rev 50627 : imported patch 8204084-last-young-gc-marker
rev 50628 : imported patch 8204084-stefanj-review
rev 50629 : imported patch 8204084-stefanj-review2
rev 50630 : imported patch 8204084-stefanj-review3
rev 50631 : [mq]: 8204084-gtest-fixes

   1 /*
   2  * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/metadataOnStackMark.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "classfile/symbolTable.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc/g1/g1Allocator.inline.hpp"
  32 #include "gc/g1/g1BarrierSet.hpp"
  33 #include "gc/g1/g1CollectedHeap.inline.hpp"
  34 #include "gc/g1/g1CollectionSet.hpp"
  35 #include "gc/g1/g1CollectorPolicy.hpp"
  36 #include "gc/g1/g1CollectorState.hpp"
  37 #include "gc/g1/g1ConcurrentRefine.hpp"
  38 #include "gc/g1/g1ConcurrentRefineThread.hpp"
  39 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  40 #include "gc/g1/g1EvacStats.inline.hpp"
  41 #include "gc/g1/g1FullCollector.hpp"
  42 #include "gc/g1/g1GCPhaseTimes.hpp"
  43 #include "gc/g1/g1HeapSizingPolicy.hpp"
  44 #include "gc/g1/g1HeapTransition.hpp"
  45 #include "gc/g1/g1HeapVerifier.hpp"
  46 #include "gc/g1/g1HotCardCache.hpp"
  47 #include "gc/g1/g1MemoryPool.hpp"
  48 #include "gc/g1/g1OopClosures.inline.hpp"
  49 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  50 #include "gc/g1/g1Policy.hpp"
  51 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  52 #include "gc/g1/g1RemSet.hpp"
  53 #include "gc/g1/g1RootClosures.hpp"
  54 #include "gc/g1/g1RootProcessor.hpp"
  55 #include "gc/g1/g1StringDedup.hpp"
  56 #include "gc/g1/g1ThreadLocalData.hpp"
  57 #include "gc/g1/g1YCTypes.hpp"
  58 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
  59 #include "gc/g1/heapRegion.inline.hpp"
  60 #include "gc/g1/heapRegionRemSet.hpp"
  61 #include "gc/g1/heapRegionSet.inline.hpp"
  62 #include "gc/g1/vm_operations_g1.hpp"
  63 #include "gc/shared/adaptiveSizePolicy.hpp"
  64 #include "gc/shared/gcHeapSummary.hpp"
  65 #include "gc/shared/gcId.hpp"
  66 #include "gc/shared/gcLocker.hpp"
  67 #include "gc/shared/gcTimer.hpp"
  68 #include "gc/shared/gcTrace.hpp"
  69 #include "gc/shared/gcTraceTime.inline.hpp"
  70 #include "gc/shared/generationSpec.hpp"
  71 #include "gc/shared/isGCActiveMark.hpp"
  72 #include "gc/shared/oopStorageParState.hpp"
  73 #include "gc/shared/preservedMarks.inline.hpp"
  74 #include "gc/shared/suspendibleThreadSet.hpp"
  75 #include "gc/shared/referenceProcessor.inline.hpp"
  76 #include "gc/shared/taskqueue.inline.hpp"
  77 #include "gc/shared/weakProcessor.hpp"
  78 #include "logging/log.hpp"
  79 #include "memory/allocation.hpp"
  80 #include "memory/iterator.hpp"
  81 #include "memory/metaspaceShared.hpp"
  82 #include "memory/resourceArea.hpp"
  83 #include "oops/access.inline.hpp"
  84 #include "oops/compressedOops.inline.hpp"
  85 #include "oops/oop.inline.hpp"
  86 #include "prims/resolvedMethodTable.hpp"
  87 #include "runtime/atomic.hpp"
  88 #include "runtime/flags/flagSetting.hpp"
  89 #include "runtime/handles.inline.hpp"
  90 #include "runtime/init.hpp"
  91 #include "runtime/orderAccess.hpp"
  92 #include "runtime/threadSMR.hpp"
  93 #include "runtime/vmThread.hpp"
  94 #include "utilities/align.hpp"
  95 #include "utilities/globalDefinitions.hpp"
  96 #include "utilities/stack.inline.hpp"
  97 
  98 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  99 
 100 // INVARIANTS/NOTES
 101 //
 102 // All allocation activity covered by the G1CollectedHeap interface is
 103 // serialized by acquiring the HeapLock.  This happens in mem_allocate
 104 // and allocate_new_tlab, which are the "entry" points to the
 105 // allocation code from the rest of the JVM.  (Note that this does not
 106 // apply to TLAB allocation, which is not part of this interface: it
 107 // is done by clients of this interface.)
 108 
 109 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 110  private:
 111   size_t _num_dirtied;
 112   G1CollectedHeap* _g1h;
 113   G1CardTable* _g1_ct;
 114 
 115   HeapRegion* region_for_card(jbyte* card_ptr) const {
 116     return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr));
 117   }
 118 
 119   bool will_become_free(HeapRegion* hr) const {
 120     // A region will be freed by free_collection_set if the region is in the
 121     // collection set and has not had an evacuation failure.
 122     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 123   }
 124 
 125  public:
 126   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
 127     _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { }
 128 
 129   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 130     HeapRegion* hr = region_for_card(card_ptr);
 131 
 132     // Should only dirty cards in regions that won't be freed.
 133     if (!will_become_free(hr)) {
 134       *card_ptr = G1CardTable::dirty_card_val();
 135       _num_dirtied++;
 136     }
 137 
 138     return true;
 139   }
 140 
 141   size_t num_dirtied()   const { return _num_dirtied; }
 142 };
 143 
 144 
 145 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 146   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 147 }
 148 
 149 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 150   // The from card cache is not the memory that is actually committed. So we cannot
 151   // take advantage of the zero_filled parameter.
 152   reset_from_card_cache(start_idx, num_regions);
 153 }
 154 
 155 
 156 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
 157                                              MemRegion mr) {
 158   return new HeapRegion(hrs_index, bot(), mr);
 159 }
 160 
 161 // Private methods.
 162 
 163 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 164   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 165          "the only time we use this to allocate a humongous region is "
 166          "when we are allocating a single humongous region");
 167 
 168   HeapRegion* res = _hrm.allocate_free_region(is_old);
 169 
 170   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 171     // Currently, only attempts to allocate GC alloc regions set
 172     // do_expand to true. So, we should only reach here during a
 173     // safepoint. If this assumption changes we might have to
 174     // reconsider the use of _expand_heap_after_alloc_failure.
 175     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 176 
 177     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 178                               word_size * HeapWordSize);
 179 
 180     if (expand(word_size * HeapWordSize)) {
 181       // Given that expand() succeeded in expanding the heap, and we
 182       // always expand the heap by an amount aligned to the heap
 183       // region size, the free list should in theory not be empty.
 184       // In either case allocate_free_region() will check for NULL.
 185       res = _hrm.allocate_free_region(is_old);
 186     } else {
 187       _expand_heap_after_alloc_failure = false;
 188     }
 189   }
 190   return res;
 191 }
 192 
 193 HeapWord*
 194 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 195                                                            uint num_regions,
 196                                                            size_t word_size) {
 197   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 198   assert(is_humongous(word_size), "word_size should be humongous");
 199   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 200 
 201   // Index of last region in the series.
 202   uint last = first + num_regions - 1;
 203 
 204   // We need to initialize the region(s) we just discovered. This is
 205   // a bit tricky given that it can happen concurrently with
 206   // refinement threads refining cards on these regions and
 207   // potentially wanting to refine the BOT as they are scanning
 208   // those cards (this can happen shortly after a cleanup; see CR
 209   // 6991377). So we have to set up the region(s) carefully and in
 210   // a specific order.
 211 
 212   // The word size sum of all the regions we will allocate.
 213   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 214   assert(word_size <= word_size_sum, "sanity");
 215 
 216   // This will be the "starts humongous" region.
 217   HeapRegion* first_hr = region_at(first);
 218   // The header of the new object will be placed at the bottom of
 219   // the first region.
 220   HeapWord* new_obj = first_hr->bottom();
 221   // This will be the new top of the new object.
 222   HeapWord* obj_top = new_obj + word_size;
 223 
 224   // First, we need to zero the header of the space that we will be
 225   // allocating. When we update top further down, some refinement
 226   // threads might try to scan the region. By zeroing the header we
 227   // ensure that any thread that will try to scan the region will
 228   // come across the zero klass word and bail out.
 229   //
 230   // NOTE: It would not have been correct to have used
 231   // CollectedHeap::fill_with_object() and make the space look like
 232   // an int array. The thread that is doing the allocation will
 233   // later update the object header to a potentially different array
 234   // type and, for a very short period of time, the klass and length
 235   // fields will be inconsistent. This could cause a refinement
 236   // thread to calculate the object size incorrectly.
 237   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 238 
 239   // Next, pad out the unused tail of the last region with filler
 240   // objects, for improved usage accounting.
 241   // How many words we use for filler objects.
 242   size_t word_fill_size = word_size_sum - word_size;
 243 
 244   // How many words memory we "waste" which cannot hold a filler object.
 245   size_t words_not_fillable = 0;
 246 
 247   if (word_fill_size >= min_fill_size()) {
 248     fill_with_objects(obj_top, word_fill_size);
 249   } else if (word_fill_size > 0) {
 250     // We have space to fill, but we cannot fit an object there.
 251     words_not_fillable = word_fill_size;
 252     word_fill_size = 0;
 253   }
 254 
 255   // We will set up the first region as "starts humongous". This
 256   // will also update the BOT covering all the regions to reflect
 257   // that there is a single object that starts at the bottom of the
 258   // first region.
 259   first_hr->set_starts_humongous(obj_top, word_fill_size);
 260   _g1_policy->remset_tracker()->update_at_allocate(first_hr);
 261   // Then, if there are any, we will set up the "continues
 262   // humongous" regions.
 263   HeapRegion* hr = NULL;
 264   for (uint i = first + 1; i <= last; ++i) {
 265     hr = region_at(i);
 266     hr->set_continues_humongous(first_hr);
 267     _g1_policy->remset_tracker()->update_at_allocate(hr);
 268   }
 269 
 270   // Up to this point no concurrent thread would have been able to
 271   // do any scanning on any region in this series. All the top
 272   // fields still point to bottom, so the intersection between
 273   // [bottom,top] and [card_start,card_end] will be empty. Before we
 274   // update the top fields, we'll do a storestore to make sure that
 275   // no thread sees the update to top before the zeroing of the
 276   // object header and the BOT initialization.
 277   OrderAccess::storestore();
 278 
 279   // Now, we will update the top fields of the "continues humongous"
 280   // regions except the last one.
 281   for (uint i = first; i < last; ++i) {
 282     hr = region_at(i);
 283     hr->set_top(hr->end());
 284   }
 285 
 286   hr = region_at(last);
 287   // If we cannot fit a filler object, we must set top to the end
 288   // of the humongous object, otherwise we cannot iterate the heap
 289   // and the BOT will not be complete.
