policy()->can_expand_young_list()) {
 436         // No need for an ergo message here, can_expand_young_list() does this when
 437         // it returns true.
 438         result = _allocator->attempt_allocation_force(word_size);
 439         if (result != NULL) {
 440           return result;
 441         }
 442       }
 443       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 444       // the GCLocker initiated GC has been performed and then retry. This includes
 445       // the case when the GC Locker is not active but has not been performed.
 446       should_try_gc = !GCLocker::needs_gc();
 447       // Read the GC count while still holding the Heap_lock.
 448       gc_count_before = total_collections();
 449     }
 450 
 451     if (should_try_gc) {
 452       bool succeeded;
 453       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 454                                    GCCause::_g1_inc_collection_pause);
 455       if (result != NULL) {
 456         assert(succeeded, "only way to get back a non-NULL result");
 457         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 458                              Thread::current()->name(), p2i(result));
 459         return result;
 460       }
 461 
 462       if (succeeded) {
 463         // We successfully scheduled a collection which failed to allocate. No
 464         // point in trying to allocate further. We'll just return NULL.
 465         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 466                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 467         return NULL;
 468       }
 469       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
 470                            Thread::current()->name(), word_size);
 471     } else {
 472       // Failed to schedule a collection.
 473       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 474         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 475                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 476         return NULL;
 477       }
 478       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 479       // The GCLocker is either active or the GCLocker initiated
 480       // GC has not yet been performed. Stall until it is and
 481       // then retry the allocation.
 482       GCLocker::stall_until_clear();
 483       gclocker_retry_count += 1;
 484     }
 485 
 486     // We can reach here if we were unsuccessful in scheduling a
 487     // collection (because another thread beat us to it) or if we were
 488     // stalled due to the GC locker. In either can we should retry the
 489     // allocation attempt in case another thread successfully
 490     // performed a collection and reclaimed enough space. We do the
 491     // first attempt (without holding the Heap_lock) here and the
 492     // follow-on attempt will be at the start of the next loop
 493     // iteration (after taking the Heap_lock).
 494 
 495     result = _allocator->attempt_allocation(word_size);
 496     if (result != NULL) {
 497       return result;
 498     }
 499 
 500     // Give a warning if we seem to be looping forever.
 501     if ((QueuedAllocationWarningCount > 0) &&
 502         (try_count % QueuedAllocationWarningCount == 0)) {
 503       log_warning(gc, alloc)("%s:  Retried allocation %u times for " SIZE_FORMAT " words",
 504                              Thread::current()->name(), try_count, word_size);
 505     }
 506   }
 507 
 508   ShouldNotReachHere();
 509   return NULL;
 510 }
 511 
 512 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
 513   assert_at_safepoint_on_vm_thread();
 514   if (_archive_allocator == NULL) {
 515     _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
 516   }
 517 }
 518 
 519 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 520   // Allocations in archive regions cannot be of a size that would be considered
 521   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 522   // may be different at archive-restore time.
 523   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 524 }
 525 
 526 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 527   assert_at_safepoint_on_vm_thread();
 528   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 529   if (is_archive_alloc_too_large(word_size)) {
 530     return NULL;
 531   }
 532   return _archive_allocator->archive_mem_allocate(word_size);
 533 }
 534 
 535 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 536                                               size_t end_alignment_in_bytes) {
 537   assert_at_safepoint_on_vm_thread();
 538   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 539 
 540   // Call complete_archive to do the real work, filling in the MemRegion
 541   // array with the archive regions.
 542   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 543   delete _archive_allocator;
 544   _archive_allocator = NULL;
 545 }
 546 
 547 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 548   assert(ranges != NULL, "MemRegion array NULL");
 549   assert(count != 0, "No MemRegions provided");
 550   MemRegion reserved = _hrm.reserved();
 551   for (size_t i = 0; i < count; i++) {
 552     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 553       return false;
 554     }
 555   }
 556   return true;
 557 }
 558 
 559 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
 560                                             size_t count,
 561                                             bool open) {
 562   assert(!is_init_completed(), "Expect to be called at JVM init time");
 563   assert(ranges != NULL, "MemRegion array NULL");
 564   assert(count != 0, "No MemRegions provided");
 565   MutexLockerEx x(Heap_lock);
 566 
 567   MemRegion reserved = _hrm.reserved();
 568   HeapWord* prev_last_addr = NULL;
 569   HeapRegion* prev_last_region = NULL;
 570 
 571   // Temporarily disable pretouching of heap pages. This interface is used
 572   // when mmap'ing archived heap data in, so pre-touching is wasted.
 573   FlagSetting fs(AlwaysPreTouch, false);
 574 
 575   // Enable archive object checking used by G1MarkSweep. We have to let it know
 576   // about each archive range, so that objects in those ranges aren't marked.
 577   G1ArchiveAllocator::enable_archive_object_check();
 578 
 579   // For each specified MemRegion range, allocate the corresponding G1
 580   // regions and mark them as archive regions. We expect the ranges
 581   // in ascending starting address order, without overlap.
 582   for (size_t i = 0; i < count; i++) {
 583     MemRegion curr_range = ranges[i];
 584     HeapWord* start_address = curr_range.start();
 585     size_t word_size = curr_range.word_size();
 586     HeapWord* last_address = curr_range.last();
 587     size_t commits = 0;
 588 
 589     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 590               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 591               p2i(start_address), p2i(last_address));
 592     guarantee(start_address > prev_last_addr,
 593               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 594               p2i(start_address), p2i(prev_last_addr));
 595     prev_last_addr = last_address;
 596 
 597     // Check for ranges that start in the same G1 region in which the previous
 598     // range ended, and adjust the start address so we don't try to allocate
 599     // the same region again. If the current range is entirely within that
 600     // region, skip it, just adjusting the recorded top.
 601     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 602     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 603       start_address = start_region->end();
 604       if (start_address > last_address) {
 605         increase_used(word_size * HeapWordSize);
 606         start_region->set_top(last_address + 1);
 607         continue;
 608       }
 609       start_region->set_top(start_address);
 610       curr_range = MemRegion(start_address, last_address + 1);
 611       start_region = _hrm.addr_to_region(start_address);
 612     }
 613 
 614     // Perform the actual region allocation, exiting if it fails.
 615     // Then note how much new space we have allocated.
 616     if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
 617       return false;
 618     }
 619     increase_used(word_size * HeapWordSize);
 620     if (commits != 0) {
 621       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 622                                 HeapRegion::GrainWords * HeapWordSize * commits);
 623 
 624     }
 625 
 626     // Mark each G1 region touched by the range as archive, add it to
 627     // the old set, and set top.
 628     HeapRegion* curr_region = _hrm.addr_to_region(start_address);
 629     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 630     prev_last_region = last_region;
 631 
 632     while (curr_region != NULL) {
 633       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 634              "Region already in use (index %u)", curr_region->hrm_index());
 635       if (open) {
 636         curr_region->set_open_archive();
 637       } else {
 638         curr_region->set_closed_archive();
 639       }
 640       _hr_printer.alloc(curr_region);
 641       _old_set.add(curr_region);
 642       HeapWord* top;
 643       HeapRegion* next_region;
 644       if (curr_region != last_region) {
 645         top = curr_region->end();
 646         next_region = _hrm.next_region_in_heap(curr_region);
 647       } else {
 648         top = last_address + 1;
 649         next_region = NULL;
 650       }
 651       curr_region->set_top(top);
 652       curr_region->set_first_dead(top);
 653       curr_region->set_end_of_live(top);
 654       curr_region = next_region;
 655     }
 656 
 657     // Notify mark-sweep of the archive
 658     G1ArchiveAllocator::set_range_archive(curr_range, open);
 659   }
 660   return true;
 661 }
 662 
 663 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 664   assert(!is_init_completed(), "Expect to be called at JVM init time");
 665   assert(ranges != NULL, "MemRegion array NULL");
 666   assert(count != 0, "No MemRegions provided");
 667   MemRegion reserved = _hrm.reserved();
 668   HeapWord *prev_last_addr = NULL;
 669   HeapRegion* prev_last_region = NULL;
 670 
 671   // For each MemRegion, create filler objects, if needed, in the G1 regions
 672   // that contain the address range. The address range actually within the
 673   // MemRegion will not be modified. That is assumed to have been initialized
 674   // elsewhere, probably via an mmap of archived heap data.
 675   MutexLockerEx x(Heap_lock);
 676   for (size_t i = 0; i < count; i++) {
 677     HeapWord* start_address = ranges[i].start();
 678     HeapWord* last_address = ranges[i].last();
 679 
 680     assert(reserved.contains(start_address) && reserved.contains(last_address),
 681            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 682            p2i(start_address), p2i(last_address));
 683     assert(start_address > prev_last_addr,
 684            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 685            p2i(start_address), p2i(prev_last_addr));
 686 
 687     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 688     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 689     HeapWord* bottom_address = start_region->bottom();
 690 
 691     // Check for a range beginning in the same region in which the
 692     // previous one ended.
 693     if (start_region == prev_last_region) {
 694       bottom_address = prev_last_addr + 1;
 695     }
 696 
 697     // Verify that the regions were all marked as archive regions by
 698     // alloc_archive_regions.
 699     HeapRegion* curr_region = start_region;
 700     while (curr_region != NULL) {
 701       guarantee(curr_region->is_archive(),
 702                 "Expected archive region at index %u", curr_region->hrm_index());
 703       if (curr_region != last_region) {
 704         curr_region = _hrm.next_region_in_heap(curr_region);
 705       } else {
 706         curr_region = NULL;
 707       }
 708     }
 709 
 710     prev_last_addr = last_address;
 711     prev_last_region = last_region;
 712 
 713     // Fill the memory below the allocated range with dummy object(s),
 714     // if the region bottom does not match the range start, or if the previous
 715     // range ended within the same G1 region, and there is a gap.
 716     if (start_address != bottom_address) {
 717       size_t fill_size = pointer_delta(start_address, bottom_address);
 718       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 719       increase_used(fill_size * HeapWordSize);
 720     }
 721   }
 722 }
 723 
 724 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size) {
 725   assert_heap_not_locked_and_not_at_safepoint();
 726   assert(!is_humongous(word_size), "attempt_allocation() should not "
 727          "be called for humongous allocation requests");
 728 
 729   HeapWord* result = _allocator->attempt_allocation(word_size);
 730 
 731   if (result == NULL) {
 732     result = attempt_allocation_slow(word_size);
 733   }
 734   assert_heap_not_locked();
 735   if (result != NULL) {
 736     dirty_young_block(result, word_size);
 737   }
 738   return result;
 739 }
 740 
 741 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
 742   assert(!is_init_completed(), "Expect to be called at JVM init time");
 743   assert(ranges != NULL, "MemRegion array NULL");
 744   assert(count != 0, "No MemRegions provided");
 745   MemRegion reserved = _hrm.reserved();
 746   HeapWord* prev_last_addr = NULL;
 747   HeapRegion* prev_last_region = NULL;
 748   size_t size_used = 0;
 749   size_t uncommitted_regions = 0;
 750 
 751   // For each Memregion, free the G1 regions that constitute it, and
 752   // notify mark-sweep that the range is no longer to be considered 'archive.'
 753   MutexLockerEx x(Heap_lock);
 754   for (size_t i = 0; i < count; i++) {
 755     HeapWord* start_address = ranges[i].start();
 756     HeapWord* last_address = ranges[i].last();
 757 
 758     assert(reserved.contains(start_address) && reserved.contains(last_address),
 759            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 760            p2i(start_address), p2i(last_address));
 761     assert(start_address > prev_last_addr,
 762            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 763            p2i(start_address), p2i(prev_last_addr));
 764     size_used += ranges[i].byte_size();
 765     prev_last_addr = last_address;
 766 
 767     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 768     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 769 
 770     // Check for ranges that start in the same G1 region in which the previous
 771     // range ended, and adjust the start address so we don't try to free
 772     // the same region again. If the current range is entirely within that
 773     // region, skip it.
 774     if (start_region == prev_last_region) {
 775       start_address = start_region->end();
 776       if (start_address > last_address) {
 777         continue;
 778       }
 779       start_region = _hrm.addr_to_region(start_address);
 780     }
 781     prev_last_region = last_region;
 782 
 783     // After verifying that each region was marked as an archive region by
 784     // alloc_archive_regions, set it free and empty and uncommit it.
 785     HeapRegion* curr_region = start_region;
 786     while (curr_region != NULL) {
 787       guarantee(curr_region->is_archive(),
 788                 "Expected archive region at index %u", curr_region->hrm_index());
 789       uint curr_index = curr_region->hrm_index();
 790       _old_set.remove(curr_region);
 791       curr_region->set_free();
 792       curr_region->set_top(curr_region->bottom());
 793       if (curr_region != last_region) {
 794         curr_region = _hrm.next_region_in_heap(curr_region);
 795       } else {
 796         curr_region = NULL;
 797       }
 798       _hrm.shrink_at(curr_index, 1);
 799       uncommitted_regions++;
 800     }
 801 
 802     // Notify mark-sweep that this is no longer an archive range.
 803     G1ArchiveAllocator::set_range_archive(ranges[i], false);
 804   }
 805 
 806   if (uncommitted_regions != 0) {
 807     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 808                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 809   }
 810   decrease_used(size_used);
 811 }
 812 
 813 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
 814   ResourceMark rm; // For retrieving the thread names in log messages.
 815 
 816   // The structure of this method has a lot of similarities to
 817   // attempt_allocation_slow(). The reason these two were not merged
 818   // into a single one is that such a method would require several "if
 819   // allocation is not humongous do this, otherwise do that"
 820   // conditional paths which would obscure its flow. In fact, an early
 821   // version of this code did use a unified method which was harder to
 822   // follow and, as a result, it had subtle bugs that were hard to
 823   // track down. So keeping these two methods separate allows each to
 824   // be more readable. It will be good to keep these two in sync as
 825   // much as possible.
 826 
 827   assert_heap_not_locked_and_not_at_safepoint();
 828   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 829          "should only be called for humongous allocations");
 830 
 831   // Humongous objects can exhaust the heap quickly, so we should check if we
 832   // need to start a marking cycle at each humongous object allocation. We do
 833   // the check before we do the actual allocation. The reason for doing it
 834   // before the allocation is that we avoid having to keep track of the newly
 835   // allocated memory while we do a GC.
 836   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
 837                                            word_size)) {
 838     collect(GCCause::_g1_humongous_allocation);
 839   }
 840 
 841   // We will loop until a) we manage to successfully perform the
 842   // allocation or b) we successfully schedule a collection which
 843   // fails to perform the allocation. b) is the only case when we'll
 844   // return NULL.
 845   HeapWord* result = NULL;
 846   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 847     bool should_try_gc;
 848     uint gc_count_before;
 849 
 850 
 851     {
 852       MutexLockerEx x(Heap_lock);
 853 
 854       // Given that humongous objects are not allocated in young
 855       // regions, we'll first try to do the allocation without doing a
 856       // collection hoping that there's enough space in the heap.
 857       result = humongous_obj_allocate(word_size);
 858       if (result != NULL) {
 859         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 860         g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 861         return result;
 862       }
 863 
 864       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 865       // the GCLocker initiated GC has been performed and then retry. This includes
 866       // the case when the GC Locker is not active but has not been performed.
 867       should_try_gc = !GCLocker::needs_gc();
 868       // Read the GC count while still holding the Heap_lock.
 869       gc_count_before = total_collections();
 870     }
 871 
 872     if (should_try_gc) {
 873       bool succeeded;
 874       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 875                                    GCCause::_g1_humongous_allocation);
 876       if (result != NULL) {
 877         assert(succeeded, "only way to get back a non-NULL result");
 878         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 879                              Thread::current()->name(), p2i(result));
 880         return result;
 881       }
 882 
 883       if (succeeded) {
 884         // We successfully scheduled a collection which failed to allocate. No
 885         // point in trying to allocate further. We'll just return NULL.
 886         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 887                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 888         return NULL;
 889       }
 890       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
 891                            Thread::current()->name(), word_size);
 892     } else {
 893       // Failed to schedule a collection.
 894       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 895         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 896                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 897         return NULL;
 898       }
 899       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 900       // The GCLocker is either active or the GCLocker initiated
 901       // GC has not yet been performed. Stall until it is and
 902       // then retry the allocation.
 903       GCLocker::stall_until_clear();
 904       gclocker_retry_count += 1;
 905     }
 906 
 907 
 908     // We can reach here if we were unsuccessful in scheduling a
 909     // collection (because another thread beat us to it) or if we were
 910     // stalled due to the GC locker. In either can we should retry the
 911     // allocation attempt in case another thread successfully
 912     // performed a collection and reclaimed enough space.
 913     // Humongous object allocation always needs a lock, so we wait for the retry
 914     // in the next iteration of the loop, unlike for the regular iteration case.
 915     // Give a warning if we seem to be looping forever.
 916 
 917     if ((QueuedAllocationWarningCount > 0) &&
 918         (try_count % QueuedAllocationWarningCount == 0)) {
 919       log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
 920                              Thread::current()->name(), try_count, word_size);
 921     }
 922   }
 923 
 924   ShouldNotReachHere();
 925   return NULL;
 926 }
 927 
 928 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
 929                                                            bool expect_null_mutator_alloc_region) {
 930   assert_at_safepoint_on_vm_thread();
 931   assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
 932          "the current alloc region was unexpectedly found to be non-NULL");
 933 
 934   if (!is_humongous(word_size)) {
 935     return _allocator->attempt_allocation_locked(word_size);
 936   } else {
 937     HeapWord* result = humongous_obj_allocate(word_size);
 938     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
 939       collector_state()->set_initiate_conc_mark_if_possible(true);
 940     }
 941     return result;
 942   }
 943 
 944   ShouldNotReachHere();
 945 }
 946 
 947 class PostCompactionPrinterClosure: public HeapRegionClosure {
 948 private:
 949   G1HRPrinter* _hr_printer;
 950 public:
 951   bool do_heap_region(HeapRegion* hr) {
 952     assert(!hr->is_young(), "not expecting to find young regions");
 953     _hr_printer->post_compaction(hr);
 954     return false;
 955   }
 956 
 957   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
 958     : _hr_printer(hr_printer) { }
 959 };
 960 
 961 void G1CollectedHeap::print_hrm_post_compaction() {
 962   if (_hr_printer.is_active()) {
 963     PostCompactionPrinterClosure cl(hr_printer());
 964     heap_region_iterate(&cl);
 965   }
 966 }
 967 
 968 void G1CollectedHeap::abort_concurrent_cycle() {
 969   // If we start the compaction before the CM threads finish
 970   // scanning the root regions we might trip them over as we'll
 971   // be moving objects / updating references. So let's wait until
 972   // they are done. By telling them to abort, they should complete
 973   // early.
 974   _cm->root_regions()->abort();
 975   _cm->root_regions()->wait_until_scan_finished();
 976 
 977   // Disable discovery and empty the discovered lists
 978   // for the CM ref processor.