 290   hr->set_top(hr->end() - words_not_fillable);
 291 
 292   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 293          "obj_top should be in last region");
 294 
 295   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 296 
 297   assert(words_not_fillable == 0 ||
 298          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 299          "Miscalculation in humongous allocation");
 300 
 301   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 302 
 303   for (uint i = first; i <= last; ++i) {
 304     hr = region_at(i);
 305     _humongous_set.add(hr);
 306     _hr_printer.alloc(hr);
 307   }
 308 
 309   return new_obj;
 310 }
 311 
 312 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 313   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 314   return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 315 }
 316 
 317 // If could fit into free regions w/o expansion, try.
 318 // Otherwise, if can expand, do so.
 319 // Otherwise, if using ex regions might help, try with ex given back.
 320 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 321   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 322 
 323   _verifier->verify_region_sets_optional();
 324 
 325   uint first = G1_NO_HRM_INDEX;
 326   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 327 
 328   if (obj_regions == 1) {
 329     // Only one region to allocate, try to use a fast path by directly allocating
 330     // from the free lists. Do not try to expand here, we will potentially do that
 331     // later.
 332     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 333     if (hr != NULL) {
 334       first = hr->hrm_index();
 335     }
 336   } else {
 337     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 338     // are lucky enough to find some.
 339     first = _hrm.find_contiguous_only_empty(obj_regions);
 340     if (first != G1_NO_HRM_INDEX) {
 341       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 342     }
 343   }
 344 
 345   if (first == G1_NO_HRM_INDEX) {
 346     // Policy: We could not find enough regions for the humongous object in the
 347     // free list. Look through the heap to find a mix of free and uncommitted regions.
 348     // If so, try expansion.
 349     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 350     if (first != G1_NO_HRM_INDEX) {
 351       // We found something. Make sure these regions are committed, i.e. expand
 352       // the heap. Alternatively we could do a defragmentation GC.
 353       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 354                                     word_size * HeapWordSize);
 355 
 356       _hrm.expand_at(first, obj_regions, workers());
 357       g1_policy()->record_new_heap_size(num_regions());
 358 
 359 #ifdef ASSERT
 360       for (uint i = first; i < first + obj_regions; ++i) {
 361         HeapRegion* hr = region_at(i);
 362         assert(hr->is_free(), "sanity");
 363         assert(hr->is_empty(), "sanity");
 364         assert(is_on_master_free_list(hr), "sanity");
 365       }
 366 #endif
 367       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 368     } else {
 369       // Policy: Potentially trigger a defragmentation GC.
 370     }
 371   }
 372 
 373   HeapWord* result = NULL;
 374   if (first != G1_NO_HRM_INDEX) {
 375     result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size);
 376     assert(result != NULL, "it should always return a valid result");
 377 
 378     // A successful humongous object allocation changes the used space
 379     // information of the old generation so we need to recalculate the
 380     // sizes and update the jstat counters here.
 381     g1mm()->update_sizes();
 382   }
 383 
 384   _verifier->verify_region_sets_optional();
 385 
 386   return result;
 387 }
 388 
 389 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size,
 390                                              size_t requested_size,
 391                                              size_t* actual_size) {
 392   assert_heap_not_locked_and_not_at_safepoint();
 393   assert(!is_humongous(requested_size), "we do not allow humongous TLABs");
 394 
 395   return attempt_allocation(min_size, requested_size, actual_size);
 396 }
 397 
 398 HeapWord*
 399 G1CollectedHeap::mem_allocate(size_t word_size,
 400                               bool*  gc_overhead_limit_was_exceeded) {
 401   assert_heap_not_locked_and_not_at_safepoint();
 402 
 403   if (is_humongous(word_size)) {
 404     return attempt_allocation_humongous(word_size);
 405   }
 406   size_t dummy = 0;
 407   return attempt_allocation(word_size, word_size, &dummy);
 408 }
 409 
 410 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
 411   ResourceMark rm; // For retrieving the thread names in log messages.
 412 
 413   // Make sure you read the note in attempt_allocation_humongous().
 414 
 415   assert_heap_not_locked_and_not_at_safepoint();
 416   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 417          "be called for humongous allocation requests");
 418 
 419   // We should only get here after the first-level allocation attempt
 420   // (attempt_allocation()) failed to allocate.
 421 
 422   // We will loop until a) we manage to successfully perform the
 423   // allocation or b) we successfully schedule a collection which
 424   // fails to perform the allocation. b) is the only case when we'll
 425   // return NULL.
 426   HeapWord* result = NULL;
 427   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 428     bool should_try_gc;
 429     uint gc_count_before;
 430 
 431     {
 432       MutexLockerEx x(Heap_lock);
 433       result = _allocator->attempt_allocation_locked(word_size);
 434       if (result != NULL) {
 435         return result;
 436       }
 437 
 438       // If the GCLocker is active and we are bound for a GC, try expanding young gen.
 439       // This is different to when only GCLocker::needs_gc() is set: try to avoid
 440       // waiting because the GCLocker is active to not wait too long.
 441       if (GCLocker::is_active_and_needs_gc() && g1_policy()->can_expand_young_list()) {
 442         // No need for an ergo message here, can_expand_young_list() does this when
 443         // it returns true.
 444         result = _allocator->attempt_allocation_force(word_size);
 445         if (result != NULL) {
 446           return result;
 447         }
 448       }
 449       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 450       // the GCLocker initiated GC has been performed and then retry. This includes
 451       // the case when the GC Locker is not active but has not been performed.
 452       should_try_gc = !GCLocker::needs_gc();
 453       // Read the GC count while still holding the Heap_lock.
 454       gc_count_before = total_collections();
 455     }
 456 
 457     if (should_try_gc) {
 458       bool succeeded;
 459       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 460                                    GCCause::_g1_inc_collection_pause);
 461       if (result != NULL) {
 462         assert(succeeded, "only way to get back a non-NULL result");
 463         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 464                              Thread::current()->name(), p2i(result));
 465         return result;
 466       }
 467 
 468       if (succeeded) {
 469         // We successfully scheduled a collection which failed to allocate. No
 470         // point in trying to allocate further. We'll just return NULL.
 471         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 472                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 473         return NULL;
 474       }
 475       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
 476                            Thread::current()->name(), word_size);
 477     } else {
 478       // Failed to schedule a collection.
 479       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 480         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 481                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 482         return NULL;
 483       }
 484       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 485       // The GCLocker is either active or the GCLocker initiated
 486       // GC has not yet been performed. Stall until it is and
 487       // then retry the allocation.
 488       GCLocker::stall_until_clear();
 489       gclocker_retry_count += 1;
 490     }
 491 
 492     // We can reach here if we were unsuccessful in scheduling a
 493     // collection (because another thread beat us to it) or if we were
 494     // stalled due to the GC locker. In either can we should retry the
 495     // allocation attempt in case another thread successfully
 496     // performed a collection and reclaimed enough space. We do the
 497     // first attempt (without holding the Heap_lock) here and the
 498     // follow-on attempt will be at the start of the next loop
 499     // iteration (after taking the Heap_lock).
 500     size_t dummy = 0;
 501     result = _allocator->attempt_allocation(word_size, word_size, &dummy);
 502     if (result != NULL) {
 503       return result;
 504     }
 505 
 506     // Give a warning if we seem to be looping forever.
 507     if ((QueuedAllocationWarningCount > 0) &&
 508         (try_count % QueuedAllocationWarningCount == 0)) {
 509       log_warning(gc, alloc)("%s:  Retried allocation %u times for " SIZE_FORMAT " words",
 510                              Thread::current()->name(), try_count, word_size);
 511     }
 512   }
 513 
 514   ShouldNotReachHere();
 515   return NULL;
 516 }
 517 
 518 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
 519   assert_at_safepoint_on_vm_thread();
 520   if (_archive_allocator == NULL) {
 521     _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
 522   }
 523 }
 524 
 525 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 526   // Allocations in archive regions cannot be of a size that would be considered
 527   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 528   // may be different at archive-restore time.
 529   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 530 }
 531 
 532 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 533   assert_at_safepoint_on_vm_thread();
 534   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 535   if (is_archive_alloc_too_large(word_size)) {
 536     return NULL;
 537   }
 538   return _archive_allocator->archive_mem_allocate(word_size);
 539 }
 540 
 541 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 542                                               size_t end_alignment_in_bytes) {
 543   assert_at_safepoint_on_vm_thread();
 544   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 545 
 546   // Call complete_archive to do the real work, filling in the MemRegion
 547   // array with the archive regions.
 548   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 549   delete _archive_allocator;
 550   _archive_allocator = NULL;
 551 }
 552 
 553 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 554   assert(ranges != NULL, "MemRegion array NULL");
 555   assert(count != 0, "No MemRegions provided");
 556   MemRegion reserved = _hrm.reserved();
 557   for (size_t i = 0; i < count; i++) {
 558     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 559       return false;
 560     }
 561   }
 562   return true;
 563 }
 564 
 565 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
 566                                             size_t count,
 567                                             bool open) {
 568   assert(!is_init_completed(), "Expect to be called at JVM init time");
 569   assert(ranges != NULL, "MemRegion array NULL");
 570   assert(count != 0, "No MemRegions provided");
 571   MutexLockerEx x(Heap_lock);
 572 
 573   MemRegion reserved = _hrm.reserved();
 574   HeapWord* prev_last_addr = NULL;
 575   HeapRegion* prev_last_region = NULL;
 576 
 577   // Temporarily disable pretouching of heap pages. This interface is used
 578   // when mmap'ing archived heap data in, so pre-touching is wasted.
 579   FlagSetting fs(AlwaysPreTouch, false);
 580 
 581   // Enable archive object checking used by G1MarkSweep. We have to let it know
 582   // about each archive range, so that objects in those ranges aren't marked.
 583   G1ArchiveAllocator::enable_archive_object_check();
 584 
 585   // For each specified MemRegion range, allocate the corresponding G1
 586   // regions and mark them as archive regions. We expect the ranges
 587   // in ascending starting address order, without overlap.
 588   for (size_t i = 0; i < count; i++) {
 589     MemRegion curr_range = ranges[i];
 590     HeapWord* start_address = curr_range.start();
 591     size_t word_size = curr_range.word_size();
 592     HeapWord* last_address = curr_range.last();
 593     size_t commits = 0;
 594 
 595     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 596               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 597               p2i(start_address), p2i(last_address));
 598     guarantee(start_address > prev_last_addr,
 599               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 600               p2i(start_address), p2i(prev_last_addr));
 601     prev_last_addr = last_address;
 602 
 603     // Check for ranges that start in the same G1 region in which the previous
 604     // range ended, and adjust the start address so we don't try to allocate
 605     // the same region again. If the current range is entirely within that
 606     // region, skip it, just adjusting the recorded top.
 607     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 608     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 609       start_address = start_region->end();
 610       if (start_address > last_address) {
 611         increase_used(word_size * HeapWordSize);
 612         start_region->set_top(last_address + 1);
 613         continue;
 614       }
 615       start_region->set_top(start_address);
 616       curr_range = MemRegion(start_address, last_address + 1);
 617       start_region = _hrm.addr_to_region(start_address);
 618     }
 619 
 620     // Perform the actual region allocation, exiting if it fails.