 979   ref_processor_cm()->disable_discovery();
 980   ref_processor_cm()->abandon_partial_discovery();
 981   ref_processor_cm()->verify_no_references_recorded();
 982 
 983   // Abandon current iterations of concurrent marking and concurrent
 984   // refinement, if any are in progress.
 985   concurrent_mark()->concurrent_cycle_abort();
 986 }
 987 
 988 void G1CollectedHeap::prepare_heap_for_full_collection() {
 989   // Make sure we'll choose a new allocation region afterwards.
 990   _allocator->release_mutator_alloc_region();
 991   _allocator->abandon_gc_alloc_regions();
 992   g1_rem_set()->cleanupHRRS();
 993 
 994   // We may have added regions to the current incremental collection
 995   // set between the last GC or pause and now. We need to clear the
 996   // incremental collection set and then start rebuilding it afresh
 997   // after this full GC.
 998   abandon_collection_set(collection_set());
 999 
1000   tear_down_region_sets(false /* free_list_only */);
1001 }
1002 
1003 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1004   assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1005   assert(used() == recalculate_used(), "Should be equal");
1006   _verifier->verify_region_sets_optional();
1007   _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
1008   _verifier->check_bitmaps("Full GC Start");
1009 }
1010 
1011 void G1CollectedHeap::prepare_heap_for_mutators() {
1012   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1013   ClassLoaderDataGraph::purge();
1014   MetaspaceUtils::verify_metrics();
1015 
1016   // Prepare heap for normal collections.
1017   assert(num_free_regions() == 0, "we should not have added any free regions");
1018   rebuild_region_sets(false /* free_list_only */);
1019   abort_refinement();
1020   resize_if_necessary_after_full_collection();
1021 
1022   // Rebuild the strong code root lists for each region
1023   rebuild_strong_code_roots();
1024 
1025   // Start a new incremental collection set for the next pause
1026   start_new_collection_set();
1027 
1028   _allocator->init_mutator_alloc_region();
1029 
1030   // Post collection state updates.
1031   MetaspaceGC::compute_new_size();
1032 }
1033 
1034 void G1CollectedHeap::abort_refinement() {
1035   if (_hot_card_cache->use_cache()) {
1036     _hot_card_cache->reset_hot_cache();
1037   }
1038 
1039   // Discard all remembered set updates.
1040   G1BarrierSet::dirty_card_queue_set().abandon_logs();
1041   assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1042 }
1043 
1044 void G1CollectedHeap::verify_after_full_collection() {
1045   _hrm.verify_optional();
1046   _verifier->verify_region_sets_optional();
1047   _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);
1048   // Clear the previous marking bitmap, if needed for bitmap verification.
1049   // Note we cannot do this when we clear the next marking bitmap in
1050   // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1051   // objects marked during a full GC against the previous bitmap.
1052   // But we need to clear it before calling check_bitmaps below since
1053   // the full GC has compacted objects and updated TAMS but not updated
1054   // the prev bitmap.
1055   if (G1VerifyBitmaps) {
1056     GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1057     _cm->clear_prev_bitmap(workers());
1058   }
1059   _verifier->check_bitmaps("Full GC End");
1060 
1061   // At this point there should be no regions in the
1062   // entire heap tagged as young.
1063   assert(check_young_list_empty(), "young list should be empty at this point");
1064 
1065   // Note: since we've just done a full GC, concurrent
1066   // marking is no longer active. Therefore we need not
1067   // re-enable reference discovery for the CM ref processor.
1068   // That will be done at the start of the next marking cycle.
1069   // We also know that the STW processor should no longer
1070   // discover any new references.
1071   assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1072   assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1073   ref_processor_stw()->verify_no_references_recorded();
1074   ref_processor_cm()->verify_no_references_recorded();
1075 }
1076 
1077 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1078   // Post collection logging.
1079   // We should do this after we potentially resize the heap so
1080   // that all the COMMIT / UNCOMMIT events are generated before
1081   // the compaction events.
1082   print_hrm_post_compaction();
1083   heap_transition->print();
1084   print_heap_after_gc();
1085   print_heap_regions();
1086 #ifdef TRACESPINNING
1087   ParallelTaskTerminator::print_termination_counts();
1088 #endif
1089 }
1090 
1091 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1092                                          bool clear_all_soft_refs) {
1093   assert_at_safepoint_on_vm_thread();
1094 
1095   if (GCLocker::check_active_before_gc()) {
1096     // Full GC was not completed.
1097     return false;
1098   }
1099 
1100   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1101       soft_ref_policy()->should_clear_all_soft_refs();
1102 
1103   G1FullCollector collector(this, &_full_gc_memory_manager, explicit_gc, do_clear_all_soft_refs);
1104   GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1105 
1106   collector.prepare_collection();
1107   collector.collect();
1108   collector.complete_collection();
1109 
1110   // Full collection was successfully completed.
1111   return true;
1112 }
1113 
1114 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1115   // Currently, there is no facility in the do_full_collection(bool) API to notify
1116   // the caller that the collection did not succeed (e.g., because it was locked
1117   // out by the GC locker). So, right now, we'll ignore the return value.
1118   bool dummy = do_full_collection(true,                /* explicit_gc */
1119                                   clear_all_soft_refs);
1120 }
1121 
1122 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1123   // Capacity, free and used after the GC counted as full regions to
1124   // include the waste in the following calculations.
1125   const size_t capacity_after_gc = capacity();
1126   const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1127 
1128   // This is enforced in arguments.cpp.
1129   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1130          "otherwise the code below doesn't make sense");
1131 
1132   // We don't have floating point command-line arguments
1133   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1134   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1135   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1136   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1137 
1138   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1139   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1140 
1141   // We have to be careful here as these two calculations can overflow
1142   // 32-bit size_t's.
1143   double used_after_gc_d = (double) used_after_gc;
1144   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1145   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1146 
1147   // Let's make sure that they are both under the max heap size, which
1148   // by default will make them fit into a size_t.
1149   double desired_capacity_upper_bound = (double) max_heap_size;
1150   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1151                                     desired_capacity_upper_bound);
1152   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1153                                     desired_capacity_upper_bound);
1154 
1155   // We can now safely turn them into size_t's.
1156   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1157   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1158 
1159   // This assert only makes sense here, before we adjust them
1160   // with respect to the min and max heap size.
1161   assert(minimum_desired_capacity <= maximum_desired_capacity,
1162          "minimum_desired_capacity = " SIZE_FORMAT ", "
1163          "maximum_desired_capacity = " SIZE_FORMAT,
1164          minimum_desired_capacity, maximum_desired_capacity);
1165 
1166   // Should not be greater than the heap max size. No need to adjust
1167   // it with respect to the heap min size as it's a lower bound (i.e.,
1168   // we'll try to make the capacity larger than it, not smaller).
1169   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1170   // Should not be less than the heap min size. No need to adjust it
1171   // with respect to the heap max size as it's an upper bound (i.e.,
1172   // we'll try to make the capacity smaller than it, not greater).
1173   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1174 
1175   if (capacity_after_gc < minimum_desired_capacity) {
1176     // Don't expand unless it's significant
1177     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1178 
1179     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1180                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1181                               "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1182                               capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1183 
1184     expand(expand_bytes, _workers);
1185 
1186     // No expansion, now see if we want to shrink
1187   } else if (capacity_after_gc > maximum_desired_capacity) {
1188     // Capacity too large, compute shrinking size
1189     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1190 
1191     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1192                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1193                               "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1194                               capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1195 
1196     shrink(shrink_bytes);
1197   }
1198 }
1199 
1200 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1201                                                             bool do_gc,
1202                                                             bool clear_all_soft_refs,
1203                                                             bool expect_null_mutator_alloc_region,
1204                                                             bool* gc_succeeded) {
1205   *gc_succeeded = true;
1206   // Let's attempt the allocation first.
1207   HeapWord* result =
1208     attempt_allocation_at_safepoint(word_size,
1209                                     expect_null_mutator_alloc_region);
1210   if (result != NULL) {
1211     return result;
1212   }
1213 
1214   // In a G1 heap, we're supposed to keep allocation from failing by
1215   // incremental pauses.  Therefore, at least for now, we'll favor
1216   // expansion over collection.  (This might change in the future if we can
1217   // do something smarter than full collection to satisfy a failed alloc.)
1218   result = expand_and_allocate(word_size);
1219   if (result != NULL) {
1220     return result;
1221   }
1222 
1223   if (do_gc) {
1224     // Expansion didn't work, we'll try to do a Full GC.
1225     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1226                                        clear_all_soft_refs);
1227   }
1228 
1229   return NULL;
1230 }
1231 
1232 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1233                                                      bool* succeeded) {
1234   assert_at_safepoint_on_vm_thread();
1235 
1236   // Attempts to allocate followed by Full GC.
1237   HeapWord* result =
1238     satisfy_failed_allocation_helper(word_size,
1239                                      true,  /* do_gc */
1240                                      false, /* clear_all_soft_refs */
1241                                      false, /* expect_null_mutator_alloc_region */
1242                                      succeeded);
1243 
1244   if (result != NULL || !*succeeded) {
1245     return result;
1246   }
1247 
1248   // Attempts to allocate followed by Full GC that will collect all soft references.
1249   result = satisfy_failed_allocation_helper(word_size,
1250                                             true, /* do_gc */
1251                                             true, /* clear_all_soft_refs */
1252                                             true, /* expect_null_mutator_alloc_region */
1253                                             succeeded);
1254 
1255   if (result != NULL || !*succeeded) {
1256     return result;
1257   }
1258 
1259   // Attempts to allocate, no GC
1260   result = satisfy_failed_allocation_helper(word_size,
1261                                             false, /* do_gc */
1262                                             false, /* clear_all_soft_refs */
1263                                             true,  /* expect_null_mutator_alloc_region */
1264                                             succeeded);
1265 
1266   if (result != NULL) {
1267     return result;
1268   }
1269 
1270   assert(!soft_ref_policy()->should_clear_all_soft_refs(),
1271          "Flag should have been handled and cleared prior to this point");
1272 
1273   // What else?  We might try synchronous finalization later.  If the total
1274   // space available is large enough for the allocation, then a more
1275   // complete compaction phase than we've tried so far might be
1276   // appropriate.
1277   return NULL;
1278 }
1279 
1280 // Attempting to expand the heap sufficiently
1281 // to support an allocation of the given "word_size".  If
1282 // successful, perform the allocation and return the address of the
1283 // allocated block, or else "NULL".
1284 
1285 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1286   assert_at_safepoint_on_vm_thread();
1287 
1288   _verifier->verify_region_sets_optional();
1289 
1290   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1291   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1292                             word_size * HeapWordSize);
1293 
1294 
1295   if (expand(expand_bytes, _workers)) {
1296     _hrm.verify_optional();
1297     _verifier->verify_region_sets_optional();
1298     return attempt_allocation_at_safepoint(word_size,
1299                                            false /* expect_null_mutator_alloc_region */);
1300   }
1301   return NULL;
1302 }
1303 
1304 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1305   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1306   aligned_expand_bytes = align_up(aligned_expand_bytes,
1307                                        HeapRegion::GrainBytes);
1308 
1309   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1310                             expand_bytes, aligned_expand_bytes);
1311 
1312   if (is_maximal_no_gc()) {
1313     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1314     return false;
1315   }
1316 
1317   double expand_heap_start_time_sec = os::elapsedTime();
1318   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1319   assert(regions_to_expand > 0, "Must expand by at least one region");
1320 
1321   uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1322   if (expand_time_ms != NULL) {
1323     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1324   }
1325 
1326   if (expanded_by > 0) {
1327     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1328     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1329     g1_policy()->record_new_heap_size(num_regions());
1330   } else {
1331     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1332 
1333     // The expansion of the virtual storage space was unsuccessful.
1334     // Let's see if it was because we ran out of swap.
1335     if (G1ExitOnExpansionFailure &&
1336         _hrm.available() >= regions_to_expand) {
1337       // We had head room...
1338       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1339     }
1340   }
1341   return regions_to_expand > 0;
1342 }
1343 
1344 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1345   size_t aligned_shrink_bytes =
1346     ReservedSpace::page_align_size_down(shrink_bytes);
1347   aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1348                                          HeapRegion::GrainBytes);
1349   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1350 
1351   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1352   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1353 
1354 
1355   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",
1356                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1357   if (num_regions_removed > 0) {
1358     g1_policy()->record_new_heap_size(num_regions());
1359   } else {
1360     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1361   }
1362 }
1363 
1364 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1365   _verifier->verify_region_sets_optional();
1366 
1367   // We should only reach here at the end of a Full GC which means we
1368   // should not not be holding to any GC alloc regions. The method
1369   // below will make sure of that and do any remaining clean up.
1370   _allocator->abandon_gc_alloc_regions();
1371 
1372   // Instead of tearing down / rebuilding the free lists here, we
1373   // could instead use the remove_all_pending() method on free_list to
1374   // remove only the ones that we need to remove.
1375   tear_down_region_sets(true /* free_list_only */);
1376   shrink_helper(shrink_bytes);
1377   rebuild_region_sets(true /* free_list_only */);
1378 
1379   _hrm.verify_optional();
1380   _verifier->verify_region_sets_optional();
1381 }
1382 
1383 // Public methods.
1384 
1385 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1386   CollectedHeap(),
1387   _young_gen_sampling_thread(NULL),
1388   _collector_policy(collector_policy),
1389   _soft_ref_policy(),
1390   _card_table(NULL),
1391   _memory_manager("G1 Young Generation", "end of minor GC"),
1392   _full_gc_memory_manager("G1 Old Generation", "end of major GC"),
1393   _eden_pool(NULL),
1394   _survivor_pool(NULL),
1395   _old_pool(NULL),
1396   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1397   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1398   _g1_policy(new G1Policy(_gc_timer_stw)),
1399   _collection_set(this, _g1_policy),
1400   _dirty_card_queue_set(false),
1401   _is_alive_closure_cm(this),
1402   _is_alive_closure_stw(this),
1403   _ref_processor_cm(NULL),
1404   _ref_processor_stw(NULL),
1405   _bot(NULL),
1406   _hot_card_cache(NULL),
1407   _g1_rem_set(NULL),
1408   _cr(NULL),
1409   _g1mm(NULL),
1410   _preserved_marks_set(true /* in_c_heap */),
1411   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1412   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1413   _humongous_reclaim_candidates(),
1414   _has_humongous_reclaim_candidates(false),
1415   _archive_allocator(NULL),
1416   _summary_bytes_used(0),
1417   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1418   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1419   _expand_heap_after_alloc_failure(true),
1420   _old_marking_cycles_started(0),
1421   _old_marking_cycles_completed(0),
1422   _in_cset_fast_test() {
1423 
1424   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1425                           /* are_GC_task_threads */true,
1426                           /* are_ConcurrentGC_threads */false);
1427   _workers->initialize_workers();
1428   _verifier = new G1HeapVerifier(this);
1429 
1430   _allocator = new G1Allocator(this);
1431 
1432   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1433 
1434   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1435 
1436   // Override the default _filler_array_max_size so that no humongous filler
1437   // objects are created.
1438   _filler_array_max_size = _humongous_object_threshold_in_words;
1439 
1440   uint n_queues = ParallelGCThreads;
1441   _task_queues = new RefToScanQueueSet(n_queues);
1442 
1443   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1444 
1445   for (uint i = 0; i < n_queues; i++) {
1446     RefToScanQueue* q = new RefToScanQueue();
1447     q->initialize();
1448     _task_queues->register_queue(i, q);
1449     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1450   }
1451 
1452   // Initialize the G1EvacuationFailureALot counters and flags.
1453   NOT_PRODUCT(reset_evacuation_should_fail();)
1454 
1455   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1456 }
1457 
1458 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1459                                                                  size_t size,
1460                                                                  size_t translation_factor) {
1461   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1462   // Allocate a new reserved space, preferring to use large pages.
1463   ReservedSpace rs(size, preferred_page_size);
1464   G1RegionToSpaceMapper* result  =
1465     G1RegionToSpaceMapper::create_mapper(rs,
1466                                          size,
1467                                          rs.alignment(),
1468                                          HeapRegion::GrainBytes,
1469                                          translation_factor,
1470                                          mtGC);
1471 
1472   os::trace_page_sizes_for_requested_size(description,
1473                                           size,
1474                                           preferred_page_size,
1475                                           rs.alignment(),
1476                                           rs.base(),
1477                                           rs.size());
1478 
1479   return result;
1480 }
1481 
1482 jint G1CollectedHeap::initialize_concurrent_refinement() {
1483   jint ecode = JNI_OK;
1484   _cr = G1ConcurrentRefine::create(&ecode);
1485   return ecode;
1486 }
1487 
1488 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1489   _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1490   if (_young_gen_sampling_thread->osthread() == NULL) {
1491     vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1492     return JNI_ENOMEM;
1493   }
1494   return JNI_OK;
1495 }
1496 
1497 jint G1CollectedHeap::initialize() {
1498   os::enable_vtime();
1499 
1500   // Necessary to satisfy locking discipline assertions.
1501 
1502   MutexLocker x(Heap_lock);
1503 
1504   // While there are no constraints in the GC code that HeapWordSize
1505   // be any particular value, there are multiple other areas in the
1506   // system which believe this to be true (e.g. oop->object_size in some
1507   // cases incorrectly returns the size in wordSize units rather than
1508   // HeapWordSize).
1509   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1510 
1511   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1512   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1513   size_t heap_alignment = collector_policy()->heap_alignment();
1514 
1515   // Ensure that the sizes are properly aligned.
1516   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1517   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1518   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1519 
1520   // Reserve the maximum.
1521 
1522   // When compressed oops are enabled, the preferred heap base
1523   // is calculated by subtracting the requested size from the
1524   // 32Gb boundary and using the result as the base address for
1525   // heap reservation. If the requested size is not aligned to
1526   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1527   // into the ReservedHeapSpace constructor) then the actual
1528   // base of the reserved heap may end up differing from the
1529   // address that was requested (i.e. the preferred heap base).
1530   // If this happens then we could end up using a non-optimal
1531   // compressed oops mode.
1532 
1533   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1534                                                  heap_alignment);
1535 
1536   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1537 
1538   // Create the barrier set for the entire reserved region.
1539   G1CardTable* ct = new G1CardTable(reserved_region());
1540   ct->initialize();
1541   G1BarrierSet* bs = new G1BarrierSet(ct);
1542   bs->initialize();
1543   assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1544   set_barrier_set(bs);
1545   _card_table = ct;
1546 
1547   // Create the hot card cache.
1548   _hot_card_cache = new G1HotCardCache(this);
1549 
1550   // Carve out the G1 part of the heap.
1551   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1552   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1553   G1RegionToSpaceMapper* heap_storage =
1554     G1RegionToSpaceMapper::create_mapper(g1_rs,
1555                                          g1_rs.size(),
1556                                          page_size,
1557                                          HeapRegion::GrainBytes,
1558                                          1,
1559                                          mtJavaHeap);
1560   os::trace_page_sizes("Heap",
1561                        collector_policy()->min_heap_byte_size(),
1562                        max_byte_size,
1563                        page_size,
1564                        heap_rs.base(),
1565                        heap_rs.size());
1566   heap_storage->set_mapping_changed_listener(&_listener);
1567 
1568   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1569   G1RegionToSpaceMapper* bot_storage =
1570     create_aux_memory_mapper("Block Offset Table",
1571                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1572                              G1BlockOffsetTable::heap_map_factor());
1573 
1574   G1RegionToSpaceMapper* cardtable_storage =
1575     create_aux_memory_mapper("Card Table",
1576                              G1CardTable::compute_size(g1_rs.size() / HeapWordSize),
1577                              G1CardTable::heap_map_factor());
1578 
1579   G1RegionToSpaceMapper* card_counts_storage =
1580     create_aux_memory_mapper("Card Counts Table",
1581                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1582                              G1CardCounts::heap_map_factor());
1583 
1584   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1585   G1RegionToSpaceMapper* prev_bitmap_storage =
1586     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1587   G1RegionToSpaceMapper* next_bitmap_storage =
1588     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1589 
1590   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1591   _card_table->initialize(cardtable_storage);
1592   // Do later initialization work for concurrent refinement.
1593   _hot_card_cache->initialize(card_counts_storage);
1594 
1595   // 6843694 - ensure that the maximum region index can fit
1596   // in the remembered set structures.
1597   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1598   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1599 
1600   // Also create a G1 rem set.
1601   _g1_rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
1602   _g1_rem_set->initialize(max_capacity(), max_regions());
1603 
1604   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1605   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1606   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1607             "too many cards per region");
1608 
1609   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1610 
1611   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1612 
1613   {
1614     HeapWord* start = _hrm.reserved().start();
1615     HeapWord* end = _hrm.reserved().end();
1616     size_t granularity = HeapRegion::GrainBytes;
1617 
1618     _in_cset_fast_test.initialize(start, end, granularity);
1619     _humongous_reclaim_candidates.initialize(start, end, granularity);
1620   }
1621 
1622   // Create the G1ConcurrentMark data structure and thread.
1623   // (Must do this late, so that "max_regions" is defined.)
1624   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1625   if (_cm == NULL || !_cm->completed_initialization()) {
1626     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1627     return JNI_ENOMEM;
1628   }
1629   _cm_thread = _cm->cm_thread();
1630 
1631   // Now expand into the initial heap size.
1632   if (!expand(init_byte_size, _workers)) {
1633     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1634     return JNI_ENOMEM;
1635   }
1636 
1637   // Perform any initialization actions delegated to the policy.
1638   g1_policy()->init(this, &_collection_set);
1639 
1640   G1BarrierSet::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1641                                                  SATB_Q_FL_lock,
1642                                                  G1SATBProcessCompletedThreshold,
1643                                                  Shared_SATB_Q_lock);
1644 
1645   jint ecode = initialize_concurrent_refinement();
1646   if (ecode != JNI_OK) {
1647     return ecode;
1648   }
1649 
1650   ecode = initialize_young_gen_sampling_thread();
1651   if (ecode != JNI_OK) {
1652     return ecode;
1653   }
1654 
1655   G1BarrierSet::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1656                                                   DirtyCardQ_FL_lock,
1657                                                   (int)concurrent_refine()->yellow_zone(),
1658                                                   (int)concurrent_refine()->red_zone(),
1659                                                   Shared_DirtyCardQ_lock,
1660                                                   NULL,  // fl_owner
1661                                                   true); // init_free_ids
1662 
1663   dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1664                                     DirtyCardQ_FL_lock,
1665                                     -1, // never trigger processing
1666                                     -1, // no limit on length
1667                                     Shared_DirtyCardQ_lock,
1668                                     &G1BarrierSet::dirty_card_queue_set());
1669 
1670   // Here we allocate the dummy HeapRegion that is required by the
1671   // G1AllocRegion class.
1672   HeapRegion* dummy_region = _hrm.get_dummy_region();
1673 
1674   // We'll re-use the same region whether the alloc region will
1675   // require BOT updates or not and, if it doesn't, then a non-young
1676   // region will complain that it cannot support allocations without
1677   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1678   dummy_region->set_eden();
1679   // Make sure it's full.
1680   dummy_region->set_top(dummy_region->end());
1681   G1AllocRegion::setup(this, dummy_region);
1682 
1683   _allocator->init_mutator_alloc_region();
1684 
1685   // Do create of the monitoring and management support so that
1686   // values in the heap have been properly initialized.
1687   _g1mm = new G1MonitoringSupport(this);
1688 
1689   G1StringDedup::initialize();
1690 
1691   _preserved_marks_set.init(ParallelGCThreads);
1692 
1693   _collection_set.initialize(max_regions());
1694 
1695   return JNI_OK;
1696 }
1697 
1698 void G1CollectedHeap::initialize_serviceability() {
1699   _eden_pool = new G1EdenPool(this);
1700   _survivor_pool = new G1SurvivorPool(this);
1701   _old_pool = new G1OldGenPool(this);
1702 
1703   _full_gc_memory_manager.add_pool(_eden_pool);
1704   _full_gc_memory_manager.add_pool(_survivor_pool);
1705   _full_gc_memory_manager.add_pool(_old_pool);
1706 
1707   _memory_manager.add_pool(_eden_pool);
1708   _memory_manager.add_pool(_survivor_pool);
1709 
1710 }
1711 
1712 void G1CollectedHeap::stop() {
1713   // Stop all concurrent threads. We do this to make sure these threads
1714   // do not continue to execute and access resources (e.g. logging)
1715   // that are destroyed during shutdown.
1716   _cr->stop();
1717   _young_gen_sampling_thread->stop();
1718   _cm_thread->stop();
1719   if (G1StringDedup::is_enabled()) {
1720     G1StringDedup::stop();
1721   }
1722 }
1723 
1724 void G1CollectedHeap::safepoint_synchronize_begin() {
1725   SuspendibleThreadSet::synchronize();
1726 }
1727 
1728 void G1CollectedHeap::safepoint_synchronize_end() {
1729   SuspendibleThreadSet::desynchronize();
1730 }
1731 
1732 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1733   return HeapRegion::max_region_size();
1734 }
1735 
1736 void G1CollectedHeap::post_initialize() {
1737   CollectedHeap::post_initialize();
1738   ref_processing_init();
1739 }
1740 
1741 void G1CollectedHeap::ref_processing_init() {
1742   // Reference processing in G1 currently works as follows:
1743   //
1744   // * There are two reference processor instances. One is
1745   //   used to record and process discovered references
1746   //   during concurrent marking; the other is used to
1747   //   record and process references during STW pauses
1748   //   (both full and incremental).
1749   // * Both ref processors need to 'span' the entire heap as
1750   //   the regions in the collection set may be dotted around.
1751   //
1752   // * For the concurrent marking ref processor:
1753   //   * Reference discovery is enabled at initial marking.
1754   //   * Reference discovery is disabled and the discovered
1755   //     references processed etc during remarking.
1756   //   * Reference discovery is MT (see below).
1757   //   * Reference discovery requires a barrier (see below).
1758   //   * Reference processing may or may not be MT
1759   //     (depending on the value of ParallelRefProcEnabled
1760   //     and ParallelGCThreads).
1761   //   * A full GC disables reference discovery by the CM
1762   //     ref processor and abandons any entries on it's
1763   //     discovered lists.
1764   //
1765   // * For the STW processor:
1766   //   * Non MT discovery is enabled at the start of a full GC.
1767   //   * Processing and enqueueing during a full GC is non-MT.
1768   //   * During a full GC, references are processed after marking.
1769   //
1770   //   * Discovery (may or may not be MT) is enabled at the start
1771   //     of an incremental evacuation pause.
1772   //   * References are processed near the end of a STW evacuation pause.
1773   //   * For both types of GC:
1774   //     * Discovery is atomic - i.e. not concurrent.
1775   //     * Reference discovery will not need a barrier.
1776 
1777   MemRegion mr = reserved_region();
1778 
1779   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1780 
1781   // Concurrent Mark ref processor
1782   _ref_processor_cm =
1783     new ReferenceProcessor(mr,    // span
1784                            mt_processing,
1785                                 // mt processing
1786                            ParallelGCThreads,
1787                                 // degree of mt processing
1788                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
1789                                 // mt discovery
1790                            MAX2(ParallelGCThreads, ConcGCThreads),
1791                                 // degree of mt discovery
1792                            false,
1793                                 // Reference discovery is not atomic
1794                            &_is_alive_closure_cm);
1795                                 // is alive closure
1796                                 // (for efficiency/performance)
1797 
1798   // STW ref processor
1799   _ref_processor_stw =
1800     new ReferenceProcessor(mr,    // span
1801                            mt_processing,
1802                                 // mt processing
1803                            ParallelGCThreads,
1804                                 // degree of mt processing
1805                            (ParallelGCThreads > 1),
1806                                 // mt discovery
1807                            ParallelGCThreads,
1808                                 // degree of mt discovery
1809                            true,
1810                                 // Reference discovery is atomic
1811                            &_is_alive_closure_stw);
1812                                 // is alive closure
1813                                 // (for efficiency/performance)
1814 }
1815 
1816 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1817   return _collector_policy;
1818 }
1819 
1820 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
1821   return &_soft_ref_policy;
1822 }
1823 
1824 size_t G1CollectedHeap::capacity() const {
1825   return _hrm.length() * HeapRegion::GrainBytes;
1826 }
1827 
1828 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1829   return _hrm.total_free_bytes();
1830 }
1831 
1832 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
1833   _hot_card_cache->drain(cl, worker_i);
1834 }
1835 
1836 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
1837   DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1838   size_t n_completed_buffers = 0;
1839   while (dcqs.apply_closure_during_gc(cl, worker_i)) {
1840     n_completed_buffers++;
1841   }
1842   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
1843   dcqs.clear_n_completed_buffers();
1844   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
1845 }
1846 
1847 // Computes the sum of the storage used by the various regions.
1848 size_t G1CollectedHeap::used() const {
1849   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1850   if (_archive_allocator != NULL) {
1851     result += _archive_allocator->used();
1852   }
1853   return result;
1854 }
1855 
1856 size_t G1CollectedHeap::used_unlocked() const {
1857   return _summary_bytes_used;
1858 }
1859 
1860 class SumUsedClosure: public HeapRegionClosure {
1861   size_t _used;
1862 public:
1863   SumUsedClosure() : _used(0) {}
1864   bool do_heap_region(HeapRegion* r) {
1865     _used += r->used();
1866     return false;
1867   }
1868   size_t result() { return _used; }
1869 };
1870 
1871 size_t G1CollectedHeap::recalculate_used() const {
1872   double recalculate_used_start = os::elapsedTime();
1873 
1874   SumUsedClosure blk;
1875   heap_region_iterate(&blk);
1876 
1877   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
1878   return blk.result();
1879 }
1880 
1881 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
1882   switch (cause) {
1883     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
1884     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
1885     case GCCause::_wb_conc_mark:                        return true;
1886     default :                                           return false;
1887   }
1888 }
1889 
1890 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
1891   switch (cause) {
1892     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
1893     case GCCause::_g1_humongous_allocation: return true;
1894     default:                                return is_user_requested_concurrent_full_gc(cause);
1895   }
1896 }
1897 
1898 #ifndef PRODUCT
1899 void G1CollectedHeap::allocate_dummy_regions() {
1900   // Let's fill up most of the region
1901   size_t word_size = HeapRegion::GrainWords - 1024;
1902   // And as a result the region we'll allocate will be humongous.
1903   guarantee(is_humongous(word_size), "sanity");
1904 
1905   // _filler_array_max_size is set to humongous object threshold
1906   // but temporarily change it to use CollectedHeap::fill_with_object().
1907   SizeTFlagSetting fs(_filler_array_max_size, word_size);
1908 
1909   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
1910     // Let's use the existing mechanism for the allocation
1911     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
1912     if (dummy_obj != NULL) {
1913       MemRegion mr(dummy_obj, word_size);
1914       CollectedHeap::fill_with_object(mr);
1915     } else {
1916       // If we can't allocate once, we probably cannot allocate
1917       // again. Let's get out of the loop.
1918       break;
1919     }
1920   }
1921 }
1922 #endif // !PRODUCT
1923 
1924 void G1CollectedHeap::increment_old_marking_cycles_started() {
1925   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
1926          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
1927          "Wrong marking cycle count (started: %d, completed: %d)",
1928          _old_marking_cycles_started, _old_marking_cycles_completed);
1929 
1930   _old_marking_cycles_started++;
1931 }
1932 
1933 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
1934   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
1935 
1936   // We assume that if concurrent == true, then the caller is a
1937   // concurrent thread that was joined the Suspendible Thread
1938   // Set. If there's ever a cheap way to check this, we should add an
1939   // assert here.
1940 
1941   // Given that this method is called at the end of a Full GC or of a
1942   // concurrent cycle, and those can be nested (i.e., a Full GC can
1943   // interrupt a concurrent cycle), the number of full collections
1944   // completed should be either one (in the case where there was no
1945   // nesting) or two (when a Full GC interrupted a concurrent cycle)
1946   // behind the number of full collections started.
1947 
1948   // This is the case for the inner caller, i.e. a Full GC.
1949   assert(concurrent ||
1950          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
1951          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
1952          "for inner caller (Full GC): _old_marking_cycles_started = %u "
1953          "is inconsistent with _old_marking_cycles_completed = %u",
1954          _old_marking_cycles_started, _old_marking_cycles_completed);
1955 
1956   // This is the case for the outer caller, i.e. the concurrent cycle.
1957   assert(!concurrent ||
1958          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
1959          "for outer caller (concurrent cycle): "
1960          "_old_marking_cycles_started = %u "
1961          "is inconsistent with _old_marking_cycles_completed = %u",
1962          _old_marking_cycles_started, _old_marking_cycles_completed);
1963 
1964   _old_marking_cycles_completed += 1;
1965 
1966   // We need to clear the "in_progress" flag in the CM thread before
1967   // we wake up any waiters (especially when ExplicitInvokesConcurrent
1968   // is set) so that if a waiter requests another System.gc() it doesn't
1969   // incorrectly see that a marking cycle is still in progress.
1970   if (concurrent) {
1971     _cm_thread->set_idle();
1972   }
1973 
1974   // This notify_all() will ensure that a thread that called
1975   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
1976   // and it's waiting for a full GC to finish will be woken up. It is
1977   // waiting in VM_G1CollectForAllocation::doit_epilogue().
1978   FullGCCount_lock->notify_all();
1979 }
1980 
1981 void G1CollectedHeap::collect(GCCause::Cause cause) {
1982   assert_heap_not_locked();
1983 
1984   uint gc_count_before;
1985   uint old_marking_count_before;
1986   uint full_gc_count_before;
1987   bool retry_gc;
1988 
1989   do {
1990     retry_gc = false;
1991 
1992     {
1993       MutexLocker ml(Heap_lock);
1994 
1995       // Read the GC count while holding the Heap_lock
1996       gc_count_before = total_collections();
1997       full_gc_count_before = total_full_collections();
1998       old_marking_count_before = _old_marking_cycles_started;
1999     }
2000 
2001     if (should_do_concurrent_full_gc(cause)) {
2002       // Schedule an initial-mark evacuation pause that will start a
2003       // concurrent cycle. We're setting word_size to 0 which means that
2004       // we are not requesting a post-GC allocation.
2005       VM_G1CollectForAllocation op(0,     /* word_size */
2006                                    gc_count_before,
2007                                    cause,
2008                                    true,  /* should_initiate_conc_mark */
2009                                    g1_policy()->max_pause_time_ms());
2010       VMThread::execute(&op);
2011       if (!op.pause_succeeded()) {
2012         if (old_marking_count_before == _old_marking_cycles_started) {
2013           retry_gc = op.should_retry_gc();
2014         } else {
2015           // A Full GC happened while we were trying to schedule the
2016           // initial-mark GC. No point in starting a new cycle given
2017           // that the whole heap was collected anyway.
2018         }
2019 
2020         if (retry_gc) {
2021           if (GCLocker::is_active_and_needs_gc()) {
2022             GCLocker::stall_until_clear();
2023           }
2024         }
2025       }
2026     } else {
2027       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2028           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2029 
2030         // Schedule a standard evacuation pause. We're setting word_size
2031         // to 0 which means that we are not requesting a post-GC allocation.
2032         VM_G1CollectForAllocation op(0,     /* word_size */
2033                                      gc_count_before,
2034                                      cause,
2035                                      false, /* should_initiate_conc_mark */
2036                                      g1_policy()->max_pause_time_ms());
2037         VMThread::execute(&op);
2038       } else {
2039         // Schedule a Full GC.
2040         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2041         VMThread::execute(&op);
2042       }
2043     }
2044   } while (retry_gc);
2045 }
2046 
2047 bool G1CollectedHeap::is_in(const void* p) const {
2048   if (_hrm.reserved().contains(p)) {
2049     // Given that we know that p is in the reserved space,
2050     // heap_region_containing() should successfully
2051     // return the containing region.
2052     HeapRegion* hr = heap_region_containing(p);
2053     return hr->is_in(p);
2054   } else {
2055     return false;
2056   }
2057 }
2058 
2059 #ifdef ASSERT
2060 bool G1CollectedHeap::is_in_exact(const void* p) const {
2061   bool contains = reserved_region().contains(p);
2062   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2063   if (contains && available) {
2064     return true;
2065   } else {
2066     return false;
2067   }
2068 }
2069 #endif
2070 
2071 // Iteration functions.
2072 
2073 // Iterates an ObjectClosure over all objects within a HeapRegion.
2074 
2075 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2076   ObjectClosure* _cl;
2077 public:
2078   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2079   bool do_heap_region(HeapRegion* r) {
2080     if (!r->is_continues_humongous()) {
2081       r->object_iterate(_cl);
2082     }
2083     return false;
2084   }
2085 };
2086 
2087 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2088   IterateObjectClosureRegionClosure blk(cl);
2089   heap_region_iterate(&blk);
2090 }
2091 
2092 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2093   _hrm.iterate(cl);
2094 }
2095 
2096 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2097                                                                  HeapRegionClaimer *hrclaimer,
2098                                                                  uint worker_id) const {
2099   _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2100 }
2101 
2102 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2103                                                          HeapRegionClaimer *hrclaimer) const {
2104   _hrm.par_iterate(cl, hrclaimer, 0);
2105 }
2106 
2107 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2108   _collection_set.iterate(cl);
2109 }
2110 
2111 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2112   _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2113 }
2114 
2115 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2116   HeapRegion* hr = heap_region_containing(addr);
2117   return hr->block_start(addr);
2118 }
2119 
2120 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2121   HeapRegion* hr = heap_region_containing(addr);
2122   return hr->block_size(addr);
2123 }
2124 
2125 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2126   HeapRegion* hr = heap_region_containing(addr);
2127   return hr->block_is_obj(addr);
2128 }
2129 
2130 bool G1CollectedHeap::supports_tlab_allocation() const {
2131   return true;
2132 }
2133 
2134 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2135   return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2136 }
2137 
2138 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2139   return _eden.length() * HeapRegion::GrainBytes;
2140 }
2141 
2142 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2143 // must be equal to the humongous object limit.