 621     // Then note how much new space we have allocated.
 622     if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
 623       return false;
 624     }
 625     increase_used(word_size * HeapWordSize);
 626     if (commits != 0) {
 627       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 628                                 HeapRegion::GrainWords * HeapWordSize * commits);
 629 
 630     }
 631 
 632     // Mark each G1 region touched by the range as archive, add it to
 633     // the old set, and set top.
 634     HeapRegion* curr_region = _hrm.addr_to_region(start_address);
 635     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 636     prev_last_region = last_region;
 637 
 638     while (curr_region != NULL) {
 639       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 640              "Region already in use (index %u)", curr_region->hrm_index());
 641       if (open) {
 642         curr_region->set_open_archive();
 643       } else {
 644         curr_region->set_closed_archive();
 645       }
 646       _hr_printer.alloc(curr_region);
 647       _old_set.add(curr_region);
 648       HeapWord* top;
 649       HeapRegion* next_region;
 650       if (curr_region != last_region) {
 651         top = curr_region->end();
 652         next_region = _hrm.next_region_in_heap(curr_region);
 653       } else {
 654         top = last_address + 1;
 655         next_region = NULL;
 656       }
 657       curr_region->set_top(top);
 658       curr_region->set_first_dead(top);
 659       curr_region->set_end_of_live(top);
 660       curr_region = next_region;
 661     }
 662 
 663     // Notify mark-sweep of the archive
 664     G1ArchiveAllocator::set_range_archive(curr_range, open);
 665   }
 666   return true;
 667 }
 668 
 669 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 670   assert(!is_init_completed(), "Expect to be called at JVM init time");
 671   assert(ranges != NULL, "MemRegion array NULL");
 672   assert(count != 0, "No MemRegions provided");
 673   MemRegion reserved = _hrm.reserved();
 674   HeapWord *prev_last_addr = NULL;
 675   HeapRegion* prev_last_region = NULL;
 676 
 677   // For each MemRegion, create filler objects, if needed, in the G1 regions
 678   // that contain the address range. The address range actually within the
 679   // MemRegion will not be modified. That is assumed to have been initialized
 680   // elsewhere, probably via an mmap of archived heap data.
 681   MutexLockerEx x(Heap_lock);
 682   for (size_t i = 0; i < count; i++) {
 683     HeapWord* start_address = ranges[i].start();
 684     HeapWord* last_address = ranges[i].last();
 685 
 686     assert(reserved.contains(start_address) && reserved.contains(last_address),
 687            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 688            p2i(start_address), p2i(last_address));
 689     assert(start_address > prev_last_addr,
 690            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 691            p2i(start_address), p2i(prev_last_addr));
 692 
 693     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 694     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 695     HeapWord* bottom_address = start_region->bottom();
 696 
 697     // Check for a range beginning in the same region in which the
 698     // previous one ended.
 699     if (start_region == prev_last_region) {
 700       bottom_address = prev_last_addr + 1;
 701     }
 702 
 703     // Verify that the regions were all marked as archive regions by
 704     // alloc_archive_regions.
 705     HeapRegion* curr_region = start_region;
 706     while (curr_region != NULL) {
 707       guarantee(curr_region->is_archive(),
 708                 "Expected archive region at index %u", curr_region->hrm_index());
 709       if (curr_region != last_region) {
 710         curr_region = _hrm.next_region_in_heap(curr_region);
 711       } else {
 712         curr_region = NULL;
 713       }
 714     }
 715 
 716     prev_last_addr = last_address;
 717     prev_last_region = last_region;
 718 
 719     // Fill the memory below the allocated range with dummy object(s),
 720     // if the region bottom does not match the range start, or if the previous
 721     // range ended within the same G1 region, and there is a gap.
 722     if (start_address != bottom_address) {
 723       size_t fill_size = pointer_delta(start_address, bottom_address);
 724       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 725       increase_used(fill_size * HeapWordSize);
 726     }
 727   }
 728 }
 729 
 730 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size,
 731                                                      size_t desired_word_size,
 732                                                      size_t* actual_word_size) {
 733   assert_heap_not_locked_and_not_at_safepoint();
 734   assert(!is_humongous(desired_word_size), "attempt_allocation() should not "
 735          "be called for humongous allocation requests");
 736 
 737   HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size);
 738 
 739   if (result == NULL) {
 740     *actual_word_size = desired_word_size;
 741     result = attempt_allocation_slow(desired_word_size);
 742   }
 743 
 744   assert_heap_not_locked();
 745   if (result != NULL) {
 746     assert(*actual_word_size != 0, "Actual size must have been set here");
 747     dirty_young_block(result, *actual_word_size);
 748   } else {
 749     *actual_word_size = 0;
 750   }
 751 
 752   return result;
 753 }
 754 
 755 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
 756   assert(!is_init_completed(), "Expect to be called at JVM init time");
 757   assert(ranges != NULL, "MemRegion array NULL");
 758   assert(count != 0, "No MemRegions provided");
 759   MemRegion reserved = _hrm.reserved();
 760   HeapWord* prev_last_addr = NULL;
 761   HeapRegion* prev_last_region = NULL;
 762   size_t size_used = 0;
 763   size_t uncommitted_regions = 0;
 764 
 765   // For each Memregion, free the G1 regions that constitute it, and
 766   // notify mark-sweep that the range is no longer to be considered 'archive.'
 767   MutexLockerEx x(Heap_lock);
 768   for (size_t i = 0; i < count; i++) {
 769     HeapWord* start_address = ranges[i].start();
 770     HeapWord* last_address = ranges[i].last();
 771 
 772     assert(reserved.contains(start_address) && reserved.contains(last_address),
 773            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 774            p2i(start_address), p2i(last_address));
 775     assert(start_address > prev_last_addr,
 776            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 777            p2i(start_address), p2i(prev_last_addr));
 778     size_used += ranges[i].byte_size();
 779     prev_last_addr = last_address;
 780 
 781     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 782     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 783 
 784     // Check for ranges that start in the same G1 region in which the previous
 785     // range ended, and adjust the start address so we don't try to free
 786     // the same region again. If the current range is entirely within that
 787     // region, skip it.
 788     if (start_region == prev_last_region) {
 789       start_address = start_region->end();
 790       if (start_address > last_address) {
 791         continue;
 792       }
 793       start_region = _hrm.addr_to_region(start_address);
 794     }
 795     prev_last_region = last_region;
 796 
 797     // After verifying that each region was marked as an archive region by
 798     // alloc_archive_regions, set it free and empty and uncommit it.
 799     HeapRegion* curr_region = start_region;
 800     while (curr_region != NULL) {
 801       guarantee(curr_region->is_archive(),
 802                 "Expected archive region at index %u", curr_region->hrm_index());
 803       uint curr_index = curr_region->hrm_index();
 804       _old_set.remove(curr_region);
 805       curr_region->set_free();
 806       curr_region->set_top(curr_region->bottom());
 807       if (curr_region != last_region) {
 808         curr_region = _hrm.next_region_in_heap(curr_region);
 809       } else {
 810         curr_region = NULL;
 811       }
 812       _hrm.shrink_at(curr_index, 1);
 813       uncommitted_regions++;
 814     }
 815 
 816     // Notify mark-sweep that this is no longer an archive range.
 817     G1ArchiveAllocator::set_range_archive(ranges[i], false);
 818   }
 819 
 820   if (uncommitted_regions != 0) {
 821     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 822                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 823   }
 824   decrease_used(size_used);
 825 }
 826 
 827 oop G1CollectedHeap::materialize_archived_object(oop obj) {
 828   assert(obj != NULL, "archived obj is NULL");
 829   assert(MetaspaceShared::is_archive_object(obj), "must be archived object");
 830 
 831   // Loading an archived object makes it strongly reachable. If it is
 832   // loaded during concurrent marking, it must be enqueued to the SATB
 833   // queue, shading the previously white object gray.
 834   G1BarrierSet::enqueue(obj);
 835 
 836   return obj;
 837 }
 838 
 839 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
 840   ResourceMark rm; // For retrieving the thread names in log messages.
 841 
 842   // The structure of this method has a lot of similarities to
 843   // attempt_allocation_slow(). The reason these two were not merged
 844   // into a single one is that such a method would require several "if
 845   // allocation is not humongous do this, otherwise do that"
 846   // conditional paths which would obscure its flow. In fact, an early
 847   // version of this code did use a unified method which was harder to
 848   // follow and, as a result, it had subtle bugs that were hard to
 849   // track down. So keeping these two methods separate allows each to
 850   // be more readable. It will be good to keep these two in sync as
 851   // much as possible.
 852 
 853   assert_heap_not_locked_and_not_at_safepoint();
 854   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 855          "should only be called for humongous allocations");
 856 
 857   // Humongous objects can exhaust the heap quickly, so we should check if we
 858   // need to start a marking cycle at each humongous object allocation. We do
 859   // the check before we do the actual allocation. The reason for doing it
 860   // before the allocation is that we avoid having to keep track of the newly
 861   // allocated memory while we do a GC.
 862   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
 863                                            word_size)) {
 864     collect(GCCause::_g1_humongous_allocation);
 865   }
 866 
 867   // We will loop until a) we manage to successfully perform the
 868   // allocation or b) we successfully schedule a collection which
 869   // fails to perform the allocation. b) is the only case when we'll
 870   // return NULL.
 871   HeapWord* result = NULL;
 872   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 873     bool should_try_gc;
 874     uint gc_count_before;
 875 
 876 
 877     {
 878       MutexLockerEx x(Heap_lock);
 879 
 880       // Given that humongous objects are not allocated in young
 881       // regions, we'll first try to do the allocation without doing a
 882       // collection hoping that there's enough space in the heap.
 883       result = humongous_obj_allocate(word_size);
 884       if (result != NULL) {
 885         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 886         g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 887         return result;
 888       }
 889 
 890       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 891       // the GCLocker initiated GC has been performed and then retry. This includes
 892       // the case when the GC Locker is not active but has not been performed.
 893       should_try_gc = !GCLocker::needs_gc();
 894       // Read the GC count while still holding the Heap_lock.
 895       gc_count_before = total_collections();
 896     }
 897 
 898     if (should_try_gc) {
 899       bool succeeded;
 900       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 901                                    GCCause::_g1_humongous_allocation);
 902       if (result != NULL) {
 903         assert(succeeded, "only way to get back a non-NULL result");
 904         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 905                              Thread::current()->name(), p2i(result));
 906         return result;
 907       }
 908 
 909       if (succeeded) {
 910         // We successfully scheduled a collection which failed to allocate. No
 911         // point in trying to allocate further. We'll just return NULL.
 912         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 913                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 914         return NULL;
 915       }
 916       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
 917                            Thread::current()->name(), word_size);
 918     } else {
 919       // Failed to schedule a collection.
 920       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 921         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 922                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 923         return NULL;
 924       }
 925       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 926       // The GCLocker is either active or the GCLocker initiated
 927       // GC has not yet been performed. Stall until it is and
 928       // then retry the allocation.