2144 size_t G1CollectedHeap::max_tlab_size() const {
2145   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2146 }
2147 
2148 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2149   return _allocator->unsafe_max_tlab_alloc();
2150 }
2151 
2152 size_t G1CollectedHeap::max_capacity() const {
2153   return _hrm.reserved().byte_size();
2154 }
2155 
2156 jlong G1CollectedHeap::millis_since_last_gc() {
2157   // See the notes in GenCollectedHeap::millis_since_last_gc()
2158   // for more information about the implementation.
2159   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2160     _g1_policy->collection_pause_end_millis();
2161   if (ret_val < 0) {
2162     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2163       ". returning zero instead.", ret_val);
2164     return 0;
2165   }
2166   return ret_val;
2167 }
2168 
2169 void G1CollectedHeap::prepare_for_verify() {
2170   _verifier->prepare_for_verify();
2171 }
2172 
2173 void G1CollectedHeap::verify(VerifyOption vo) {
2174   _verifier->verify(vo);
2175 }
2176 
2177 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2178   return true;
2179 }
2180 
2181 const char* const* G1CollectedHeap::concurrent_phases() const {
2182   return _cm_thread->concurrent_phases();
2183 }
2184 
2185 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2186   return _cm_thread->request_concurrent_phase(phase);
2187 }
2188 
2189 class PrintRegionClosure: public HeapRegionClosure {
2190   outputStream* _st;
2191 public:
2192   PrintRegionClosure(outputStream* st) : _st(st) {}
2193   bool do_heap_region(HeapRegion* r) {
2194     r->print_on(_st);
2195     return false;
2196   }
2197 };
2198 
2199 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2200                                        const HeapRegion* hr,
2201                                        const VerifyOption vo) const {
2202   switch (vo) {
2203   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2204   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2205   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2206   default:                            ShouldNotReachHere();
2207   }
2208   return false; // keep some compilers happy
2209 }
2210 
2211 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2212                                        const VerifyOption vo) const {
2213   switch (vo) {
2214   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2215   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2216   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2217   default:                            ShouldNotReachHere();
2218   }
2219   return false; // keep some compilers happy
2220 }
2221 
2222 void G1CollectedHeap::print_heap_regions() const {
2223   LogTarget(Trace, gc, heap, region) lt;
2224   if (lt.is_enabled()) {
2225     LogStream ls(lt);
2226     print_regions_on(&ls);
2227   }
2228 }
2229 
2230 void G1CollectedHeap::print_on(outputStream* st) const {
2231   st->print(" %-20s", "garbage-first heap");
2232   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2233             capacity()/K, used_unlocked()/K);
2234   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2235             p2i(_hrm.reserved().start()),
2236             p2i(_hrm.reserved().end()));
2237   st->cr();
2238   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2239   uint young_regions = young_regions_count();
2240   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2241             (size_t) young_regions * HeapRegion::GrainBytes / K);
2242   uint survivor_regions = survivor_regions_count();
2243   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2244             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2245   st->cr();
2246   MetaspaceUtils::print_on(st);
2247 }
2248 
2249 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2250   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2251                "HS=humongous(starts), HC=humongous(continues), "
2252                "CS=collection set, F=free, A=archive, "
2253                "TAMS=top-at-mark-start (previous, next)");
2254   PrintRegionClosure blk(st);
2255   heap_region_iterate(&blk);
2256 }
2257 
2258 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2259   print_on(st);
2260 
2261   // Print the per-region information.
2262   print_regions_on(st);
2263 }
2264 
2265 void G1CollectedHeap::print_on_error(outputStream* st) const {
2266   this->CollectedHeap::print_on_error(st);
2267 
2268   if (_cm != NULL) {
2269     st->cr();
2270     _cm->print_on_error(st);
2271   }
2272 }
2273 
2274 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2275   workers()->print_worker_threads_on(st);
2276   _cm_thread->print_on(st);
2277   st->cr();
2278   _cm->print_worker_threads_on(st);
2279   _cr->print_threads_on(st);
2280   _young_gen_sampling_thread->print_on(st);
2281   if (G1StringDedup::is_enabled()) {
2282     G1StringDedup::print_worker_threads_on(st);
2283   }
2284 }
2285 
2286 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2287   workers()->threads_do(tc);
2288   tc->do_thread(_cm_thread);
2289   _cm->threads_do(tc);
2290   _cr->threads_do(tc);
2291   tc->do_thread(_young_gen_sampling_thread);
2292   if (G1StringDedup::is_enabled()) {
2293     G1StringDedup::threads_do(tc);
2294   }
2295 }
2296 
2297 void G1CollectedHeap::print_tracing_info() const {
2298   g1_rem_set()->print_summary_info();
2299   concurrent_mark()->print_summary_info();
2300 }
2301 
2302 #ifndef PRODUCT
2303 // Helpful for debugging RSet issues.
2304 
2305 class PrintRSetsClosure : public HeapRegionClosure {
2306 private:
2307   const char* _msg;
2308   size_t _occupied_sum;
2309 
2310 public:
2311   bool do_heap_region(HeapRegion* r) {
2312     HeapRegionRemSet* hrrs = r->rem_set();
2313     size_t occupied = hrrs->occupied();
2314     _occupied_sum += occupied;
2315 
2316     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2317     if (occupied == 0) {
2318       tty->print_cr("  RSet is empty");
2319     } else {
2320       hrrs->print();
2321     }
2322     tty->print_cr("----------");
2323     return false;
2324   }
2325 
2326   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2327     tty->cr();
2328     tty->print_cr("========================================");
2329     tty->print_cr("%s", msg);
2330     tty->cr();
2331   }
2332 
2333   ~PrintRSetsClosure() {
2334     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2335     tty->print_cr("========================================");
2336     tty->cr();
2337   }
2338 };
2339 
2340 void G1CollectedHeap::print_cset_rsets() {
2341   PrintRSetsClosure cl("Printing CSet RSets");
2342   collection_set_iterate(&cl);
2343 }
2344 
2345 void G1CollectedHeap::print_all_rsets() {
2346   PrintRSetsClosure cl("Printing All RSets");;
2347   heap_region_iterate(&cl);
2348 }
2349 #endif // PRODUCT
2350 
2351 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2352 
2353   size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2354   size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2355   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2356 
2357   size_t eden_capacity_bytes =
2358     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2359 
2360   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2361   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2362                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2363 }
2364 
2365 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2366   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2367                        stats->unused(), stats->used(), stats->region_end_waste(),
2368                        stats->regions_filled(), stats->direct_allocated(),
2369                        stats->failure_used(), stats->failure_waste());
2370 }
2371 
2372 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2373   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2374   gc_tracer->report_gc_heap_summary(when, heap_summary);
2375 
2376   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2377   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2378 }
2379 
2380 G1CollectedHeap* G1CollectedHeap::heap() {
2381   CollectedHeap* heap = Universe::heap();
2382   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2383   assert(heap->kind() == CollectedHeap::G1, "Invalid name");
2384   return (G1CollectedHeap*)heap;
2385 }
2386 
2387 void G1CollectedHeap::gc_prologue(bool full) {
2388   // always_do_update_barrier = false;
2389   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2390 
2391   // This summary needs to be printed before incrementing total collections.
2392   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2393 
2394   // Update common counters.
2395   increment_total_collections(full /* full gc */);
2396   if (full) {
2397     increment_old_marking_cycles_started();
2398   }
2399 
2400   // Fill TLAB's and such
2401   double start = os::elapsedTime();
2402   accumulate_statistics_all_tlabs();
2403   ensure_parsability(true);
2404   g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2405 }
2406 
2407 void G1CollectedHeap::gc_epilogue(bool full) {
2408   // Update common counters.
2409   if (full) {
2410     // Update the number of full collections that have been completed.
2411     increment_old_marking_cycles_completed(false /* concurrent */);
2412   }
2413 
2414   // We are at the end of the GC. Total collections has already been increased.
2415   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2416 
2417   // FIXME: what is this about?
2418   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2419   // is set.
2420 #if COMPILER2_OR_JVMCI
2421   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2422 #endif
2423   // always_do_update_barrier = true;
2424 
2425   double start = os::elapsedTime();
2426   resize_all_tlabs();
2427   g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2428 
2429   MemoryService::track_memory_usage();
2430   // We have just completed a GC. Update the soft reference
2431   // policy with the new heap occupancy
2432   Universe::update_heap_info_at_gc();
2433 }
2434 
2435 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2436                                                uint gc_count_before,
2437                                                bool* succeeded,
2438                                                GCCause::Cause gc_cause) {
2439   assert_heap_not_locked_and_not_at_safepoint();
2440   VM_G1CollectForAllocation op(word_size,
2441                                gc_count_before,
2442                                gc_cause,
2443                                false, /* should_initiate_conc_mark */
2444                                g1_policy()->max_pause_time_ms());
2445   VMThread::execute(&op);
2446 
2447   HeapWord* result = op.result();
2448   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2449   assert(result == NULL || ret_succeeded,
2450          "the result should be NULL if the VM did not succeed");
2451   *succeeded = ret_succeeded;
2452 
2453   assert_heap_not_locked();
2454   return result;
2455 }
2456 
2457 void G1CollectedHeap::do_concurrent_mark() {
2458   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2459   if (!_cm_thread->in_progress()) {
2460     _cm_thread->set_started();
2461     CGC_lock->notify();
2462   }
2463 }
2464 
2465 size_t G1CollectedHeap::pending_card_num() {
2466   size_t extra_cards = 0;
2467   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) {
2468     DirtyCardQueue& dcq = curr->dirty_card_queue();
2469     extra_cards += dcq.size();
2470   }
2471   DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
2472   size_t buffer_size = dcqs.buffer_size();
2473   size_t buffer_num = dcqs.completed_buffers_num();
2474 
2475   return buffer_size * buffer_num + extra_cards;
2476 }
2477 
2478 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
2479   // We don't nominate objects with many remembered set entries, on
2480   // the assumption that such objects are likely still live.
2481   HeapRegionRemSet* rem_set = r->rem_set();
2482 
2483   return G1EagerReclaimHumongousObjectsWithStaleRefs ?
2484          rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) :
2485          G1EagerReclaimHumongousObjects && rem_set->is_empty();
2486 }
2487 
2488 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2489  private:
2490   size_t _total_humongous;
2491   size_t _candidate_humongous;
2492 
2493   DirtyCardQueue _dcq;
2494 
2495   bool humongous_region_is_candidate(G1CollectedHeap* g1h, HeapRegion* region) const {
2496     assert(region->is_starts_humongous(), "Must start a humongous object");
2497 
2498     oop obj = oop(region->bottom());
2499 
2500     // Dead objects cannot be eager reclaim candidates. Due to class
2501     // unloading it is unsafe to query their classes so we return early.
2502     if (g1h->is_obj_dead(obj, region)) {
2503       return false;
2504     }
2505 
2506     // If we do not have a complete remembered set for the region, then we can
2507     // not be sure that we have all references to it.
2508     if (!region->rem_set()->is_complete()) {
2509       return false;
2510     }
2511     // Candidate selection must satisfy the following constraints
2512     // while concurrent marking is in progress:
2513     //
2514     // * In order to maintain SATB invariants, an object must not be
2515     // reclaimed if it was allocated before the start of marking and
2516     // has not had its references scanned.  Such an object must have
2517     // its references (including type metadata) scanned to ensure no
2518     // live objects are missed by the marking process.  Objects
2519     // allocated after the start of concurrent marking don't need to
2520     // be scanned.
2521     //
2522     // * An object must not be reclaimed if it is on the concurrent
2523     // mark stack.  Objects allocated after the start of concurrent
2524     // marking are never pushed on the mark stack.
2525     //
2526     // Nominating only objects allocated after the start of concurrent
2527     // marking is sufficient to meet both constraints.  This may miss
2528     // some objects that satisfy the constraints, but the marking data
2529     // structures don't support efficiently performing the needed
2530     // additional tests or scrubbing of the mark stack.
2531     //
2532     // However, we presently only nominate is_typeArray() objects.
2533     // A humongous object containing references induces remembered
2534     // set entries on other regions.  In order to reclaim such an
2535     // object, those remembered sets would need to be cleaned up.
2536     //
2537     // We also treat is_typeArray() objects specially, allowing them
2538     // to be reclaimed even if allocated before the start of
2539     // concurrent mark.  For this we rely on mark stack insertion to
2540     // exclude is_typeArray() objects, preventing reclaiming an object
2541     // that is in the mark stack.  We also rely on the metadata for
2542     // such objects to be built-in and so ensured to be kept live.
2543     // Frequent allocation and drop of large binary blobs is an
2544     // important use case for eager reclaim, and this special handling
2545     // may reduce needed headroom.
2546 
2547     return obj->is_typeArray() &&
2548            g1h->is_potential_eager_reclaim_candidate(region);
2549   }
2550 
2551  public:
2552   RegisterHumongousWithInCSetFastTestClosure()
2553   : _total_humongous(0),
2554     _candidate_humongous(0),
2555     _dcq(&G1BarrierSet::dirty_card_queue_set()) {
2556   }
2557 
2558   virtual bool do_heap_region(HeapRegion* r) {
2559     if (!r->is_starts_humongous()) {
2560       return false;
2561     }
2562     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2563 
2564     bool is_candidate = humongous_region_is_candidate(g1h, r);
2565     uint rindex = r->hrm_index();
2566     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2567     if (is_candidate) {
2568       _candidate_humongous++;
2569       g1h->register_humongous_region_with_cset(rindex);
2570       // Is_candidate already filters out humongous object with large remembered sets.
2571       // If we have a humongous object with a few remembered sets, we simply flush these
2572       // remembered set entries into the DCQS. That will result in automatic
2573       // re-evaluation of their remembered set entries during the following evacuation
2574       // phase.
2575       if (!r->rem_set()->is_empty()) {
2576         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2577                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2578         G1CardTable* ct = g1h->card_table();
2579         HeapRegionRemSetIterator hrrs(r->rem_set());
2580         size_t card_index;
2581         while (hrrs.has_next(card_index)) {
2582           jbyte* card_ptr = (jbyte*)ct->byte_for_index(card_index);
2583           // The remembered set might contain references to already freed
2584           // regions. Filter out such entries to avoid failing card table
2585           // verification.
2586           if (g1h->is_in_closed_subset(ct->addr_for(card_ptr))) {
2587             if (*card_ptr != G1CardTable::dirty_card_val()) {
2588               *card_ptr = G1CardTable::dirty_card_val();
2589               _dcq.enqueue(card_ptr);
2590             }
2591           }
2592         }
2593         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2594                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2595                hrrs.n_yielded(), r->rem_set()->occupied());
2596         // We should only clear the card based remembered set here as we will not
2597         // implicitly rebuild anything else during eager reclaim. Note that at the moment
2598         // (and probably never) we do not enter this path if there are other kind of
2599         // remembered sets for this region.
2600         r->rem_set()->clear_locked(true /* only_cardset */);
2601         // Clear_locked() above sets the state to Empty. However we want to continue
2602         // collecting remembered set entries for humongous regions that were not
2603         // reclaimed.
2604         r->rem_set()->set_state_complete();
2605       }
2606       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2607     }
2608     _total_humongous++;
2609 
2610     return false;
2611   }
2612 
2613   size_t total_humongous() const { return _total_humongous; }
2614   size_t candidate_humongous() const { return _candidate_humongous; }
2615 
2616   void flush_rem_set_entries() { _dcq.flush(); }
2617 };
2618 
2619 void G1CollectedHeap::register_humongous_regions_with_cset() {
2620   if (!G1EagerReclaimHumongousObjects) {
2621     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2622     return;
2623   }
2624   double time = os::elapsed_counter();
2625 
2626   // Collect reclaim candidate information and register candidates with cset.
2627   RegisterHumongousWithInCSetFastTestClosure cl;
2628   heap_region_iterate(&cl);
2629 
2630   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2631   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2632                                                                   cl.total_humongous(),
2633                                                                   cl.candidate_humongous());
2634   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2635 
2636   // Finally flush all remembered set entries to re-check into the global DCQS.
2637   cl.flush_rem_set_entries();
2638 }
2639 
2640 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2641   public:
2642     bool do_heap_region(HeapRegion* hr) {
2643       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2644         hr->verify_rem_set();
2645       }
2646       return false;
2647     }
2648 };
2649 
2650 uint G1CollectedHeap::num_task_queues() const {
2651   return _task_queues->size();
2652 }
2653 
2654 #if TASKQUEUE_STATS
2655 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2656   st->print_raw_cr("GC Task Stats");
2657   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2658   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2659 }
2660 
2661 void G1CollectedHeap::print_taskqueue_stats() const {
2662   if (!log_is_enabled(Trace, gc, task, stats)) {
2663     return;
2664   }
2665   Log(gc, task, stats) log;
2666   ResourceMark rm;
2667   LogStream ls(log.trace());
2668   outputStream* st = &ls;
2669 
2670   print_taskqueue_stats_hdr(st);
2671 
2672   TaskQueueStats totals;
2673   const uint n = num_task_queues();
2674   for (uint i = 0; i < n; ++i) {
2675     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2676     totals += task_queue(i)->stats;
2677   }
2678   st->print_raw("tot "); totals.print(st); st->cr();
2679 
2680   DEBUG_ONLY(totals.verify());
2681 }
2682 
2683 void G1CollectedHeap::reset_taskqueue_stats() {
2684   const uint n = num_task_queues();
2685   for (uint i = 0; i < n; ++i) {
2686     task_queue(i)->stats.reset();
2687   }
2688 }
2689 #endif // TASKQUEUE_STATS
2690 
2691 void G1CollectedHeap::wait_for_root_region_scanning() {
2692   double scan_wait_start = os::elapsedTime();
2693   // We have to wait until the CM threads finish scanning the
2694   // root regions as it's the only way to ensure that all the
2695   // objects on them have been correctly scanned before we start
2696   // moving them during the GC.