 929       GCLocker::stall_until_clear();
 930       gclocker_retry_count += 1;
 931     }
 932 
 933 
 934     // We can reach here if we were unsuccessful in scheduling a
 935     // collection (because another thread beat us to it) or if we were
 936     // stalled due to the GC locker. In either can we should retry the
 937     // allocation attempt in case another thread successfully
 938     // performed a collection and reclaimed enough space.
 939     // Humongous object allocation always needs a lock, so we wait for the retry
 940     // in the next iteration of the loop, unlike for the regular iteration case.
 941     // Give a warning if we seem to be looping forever.
 942 
 943     if ((QueuedAllocationWarningCount > 0) &&
 944         (try_count % QueuedAllocationWarningCount == 0)) {
 945       log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
 946                              Thread::current()->name(), try_count, word_size);
 947     }
 948   }
 949 
 950   ShouldNotReachHere();
 951   return NULL;
 952 }
 953 
 954 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
 955                                                            bool expect_null_mutator_alloc_region) {
 956   assert_at_safepoint_on_vm_thread();
 957   assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
 958          "the current alloc region was unexpectedly found to be non-NULL");
 959 
 960   if (!is_humongous(word_size)) {
 961     return _allocator->attempt_allocation_locked(word_size);
 962   } else {
 963     HeapWord* result = humongous_obj_allocate(word_size);
 964     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
 965       collector_state()->set_initiate_conc_mark_if_possible(true);
 966     }
 967     return result;
 968   }
 969 
 970   ShouldNotReachHere();
 971 }
 972 
 973 class PostCompactionPrinterClosure: public HeapRegionClosure {
 974 private:
 975   G1HRPrinter* _hr_printer;
 976 public:
 977   bool do_heap_region(HeapRegion* hr) {
 978     assert(!hr->is_young(), "not expecting to find young regions");
 979     _hr_printer->post_compaction(hr);
 980     return false;
 981   }
 982 
 983   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
 984     : _hr_printer(hr_printer) { }
 985 };
 986 
 987 void G1CollectedHeap::print_hrm_post_compaction() {
 988   if (_hr_printer.is_active()) {
 989     PostCompactionPrinterClosure cl(hr_printer());
 990     heap_region_iterate(&cl);
 991   }
 992 }
 993 
 994 void G1CollectedHeap::abort_concurrent_cycle() {
 995   // If we start the compaction before the CM threads finish
 996   // scanning the root regions we might trip them over as we'll
 997   // be moving objects / updating references. So let's wait until
 998   // they are done. By telling them to abort, they should complete
 999   // early.
1000   _cm->root_regions()->abort();
1001   _cm->root_regions()->wait_until_scan_finished();
1002 
1003   // Disable discovery and empty the discovered lists
1004   // for the CM ref processor.
1005   _ref_processor_cm->disable_discovery();
1006   _ref_processor_cm->abandon_partial_discovery();
1007   _ref_processor_cm->verify_no_references_recorded();
1008 
1009   // Abandon current iterations of concurrent marking and concurrent
1010   // refinement, if any are in progress.
1011   concurrent_mark()->concurrent_cycle_abort();
1012 }
1013 
1014 void G1CollectedHeap::prepare_heap_for_full_collection() {
1015   // Make sure we'll choose a new allocation region afterwards.
1016   _allocator->release_mutator_alloc_region();
1017   _allocator->abandon_gc_alloc_regions();
1018   g1_rem_set()->cleanupHRRS();
1019 
1020   // We may have added regions to the current incremental collection
1021   // set between the last GC or pause and now. We need to clear the
1022   // incremental collection set and then start rebuilding it afresh
1023   // after this full GC.
1024   abandon_collection_set(collection_set());
1025 
1026   tear_down_region_sets(false /* free_list_only */);
1027 }
1028 
1029 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1030   assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1031   assert(used() == recalculate_used(), "Should be equal");
1032   _verifier->verify_region_sets_optional();
1033   _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
1034   _verifier->check_bitmaps("Full GC Start");
1035 }
1036 
1037 void G1CollectedHeap::prepare_heap_for_mutators() {
1038   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1039   ClassLoaderDataGraph::purge();
1040   MetaspaceUtils::verify_metrics();
1041 
1042   // Prepare heap for normal collections.
1043   assert(num_free_regions() == 0, "we should not have added any free regions");
1044   rebuild_region_sets(false /* free_list_only */);
1045   abort_refinement();
1046   resize_if_necessary_after_full_collection();
1047 
1048   // Rebuild the strong code root lists for each region
1049   rebuild_strong_code_roots();
1050 
1051   // Start a new incremental collection set for the next pause
1052   start_new_collection_set();
1053 
1054   _allocator->init_mutator_alloc_region();
1055 
1056   // Post collection state updates.
1057   MetaspaceGC::compute_new_size();
1058 }
1059 
1060 void G1CollectedHeap::abort_refinement() {
1061   if (_hot_card_cache->use_cache()) {
1062     _hot_card_cache->reset_hot_cache();
1063   }
1064 
1065   // Discard all remembered set updates.
1066   G1BarrierSet::dirty_card_queue_set().abandon_logs();
1067   assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1068 }
1069 
1070 void G1CollectedHeap::verify_after_full_collection() {
1071   _hrm.verify_optional();
1072   _verifier->verify_region_sets_optional();
1073   _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);
1074   // Clear the previous marking bitmap, if needed for bitmap verification.
1075   // Note we cannot do this when we clear the next marking bitmap in
1076   // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1077   // objects marked during a full GC against the previous bitmap.
1078   // But we need to clear it before calling check_bitmaps below since
1079   // the full GC has compacted objects and updated TAMS but not updated
1080   // the prev bitmap.
1081   if (G1VerifyBitmaps) {
1082     GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1083     _cm->clear_prev_bitmap(workers());
1084   }
1085   _verifier->check_bitmaps("Full GC End");
1086 
1087   // At this point there should be no regions in the
1088   // entire heap tagged as young.
1089   assert(check_young_list_empty(), "young list should be empty at this point");
1090 
1091   // Note: since we've just done a full GC, concurrent
1092   // marking is no longer active. Therefore we need not
1093   // re-enable reference discovery for the CM ref processor.
1094   // That will be done at the start of the next marking cycle.
1095   // We also know that the STW processor should no longer
1096   // discover any new references.
1097   assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
1098   assert(!_ref_processor_cm->discovery_enabled(), "Postcondition");
1099   _ref_processor_stw->verify_no_references_recorded();
1100   _ref_processor_cm->verify_no_references_recorded();
1101 }
1102 
1103 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1104   // Post collection logging.
1105   // We should do this after we potentially resize the heap so
1106   // that all the COMMIT / UNCOMMIT events are generated before
1107   // the compaction events.
1108   print_hrm_post_compaction();
1109   heap_transition->print();
1110   print_heap_after_gc();
1111   print_heap_regions();
1112 #ifdef TRACESPINNING
1113   ParallelTaskTerminator::print_termination_counts();
1114 #endif
1115 }
1116 
1117 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1118                                          bool clear_all_soft_refs) {
1119   assert_at_safepoint_on_vm_thread();
1120 
1121   if (GCLocker::check_active_before_gc()) {
1122     // Full GC was not completed.
1123     return false;
1124   }
1125 
1126   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1127       soft_ref_policy()->should_clear_all_soft_refs();
1128 
1129   G1FullCollector collector(this, &_full_gc_memory_manager, explicit_gc, do_clear_all_soft_refs);
1130   GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1131 
1132   collector.prepare_collection();
1133   collector.collect();
1134   collector.complete_collection();
1135 
1136   // Full collection was successfully completed.
1137   return true;
1138 }
1139 
1140 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1141   // Currently, there is no facility in the do_full_collection(bool) API to notify
1142   // the caller that the collection did not succeed (e.g., because it was locked
1143   // out by the GC locker). So, right now, we'll ignore the return value.
1144   bool dummy = do_full_collection(true,                /* explicit_gc */
1145                                   clear_all_soft_refs);
1146 }
1147 
1148 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1149   // Capacity, free and used after the GC counted as full regions to
1150   // include the waste in the following calculations.
1151   const size_t capacity_after_gc = capacity();
1152   const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1153 
1154   // This is enforced in arguments.cpp.
1155   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1156          "otherwise the code below doesn't make sense");
1157 
1158   // We don't have floating point command-line arguments
1159   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1160   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1161   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1162   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1163 
1164   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1165   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1166 
1167   // We have to be careful here as these two calculations can overflow
1168   // 32-bit size_t's.
1169   double used_after_gc_d = (double) used_after_gc;
1170   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1171   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1172 
1173   // Let's make sure that they are both under the max heap size, which
1174   // by default will make them fit into a size_t.
1175   double desired_capacity_upper_bound = (double) max_heap_size;
1176   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1177                                     desired_capacity_upper_bound);
1178   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1179                                     desired_capacity_upper_bound);
1180 
1181   // We can now safely turn them into size_t's.
1182   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1183   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1184 
1185   // This assert only makes sense here, before we adjust them
1186   // with respect to the min and max heap size.
1187   assert(minimum_desired_capacity <= maximum_desired_capacity,
1188          "minimum_desired_capacity = " SIZE_FORMAT ", "
1189          "maximum_desired_capacity = " SIZE_FORMAT,
1190          minimum_desired_capacity, maximum_desired_capacity);
1191 
1192   // Should not be greater than the heap max size. No need to adjust
1193   // it with respect to the heap min size as it's a lower bound (i.e.,
1194   // we'll try to make the capacity larger than it, not smaller).
1195   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1196   // Should not be less than the heap min size. No need to adjust it
1197   // with respect to the heap max size as it's an upper bound (i.e.,
1198   // we'll try to make the capacity smaller than it, not greater).
1199   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1200 
1201   if (capacity_after_gc < minimum_desired_capacity) {
1202     // Don't expand unless it's significant
1203     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1204 
1205     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1206                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1207                               "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1208                               capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1209 
1210     expand(expand_bytes, _workers);
1211 
1212     // No expansion, now see if we want to shrink
1213   } else if (capacity_after_gc > maximum_desired_capacity) {
1214     // Capacity too large, compute shrinking size
1215     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1216 
1217     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1218                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1219                               "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1220                               capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1221 
1222     shrink(shrink_bytes);
1223   }
1224 }
1225 
1226 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1227                                                             bool do_gc,
1228                                                             bool clear_all_soft_refs,
1229                                                             bool expect_null_mutator_alloc_region,
1230                                                             bool* gc_succeeded) {
1231   *gc_succeeded = true;
1232   // Let's attempt the allocation first.
1233   HeapWord* result =
1234     attempt_allocation_at_safepoint(word_size,
1235                                     expect_null_mutator_alloc_region);
1236   if (result != NULL) {
1237     return result;
1238   }
1239 
1240   // In a G1 heap, we're supposed to keep allocation from failing by
1241   // incremental pauses.  Therefore, at least for now, we'll favor
1242   // expansion over collection.  (This might change in the future if we can
1243   // do something smarter than full collection to satisfy a failed alloc.)
1244   result = expand_and_allocate(word_size);
1245   if (result != NULL) {
1246     return result;
1247   }
1248 
1249   if (do_gc) {
1250     // Expansion didn't work, we'll try to do a Full GC.
1251     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1252                                        clear_all_soft_refs);
1253   }
1254 
1255   return NULL;
1256 }
1257 
1258 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1259                                                      bool* succeeded) {
1260   assert_at_safepoint_on_vm_thread();
1261 
1262   // Attempts to allocate followed by Full GC.
1263   HeapWord* result =
1264     satisfy_failed_allocation_helper(word_size,
1265                                      true,  /* do_gc */
1266                                      false, /* clear_all_soft_refs */
1267                                      false, /* expect_null_mutator_alloc_region */
1268                                      succeeded);
1269 
1270   if (result != NULL || !*succeeded) {
1271     return result;
1272   }
1273 
1274   // Attempts to allocate followed by Full GC that will collect all soft references.
1275   result = satisfy_failed_allocation_helper(word_size,
1276                                             true, /* do_gc */
1277                                             true, /* clear_all_soft_refs */
1278                                             true, /* expect_null_mutator_alloc_region */
1279                                             succeeded);
1280 
1281   if (result != NULL || !*succeeded) {
1282     return result;
1283   }
1284 
1285   // Attempts to allocate, no GC
1286   result = satisfy_failed_allocation_helper(word_size,
1287                                             false, /* do_gc */
1288                                             false, /* clear_all_soft_refs */
1289                                             true,  /* expect_null_mutator_alloc_region */
1290                                             succeeded);
1291 
1292   if (result != NULL) {
1293     return result;
1294   }
1295 
1296   assert(!soft_ref_policy()->should_clear_all_soft_refs(),
1297          "Flag should have been handled and cleared prior to this point");
1298 
1299   // What else?  We might try synchronous finalization later.  If the total
1300   // space available is large enough for the allocation, then a more
1301   // complete compaction phase than we've tried so far might be
1302   // appropriate.
1303   return NULL;
1304 }
1305 
1306 // Attempting to expand the heap sufficiently
1307 // to support an allocation of the given "word_size".  If
1308 // successful, perform the allocation and return the address of the
1309 // allocated block, or else "NULL".
1310 
1311 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1312   assert_at_safepoint_on_vm_thread();
1313 
1314   _verifier->verify_region_sets_optional();
1315 
1316   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1317   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1318                             word_size * HeapWordSize);
1319 
1320 
1321   if (expand(expand_bytes, _workers)) {
1322     _hrm.verify_optional();
1323     _verifier->verify_region_sets_optional();
1324     return attempt_allocation_at_safepoint(word_size,
1325                                            false /* expect_null_mutator_alloc_region */);
1326   }
1327   return NULL;
1328 }
1329 
1330 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1331   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1332   aligned_expand_bytes = align_up(aligned_expand_bytes,
1333                                        HeapRegion::GrainBytes);
1334 
1335   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1336                             expand_bytes, aligned_expand_bytes);
1337 
1338   if (is_maximal_no_gc()) {
1339     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1340     return false;
1341   }
1342 
1343   double expand_heap_start_time_sec = os::elapsedTime();
1344   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1345   assert(regions_to_expand > 0, "Must expand by at least one region");
1346 
1347   uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1348   if (expand_time_ms != NULL) {
1349     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1350   }
1351 
1352   if (expanded_by > 0) {
1353     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1354     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1355     g1_policy()->record_new_heap_size(num_regions());
1356   } else {
1357     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1358 
1359     // The expansion of the virtual storage space was unsuccessful.
1360     // Let's see if it was because we ran out of swap.
1361     if (G1ExitOnExpansionFailure &&
1362         _hrm.available() >= regions_to_expand) {
1363       // We had head room...
1364       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1365     }
1366   }
1367   return regions_to_expand > 0;
1368 }
1369 
1370 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1371   size_t aligned_shrink_bytes =
1372     ReservedSpace::page_align_size_down(shrink_bytes);
1373   aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1374                                          HeapRegion::GrainBytes);
1375   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1376 
1377   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1378   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1379 
1380 
1381   log_debug(gc, ergo, heap)("Shrink the heap. requested shrinking amount: " SIZE_FORMAT "B aligned shrinking amount: " SIZE_FORMAT "B attempted shrinking amount: " SIZE_FORMAT "B",
1382                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1383   if (num_regions_removed > 0) {
1384     g1_policy()->record_new_heap_size(num_regions());
1385   } else {
1386     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1387   }
1388 }
1389 
1390 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1391   _verifier->verify_region_sets_optional();
1392 
1393   // We should only reach here at the end of a Full GC which means we
1394   // should not not be holding to any GC alloc regions. The method
1395   // below will make sure of that and do any remaining clean up.
1396   _allocator->abandon_gc_alloc_regions();
1397 
1398   // Instead of tearing down / rebuilding the free lists here, we
1399   // could instead use the remove_all_pending() method on free_list to
1400   // remove only the ones that we need to remove.
1401   tear_down_region_sets(true /* free_list_only */);
1402   shrink_helper(shrink_bytes);
1403   rebuild_region_sets(true /* free_list_only */);
1404 
1405   _hrm.verify_optional();
1406   _verifier->verify_region_sets_optional();
1407 }
1408 
1409 // Public methods.
1410 
1411 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1412   CollectedHeap(),
1413   _young_gen_sampling_thread(NULL),
1414   _collector_policy(collector_policy),
1415   _soft_ref_policy(),
1416   _card_table(NULL),
1417   _memory_manager("G1 Young Generation", "end of minor GC"),
1418   _full_gc_memory_manager("G1 Old Generation", "end of major GC"),
1419   _eden_pool(NULL),
1420   _survivor_pool(NULL),
1421   _old_pool(NULL),
1422   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1423   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1424   _g1_policy(new G1Policy(_gc_timer_stw)),
1425   _collection_set(this, _g1_policy),
1426   _dirty_card_queue_set(false),
1427   _ref_processor_stw(NULL),
1428   _is_alive_closure_stw(this),
1429   _is_subject_to_discovery_stw(this),
1430   _ref_processor_cm(NULL),
1431   _is_alive_closure_cm(this),
1432   _is_subject_to_discovery_cm(this),
1433   _bot(NULL),
1434   _hot_card_cache(NULL),
1435   _g1_rem_set(NULL),
1436   _cr(NULL),
1437   _g1mm(NULL),
1438   _preserved_marks_set(true /* in_c_heap */),
1439   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1440   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1441   _humongous_reclaim_candidates(),
1442   _has_humongous_reclaim_candidates(false),
1443   _archive_allocator(NULL),
1444   _summary_bytes_used(0),
1445   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1446   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1447   _expand_heap_after_alloc_failure(true),
1448   _old_marking_cycles_started(0),
1449   _old_marking_cycles_completed(0),
1450   _in_cset_fast_test() {
1451 
1452   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1453                           /* are_GC_task_threads */true,
1454                           /* are_ConcurrentGC_threads */false);
1455   _workers->initialize_workers();
1456   _verifier = new G1HeapVerifier(this);
1457 
1458   _allocator = new G1Allocator(this);
1459 
1460   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1461 
1462   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1463 
1464   // Override the default _filler_array_max_size so that no humongous filler
1465   // objects are created.
1466   _filler_array_max_size = _humongous_object_threshold_in_words;
1467 
1468   uint n_queues = ParallelGCThreads;
1469   _task_queues = new RefToScanQueueSet(n_queues);
1470 
1471   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1472 
1473   for (uint i = 0; i < n_queues; i++) {
1474     RefToScanQueue* q = new RefToScanQueue();
1475     q->initialize();
1476     _task_queues->register_queue(i, q);
1477     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1478   }
1479 
1480   // Initialize the G1EvacuationFailureALot counters and flags.
1481   NOT_PRODUCT(reset_evacuation_should_fail();)
1482 
1483   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1484 }
1485 
1486 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1487                                                                  size_t size,
1488                                                                  size_t translation_factor) {
1489   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1490   // Allocate a new reserved space, preferring to use large pages.
1491   ReservedSpace rs(size, preferred_page_size);
1492   G1RegionToSpaceMapper* result  =
1493     G1RegionToSpaceMapper::create_mapper(rs,
1494                                          size,
1495                                          rs.alignment(),
1496                                          HeapRegion::GrainBytes,
1497                                          translation_factor,
1498                                          mtGC);
1499 
1500   os::trace_page_sizes_for_requested_size(description,
1501                                           size,
1502                                           preferred_page_size,
1503                                           rs.alignment(),
1504                                           rs.base(),
1505                                           rs.size());
1506 
1507   return result;
1508 }
1509 
1510 jint G1CollectedHeap::initialize_concurrent_refinement() {
1511   jint ecode = JNI_OK;
1512   _cr = G1ConcurrentRefine::create(&ecode);
1513   return ecode;
1514 }
1515 
1516 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1517   _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1518   if (_young_gen_sampling_thread->osthread() == NULL) {
1519     vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1520     return JNI_ENOMEM;
1521   }
1522   return JNI_OK;
1523 }
1524 
1525 jint G1CollectedHeap::initialize() {
1526   os::enable_vtime();
1527 
1528   // Necessary to satisfy locking discipline assertions.
1529 
1530   MutexLocker x(Heap_lock);
1531 
1532   // While there are no constraints in the GC code that HeapWordSize
1533   // be any particular value, there are multiple other areas in the
1534   // system which believe this to be true (e.g. oop->object_size in some
1535   // cases incorrectly returns the size in wordSize units rather than
1536   // HeapWordSize).
1537   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1538 
1539   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1540   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1541   size_t heap_alignment = collector_policy()->heap_alignment();
1542 
1543   // Ensure that the sizes are properly aligned.
1544   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1545   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1546   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1547 
1548   // Reserve the maximum.
1549 
1550   // When compressed oops are enabled, the preferred heap base
1551   // is calculated by subtracting the requested size from the
1552   // 32Gb boundary and using the result as the base address for
1553   // heap reservation. If the requested size is not aligned to
1554   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1555   // into the ReservedHeapSpace constructor) then the actual
1556   // base of the reserved heap may end up differing from the
1557   // address that was requested (i.e. the preferred heap base).
1558   // If this happens then we could end up using a non-optimal
1559   // compressed oops mode.
1560 
1561   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1562                                                  heap_alignment);
1563 
1564   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1565 
1566   // Create the barrier set for the entire reserved region.
1567   G1CardTable* ct = new G1CardTable(reserved_region());
1568   ct->initialize();
1569   G1BarrierSet* bs = new G1BarrierSet(ct);
1570   bs->initialize();
1571   assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1572   BarrierSet::set_barrier_set(bs);
1573   _card_table = ct;
1574 
1575   // Create the hot card cache.
1576   _hot_card_cache = new G1HotCardCache(this);
1577 
1578   // Carve out the G1 part of the heap.