2697   bool waited = _cm->root_regions()->wait_until_scan_finished();
2698   double wait_time_ms = 0.0;
2699   if (waited) {
2700     double scan_wait_end = os::elapsedTime();
2701     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2702   }
2703   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2704 }
2705 
2706 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2707 private:
2708   G1HRPrinter* _hr_printer;
2709 public:
2710   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2711 
2712   virtual bool do_heap_region(HeapRegion* r) {
2713     _hr_printer->cset(r);
2714     return false;
2715   }
2716 };
2717 
2718 void G1CollectedHeap::start_new_collection_set() {
2719   collection_set()->start_incremental_building();
2720 
2721   clear_cset_fast_test();
2722 
2723   guarantee(_eden.length() == 0, "eden should have been cleared");
2724   g1_policy()->transfer_survivors_to_cset(survivor());
2725 }
2726 
2727 bool
2728 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2729   assert_at_safepoint_on_vm_thread();
2730   guarantee(!is_gc_active(), "collection is not reentrant");
2731 
2732   if (GCLocker::check_active_before_gc()) {
2733     return false;
2734   }
2735 
2736   _gc_timer_stw->register_gc_start();
2737 
2738   GCIdMark gc_id_mark;
2739   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2740 
2741   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2742   ResourceMark rm;
2743 
2744   g1_policy()->note_gc_start();
2745 
2746   wait_for_root_region_scanning();
2747 
2748   print_heap_before_gc();
2749   print_heap_regions();
2750   trace_heap_before_gc(_gc_tracer_stw);
2751 
2752   _verifier->verify_region_sets_optional();
2753   _verifier->verify_dirty_young_regions();
2754 
2755   // We should not be doing initial mark unless the conc mark thread is running
2756   if (!_cm_thread->should_terminate()) {
2757     // This call will decide whether this pause is an initial-mark
2758     // pause. If it is, in_initial_mark_gc() will return true
2759     // for the duration of this pause.
2760     g1_policy()->decide_on_conc_mark_initiation();
2761   }
2762 
2763   // We do not allow initial-mark to be piggy-backed on a mixed GC.
2764   assert(!collector_state()->in_initial_mark_gc() ||
2765           collector_state()->in_young_only_phase(), "sanity");
2766 
2767   // We also do not allow mixed GCs during marking.
2768   assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity");
2769 
2770   // Record whether this pause is an initial mark. When the current
2771   // thread has completed its logging output and it's safe to signal
2772   // the CM thread, the flag's value in the policy has been reset.
2773   bool should_start_conc_mark = collector_state()->in_initial_mark_gc();
2774 
2775   // Inner scope for scope based logging, timers, and stats collection
2776   {
2777     EvacuationInfo evacuation_info;
2778 
2779     if (collector_state()->in_initial_mark_gc()) {
2780       // We are about to start a marking cycle, so we increment the
2781       // full collection counter.
2782       increment_old_marking_cycles_started();
2783       _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2784     }
2785 
2786     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2787 
2788     GCTraceCPUTime tcpu;
2789 
2790     G1HeapVerifier::G1VerifyType verify_type;
2791     FormatBuffer<> gc_string("Pause ");
2792     if (collector_state()->in_initial_mark_gc()) {
2793       gc_string.append("Initial Mark");
2794       verify_type = G1HeapVerifier::G1VerifyInitialMark;
2795     } else if (collector_state()->in_young_only_phase()) {
2796       gc_string.append("Young");
2797       verify_type = G1HeapVerifier::G1VerifyYoungOnly;
2798     } else {
2799       gc_string.append("Mixed");
2800       verify_type = G1HeapVerifier::G1VerifyMixed;
2801     }
2802     GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2803 
2804     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2805                                                                   workers()->active_workers(),
2806                                                                   Threads::number_of_non_daemon_threads());
2807     active_workers = workers()->update_active_workers(active_workers);
2808     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2809 
2810     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2811     TraceMemoryManagerStats tms(&_memory_manager, gc_cause());
2812 
2813     G1HeapTransition heap_transition(this);
2814     size_t heap_used_bytes_before_gc = used();
2815 
2816     // Don't dynamically change the number of GC threads this early.  A value of
2817     // 0 is used to indicate serial work.  When parallel work is done,
2818     // it will be set.
2819 
2820     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2821       IsGCActiveMark x;
2822 
2823       gc_prologue(false);
2824 
2825       if (VerifyRememberedSets) {
2826         log_info(gc, verify)("[Verifying RemSets before GC]");
2827         VerifyRegionRemSetClosure v_cl;
2828         heap_region_iterate(&v_cl);
2829       }
2830 
2831       _verifier->verify_before_gc(verify_type);
2832 
2833       _verifier->check_bitmaps("GC Start");
2834 
2835 #if COMPILER2_OR_JVMCI
2836       DerivedPointerTable::clear();
2837 #endif
2838 
2839       // Please see comment in g1CollectedHeap.hpp and
2840       // G1CollectedHeap::ref_processing_init() to see how
2841       // reference processing currently works in G1.
2842 
2843       // Enable discovery in the STW reference processor
2844       if (g1_policy()->should_process_references()) {
2845         ref_processor_stw()->enable_discovery();
2846       } else {
2847         ref_processor_stw()->disable_discovery();
2848       }
2849 
2850       {
2851         // We want to temporarily turn off discovery by the
2852         // CM ref processor, if necessary, and turn it back on
2853         // on again later if we do. Using a scoped
2854         // NoRefDiscovery object will do this.
2855         NoRefDiscovery no_cm_discovery(ref_processor_cm());
2856 
2857         // Forget the current alloc region (we might even choose it to be part
2858         // of the collection set!).
2859         _allocator->release_mutator_alloc_region();
2860 
2861         // This timing is only used by the ergonomics to handle our pause target.
2862         // It is unclear why this should not include the full pause. We will
2863         // investigate this in CR 7178365.
2864         //
2865         // Preserving the old comment here if that helps the investigation:
2866         //
2867         // The elapsed time induced by the start time below deliberately elides
2868         // the possible verification above.
2869         double sample_start_time_sec = os::elapsedTime();
2870 
2871         g1_policy()->record_collection_pause_start(sample_start_time_sec);
2872 
2873         if (collector_state()->in_initial_mark_gc()) {
2874           concurrent_mark()->pre_initial_mark();
2875         }
2876 
2877         g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
2878 
2879         evacuation_info.set_collectionset_regions(collection_set()->region_length());
2880 
2881         // Make sure the remembered sets are up to date. This needs to be
2882         // done before register_humongous_regions_with_cset(), because the
2883         // remembered sets are used there to choose eager reclaim candidates.
2884         // If the remembered sets are not up to date we might miss some
2885         // entries that need to be handled.
2886         g1_rem_set()->cleanupHRRS();
2887 
2888         register_humongous_regions_with_cset();
2889 
2890         assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
2891 
2892         // We call this after finalize_cset() to
2893         // ensure that the CSet has been finalized.
2894         _cm->verify_no_cset_oops();
2895 
2896         if (_hr_printer.is_active()) {
2897           G1PrintCollectionSetClosure cl(&_hr_printer);
2898           _collection_set.iterate(&cl);
2899         }
2900 
2901         // Initialize the GC alloc regions.
2902         _allocator->init_gc_alloc_regions(evacuation_info);
2903 
2904         G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
2905         pre_evacuate_collection_set();
2906 
2907         // Actually do the work...
2908         evacuate_collection_set(&per_thread_states);
2909 
2910         post_evacuate_collection_set(evacuation_info, &per_thread_states);
2911 
2912         const size_t* surviving_young_words = per_thread_states.surviving_young_words();
2913         free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
2914 
2915         eagerly_reclaim_humongous_regions();
2916 
2917         record_obj_copy_mem_stats();
2918         _survivor_evac_stats.adjust_desired_plab_sz();
2919         _old_evac_stats.adjust_desired_plab_sz();
2920 
2921         double start = os::elapsedTime();
2922         start_new_collection_set();
2923         g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
2924 
2925         if (evacuation_failed()) {
2926           set_used(recalculate_used());
2927           if (_archive_allocator != NULL) {
2928             _archive_allocator->clear_used();
2929           }
2930           for (uint i = 0; i < ParallelGCThreads; i++) {
2931             if (_evacuation_failed_info_array[i].has_failed()) {
2932               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
2933             }
2934           }
2935         } else {
2936           // The "used" of the the collection set have already been subtracted
2937           // when they were freed.  Add in the bytes evacuated.
2938           increase_used(g1_policy()->bytes_copied_during_gc());
2939         }
2940 
2941         if (collector_state()->in_initial_mark_gc()) {
2942           // We have to do this before we notify the CM threads that
2943           // they can start working to make sure that all the
2944           // appropriate initialization is done on the CM object.
2945           concurrent_mark()->post_initial_mark();
2946           // Note that we don't actually trigger the CM thread at
2947           // this point. We do that later when we're sure that
2948           // the current thread has completed its logging output.
2949         }
2950 
2951         allocate_dummy_regions();
2952 
2953         _allocator->init_mutator_alloc_region();
2954 
2955         {
2956           size_t expand_bytes = _heap_sizing_policy->expansion_amount();
2957           if (expand_bytes > 0) {
2958             size_t bytes_before = capacity();
2959             // No need for an ergo logging here,
2960             // expansion_amount() does this when it returns a value > 0.
2961             double expand_ms;
2962             if (!expand(expand_bytes, _workers, &expand_ms)) {
2963               // We failed to expand the heap. Cannot do anything about it.
2964             }
2965             g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
2966           }
2967         }
2968 
2969         // We redo the verification but now wrt to the new CSet which
2970         // has just got initialized after the previous CSet was freed.
2971         _cm->verify_no_cset_oops();
2972 
2973         // This timing is only used by the ergonomics to handle our pause target.
2974         // It is unclear why this should not include the full pause. We will
2975         // investigate this in CR 7178365.
2976         double sample_end_time_sec = os::elapsedTime();
2977         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
2978         size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
2979         g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
2980 
2981         evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
2982         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
2983 
2984         if (VerifyRememberedSets) {
2985           log_info(gc, verify)("[Verifying RemSets after GC]");
2986           VerifyRegionRemSetClosure v_cl;
2987           heap_region_iterate(&v_cl);
2988         }
2989 
2990         _verifier->verify_after_gc(verify_type);
2991         _verifier->check_bitmaps("GC End");
2992 
2993         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
2994         ref_processor_stw()->verify_no_references_recorded();
2995 
2996         // CM reference discovery will be re-enabled if necessary.
2997       }
2998 
2999 #ifdef TRACESPINNING
3000       ParallelTaskTerminator::print_termination_counts();
3001 #endif
3002 
3003       gc_epilogue(false);
3004     }
3005 
3006     // Print the remainder of the GC log output.
3007     if (evacuation_failed()) {
3008       log_info(gc)("To-space exhausted");
3009     }
3010 
3011     g1_policy()->print_phases();
3012     heap_transition.print();
3013 
3014     // It is not yet to safe to tell the concurrent mark to
3015     // start as we have some optional output below. We don't want the
3016     // output from the concurrent mark thread interfering with this
3017     // logging output either.
3018 
3019     _hrm.verify_optional();
3020     _verifier->verify_region_sets_optional();
3021 
3022     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3023     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3024 
3025     print_heap_after_gc();
3026     print_heap_regions();
3027     trace_heap_after_gc(_gc_tracer_stw);
3028 
3029     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3030     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3031     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3032     // before any GC notifications are raised.
3033     g1mm()->update_sizes();
3034 
3035     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3036     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3037     _gc_timer_stw->register_gc_end();
3038     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3039   }
3040   // It should now be safe to tell the concurrent mark thread to start
3041   // without its logging output interfering with the logging output
3042   // that came from the pause.
3043 
3044   if (should_start_conc_mark) {
3045     // CAUTION: after the doConcurrentMark() call below,
3046     // the concurrent marking thread(s) could be running
3047     // concurrently with us. Make sure that anything after
3048     // this point does not assume that we are the only GC thread
3049     // running. Note: of course, the actual marking work will
3050     // not start until the safepoint itself is released in
3051     // SuspendibleThreadSet::desynchronize().
3052     do_concurrent_mark();
3053   }
3054 
3055   return true;
3056 }
3057 
3058 void G1CollectedHeap::remove_self_forwarding_pointers() {
3059   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3060   workers()->run_task(&rsfp_task);
3061 }
3062 
3063 void G1CollectedHeap::restore_after_evac_failure() {
3064   double remove_self_forwards_start = os::elapsedTime();
3065 
3066   remove_self_forwarding_pointers();
3067   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3068   _preserved_marks_set.restore(&task_executor);
3069 
3070   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3071 }
3072 
3073 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3074   if (!_evacuation_failed) {
3075     _evacuation_failed = true;
3076   }
3077 
3078   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3079   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3080 }
3081 
3082 bool G1ParEvacuateFollowersClosure::offer_termination() {
3083   G1ParScanThreadState* const pss = par_scan_state();
3084   start_term_time();
3085   const bool res = terminator()->offer_termination();
3086   end_term_time();
3087   return res;
3088 }
3089 
3090 void G1ParEvacuateFollowersClosure::do_void() {
3091   G1ParScanThreadState* const pss = par_scan_state();
3092   pss->trim_queue();
3093   do {
3094     pss->steal_and_trim_queue(queues());
3095   } while (!offer_termination());
3096 }
3097 
3098 class G1ParTask : public AbstractGangTask {
3099 protected:
3100   G1CollectedHeap*         _g1h;
3101   G1ParScanThreadStateSet* _pss;
3102   RefToScanQueueSet*       _queues;
3103   G1RootProcessor*         _root_processor;
3104   ParallelTaskTerminator   _terminator;
3105   uint                     _n_workers;
3106 
3107 public:
3108   G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3109     : AbstractGangTask("G1 collection"),
3110       _g1h(g1h),
3111       _pss(per_thread_states),
3112       _queues(task_queues),
3113       _root_processor(root_processor),
3114       _terminator(n_workers, _queues),
3115       _n_workers(n_workers)
3116   {}
3117 
3118   void work(uint worker_id) {
3119     if (worker_id >= _n_workers) return;  // no work needed this round
3120 
3121     double start_sec = os::elapsedTime();
3122     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3123 
3124     {
3125       ResourceMark rm;
3126       HandleMark   hm;
3127 
3128       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
3129 
3130       G1ParScanThreadState*           pss = _pss->state_for_worker(worker_id);
3131       pss->set_ref_processor(rp);
3132 
3133       double start_strong_roots_sec = os::elapsedTime();
3134 
3135       _root_processor->evacuate_roots(pss->closures(), worker_id);
3136 
3137       // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3138       // treating the nmethods visited to act as roots for concurrent marking.
3139       // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3140       // objects copied by the current evacuation.
3141       _g1h->g1_rem_set()->oops_into_collection_set_do(pss,
3142                                                       pss->closures()->weak_codeblobs(),
3143                                                       worker_id);
3144 
3145       double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3146 
3147       double term_sec = 0.0;
3148       size_t evac_term_attempts = 0;
3149       {
3150         double start = os::elapsedTime();
3151         G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3152         evac.do_void();
3153 
3154         evac_term_attempts = evac.term_attempts();
3155         term_sec = evac.term_time();
3156         double elapsed_sec = os::elapsedTime() - start;
3157         _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3158         _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3159         _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3160       }
3161 
3162       assert(pss->queue_is_empty(), "should be empty");
3163 
3164       if (log_is_enabled(Debug, gc, task, stats)) {
3165         MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3166         size_t lab_waste;
3167         size_t lab_undo_waste;
3168         pss->waste(lab_waste, lab_undo_waste);
3169         _g1h->print_termination_stats(worker_id,
3170                                       (os::elapsedTime() - start_sec) * 1000.0,   /* elapsed time */
3171                                       strong_roots_sec * 1000.0,                  /* strong roots time */
3172                                       term_sec * 1000.0,                          /* evac term time */
3173                                       evac_term_attempts,                         /* evac term attempts */
3174                                       lab_waste,                                  /* alloc buffer waste */
3175                                       lab_undo_waste                              /* undo waste */
3176                                       );
3177       }
3178 
3179       // Close the inner scope so that the ResourceMark and HandleMark
3180       // destructors are executed here and are included as part of the
3181       // "GC Worker Time".
3182     }
3183     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3184   }
3185 };
3186 
3187 void G1CollectedHeap::print_termination_stats_hdr() {
3188   log_debug(gc, task, stats)("GC Termination Stats");
3189   log_debug(gc, task, stats)("     elapsed  --strong roots-- -------termination------- ------waste (KiB)------");
3190   log_debug(gc, task, stats)("thr     ms        ms      %%        ms      %%    attempts  total   alloc    undo");
3191   log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3192 }
3193 
3194 void G1CollectedHeap::print_termination_stats(uint worker_id,
3195                                               double elapsed_ms,
3196                                               double strong_roots_ms,
3197                                               double term_ms,
3198                                               size_t term_attempts,
3199                                               size_t alloc_buffer_waste,
3200                                               size_t undo_waste) const {
3201   log_debug(gc, task, stats)
3202               ("%3d %9.2f %9.2f %6.2f "
3203                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3204                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3205                worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3206                term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3207                (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3208                alloc_buffer_waste * HeapWordSize / K,
3209                undo_waste * HeapWordSize / K);
3210 }
3211 
3212 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3213 private:
3214   BoolObjectClosure* _is_alive;
3215   G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3216 
3217   int _initial_string_table_size;
3218   int _initial_symbol_table_size;
3219 
3220   bool  _process_strings;
3221   int _strings_processed;
3222   int _strings_removed;
3223 
3224   bool  _process_symbols;
3225   int _symbols_processed;
3226   int _symbols_removed;
3227 
3228   bool _process_string_dedup;
3229 
3230 public:
3231   G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3232     AbstractGangTask("String/Symbol Unlinking"),
3233     _is_alive(is_alive),
3234     _dedup_closure(is_alive, NULL, false),
3235     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3236     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3237     _process_string_dedup(process_string_dedup) {
3238 
3239     _initial_string_table_size = StringTable::the_table()->table_size();
3240     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3241     if (process_strings) {
3242       StringTable::clear_parallel_claimed_index();
3243     }
3244     if (process_symbols) {
3245       SymbolTable::clear_parallel_claimed_index();
3246     }
3247   }
3248 
3249   ~G1StringAndSymbolCleaningTask() {
3250     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3251               "claim value %d after unlink less than initial string table size %d",
3252               StringTable::parallel_claimed_index(), _initial_string_table_size);
3253     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3254               "claim value %d after unlink less than initial symbol table size %d",
3255               SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3256 
3257     log_info(gc, stringtable)(
3258         "Cleaned string and symbol table, "
3259         "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3260         "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3261         strings_processed(), strings_removed(),
3262         symbols_processed(), symbols_removed());
3263   }
3264 
3265   void work(uint worker_id) {
3266     int strings_processed = 0;
3267     int strings_removed = 0;
3268     int symbols_processed = 0;
3269     int symbols_removed = 0;
3270     if (_process_strings) {
3271       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3272       Atomic::add(strings_processed, &_strings_processed);
3273       Atomic::add(strings_removed, &_strings_removed);
3274     }
3275     if (_process_symbols) {
3276       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3277       Atomic::add(symbols_processed, &_symbols_processed);
3278       Atomic::add(symbols_removed, &_symbols_removed);
3279     }
3280     if (_process_string_dedup) {
3281       G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3282     }
3283   }
3284 
3285   size_t strings_processed() const { return (size_t)_strings_processed; }
3286   size_t strings_removed()   const { return (size_t)_strings_removed; }
3287 
3288   size_t symbols_processed() const { return (size_t)_symbols_processed; }
3289   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
3290 };
3291 
3292 class G1CodeCacheUnloadingTask {
3293 private:
3294   static Monitor* _lock;
3295 
3296   BoolObjectClosure* const _is_alive;
3297   const bool               _unloading_occurred;
3298   const uint               _num_workers;
3299 
3300   // Variables used to claim nmethods.
3301   CompiledMethod* _first_nmethod;
3302   CompiledMethod* volatile _claimed_nmethod;
3303 
3304   // The list of nmethods that need to be processed by the second pass.
3305   CompiledMethod* volatile _postponed_list;
3306   volatile uint            _num_entered_barrier;
3307 
3308  public:
3309   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3310       _is_alive(is_alive),
3311       _unloading_occurred(unloading_occurred),
3312       _num_workers(num_workers),
3313       _first_nmethod(NULL),
3314       _claimed_nmethod(NULL),
3315       _postponed_list(NULL),
3316       _num_entered_barrier(0)
3317   {
3318     CompiledMethod::increase_unloading_clock();
3319     // Get first alive nmethod
3320     CompiledMethodIterator iter = CompiledMethodIterator();
3321     if(iter.next_alive()) {
3322       _first_nmethod = iter.method();
3323     }
3324     _claimed_nmethod = _first_nmethod;
3325   }
3326 
3327   ~G1CodeCacheUnloadingTask() {
3328     CodeCache::verify_clean_inline_caches();
3329 
3330     CodeCache::set_needs_cache_clean(false);
3331     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3332 
3333     CodeCache::verify_icholder_relocations();
3334   }
3335 
3336  private:
3337   void add_to_postponed_list(CompiledMethod* nm) {
3338       CompiledMethod* old;
3339       do {
3340         old = _postponed_list;
3341         nm->set_unloading_next(old);
3342       } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
3343   }
3344 
3345   void clean_nmethod(CompiledMethod* nm) {
3346     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3347 
3348     if (postponed) {
3349       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3350       add_to_postponed_list(nm);
3351     }
3352 
3353     // Mark that this thread has been cleaned/unloaded.
3354     // After this call, it will be safe to ask if this nmethod was unloaded or not.
3355     nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3356   }
3357 
3358   void clean_nmethod_postponed(CompiledMethod* nm) {
3359     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3360   }
3361 
3362   static const int MaxClaimNmethods = 16;
3363 
3364   void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3365     CompiledMethod* first;
3366     CompiledMethodIterator last;
3367 
3368     do {
3369       *num_claimed_nmethods = 0;
3370 
3371       first = _claimed_nmethod;
3372       last = CompiledMethodIterator(first);
3373 
3374       if (first != NULL) {
3375 
3376         for (int i = 0; i < MaxClaimNmethods; i++) {
3377           if (!last.next_alive()) {
3378             break;
3379           }
3380           claimed_nmethods[i] = last.method();
3381           (*num_claimed_nmethods)++;
3382         }
3383       }
3384 
3385     } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
3386   }
3387 
3388   CompiledMethod* claim_postponed_nmethod() {
3389     CompiledMethod* claim;
3390     CompiledMethod* next;
3391 
3392     do {
3393       claim = _postponed_list;
3394       if (claim == NULL) {
3395         return NULL;
3396       }
3397 
3398       next = claim->unloading_next();
3399 
3400     } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
3401 
3402     return claim;
3403   }
3404 
3405  public:
3406   // Mark that we're done with the first pass of nmethod cleaning.
3407   void barrier_mark(uint worker_id) {
3408     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3409     _num_entered_barrier++;
3410     if (_num_entered_barrier == _num_workers) {
3411       ml.notify_all();
3412     }
3413   }
3414 
3415   // See if we have to wait for the other workers to
3416   // finish their first-pass nmethod cleaning work.
3417   void barrier_wait(uint worker_id) {
3418     if (_num_entered_barrier < _num_workers) {
3419       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3420       while (_num_entered_barrier < _num_workers) {
3421           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3422       }
3423     }
3424   }
3425 
3426   // Cleaning and unloading of nmethods. Some work has to be postponed
3427   // to the second pass, when we know which nmethods survive.
3428   void work_first_pass(uint worker_id) {
3429     // The first nmethods is claimed by the first worker.
3430     if (worker_id == 0 && _first_nmethod != NULL) {
3431       clean_nmethod(_first_nmethod);
3432       _first_nmethod = NULL;
3433     }
3434 
3435     int num_claimed_nmethods;
3436     CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3437 
3438     while (true) {
3439       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3440 
3441       if (num_claimed_nmethods == 0) {
3442         break;
3443       }
3444 
3445       for (int i = 0; i < num_claimed_nmethods; i++) {
3446         clean_nmethod(claimed_nmethods[i]);
3447       }
3448     }
3449   }
3450 
3451   void work_second_pass(uint worker_id) {
3452     CompiledMethod* nm;
3453     // Take care of postponed nmethods.
3454     while ((nm = claim_postponed_nmethod()) != NULL) {
3455       clean_nmethod_postponed(nm);
3456     }
3457   }
3458 };
3459 
3460 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3461 
3462 class G1KlassCleaningTask : public StackObj {
3463   BoolObjectClosure*                      _is_alive;
3464   volatile int                            _clean_klass_tree_claimed;
3465   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3466 
3467  public:
3468   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3469       _is_alive(is_alive),
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(_is_alive);
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(_is_alive);
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   BoolObjectClosure* _is_alive;
3517   volatile int       _resolved_method_task_claimed;
3518 public:
3519   G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) :
3520       _is_alive(is_alive), _resolved_method_task_claimed(0) {}
3521 
3522   bool claim_resolved_method_task() {
3523     if (_resolved_method_task_claimed) {
3524       return false;
3525     }
3526     return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0;
3527   }
3528 
3529   // These aren't big, one thread can do it all.
3530   void work() {
3531     if (claim_resolved_method_task()) {
3532       ResolvedMethodTable::unlink(_is_alive);
3533     }
3534   }
3535 };
3536 
3537 
3538 // To minimize the remark pause times, the tasks below are done in parallel.
3539 class G1ParallelCleaningTask : public AbstractGangTask {
3540 private:
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(is_alive),
3553       _resolved_method_cleaning_task(is_alive) {
3554   }
3555 
3556   // The parallel work done by all worker threads.
3557   void work(uint worker_id) {
3558     // Do first pass of code cache cleaning.
3559     _code_cache_task.work_first_pass(worker_id);
3560 
3561     // Let the threads mark that the first pass is done.
3562     _code_cache_task.barrier_mark(worker_id);
3563 
3564     // Clean the Strings and Symbols.
3565     _string_symbol_task.work(worker_id);
3566 
3567     // Clean unreferenced things in the ResolvedMethodTable
3568     _resolved_method_cleaning_task.work();
3569 
3570     // Wait for all workers to finish the first code cache cleaning pass.
3571     _code_cache_task.barrier_wait(worker_id);
3572 
3573     // Do the second code cache cleaning work, which realize on
3574     // the liveness information gathered during the first pass.
3575     _code_cache_task.work_second_pass(worker_id);
3576 
3577     // Clean all klasses that were not unloaded.
3578     _klass_cleaning_task.work();
3579   }
3580 };
3581 
3582 
3583 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3584                                         bool class_unloading_occurred) {
3585   uint n_workers = workers()->active_workers();
3586 
3587   G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3588   workers()->run_task(&g1_unlink_task);
3589 }
3590 
3591 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3592                                        bool process_strings,
3593                                        bool process_symbols,
3594                                        bool process_string_dedup) {
3595   if (!process_strings && !process_symbols && !process_string_dedup) {
3596     // Nothing to clean.
3597     return;
3598   }
3599 
3600   G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3601   workers()->run_task(&g1_unlink_task);
3602 
3603 }
3604 
3605 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3606  private:
3607   DirtyCardQueueSet* _queue;
3608   G1CollectedHeap* _g1h;
3609  public:
3610   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3611     _queue(queue), _g1h(g1h) { }
3612 
3613   virtual void work(uint worker_id) {
3614     G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3615     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3616 
3617     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3618     _queue->par_apply_closure_to_all_completed_buffers(&cl);
3619 
3620     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3621   }
3622 };
3623 
3624 void G1CollectedHeap::redirty_logged_cards() {
3625   double redirty_logged_cards_start = os::elapsedTime();
3626 
3627   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3628   dirty_card_queue_set().reset_for_par_iteration();
3629   workers()->run_task(&redirty_task);
3630 
3631   DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set();
3632   dcq.merge_bufferlists(&dirty_card_queue_set());
3633   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3634 
3635   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3636 }
3637 
3638 // Weak Reference Processing support
3639 
3640 // An always "is_alive" closure that is used to preserve referents.
3641 // If the object is non-null then it's alive.  Used in the preservation
3642 // of referent objects that are pointed to by reference objects
3643 // discovered by the CM ref processor.
3644 class G1AlwaysAliveClosure: public BoolObjectClosure {
3645   G1CollectedHeap* _g1;
3646 public:
3647   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3648   bool do_object_b(oop p) {
3649     if (p != NULL) {
3650       return true;
3651     }
3652     return false;
3653   }
3654 };
3655 
3656 bool G1STWIsAliveClosure::do_object_b(oop p) {
3657   // An object is reachable if it is outside the collection set,
3658   // or is inside and copied.
3659   return !_g1->is_in_cset(p) || p->is_forwarded();
3660 }
3661 
3662 // Non Copying Keep Alive closure
3663 class G1KeepAliveClosure: public OopClosure {
3664   G1CollectedHeap* _g1;
3665 public:
3666   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3667   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3668   void do_oop(oop* p) {
3669     oop obj = *p;
3670     assert(obj != NULL, "the caller should have filtered out NULL values");
3671 
3672     const InCSetState cset_state = _g1->in_cset_state(obj);
3673     if (!cset_state.is_in_cset_or_humongous()) {
3674       return;
3675     }
3676     if (cset_state.is_in_cset()) {
3677       assert( obj->is_forwarded(), "invariant" );
3678       *p = obj->forwardee();
3679     } else {
3680       assert(!obj->is_forwarded(), "invariant" );
3681       assert(cset_state.is_humongous(),
3682              "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3683       _g1->set_humongous_is_live(obj);
3684     }
3685   }
3686 };
3687 
3688 // Copying Keep Alive closure - can be called from both
3689 // serial and parallel code as long as different worker
3690 // threads utilize different G1ParScanThreadState instances
3691 // and different queues.
3692 
3693 class G1CopyingKeepAliveClosure: public OopClosure {
3694   G1CollectedHeap*         _g1h;
3695   OopClosure*              _copy_non_heap_obj_cl;
3696   G1ParScanThreadState*    _par_scan_state;
3697 
3698 public:
3699   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3700                             OopClosure* non_heap_obj_cl,
3701                             G1ParScanThreadState* pss):
3702     _g1h(g1h),
3703     _copy_non_heap_obj_cl(non_heap_obj_cl),
3704     _par_scan_state(pss)
3705   {}
3706 
3707   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3708   virtual void do_oop(      oop* p) { do_oop_work(p); }
3709 
3710   template <class T> void do_oop_work(T* p) {
3711     oop obj = RawAccess<>::oop_load(p);
3712 
3713     if (_g1h->is_in_cset_or_humongous(obj)) {
3714       // If the referent object has been forwarded (either copied
3715       // to a new location or to itself in the event of an
3716       // evacuation failure) then we need to update the reference
3717       // field and, if both reference and referent are in the G1
3718       // heap, update the RSet for the referent.
3719       //
3720       // If the referent has not been forwarded then we have to keep
3721       // it alive by policy. Therefore we have copy the referent.
3722       //
3723       // If the reference field is in the G1 heap then we can push
3724       // on the PSS queue. When the queue is drained (after each
3725       // phase of reference processing) the object and it's followers
3726       // will be copied, the reference field set to point to the
3727       // new location, and the RSet updated. Otherwise we need to
3728       // use the the non-heap or metadata closures directly to copy
3729       // the referent object and update the pointer, while avoiding
3730       // updating the RSet.
3731 
3732       if (_g1h->is_in_g1_reserved(p)) {
3733         _par_scan_state->push_on_queue(p);
3734       } else {
3735         assert(!Metaspace::contains((const void*)p),
3736                "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3737         _copy_non_heap_obj_cl->do_oop(p);
3738       }
3739     }
3740   }
3741 };
3742 
3743 // Serial drain queue closure. Called as the 'complete_gc'
3744 // closure for each discovered list in some of the
3745 // reference processing phases.
3746 
3747 class G1STWDrainQueueClosure: public VoidClosure {
3748 protected:
3749   G1CollectedHeap* _g1h;
3750   G1ParScanThreadState* _par_scan_state;
3751 
3752   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3753 
3754 public:
3755   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3756     _g1h(g1h),
3757     _par_scan_state(pss)
3758   { }
3759 
3760   void do_void() {
3761     G1ParScanThreadState* const pss = par_scan_state();
3762     pss->trim_queue();
3763   }
3764 };
3765 
3766 // Parallel Reference Processing closures
3767 
3768 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3769 // processing during G1 evacuation pauses.
3770 
3771 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3772 private:
3773   G1CollectedHeap*          _g1h;
3774   G1ParScanThreadStateSet*  _pss;
3775   RefToScanQueueSet*        _queues;
3776   WorkGang*                 _workers;
3777   uint                      _active_workers;
3778 
3779 public:
3780   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3781                            G1ParScanThreadStateSet* per_thread_states,
3782                            WorkGang* workers,
3783                            RefToScanQueueSet *task_queues,
3784                            uint n_workers) :
3785     _g1h(g1h),
3786     _pss(per_thread_states),
3787     _queues(task_queues),
3788     _workers(workers),
3789     _active_workers(n_workers)
3790   {
3791     g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
3792   }
3793 
3794   // Executes the given task using concurrent marking worker threads.
3795   virtual void execute(ProcessTask& task);
3796   virtual void execute(EnqueueTask& task);
3797 };
3798 
3799 // Gang task for possibly parallel reference processing
3800 
3801 class G1STWRefProcTaskProxy: public AbstractGangTask {
3802   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3803   ProcessTask&     _proc_task;
3804   G1CollectedHeap* _g1h;
3805   G1ParScanThreadStateSet* _pss;
3806   RefToScanQueueSet* _task_queues;
3807   ParallelTaskTerminator* _terminator;
3808 
3809 public:
3810   G1STWRefProcTaskProxy(ProcessTask& proc_task,
3811                         G1CollectedHeap* g1h,
3812                         G1ParScanThreadStateSet* per_thread_states,
3813                         RefToScanQueueSet *task_queues,
3814                         ParallelTaskTerminator* terminator) :
3815     AbstractGangTask("Process reference objects in parallel"),
3816     _proc_task(proc_task),
3817     _g1h(g1h),
3818     _pss(per_thread_states),
3819     _task_queues(task_queues),
3820     _terminator(terminator)
3821   {}
3822 
3823   virtual void work(uint worker_id) {
3824     // The reference processing task executed by a single worker.
3825     ResourceMark rm;
3826     HandleMark   hm;
3827 
3828     G1STWIsAliveClosure is_alive(_g1h);
3829 
3830     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
3831     pss->set_ref_processor(NULL);
3832 
3833     // Keep alive closure.
3834     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
3835 
3836     // Complete GC closure
3837     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
3838 
3839     // Call the reference processing task's work routine.
3840     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3841 
3842     // Note we cannot assert that the refs array is empty here as not all
3843     // of the processing tasks (specifically phase2 - pp2_work) execute
3844     // the complete_gc closure (which ordinarily would drain the queue) so
3845     // the queue may not be empty.
3846   }
3847 };
3848 
3849 // Driver routine for parallel reference processing.
3850 // Creates an instance of the ref processing gang
3851 // task and has the worker threads execute it.
3852 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
3853   assert(_workers != NULL, "Need parallel worker threads.");
3854 
3855   ParallelTaskTerminator terminator(_active_workers, _queues);
3856   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
3857 
3858   _workers->run_task(&proc_task_proxy);
3859 }
3860 
3861 // Gang task for parallel reference enqueueing.
3862 
3863 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
3864   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
3865   EnqueueTask& _enq_task;
3866 
3867 public:
3868   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
3869     AbstractGangTask("Enqueue reference objects in parallel"),
3870     _enq_task(enq_task)
3871   { }
3872 
3873   virtual void work(uint worker_id) {
3874     _enq_task.work(worker_id);
3875   }
3876 };
3877 
3878 // Driver routine for parallel reference enqueueing.
3879 // Creates an instance of the ref enqueueing gang
3880 // task and has the worker threads execute it.
3881 
3882 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
3883   assert(_workers != NULL, "Need parallel worker threads.");
3884 
3885   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
3886 
3887   _workers->run_task(&enq_task_proxy);
3888 }
3889 
3890 // End of weak reference support closures
3891 
3892 // Abstract task used to preserve (i.e. copy) any referent objects
3893 // that are in the collection set and are pointed to by reference
3894 // objects discovered by the CM ref processor.
3895 
3896 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
3897 protected:
3898   G1CollectedHeap*         _g1h;
3899   G1ParScanThreadStateSet* _pss;
3900   RefToScanQueueSet*       _queues;
3901   ParallelTaskTerminator   _terminator;
3902   uint                     _n_workers;
3903 
3904 public:
3905   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
3906     AbstractGangTask("ParPreserveCMReferents"),
3907     _g1h(g1h),
3908     _pss(per_thread_states),
3909     _queues(task_queues),
3910     _terminator(workers, _queues),
3911     _n_workers(workers)
3912   {
3913     g1h->ref_processor_cm()->set_active_mt_degree(workers);
3914   }
3915 
3916   void work(uint worker_id) {
3917     G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
3918 
3919     ResourceMark rm;
3920     HandleMark   hm;
3921 
3922     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
3923     pss->set_ref_processor(NULL);
3924     assert(pss->queue_is_empty(), "both queue and overflow should be empty");
3925 
3926     // Is alive closure
3927     G1AlwaysAliveClosure always_alive(_g1h);
3928 
3929     // Copying keep alive closure. Applied to referent objects that need
3930     // to be copied.
3931     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
3932 
3933     ReferenceProcessor* rp = _g1h->ref_processor_cm();
3934 
3935     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
3936     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
3937 
3938     // limit is set using max_num_q() - which was set using ParallelGCThreads.
3939     // So this must be true - but assert just in case someone decides to
3940     // change the worker ids.
3941     assert(worker_id < limit, "sanity");
3942     assert(!rp->discovery_is_atomic(), "check this code");
3943 
3944     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
3945     for (uint idx = worker_id; idx < limit; idx += stride) {
3946       DiscoveredList& ref_list = rp->discovered_refs()[idx];
3947 
3948       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
3949       while (iter.has_next()) {
3950         // Since discovery is not atomic for the CM ref processor, we
3951         // can see some null referent objects.
3952         iter.load_ptrs(DEBUG_ONLY(true));
3953         oop ref = iter.obj();
3954 
3955         // This will filter nulls.