1579   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1580   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1581   G1RegionToSpaceMapper* heap_storage =
1582     G1RegionToSpaceMapper::create_mapper(g1_rs,
1583                                          g1_rs.size(),
1584                                          page_size,
1585                                          HeapRegion::GrainBytes,
1586                                          1,
1587                                          mtJavaHeap);
1588   os::trace_page_sizes("Heap",
1589                        collector_policy()->min_heap_byte_size(),
1590                        max_byte_size,
1591                        page_size,
1592                        heap_rs.base(),
1593                        heap_rs.size());
1594   heap_storage->set_mapping_changed_listener(&_listener);
1595 
1596   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1597   G1RegionToSpaceMapper* bot_storage =
1598     create_aux_memory_mapper("Block Offset Table",
1599                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1600                              G1BlockOffsetTable::heap_map_factor());
1601 
1602   G1RegionToSpaceMapper* cardtable_storage =
1603     create_aux_memory_mapper("Card Table",
1604                              G1CardTable::compute_size(g1_rs.size() / HeapWordSize),
1605                              G1CardTable::heap_map_factor());
1606 
1607   G1RegionToSpaceMapper* card_counts_storage =
1608     create_aux_memory_mapper("Card Counts Table",
1609                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1610                              G1CardCounts::heap_map_factor());
1611 
1612   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1613   G1RegionToSpaceMapper* prev_bitmap_storage =
1614     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1615   G1RegionToSpaceMapper* next_bitmap_storage =
1616     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1617 
1618   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1619   _card_table->initialize(cardtable_storage);
1620   // Do later initialization work for concurrent refinement.
1621   _hot_card_cache->initialize(card_counts_storage);
1622 
1623   // 6843694 - ensure that the maximum region index can fit
1624   // in the remembered set structures.
1625   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1626   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1627 
1628   // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
1629   // start within the first card.
1630   guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card.");
1631   // Also create a G1 rem set.
1632   _g1_rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
1633   _g1_rem_set->initialize(max_capacity(), max_regions());
1634 
1635   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1636   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1637   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1638             "too many cards per region");
1639 
1640   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1641 
1642   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1643 
1644   {
1645     HeapWord* start = _hrm.reserved().start();
1646     HeapWord* end = _hrm.reserved().end();
1647     size_t granularity = HeapRegion::GrainBytes;
1648 
1649     _in_cset_fast_test.initialize(start, end, granularity);
1650     _humongous_reclaim_candidates.initialize(start, end, granularity);
1651   }
1652 
1653   // Create the G1ConcurrentMark data structure and thread.
1654   // (Must do this late, so that "max_regions" is defined.)
1655   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1656   if (_cm == NULL || !_cm->completed_initialization()) {
1657     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1658     return JNI_ENOMEM;
1659   }
1660   _cm_thread = _cm->cm_thread();
1661 
1662   // Now expand into the initial heap size.
1663   if (!expand(init_byte_size, _workers)) {
1664     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1665     return JNI_ENOMEM;
1666   }
1667 
1668   // Perform any initialization actions delegated to the policy.
1669   g1_policy()->init(this, &_collection_set);
1670 
1671   G1BarrierSet::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1672                                                  SATB_Q_FL_lock,
1673                                                  G1SATBProcessCompletedThreshold,
1674                                                  Shared_SATB_Q_lock);
1675 
1676   jint ecode = initialize_concurrent_refinement();
1677   if (ecode != JNI_OK) {
1678     return ecode;
1679   }
1680 
1681   ecode = initialize_young_gen_sampling_thread();
1682   if (ecode != JNI_OK) {
1683     return ecode;
1684   }
1685 
1686   G1BarrierSet::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1687                                                   DirtyCardQ_FL_lock,
1688                                                   (int)concurrent_refine()->yellow_zone(),
1689                                                   (int)concurrent_refine()->red_zone(),
1690                                                   Shared_DirtyCardQ_lock,
1691                                                   NULL,  // fl_owner
1692                                                   true); // init_free_ids
1693 
1694   dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1695                                     DirtyCardQ_FL_lock,
1696                                     -1, // never trigger processing
1697                                     -1, // no limit on length
1698                                     Shared_DirtyCardQ_lock,
1699                                     &G1BarrierSet::dirty_card_queue_set());
1700 
1701   // Here we allocate the dummy HeapRegion that is required by the
1702   // G1AllocRegion class.
1703   HeapRegion* dummy_region = _hrm.get_dummy_region();
1704 
1705   // We'll re-use the same region whether the alloc region will
1706   // require BOT updates or not and, if it doesn't, then a non-young
1707   // region will complain that it cannot support allocations without
1708   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1709   dummy_region->set_eden();
1710   // Make sure it's full.
1711   dummy_region->set_top(dummy_region->end());
1712   G1AllocRegion::setup(this, dummy_region);
1713 
1714   _allocator->init_mutator_alloc_region();
1715 
1716   // Do create of the monitoring and management support so that
1717   // values in the heap have been properly initialized.
1718   _g1mm = new G1MonitoringSupport(this);
1719 
1720   G1StringDedup::initialize();
1721 
1722   _preserved_marks_set.init(ParallelGCThreads);
1723 
1724   _collection_set.initialize(max_regions());
1725 
1726   return JNI_OK;
1727 }
1728 
1729 void G1CollectedHeap::initialize_serviceability() {
1730   _eden_pool = new G1EdenPool(this);
1731   _survivor_pool = new G1SurvivorPool(this);
1732   _old_pool = new G1OldGenPool(this);
1733 
1734   _full_gc_memory_manager.add_pool(_eden_pool);
1735   _full_gc_memory_manager.add_pool(_survivor_pool);
1736   _full_gc_memory_manager.add_pool(_old_pool);
1737 
1738   _memory_manager.add_pool(_eden_pool);
1739   _memory_manager.add_pool(_survivor_pool);
1740 
1741 }
1742 
1743 void G1CollectedHeap::stop() {
1744   // Stop all concurrent threads. We do this to make sure these threads
1745   // do not continue to execute and access resources (e.g. logging)
1746   // that are destroyed during shutdown.
1747   _cr->stop();
1748   _young_gen_sampling_thread->stop();
1749   _cm_thread->stop();
1750   if (G1StringDedup::is_enabled()) {
1751     G1StringDedup::stop();
1752   }
1753 }
1754 
1755 void G1CollectedHeap::safepoint_synchronize_begin() {
1756   SuspendibleThreadSet::synchronize();
1757 }
1758 
1759 void G1CollectedHeap::safepoint_synchronize_end() {
1760   SuspendibleThreadSet::desynchronize();
1761 }
1762 
1763 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1764   return HeapRegion::max_region_size();
1765 }
1766 
1767 void G1CollectedHeap::post_initialize() {
1768   CollectedHeap::post_initialize();
1769   ref_processing_init();
1770 }
1771 
1772 void G1CollectedHeap::ref_processing_init() {
1773   // Reference processing in G1 currently works as follows:
1774   //
1775   // * There are two reference processor instances. One is
1776   //   used to record and process discovered references
1777   //   during concurrent marking; the other is used to
1778   //   record and process references during STW pauses
1779   //   (both full and incremental).
1780   // * Both ref processors need to 'span' the entire heap as
1781   //   the regions in the collection set may be dotted around.
1782   //
1783   // * For the concurrent marking ref processor:
1784   //   * Reference discovery is enabled at initial marking.
1785   //   * Reference discovery is disabled and the discovered
1786   //     references processed etc during remarking.
1787   //   * Reference discovery is MT (see below).
1788   //   * Reference discovery requires a barrier (see below).
1789   //   * Reference processing may or may not be MT
1790   //     (depending on the value of ParallelRefProcEnabled
1791   //     and ParallelGCThreads).
1792   //   * A full GC disables reference discovery by the CM
1793   //     ref processor and abandons any entries on it's
1794   //     discovered lists.
1795   //
1796   // * For the STW processor:
1797   //   * Non MT discovery is enabled at the start of a full GC.
1798   //   * Processing and enqueueing during a full GC is non-MT.
1799   //   * During a full GC, references are processed after marking.
1800   //
1801   //   * Discovery (may or may not be MT) is enabled at the start
1802   //     of an incremental evacuation pause.
1803   //   * References are processed near the end of a STW evacuation pause.
1804   //   * For both types of GC:
1805   //     * Discovery is atomic - i.e. not concurrent.
1806   //     * Reference discovery will not need a barrier.
1807 
1808   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1809 
1810   // Concurrent Mark ref processor
1811   _ref_processor_cm =
1812     new ReferenceProcessor(&_is_subject_to_discovery_cm,
1813                            mt_processing,                                  // mt processing
1814                            ParallelGCThreads,                              // degree of mt processing
1815                            (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery
1816                            MAX2(ParallelGCThreads, ConcGCThreads),         // degree of mt discovery
1817                            false,                                          // Reference discovery is not atomic
1818                            &_is_alive_closure_cm,                          // is alive closure
1819                            true);                                          // allow changes to number of processing threads
1820 
1821   // STW ref processor
1822   _ref_processor_stw =
1823     new ReferenceProcessor(&_is_subject_to_discovery_stw,
1824                            mt_processing,                        // mt processing
1825                            ParallelGCThreads,                    // degree of mt processing
1826                            (ParallelGCThreads > 1),              // mt discovery
1827                            ParallelGCThreads,                    // degree of mt discovery
1828                            true,                                 // Reference discovery is atomic
1829                            &_is_alive_closure_stw,               // is alive closure
1830                            true);                                // allow changes to number of processing threads
1831 }
1832 
1833 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1834   return _collector_policy;
1835 }
1836 
1837 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
1838   return &_soft_ref_policy;
1839 }
1840 
1841 size_t G1CollectedHeap::capacity() const {
1842   return _hrm.length() * HeapRegion::GrainBytes;
1843 }
1844 
1845 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1846   return _hrm.total_free_bytes();
1847 }
1848 
1849 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
1850   _hot_card_cache->drain(cl, worker_i);
1851 }
1852 
1853 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
1854   DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1855   size_t n_completed_buffers = 0;
1856   while (dcqs.apply_closure_during_gc(cl, worker_i)) {
1857     n_completed_buffers++;
1858   }
1859   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers, G1GCPhaseTimes::UpdateRSProcessedBuffers);
1860   dcqs.clear_n_completed_buffers();
1861   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
1862 }
1863 
1864 // Computes the sum of the storage used by the various regions.
1865 size_t G1CollectedHeap::used() const {
1866   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1867   if (_archive_allocator != NULL) {
1868     result += _archive_allocator->used();
1869   }
1870   return result;
1871 }
1872 
1873 size_t G1CollectedHeap::used_unlocked() const {
1874   return _summary_bytes_used;
1875 }
1876 
1877 class SumUsedClosure: public HeapRegionClosure {
1878   size_t _used;
1879 public:
1880   SumUsedClosure() : _used(0) {}
1881   bool do_heap_region(HeapRegion* r) {
1882     _used += r->used();
1883     return false;
1884   }
1885   size_t result() { return _used; }
1886 };
1887 
1888 size_t G1CollectedHeap::recalculate_used() const {
1889   double recalculate_used_start = os::elapsedTime();
1890 
1891   SumUsedClosure blk;
1892   heap_region_iterate(&blk);
1893 
1894   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
1895   return blk.result();
1896 }
1897 
1898 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
1899   switch (cause) {
1900     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
1901     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
1902     case GCCause::_wb_conc_mark:                        return true;
1903     default :                                           return false;
1904   }
1905 }
1906 
1907 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
1908   switch (cause) {
1909     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
1910     case GCCause::_g1_humongous_allocation: return true;
1911     default:                                return is_user_requested_concurrent_full_gc(cause);
1912   }
1913 }
1914 
1915 #ifndef PRODUCT
1916 void G1CollectedHeap::allocate_dummy_regions() {
1917   // Let's fill up most of the region
1918   size_t word_size = HeapRegion::GrainWords - 1024;
1919   // And as a result the region we'll allocate will be humongous.