3956         if (iter.is_referent_alive()) {
3957           iter.make_referent_alive();
3958         }
3959         iter.move_to_next();
3960       }
3961     }
3962 
3963     // Drain the queue - which may cause stealing
3964     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
3965     drain_queue.do_void();
3966     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
3967     assert(pss->queue_is_empty(), "should be");
3968   }
3969 };
3970 
3971 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
3972   // Any reference objects, in the collection set, that were 'discovered'
3973   // by the CM ref processor should have already been copied (either by
3974   // applying the external root copy closure to the discovered lists, or
3975   // by following an RSet entry).
3976   //
3977   // But some of the referents, that are in the collection set, that these
3978   // reference objects point to may not have been copied: the STW ref
3979   // processor would have seen that the reference object had already
3980   // been 'discovered' and would have skipped discovering the reference,
3981   // but would not have treated the reference object as a regular oop.
3982   // As a result the copy closure would not have been applied to the
3983   // referent object.
3984   //
3985   // We need to explicitly copy these referent objects - the references
3986   // will be processed at the end of remarking.
3987   //
3988   // We also need to do this copying before we process the reference
3989   // objects discovered by the STW ref processor in case one of these
3990   // referents points to another object which is also referenced by an
3991   // object discovered by the STW ref processor.
3992   double preserve_cm_referents_time = 0.0;
3993 
3994   // To avoid spawning task when there is no work to do, check that
3995   // a concurrent cycle is active and that some references have been
3996   // discovered.
3997   if (concurrent_mark()->cm_thread()->during_cycle() &&
3998       ref_processor_cm()->has_discovered_references()) {
3999     double preserve_cm_referents_start = os::elapsedTime();
4000     uint no_of_gc_workers = workers()->active_workers();
4001     G1ParPreserveCMReferentsTask keep_cm_referents(this,
4002                                                    per_thread_states,
4003                                                    no_of_gc_workers,
4004                                                    _task_queues);
4005     workers()->run_task(&keep_cm_referents);
4006     preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4007   }
4008 
4009   g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4010 }
4011 
4012 // Weak Reference processing during an evacuation pause (part 1).
4013 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4014   double ref_proc_start = os::elapsedTime();
4015 
4016   ReferenceProcessor* rp = _ref_processor_stw;
4017   assert(rp->discovery_enabled(), "should have been enabled");
4018 
4019   // Closure to test whether a referent is alive.
4020   G1STWIsAliveClosure is_alive(this);
4021 
4022   // Even when parallel reference processing is enabled, the processing
4023   // of JNI refs is serial and performed serially by the current thread
4024   // rather than by a worker. The following PSS will be used for processing
4025   // JNI refs.
4026 
4027   // Use only a single queue for this PSS.
4028   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
4029   pss->set_ref_processor(NULL);
4030   assert(pss->queue_is_empty(), "pre-condition");
4031 
4032   // Keep alive closure.
4033   G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4034 
4035   // Serial Complete GC closure
4036   G1STWDrainQueueClosure drain_queue(this, pss);
4037 
4038   // Setup the soft refs policy...
4039   rp->setup_policy(false);
4040 
4041   ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4042 
4043   ReferenceProcessorStats stats;
4044   if (!rp->processing_is_mt()) {
4045     // Serial reference processing...
4046     stats = rp->process_discovered_references(&is_alive,
4047                                               &keep_alive,
4048                                               &drain_queue,
4049                                               NULL,
4050                                               pt);
4051   } else {
4052     uint no_of_gc_workers = workers()->active_workers();
4053 
4054     // Parallel reference processing
4055     assert(no_of_gc_workers <= rp->max_num_q(),
4056            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4057            no_of_gc_workers,  rp->max_num_q());
4058 
4059     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4060     stats = rp->process_discovered_references(&is_alive,
4061                                               &keep_alive,
4062                                               &drain_queue,
4063                                               &par_task_executor,
4064                                               pt);
4065   }
4066 
4067   _gc_tracer_stw->report_gc_reference_stats(stats);
4068 
4069   // We have completed copying any necessary live referent objects.
4070   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4071 
4072   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4073   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4074 }
4075 
4076 // Weak Reference processing during an evacuation pause (part 2).
4077 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4078   double ref_enq_start = os::elapsedTime();
4079 
4080   ReferenceProcessor* rp = _ref_processor_stw;
4081   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4082 
4083   ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4084 
4085   // Now enqueue any remaining on the discovered lists on to
4086   // the pending list.
4087   if (!rp->processing_is_mt()) {
4088     // Serial reference processing...
4089     rp->enqueue_discovered_references(NULL, pt);
4090   } else {
4091     // Parallel reference enqueueing
4092 
4093     uint n_workers = workers()->active_workers();
4094 
4095     assert(n_workers <= rp->max_num_q(),
4096            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4097            n_workers,  rp->max_num_q());
4098 
4099     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4100     rp->enqueue_discovered_references(&par_task_executor, pt);
4101   }
4102 
4103   rp->verify_no_references_recorded();
4104   assert(!rp->discovery_enabled(), "should have been disabled");
4105 
4106   // If during an initial mark pause we install a pending list head which is not otherwise reachable
4107   // ensure that it is marked in the bitmap for concurrent marking to discover.
4108   if (collector_state()->in_initial_mark_gc()) {
4109     oop pll_head = Universe::reference_pending_list();
4110     if (pll_head != NULL) {
4111       // Any valid worker id is fine here as we are in the VM thread and single-threaded.
4112       _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head);
4113     }
4114   }
4115 
4116   // FIXME
4117   // CM's reference processing also cleans up the string and symbol tables.
4118   // Should we do that here also? We could, but it is a serial operation
4119   // and could significantly increase the pause time.
4120 
4121   double ref_enq_time = os::elapsedTime() - ref_enq_start;
4122   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4123 }
4124 
4125 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4126   double merge_pss_time_start = os::elapsedTime();
4127   per_thread_states->flush();
4128   g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4129 }
4130 
4131 void G1CollectedHeap::pre_evacuate_collection_set() {
4132   _expand_heap_after_alloc_failure = true;
4133   _evacuation_failed = false;
4134 
4135   // Disable the hot card cache.
4136   _hot_card_cache->reset_hot_cache_claimed_index();
4137   _hot_card_cache->set_use_cache(false);
4138 
4139   g1_rem_set()->prepare_for_oops_into_collection_set_do();
4140   _preserved_marks_set.assert_empty();
4141 
4142   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4143 
4144   // InitialMark needs claim bits to keep track of the marked-through CLDs.
4145   if (collector_state()->in_initial_mark_gc()) {
4146     double start_clear_claimed_marks = os::elapsedTime();
4147 
4148     ClassLoaderDataGraph::clear_claimed_marks();
4149 
4150     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
4151     phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
4152   }
4153 }
4154 
4155 void G1CollectedHeap::evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states) {
4156   // Should G1EvacuationFailureALot be in effect for this GC?
4157   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4158 
4159   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4160 
4161   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4162 
4163   double start_par_time_sec = os::elapsedTime();
4164   double end_par_time_sec;
4165 
4166   {
4167     const uint n_workers = workers()->active_workers();
4168     G1RootProcessor root_processor(this, n_workers);
4169     G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4170 
4171     print_termination_stats_hdr();
4172 
4173     workers()->run_task(&g1_par_task);
4174     end_par_time_sec = os::elapsedTime();
4175 
4176     // Closing the inner scope will execute the destructor
4177     // for the G1RootProcessor object. We record the current
4178     // elapsed time before closing the scope so that time
4179     // taken for the destructor is NOT included in the
4180     // reported parallel time.
4181   }
4182 
4183   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4184   phase_times->record_par_time(par_time_ms);
4185 
4186   double code_root_fixup_time_ms =
4187         (os::elapsedTime() - end_par_time_sec) * 1000.0;
4188   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4189 }
4190 
4191 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4192   // Process any discovered reference objects - we have
4193   // to do this _before_ we retire the GC alloc regions
4194   // as we may have to copy some 'reachable' referent
4195   // objects (and their reachable sub-graphs) that were
4196   // not copied during the pause.
4197   if (g1_policy()->should_process_references()) {
4198     preserve_cm_referents(per_thread_states);
4199     process_discovered_references(per_thread_states);
4200   } else {
4201     ref_processor_stw()->verify_no_references_recorded();
4202   }
4203 
4204   G1STWIsAliveClosure is_alive(this);
4205   G1KeepAliveClosure keep_alive(this);
4206 
4207   {
4208     double start = os::elapsedTime();
4209 
4210     WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
4211 
4212     double time_ms = (os::elapsedTime() - start) * 1000.0;
4213     g1_policy()->phase_times()->record_ref_proc_time(time_ms);
4214   }
4215 
4216   if (G1StringDedup::is_enabled()) {
4217     double fixup_start = os::elapsedTime();
4218 
4219     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4220 
4221     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4222     g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4223   }
4224 
4225   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4226 
4227   if (evacuation_failed()) {
4228     restore_after_evac_failure();
4229 
4230     // Reset the G1EvacuationFailureALot counters and flags
4231     // Note: the values are reset only when an actual
4232     // evacuation failure occurs.
4233     NOT_PRODUCT(reset_evacuation_should_fail();)
4234   }
4235 
4236   _preserved_marks_set.assert_empty();
4237 
4238   // Enqueue any remaining references remaining on the STW
4239   // reference processor's discovered lists. We need to do
4240   // this after the card table is cleaned (and verified) as
4241   // the act of enqueueing entries on to the pending list
4242   // will log these updates (and dirty their associated
4243   // cards). We need these updates logged to update any
4244   // RSets.
4245   if (g1_policy()->should_process_references()) {
4246     enqueue_discovered_references(per_thread_states);
4247   } else {
4248     g1_policy()->phase_times()->record_ref_enq_time(0);
4249   }
4250 
4251   _allocator->release_gc_alloc_regions(evacuation_info);
4252 
4253   merge_per_thread_state_info(per_thread_states);
4254 
4255   // Reset and re-enable the hot card cache.
4256   // Note the counts for the cards in the regions in the
4257   // collection set are reset when the collection set is freed.
4258   _hot_card_cache->reset_hot_cache();
4259   _hot_card_cache->set_use_cache(true);
4260 
4261   purge_code_root_memory();
4262 
4263   redirty_logged_cards();
4264 #if COMPILER2_OR_JVMCI
4265   double start = os::elapsedTime();
4266   DerivedPointerTable::update_pointers();
4267   g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4268 #endif
4269   g1_policy()->print_age_table();
4270 }
4271 
4272 void G1CollectedHeap::record_obj_copy_mem_stats() {
4273   g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4274 
4275   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4276                                                create_g1_evac_summary(&_old_evac_stats));
4277 }
4278 
4279 void G1CollectedHeap::free_region(HeapRegion* hr,
4280                                   FreeRegionList* free_list,
4281                                   bool skip_remset,
4282                                   bool skip_hot_card_cache,
4283                                   bool locked) {
4284   assert(!hr->is_free(), "the region should not be free");
4285   assert(!hr->is_empty(), "the region should not be empty");
4286   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4287   assert(free_list != NULL, "pre-condition");
4288 
4289   if (G1VerifyBitmaps) {
4290     MemRegion mr(hr->bottom(), hr->end());
4291     concurrent_mark()->clear_range_in_prev_bitmap(mr);
4292   }
4293 
4294   // Clear the card counts for this region.
4295   // Note: we only need to do this if the region is not young
4296   // (since we don't refine cards in young regions).
4297   if (!skip_hot_card_cache && !hr->is_young()) {
4298     _hot_card_cache->reset_card_counts(hr);
4299   }
4300   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4301   _g1_policy->remset_tracker()->update_at_free(hr);
4302   free_list->add_ordered(hr);
4303 }
4304 
4305 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4306                                             FreeRegionList* free_list) {
4307   assert(hr->is_humongous(), "this is only for humongous regions");
4308   assert(free_list != NULL, "pre-condition");
4309   hr->clear_humongous();
4310   free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */);
4311 }
4312 
4313 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4314                                            const uint humongous_regions_removed) {
4315   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4316     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4317     _old_set.bulk_remove(old_regions_removed);
4318     _humongous_set.bulk_remove(humongous_regions_removed);
4319   }
4320 
4321 }
4322 
4323 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4324   assert(list != NULL, "list can't be null");
4325   if (!list->is_empty()) {
4326     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4327     _hrm.insert_list_into_free_list(list);
4328   }
4329 }
4330 
4331 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4332   decrease_used(bytes);
4333 }
4334 
4335 class G1FreeCollectionSetTask : public AbstractGangTask {
4336 private:
4337 
4338   // Closure applied to all regions in the collection set to do work that needs to
4339   // be done serially in a single thread.
4340   class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4341   private:
4342     EvacuationInfo* _evacuation_info;
4343     const size_t* _surviving_young_words;
4344 
4345     // Bytes used in successfully evacuated regions before the evacuation.
4346     size_t _before_used_bytes;
4347     // Bytes used in unsucessfully evacuated regions before the evacuation
4348     size_t _after_used_bytes;
4349 
4350     size_t _bytes_allocated_in_old_since_last_gc;
4351 
4352     size_t _failure_used_words;
4353     size_t _failure_waste_words;
4354 
4355     FreeRegionList _local_free_list;
4356   public:
4357     G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4358       HeapRegionClosure(),
4359       _evacuation_info(evacuation_info),
4360       _surviving_young_words(surviving_young_words),
4361       _before_used_bytes(0),
4362       _after_used_bytes(0),
4363       _bytes_allocated_in_old_since_last_gc(0),
4364       _failure_used_words(0),
4365       _failure_waste_words(0),
4366       _local_free_list("Local Region List for CSet Freeing") {
4367     }
4368 
4369     virtual bool do_heap_region(HeapRegion* r) {
4370       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4371 
4372       assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4373       g1h->clear_in_cset(r);
4374 
4375       if (r->is_young()) {
4376         assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4377                "Young index %d is wrong for region %u of type %s with %u young regions",
4378                r->young_index_in_cset(),
4379                r->hrm_index(),
4380                r->get_type_str(),
4381                g1h->collection_set()->young_region_length());
4382         size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4383         r->record_surv_words_in_group(words_survived);
4384       }
4385 
4386       if (!r->evacuation_failed()) {
4387         assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4388         _before_used_bytes += r->used();
4389         g1h->free_region(r,
4390                          &_local_free_list,
4391                          true, /* skip_remset */
4392                          true, /* skip_hot_card_cache */
4393                          true  /* locked */);
4394       } else {
4395         r->uninstall_surv_rate_group();
4396         r->set_young_index_in_cset(-1);
4397         r->set_evacuation_failed(false);
4398         // When moving a young gen region to old gen, we "allocate" that whole region
4399         // there. This is in addition to any already evacuated objects. Notify the
4400         // policy about that.
4401         // Old gen regions do not cause an additional allocation: both the objects
4402         // still in the region and the ones already moved are accounted for elsewhere.
4403         if (r->is_young()) {
4404           _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4405         }
4406         // The region is now considered to be old.
4407         r->set_old();
4408         // Do some allocation statistics accounting. Regions that failed evacuation
4409         // are always made old, so there is no need to update anything in the young
4410         // gen statistics, but we need to update old gen statistics.
4411         size_t used_words = r->marked_bytes() / HeapWordSize;
4412 
4413         _failure_used_words += used_words;
4414         _failure_waste_words += HeapRegion::GrainWords - used_words;
4415 
4416         g1h->old_set_add(r);
4417         _after_used_bytes += r->used();
4418       }
4419       return false;
4420     }
4421 
4422     void complete_work() {
4423       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4424 
4425       _evacuation_info->set_regions_freed(_local_free_list.length());
4426       _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4427 
4428       g1h->prepend_to_freelist(&_local_free_list);
4429       g1h->decrement_summary_bytes(_before_used_bytes);
4430 
4431       G1Policy* policy = g1h->g1_policy();
4432       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4433 
4434       g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4435     }
4436   };
4437 
4438   G1CollectionSet* _collection_set;
4439   G1SerialFreeCollectionSetClosure _cl;
4440   const size_t* _surviving_young_words;
4441 
4442   size_t _rs_lengths;
4443 
4444   volatile jint _serial_work_claim;
4445 
4446   struct WorkItem {
4447     uint region_idx;
4448     bool is_young;
4449     bool evacuation_failed;
4450 
4451     WorkItem(HeapRegion* r) {
4452       region_idx = r->hrm_index();
4453       is_young = r->is_young();
4454       evacuation_failed = r->evacuation_failed();
4455     }
4456   };
4457 
4458   volatile size_t _parallel_work_claim;
4459   size_t _num_work_items;
4460   WorkItem* _work_items;
4461 
4462   void do_serial_work() {
4463     // Need to grab the lock to be allowed to modify the old region list.
4464     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4465     _collection_set->iterate(&_cl);
4466   }
4467 
4468   void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4469     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4470 
4471     HeapRegion* r = g1h->region_at(region_idx);
4472     assert(!g1h->is_on_master_free_list(r), "sanity");
4473 
4474     Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4475 
4476     if (!is_young) {
4477       g1h->_hot_card_cache->reset_card_counts(r);
4478     }
4479 
4480     if (!evacuation_failed) {
4481       r->rem_set()->clear_locked();
4482     }
4483   }
4484 
4485   class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4486   private:
4487     size_t _cur_idx;
4488     WorkItem* _work_items;
4489   public:
4490     G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4491 
4492     virtual bool do_heap_region(HeapRegion* r) {
4493       _work_items[_cur_idx++] = WorkItem(r);
4494       return false;
4495     }
4496   };
4497 
4498   void prepare_work() {
4499     G1PrepareFreeCollectionSetClosure cl(_work_items);
4500     _collection_set->iterate(&cl);
4501   }
4502 
4503   void complete_work() {
4504     _cl.complete_work();
4505 
4506     G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4507     policy->record_max_rs_lengths(_rs_lengths);
4508     policy->cset_regions_freed();
4509   }
4510 public:
4511   G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4512     AbstractGangTask("G1 Free Collection Set"),
4513     _cl(evacuation_info, surviving_young_words),
4514     _collection_set(collection_set),
4515     _surviving_young_words(surviving_young_words),
4516     _serial_work_claim(0),
4517     _rs_lengths(0),
4518     _parallel_work_claim(0),
4519     _num_work_items(collection_set->region_length()),
4520     _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4521     prepare_work();
4522   }
4523 
4524   ~G1FreeCollectionSetTask() {
4525     complete_work();
4526     FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4527   }
4528 
4529   // Chunk size for work distribution. The chosen value has been determined experimentally
4530   // to be a good tradeoff between overhead and achievable parallelism.
4531   static uint chunk_size() { return 32; }
4532 
4533   virtual void work(uint worker_id) {
4534     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4535 
4536     // Claim serial work.
4537     if (_serial_work_claim == 0) {
4538       jint value = Atomic::add(1, &_serial_work_claim) - 1;
4539       if (value == 0) {
4540         double serial_time = os::elapsedTime();
4541         do_serial_work();
4542         timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4543       }
4544     }
4545 
4546     // Start parallel work.