1920   guarantee(is_humongous(word_size), "sanity");
1921 
1922   // _filler_array_max_size is set to humongous object threshold
1923   // but temporarily change it to use CollectedHeap::fill_with_object().
1924   SizeTFlagSetting fs(_filler_array_max_size, word_size);
1925 
1926   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
1927     // Let's use the existing mechanism for the allocation
1928     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
1929     if (dummy_obj != NULL) {
1930       MemRegion mr(dummy_obj, word_size);
1931       CollectedHeap::fill_with_object(mr);
1932     } else {
1933       // If we can't allocate once, we probably cannot allocate
1934       // again. Let's get out of the loop.
1935       break;
1936     }
1937   }
1938 }
1939 #endif // !PRODUCT
1940 
1941 void G1CollectedHeap::increment_old_marking_cycles_started() {
1942   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
1943          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
1944          "Wrong marking cycle count (started: %d, completed: %d)",
1945          _old_marking_cycles_started, _old_marking_cycles_completed);
1946 
1947   _old_marking_cycles_started++;
1948 }
1949 
1950 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
1951   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
1952 
1953   // We assume that if concurrent == true, then the caller is a
1954   // concurrent thread that was joined the Suspendible Thread
1955   // Set. If there's ever a cheap way to check this, we should add an
1956   // assert here.
1957 
1958   // Given that this method is called at the end of a Full GC or of a
1959   // concurrent cycle, and those can be nested (i.e., a Full GC can
1960   // interrupt a concurrent cycle), the number of full collections
1961   // completed should be either one (in the case where there was no
1962   // nesting) or two (when a Full GC interrupted a concurrent cycle)
1963   // behind the number of full collections started.
1964 
1965   // This is the case for the inner caller, i.e. a Full GC.
1966   assert(concurrent ||
1967          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
1968          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
1969          "for inner caller (Full GC): _old_marking_cycles_started = %u "
1970          "is inconsistent with _old_marking_cycles_completed = %u",
1971          _old_marking_cycles_started, _old_marking_cycles_completed);
1972 
1973   // This is the case for the outer caller, i.e. the concurrent cycle.
1974   assert(!concurrent ||
1975          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
1976          "for outer caller (concurrent cycle): "
1977          "_old_marking_cycles_started = %u "
1978          "is inconsistent with _old_marking_cycles_completed = %u",
1979          _old_marking_cycles_started, _old_marking_cycles_completed);
1980 
1981   _old_marking_cycles_completed += 1;
1982 
1983   // We need to clear the "in_progress" flag in the CM thread before
1984   // we wake up any waiters (especially when ExplicitInvokesConcurrent
1985   // is set) so that if a waiter requests another System.gc() it doesn't
1986   // incorrectly see that a marking cycle is still in progress.
1987   if (concurrent) {
1988     _cm_thread->set_idle();
1989   }
1990 
1991   // This notify_all() will ensure that a thread that called
1992   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
1993   // and it's waiting for a full GC to finish will be woken up. It is
1994   // waiting in VM_G1CollectForAllocation::doit_epilogue().
1995   FullGCCount_lock->notify_all();
1996 }
1997 
1998 void G1CollectedHeap::collect(GCCause::Cause cause) {
1999   assert_heap_not_locked();
2000 
2001   uint gc_count_before;
2002   uint old_marking_count_before;
2003   uint full_gc_count_before;
2004   bool retry_gc;
2005 
2006   do {
2007     retry_gc = false;
2008 
2009     {
2010       MutexLocker ml(Heap_lock);
2011 
2012       // Read the GC count while holding the Heap_lock
2013       gc_count_before = total_collections();
2014       full_gc_count_before = total_full_collections();
2015       old_marking_count_before = _old_marking_cycles_started;
2016     }
2017 
2018     if (should_do_concurrent_full_gc(cause)) {
2019       // Schedule an initial-mark evacuation pause that will start a
2020       // concurrent cycle. We're setting word_size to 0 which means that
2021       // we are not requesting a post-GC allocation.
2022       VM_G1CollectForAllocation op(0,     /* word_size */
2023                                    gc_count_before,
2024                                    cause,
2025                                    true,  /* should_initiate_conc_mark */
2026                                    g1_policy()->max_pause_time_ms());
2027       VMThread::execute(&op);
2028       if (!op.pause_succeeded()) {
2029         if (old_marking_count_before == _old_marking_cycles_started) {
2030           retry_gc = op.should_retry_gc();
2031         } else {
2032           // A Full GC happened while we were trying to schedule the
2033           // initial-mark GC. No point in starting a new cycle given
2034           // that the whole heap was collected anyway.
2035         }
2036 
2037         if (retry_gc) {
2038           if (GCLocker::is_active_and_needs_gc()) {
2039             GCLocker::stall_until_clear();
2040           }
2041         }
2042       }
2043     } else {
2044       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2045           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2046 
2047         // Schedule a standard evacuation pause. We're setting word_size
2048         // to 0 which means that we are not requesting a post-GC allocation.
2049         VM_G1CollectForAllocation op(0,     /* word_size */
2050                                      gc_count_before,
2051                                      cause,
2052                                      false, /* should_initiate_conc_mark */
2053                                      g1_policy()->max_pause_time_ms());
2054         VMThread::execute(&op);
2055       } else {
2056         // Schedule a Full GC.
2057         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2058         VMThread::execute(&op);
2059       }
2060     }
2061   } while (retry_gc);
2062 }
2063 
2064 bool G1CollectedHeap::is_in(const void* p) const {
2065   if (_hrm.reserved().contains(p)) {
2066     // Given that we know that p is in the reserved space,
2067     // heap_region_containing() should successfully
2068     // return the containing region.
2069     HeapRegion* hr = heap_region_containing(p);
2070     return hr->is_in(p);
2071   } else {
2072     return false;
2073   }
2074 }
2075 
2076 #ifdef ASSERT
2077 bool G1CollectedHeap::is_in_exact(const void* p) const {
2078   bool contains = reserved_region().contains(p);
2079   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2080   if (contains && available) {
2081     return true;
2082   } else {
2083     return false;
2084   }
2085 }
2086 #endif
2087 
2088 // Iteration functions.
2089 
2090 // Iterates an ObjectClosure over all objects within a HeapRegion.
2091 
2092 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2093   ObjectClosure* _cl;
2094 public:
2095   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2096   bool do_heap_region(HeapRegion* r) {
2097     if (!r->is_continues_humongous()) {
2098       r->object_iterate(_cl);
2099     }
2100     return false;
2101   }
2102 };
2103 
2104 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2105   IterateObjectClosureRegionClosure blk(cl);
2106   heap_region_iterate(&blk);
2107 }
2108 
2109 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2110   _hrm.iterate(cl);
2111 }
2112 
2113 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2114                                                                  HeapRegionClaimer *hrclaimer,
2115                                                                  uint worker_id) const {
2116   _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2117 }
2118 
2119 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2120                                                          HeapRegionClaimer *hrclaimer) const {
2121   _hrm.par_iterate(cl, hrclaimer, 0);
2122 }
2123 
2124 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2125   _collection_set.iterate(cl);
2126 }
2127 
2128 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2129   _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2130 }
2131 
2132 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2133   HeapRegion* hr = heap_region_containing(addr);
2134   return hr->block_start(addr);
2135 }
2136 
2137 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2138   HeapRegion* hr = heap_region_containing(addr);
2139   return hr->block_size(addr);
2140 }
2141 
2142 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2143   HeapRegion* hr = heap_region_containing(addr);
2144   return hr->block_is_obj(addr);
2145 }
2146 
2147 bool G1CollectedHeap::supports_tlab_allocation() const {
2148   return true;
2149 }
2150 
2151 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2152   return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2153 }
2154 
2155 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2156   return _eden.length() * HeapRegion::GrainBytes;
2157 }
2158 
2159 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2160 // must be equal to the humongous object limit.
2161 size_t G1CollectedHeap::max_tlab_size() const {
2162   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2163 }
2164 
2165 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2166   return _allocator->unsafe_max_tlab_alloc();
2167 }
2168 
2169 size_t G1CollectedHeap::max_capacity() const {
2170   return _hrm.reserved().byte_size();
2171 }
2172 
2173 jlong G1CollectedHeap::millis_since_last_gc() {
2174   // See the notes in GenCollectedHeap::millis_since_last_gc()
2175   // for more information about the implementation.
2176   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2177     _g1_policy->collection_pause_end_millis();
2178   if (ret_val < 0) {
2179     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2180       ". returning zero instead.", ret_val);
2181     return 0;
2182   }
2183   return ret_val;
2184 }
2185 
2186 void G1CollectedHeap::deduplicate_string(oop str) {
2187   assert(java_lang_String::is_instance(str), "invariant");
2188 
2189   if (G1StringDedup::is_enabled()) {
2190     G1StringDedup::deduplicate(str);
2191   }
2192 }
2193 
2194 void G1CollectedHeap::prepare_for_verify() {
2195   _verifier->prepare_for_verify();
2196 }
2197 
2198 void G1CollectedHeap::verify(VerifyOption vo) {
2199   _verifier->verify(vo);
2200 }
2201 
2202 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2203   return true;
2204 }
2205 
2206 const char* const* G1CollectedHeap::concurrent_phases() const {
2207   return _cm_thread->concurrent_phases();
2208 }
2209 
2210 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2211   return _cm_thread->request_concurrent_phase(phase);
2212 }
2213 
2214 class PrintRegionClosure: public HeapRegionClosure {
2215   outputStream* _st;
2216 public:
2217   PrintRegionClosure(outputStream* st) : _st(st) {}
2218   bool do_heap_region(HeapRegion* r) {
2219     r->print_on(_st);
2220     return false;
2221   }
2222 };
2223 
2224 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2225                                        const HeapRegion* hr,
2226                                        const VerifyOption vo) const {
2227   switch (vo) {
2228   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2229   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2230   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2231   default:                            ShouldNotReachHere();
2232   }
2233   return false; // keep some compilers happy
2234 }
2235 
2236 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2237                                        const VerifyOption vo) const {
2238   switch (vo) {
2239   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2240   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2241   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2242   default:                            ShouldNotReachHere();
2243   }
2244   return false; // keep some compilers happy
2245 }
2246 
2247 void G1CollectedHeap::print_heap_regions() const {
2248   LogTarget(Trace, gc, heap, region) lt;
2249   if (lt.is_enabled()) {
2250     LogStream ls(lt);
2251     print_regions_on(&ls);
2252   }
2253 }
2254 
2255 void G1CollectedHeap::print_on(outputStream* st) const {
2256   st->print(" %-20s", "garbage-first heap");
2257   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2258             capacity()/K, used_unlocked()/K);
2259   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2260             p2i(_hrm.reserved().start()),
2261             p2i(_hrm.reserved().end()));
2262   st->cr();
2263   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2264   uint young_regions = young_regions_count();
2265   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2266             (size_t) young_regions * HeapRegion::GrainBytes / K);
2267   uint survivor_regions = survivor_regions_count();
2268   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2269             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2270   st->cr();
2271   MetaspaceUtils::print_on(st);
2272 }
2273 
2274 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2275   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2276                "HS=humongous(starts), HC=humongous(continues), "
2277                "CS=collection set, F=free, A=archive, "
2278                "TAMS=top-at-mark-start (previous, next)");
2279   PrintRegionClosure blk(st);
2280   heap_region_iterate(&blk);
2281 }
2282 
2283 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2284   print_on(st);
2285 
2286   // Print the per-region information.