4547     double young_time = 0.0;
4548     bool has_young_time = false;
4549     double non_young_time = 0.0;
4550     bool has_non_young_time = false;
4551 
4552     while (true) {
4553       size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4554       size_t cur = end - chunk_size();
4555 
4556       if (cur >= _num_work_items) {
4557         break;
4558       }
4559 
4560       double start_time = os::elapsedTime();
4561 
4562       end = MIN2(end, _num_work_items);
4563 
4564       for (; cur < end; cur++) {
4565         bool is_young = _work_items[cur].is_young;
4566 
4567         do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4568 
4569         double end_time = os::elapsedTime();
4570         double time_taken = end_time - start_time;
4571         if (is_young) {
4572           young_time += time_taken;
4573           has_young_time = true;
4574         } else {
4575           non_young_time += time_taken;
4576           has_non_young_time = true;
4577         }
4578         start_time = end_time;
4579       }
4580     }
4581 
4582     if (has_young_time) {
4583       timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4584     }
4585     if (has_non_young_time) {
4586       timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, non_young_time);
4587     }
4588   }
4589 };
4590 
4591 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4592   _eden.clear();
4593 
4594   double free_cset_start_time = os::elapsedTime();
4595 
4596   {
4597     uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4598     uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4599 
4600     G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4601 
4602     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4603                         cl.name(),
4604                         num_workers,
4605                         _collection_set.region_length());
4606     workers()->run_task(&cl, num_workers);
4607   }
4608   g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4609 
4610   collection_set->clear();
4611 }
4612 
4613 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4614  private:
4615   FreeRegionList* _free_region_list;
4616   HeapRegionSet* _proxy_set;
4617   uint _humongous_objects_reclaimed;
4618   uint _humongous_regions_reclaimed;
4619   size_t _freed_bytes;
4620  public:
4621 
4622   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4623     _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4624   }
4625 
4626   virtual bool do_heap_region(HeapRegion* r) {
4627     if (!r->is_starts_humongous()) {
4628       return false;
4629     }
4630 
4631     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4632 
4633     oop obj = (oop)r->bottom();
4634     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4635 
4636     // The following checks whether the humongous object is live are sufficient.
4637     // The main additional check (in addition to having a reference from the roots
4638     // or the young gen) is whether the humongous object has a remembered set entry.
4639     //
4640     // A humongous object cannot be live if there is no remembered set for it
4641     // because:
4642     // - there can be no references from within humongous starts regions referencing
4643     // the object because we never allocate other objects into them.
4644     // (I.e. there are no intra-region references that may be missed by the
4645     // remembered set)
4646     // - as soon there is a remembered set entry to the humongous starts region
4647     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4648     // until the end of a concurrent mark.
4649     //
4650     // It is not required to check whether the object has been found dead by marking
4651     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4652     // all objects allocated during that time are considered live.
4653     // SATB marking is even more conservative than the remembered set.
4654     // So if at this point in the collection there is no remembered set entry,
4655     // nobody has a reference to it.
4656     // At the start of collection we flush all refinement logs, and remembered sets
4657     // are completely up-to-date wrt to references to the humongous object.
4658     //
4659     // Other implementation considerations:
4660     // - never consider object arrays at this time because they would pose
4661     // considerable effort for cleaning up the the remembered sets. This is
4662     // required because stale remembered sets might reference locations that
4663     // are currently allocated into.
4664     uint region_idx = r->hrm_index();
4665     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4666         !r->rem_set()->is_empty()) {
4667       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",
4668                                region_idx,
4669                                (size_t)obj->size() * HeapWordSize,
4670                                p2i(r->bottom()),
4671                                r->rem_set()->occupied(),
4672                                r->rem_set()->strong_code_roots_list_length(),
4673                                next_bitmap->is_marked(r->bottom()),
4674                                g1h->is_humongous_reclaim_candidate(region_idx),
4675                                obj->is_typeArray()
4676                               );
4677       return false;
4678     }
4679 
4680     guarantee(obj->is_typeArray(),
4681               "Only eagerly reclaiming type arrays is supported, but the object "
4682               PTR_FORMAT " is not.", p2i(r->bottom()));
4683 
4684     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",
4685                              region_idx,
4686                              (size_t)obj->size() * HeapWordSize,
4687                              p2i(r->bottom()),
4688                              r->rem_set()->occupied(),
4689                              r->rem_set()->strong_code_roots_list_length(),
4690                              next_bitmap->is_marked(r->bottom()),
4691                              g1h->is_humongous_reclaim_candidate(region_idx),
4692                              obj->is_typeArray()
4693                             );
4694 
4695     g1h->concurrent_mark()->humongous_object_eagerly_reclaimed(r);
4696     _humongous_objects_reclaimed++;
4697     do {
4698       HeapRegion* next = g1h->next_region_in_humongous(r);
4699       _freed_bytes += r->used();
4700       r->set_containing_set(NULL);
4701       _humongous_regions_reclaimed++;
4702       g1h->free_humongous_region(r, _free_region_list);
4703       r = next;
4704     } while (r != NULL);
4705 
4706     return false;
4707   }
4708 
4709   uint humongous_objects_reclaimed() {
4710     return _humongous_objects_reclaimed;
4711   }
4712 
4713   uint humongous_regions_reclaimed() {
4714     return _humongous_regions_reclaimed;
4715   }
4716 
4717   size_t bytes_freed() const {
4718     return _freed_bytes;
4719   }
4720 };
4721 
4722 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4723   assert_at_safepoint_on_vm_thread();
4724 
4725   if (!G1EagerReclaimHumongousObjects ||
4726       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4727     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4728     return;
4729   }
4730 
4731   double start_time = os::elapsedTime();
4732 
4733   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4734 
4735   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4736   heap_region_iterate(&cl);
4737 
4738   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4739 
4740   G1HRPrinter* hrp = hr_printer();
4741   if (hrp->is_active()) {
4742     FreeRegionListIterator iter(&local_cleanup_list);
4743     while (iter.more_available()) {
4744       HeapRegion* hr = iter.get_next();
4745       hrp->cleanup(hr);
4746     }
4747   }
4748 
4749   prepend_to_freelist(&local_cleanup_list);
4750   decrement_summary_bytes(cl.bytes_freed());
4751 
4752   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4753                                                                     cl.humongous_objects_reclaimed());
4754 }
4755 
4756 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4757 public:
4758   virtual bool do_heap_region(HeapRegion* r) {
4759     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4760     G1CollectedHeap::heap()->clear_in_cset(r);
4761     r->set_young_index_in_cset(-1);
4762     return false;
4763   }
4764 };
4765 
4766 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4767   G1AbandonCollectionSetClosure cl;
4768   collection_set->iterate(&cl);
4769 
4770   collection_set->clear();
4771   collection_set->stop_incremental_building();
4772 }
4773 
4774 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4775   return _allocator->is_retained_old_region(hr);
4776 }
4777 
4778 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4779   _eden.add(hr);
4780   _g1_policy->set_region_eden(hr);
4781 }
4782 
4783 #ifdef ASSERT
4784 
4785 class NoYoungRegionsClosure: public HeapRegionClosure {
4786 private:
4787   bool _success;
4788 public:
4789   NoYoungRegionsClosure() : _success(true) { }
4790   bool do_heap_region(HeapRegion* r) {
4791     if (r->is_young()) {
4792       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4793                             p2i(r->bottom()), p2i(r->end()));
4794       _success = false;
4795     }
4796     return false;
4797   }
4798   bool success() { return _success; }
4799 };
4800 
4801 bool G1CollectedHeap::check_young_list_empty() {
4802   bool ret = (young_regions_count() == 0);
4803 
4804   NoYoungRegionsClosure closure;
4805   heap_region_iterate(&closure);
4806   ret = ret && closure.success();
4807 
4808   return ret;
4809 }
4810 
4811 #endif // ASSERT
4812 
4813 class TearDownRegionSetsClosure : public HeapRegionClosure {
4814 private:
4815   HeapRegionSet *_old_set;
4816 
4817 public:
4818   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
4819 
4820   bool do_heap_region(HeapRegion* r) {
4821     if (r->is_old()) {
4822       _old_set->remove(r);
4823     } else if(r->is_young()) {
4824       r->uninstall_surv_rate_group();
4825     } else {
4826       // We ignore free regions, we'll empty the free list afterwards.
4827       // We ignore humongous regions, we're not tearing down the
4828       // humongous regions set.
4829       assert(r->is_free() || r->is_humongous(),
4830              "it cannot be another type");
4831     }
4832     return false;
4833   }
4834 
4835   ~TearDownRegionSetsClosure() {
4836     assert(_old_set->is_empty(), "post-condition");
4837   }
4838 };
4839 
4840 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
4841   assert_at_safepoint_on_vm_thread();
4842 
4843   if (!free_list_only) {
4844     TearDownRegionSetsClosure cl(&_old_set);
4845     heap_region_iterate(&cl);
4846 
4847     // Note that emptying the _young_list is postponed and instead done as
4848     // the first step when rebuilding the regions sets again. The reason for
4849     // this is that during a full GC string deduplication needs to know if
4850     // a collected region was young or old when the full GC was initiated.
4851   }
4852   _hrm.remove_all_free_regions();
4853 }
4854 
4855 void G1CollectedHeap::increase_used(size_t bytes) {
4856   _summary_bytes_used += bytes;
4857 }
4858 
4859 void G1CollectedHeap::decrease_used(size_t bytes) {
4860   assert(_summary_bytes_used >= bytes,
4861          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
4862          _summary_bytes_used, bytes);
4863   _summary_bytes_used -= bytes;
4864 }
4865 
4866 void G1CollectedHeap::set_used(size_t bytes) {
4867   _summary_bytes_used = bytes;
4868 }
4869 
4870 class RebuildRegionSetsClosure : public HeapRegionClosure {
4871 private:
4872   bool            _free_list_only;
4873   HeapRegionSet*   _old_set;
4874   HeapRegionManager*   _hrm;
4875   size_t          _total_used;
4876 
4877 public:
4878   RebuildRegionSetsClosure(bool free_list_only,
4879                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
4880     _free_list_only(free_list_only),
4881     _old_set(old_set), _hrm(hrm), _total_used(0) {
4882     assert(_hrm->num_free_regions() == 0, "pre-condition");
4883     if (!free_list_only) {
4884       assert(_old_set->is_empty(), "pre-condition");
4885     }
4886   }
4887 
4888   bool do_heap_region(HeapRegion* r) {
4889     // After full GC, no region should have a remembered set.
4890     r->rem_set()->clear(true);
4891     if (r->is_empty()) {
4892       // Add free regions to the free list
4893       r->set_free();
4894       _hrm->insert_into_free_list(r);
4895     } else if (!_free_list_only) {
4896 
4897       if (r->is_humongous()) {
4898         // We ignore humongous regions. We left the humongous set unchanged.
4899       } else {
4900         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
4901         // We now move all (non-humongous, non-old) regions to old gen, and register them as such.
4902         r->move_to_old();
4903         _old_set->add(r);
4904       }
4905       _total_used += r->used();
4906     }
4907 
4908     return false;
4909   }
4910 
4911   size_t total_used() {
4912     return _total_used;
4913   }
4914 };
4915 
4916 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
4917   assert_at_safepoint_on_vm_thread();
4918 
4919   if (!free_list_only) {
4920     _eden.clear();
4921     _survivor.clear();
4922   }
4923 
4924   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
4925   heap_region_iterate(&cl);
4926 
4927   if (!free_list_only) {
4928     set_used(cl.total_used());
4929     if (_archive_allocator != NULL) {
4930       _archive_allocator->clear_used();
4931     }
4932   }
4933   assert(used_unlocked() == recalculate_used(),
4934          "inconsistent used_unlocked(), "
4935          "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
4936          used_unlocked(), recalculate_used());
4937 }
4938 
4939 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
4940   HeapRegion* hr = heap_region_containing(p);
4941   return hr->is_in(p);
4942 }
4943 
4944 // Methods for the mutator alloc region
4945 
4946 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
4947                                                       bool force) {
4948   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4949   bool should_allocate = g1_policy()->should_allocate_mutator_region();
4950   if (force || should_allocate) {
4951     HeapRegion* new_alloc_region = new_region(word_size,
4952                                               false /* is_old */,
4953                                               false /* do_expand */);
4954     if (new_alloc_region != NULL) {
4955       set_region_short_lived_locked(new_alloc_region);
4956       _hr_printer.alloc(new_alloc_region, !should_allocate);
4957       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
4958       _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region);
4959       return new_alloc_region;
4960     }
4961   }
4962   return NULL;
4963 }
4964 
4965 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
4966                                                   size_t allocated_bytes) {
4967   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4968   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
4969 
4970   collection_set()->add_eden_region(alloc_region);
4971   increase_used(allocated_bytes);
4972   _hr_printer.retire(alloc_region);
4973   // We update the eden sizes here, when the region is retired,
4974   // instead of when it's allocated, since this is the point that its
4975   // used space has been recored in _summary_bytes_used.
4976   g1mm()->update_eden_size();
4977 }
4978 
4979 // Methods for the GC alloc regions
4980 
4981 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
4982   if (dest.is_old()) {
4983     return true;
4984   } else {
4985     return survivor_regions_count() < g1_policy()->max_survivor_regions();
4986   }
4987 }
4988 
4989 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
4990   assert(FreeList_lock->owned_by_self(), "pre-condition");
4991 
4992   if (!has_more_regions(dest)) {
4993     return NULL;
4994   }
4995 
4996   const bool is_survivor = dest.is_young();
4997 
4998   HeapRegion* new_alloc_region = new_region(word_size,
4999                                             !is_survivor,
5000                                             true /* do_expand */);
5001   if (new_alloc_region != NULL) {
5002     if (is_survivor) {
5003       new_alloc_region->set_survivor();
5004       _survivor.add(new_alloc_region);
5005       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5006     } else {
5007       new_alloc_region->set_old();
5008       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5009     }
5010     _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region);
5011     _hr_printer.alloc(new_alloc_region);
5012     bool during_im = collector_state()->in_initial_mark_gc();
5013     new_alloc_region->note_start_of_copying(during_im);
5014     return new_alloc_region;
5015   }
5016   return NULL;
5017 }
5018 
5019 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5020                                              size_t allocated_bytes,
5021                                              InCSetState dest) {
5022   bool during_im = collector_state()->in_initial_mark_gc();
5023   alloc_region->note_end_of_copying(during_im);
5024   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5025   if (dest.is_old()) {
5026     _old_set.add(alloc_region);
5027   }
5028   _hr_printer.retire(alloc_region);
5029 }
5030 
5031 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5032   bool expanded = false;
5033   uint index = _hrm.find_highest_free(&expanded);
5034 
5035   if (index != G1_NO_HRM_INDEX) {
5036     if (expanded) {
5037       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5038                                 HeapRegion::GrainWords * HeapWordSize);
5039     }
5040     _hrm.allocate_free_regions_starting_at(index, 1);
5041     return region_at(index);
5042   }
5043   return NULL;
5044 }
5045 
5046 // Optimized nmethod scanning
5047 
5048 class RegisterNMethodOopClosure: public OopClosure {
5049   G1CollectedHeap* _g1h;
5050   nmethod* _nm;
5051 
5052   template <class T> void do_oop_work(T* p) {
5053     T heap_oop = RawAccess<>::oop_load(p);
5054     if (!CompressedOops::is_null(heap_oop)) {
5055       oop obj = CompressedOops::decode_not_null(heap_oop);
5056       HeapRegion* hr = _g1h->heap_region_containing(obj);
5057       assert(!hr->is_continues_humongous(),
5058              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5059              " starting at " HR_FORMAT,
5060              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5061 
5062       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5063       hr->add_strong_code_root_locked(_nm);
5064     }
5065   }
5066 
5067 public:
5068   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5069     _g1h(g1h), _nm(nm) {}
5070 
5071   void do_oop(oop* p)       { do_oop_work(p); }
5072   void do_oop(narrowOop* p) { do_oop_work(p); }
5073 };
5074 
5075 class UnregisterNMethodOopClosure: public OopClosure {
5076   G1CollectedHeap* _g1h;
5077   nmethod* _nm;
5078 
5079   template <class T> void do_oop_work(T* p) {
5080     T heap_oop = RawAccess<>::oop_load(p);
5081     if (!CompressedOops::is_null(heap_oop)) {
5082       oop obj = CompressedOops::decode_not_null(heap_oop);
5083       HeapRegion* hr = _g1h->heap_region_containing(obj);
5084       assert(!hr->is_continues_humongous(),
5085              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5086              " starting at " HR_FORMAT,
5087              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5088 
5089       hr->remove_strong_code_root(_nm);
5090     }
5091   }
5092 
5093 public:
5094   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5095     _g1h(g1h), _nm(nm) {}
5096 
5097   void do_oop(oop* p)       { do_oop_work(p); }
5098   void do_oop(narrowOop* p) { do_oop_work(p); }
5099 };
5100 
5101 // Returns true if the reference points to an object that
5102 // can move in an incremental collection.
5103 bool G1CollectedHeap::is_scavengable(oop obj) {
5104   HeapRegion* hr = heap_region_containing(obj);
5105   return !hr->is_pinned();
5106 }
5107 
5108 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5109   guarantee(nm != NULL, "sanity");
5110   RegisterNMethodOopClosure reg_cl(this, nm);
5111   nm->oops_do(&reg_cl);
5112 }
5113 
5114 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5115   guarantee(nm != NULL, "sanity");
5116   UnregisterNMethodOopClosure reg_cl(this, nm);
5117   nm->oops_do(&reg_cl, true);
5118 }
5119 
5120 void G1CollectedHeap::purge_code_root_memory() {
5121   double purge_start = os::elapsedTime();
5122   G1CodeRootSet::purge();
5123   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5124   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5125 }
5126 
5127 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5128   G1CollectedHeap* _g1h;
5129 
5130 public:
5131   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5132     _g1h(g1h) {}
5133 
5134   void do_code_blob(CodeBlob* cb) {
5135     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5136     if (nm == NULL) {
5137       return;
5138     }
5139 
5140     if (ScavengeRootsInCode) {
5141       _g1h->register_nmethod(nm);
5142     }
5143   }
5144 };
5145 
5146 void G1CollectedHeap::rebuild_strong_code_roots() {
5147   RebuildStrongCodeRootClosure blob_cl(this);
5148   CodeCache::blobs_do(&blob_cl);
5149 }
5150 
5151 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
5152   GrowableArray<GCMemoryManager*> memory_managers(2);
5153   memory_managers.append(&_memory_manager);
5154   memory_managers.append(&_full_gc_memory_manager);
5155   return memory_managers;
5156 }
5157 
5158 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
5159   GrowableArray<MemoryPool*> memory_pools(3);
5160   memory_pools.append(_eden_pool);
5161   memory_pools.append(_survivor_pool);
5162   memory_pools.append(_old_pool);
5163   return memory_pools;
5164 }