2287   print_regions_on(st);
2288 }
2289 
2290 void G1CollectedHeap::print_on_error(outputStream* st) const {
2291   this->CollectedHeap::print_on_error(st);
2292 
2293   if (_cm != NULL) {
2294     st->cr();
2295     _cm->print_on_error(st);
2296   }
2297 }
2298 
2299 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2300   workers()->print_worker_threads_on(st);
2301   _cm_thread->print_on(st);
2302   st->cr();
2303   _cm->print_worker_threads_on(st);
2304   _cr->print_threads_on(st);
2305   _young_gen_sampling_thread->print_on(st);
2306   if (G1StringDedup::is_enabled()) {
2307     G1StringDedup::print_worker_threads_on(st);
2308   }
2309 }
2310 
2311 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2312   workers()->threads_do(tc);
2313   tc->do_thread(_cm_thread);
2314   _cm->threads_do(tc);
2315   _cr->threads_do(tc);
2316   tc->do_thread(_young_gen_sampling_thread);
2317   if (G1StringDedup::is_enabled()) {
2318     G1StringDedup::threads_do(tc);
2319   }
2320 }
2321 
2322 void G1CollectedHeap::print_tracing_info() const {
2323   g1_rem_set()->print_summary_info();
2324   concurrent_mark()->print_summary_info();
2325 }
2326 
2327 #ifndef PRODUCT
2328 // Helpful for debugging RSet issues.
2329 
2330 class PrintRSetsClosure : public HeapRegionClosure {
2331 private:
2332   const char* _msg;
2333   size_t _occupied_sum;
2334 
2335 public:
2336   bool do_heap_region(HeapRegion* r) {
2337     HeapRegionRemSet* hrrs = r->rem_set();
2338     size_t occupied = hrrs->occupied();
2339     _occupied_sum += occupied;
2340 
2341     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2342     if (occupied == 0) {
2343       tty->print_cr("  RSet is empty");
2344     } else {
2345       hrrs->print();
2346     }
2347     tty->print_cr("----------");
2348     return false;
2349   }
2350 
2351   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2352     tty->cr();
2353     tty->print_cr("========================================");
2354     tty->print_cr("%s", msg);
2355     tty->cr();
2356   }
2357 
2358   ~PrintRSetsClosure() {
2359     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2360     tty->print_cr("========================================");
2361     tty->cr();
2362   }
2363 };
2364 
2365 void G1CollectedHeap::print_cset_rsets() {
2366   PrintRSetsClosure cl("Printing CSet RSets");
2367   collection_set_iterate(&cl);
2368 }
2369 
2370 void G1CollectedHeap::print_all_rsets() {
2371   PrintRSetsClosure cl("Printing All RSets");;
2372   heap_region_iterate(&cl);
2373 }
2374 #endif // PRODUCT
2375 
2376 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2377 
2378   size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2379   size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2380   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2381 
2382   size_t eden_capacity_bytes =
2383     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2384 
2385   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2386   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2387                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2388 }
2389 
2390 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2391   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2392                        stats->unused(), stats->used(), stats->region_end_waste(),
2393                        stats->regions_filled(), stats->direct_allocated(),
2394                        stats->failure_used(), stats->failure_waste());
2395 }
2396 
2397 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2398   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2399   gc_tracer->report_gc_heap_summary(when, heap_summary);
2400 
2401   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2402   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2403 }
2404 
2405 G1CollectedHeap* G1CollectedHeap::heap() {
2406   CollectedHeap* heap = Universe::heap();
2407   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2408   assert(heap->kind() == CollectedHeap::G1, "Invalid name");
2409   return (G1CollectedHeap*)heap;
2410 }
2411 
2412 void G1CollectedHeap::gc_prologue(bool full) {
2413   // always_do_update_barrier = false;
2414   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2415 
2416   // This summary needs to be printed before incrementing total collections.
2417   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2418 
2419   // Update common counters.
2420   increment_total_collections(full /* full gc */);
2421   if (full) {
2422     increment_old_marking_cycles_started();
2423   }
2424 
2425   // Fill TLAB's and such
2426   double start = os::elapsedTime();
2427   accumulate_statistics_all_tlabs();
2428   ensure_parsability(true);
2429   g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2430 }
2431 
2432 void G1CollectedHeap::gc_epilogue(bool full) {
2433   // Update common counters.
2434   if (full) {
2435     // Update the number of full collections that have been completed.
2436     increment_old_marking_cycles_completed(false /* concurrent */);
2437   }
2438 
2439   // We are at the end of the GC. Total collections has already been increased.
2440   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2441 
2442   // FIXME: what is this about?
2443   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2444   // is set.
2445 #if COMPILER2_OR_JVMCI
2446   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2447 #endif
2448   // always_do_update_barrier = true;
2449 
2450   double start = os::elapsedTime();
2451   resize_all_tlabs();
2452   g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2453 
2454   MemoryService::track_memory_usage();
2455   // We have just completed a GC. Update the soft reference
2456   // policy with the new heap occupancy
2457   Universe::update_heap_info_at_gc();
2458 }
2459 
2460 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2461                                                uint gc_count_before,
2462                                                bool* succeeded,
2463                                                GCCause::Cause gc_cause) {
2464   assert_heap_not_locked_and_not_at_safepoint();
2465   VM_G1CollectForAllocation op(word_size,
2466                                gc_count_before,
2467                                gc_cause,
2468                                false, /* should_initiate_conc_mark */
2469                                g1_policy()->max_pause_time_ms());
2470   VMThread::execute(&op);
2471 
2472   HeapWord* result = op.result();
2473   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2474   assert(result == NULL || ret_succeeded,
2475          "the result should be NULL if the VM did not succeed");
2476   *succeeded = ret_succeeded;
2477 
2478   assert_heap_not_locked();
2479   return result;
2480 }
2481 
2482 void G1CollectedHeap::do_concurrent_mark() {
2483   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2484   if (!_cm_thread->in_progress()) {
2485     _cm_thread->set_started();
2486     CGC_lock->notify();
2487   }
2488 }
2489 
2490 size_t G1CollectedHeap::pending_card_num() {
2491   size_t extra_cards = 0;
2492   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) {
2493     DirtyCardQueue& dcq = G1ThreadLocalData::dirty_card_queue(curr);
2494     extra_cards += dcq.size();
2495   }
2496   DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
2497   size_t buffer_size = dcqs.buffer_size();
2498   size_t buffer_num = dcqs.completed_buffers_num();
2499 
2500   return buffer_size * buffer_num + extra_cards;
2501 }
2502 
2503 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
2504   // We don't nominate objects with many remembered set entries, on
2505   // the assumption that such objects are likely still live.
2506   HeapRegionRemSet* rem_set = r->rem_set();
2507 
2508   return G1EagerReclaimHumongousObjectsWithStaleRefs ?
2509          rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) :
2510          G1EagerReclaimHumongousObjects && rem_set->is_empty();
2511 }
2512 
2513 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2514  private:
2515   size_t _total_humongous;
2516   size_t _candidate_humongous;
2517 
2518   DirtyCardQueue _dcq;
2519 
2520   bool humongous_region_is_candidate(G1CollectedHeap* g1h, HeapRegion* region) const {
2521     assert(region->is_starts_humongous(), "Must start a humongous object");
2522 
2523     oop obj = oop(region->bottom());
2524 
2525     // Dead objects cannot be eager reclaim candidates. Due to class
2526     // unloading it is unsafe to query their classes so we return early.
2527     if (g1h->is_obj_dead(obj, region)) {
2528       return false;
2529     }
2530 
2531     // If we do not have a complete remembered set for the region, then we can
2532     // not be sure that we have all references to it.
2533     if (!region->rem_set()->is_complete()) {
2534       return false;
2535     }
2536     // Candidate selection must satisfy the following constraints
2537     // while concurrent marking is in progress:
2538     //
2539     // * In order to maintain SATB invariants, an object must not be
2540     // reclaimed if it was allocated before the start of marking and
2541     // has not had its references scanned.  Such an object must have
2542     // its references (including type metadata) scanned to ensure no
2543     // live objects are missed by the marking process.  Objects
2544     // allocated after the start of concurrent marking don't need to
2545     // be scanned.
2546     //
2547     // * An object must not be reclaimed if it is on the concurrent
2548     // mark stack.  Objects allocated after the start of concurrent
2549     // marking are never pushed on the mark stack.
2550     //
2551     // Nominating only objects allocated after the start of concurrent
2552     // marking is sufficient to meet both constraints.  This may miss
2553     // some objects that satisfy the constraints, but the marking data
2554     // structures don't support efficiently performing the needed
2555     // additional tests or scrubbing of the mark stack.
2556     //
2557     // However, we presently only nominate is_typeArray() objects.
2558     // A humongous object containing references induces remembered
2559     // set entries on other regions.  In order to reclaim such an
2560     // object, those remembered sets would need to be cleaned up.
2561     //
2562     // We also treat is_typeArray() objects specially, allowing them
2563     // to be reclaimed even if allocated before the start of
2564     // concurrent mark.  For this we rely on mark stack insertion to
2565     // exclude is_typeArray() objects, preventing reclaiming an object
2566     // that is in the mark stack.  We also rely on the metadata for
2567     // such objects to be built-in and so ensured to be kept live.
2568     // Frequent allocation and drop of large binary blobs is an
2569     // important use case for eager reclaim, and this special handling
2570     // may reduce needed headroom.
2571 
2572     return obj->is_typeArray() &&
2573            g1h->is_potential_eager_reclaim_candidate(region);
2574   }
2575 
2576  public:
2577   RegisterHumongousWithInCSetFastTestClosure()
2578   : _total_humongous(0),
2579     _candidate_humongous(0),
2580     _dcq(&G1BarrierSet::dirty_card_queue_set()) {
2581   }
2582 
2583   virtual bool do_heap_region(HeapRegion* r) {
2584     if (!r->is_starts_humongous()) {
2585       return false;
2586     }
2587     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2588 
2589     bool is_candidate = humongous_region_is_candidate(g1h, r);
2590     uint rindex = r->hrm_index();
2591     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2592     if (is_candidate) {
2593       _candidate_humongous++;
2594       g1h->register_humongous_region_with_cset(rindex);
2595       // Is_candidate already filters out humongous object with large remembered sets.
2596       // If we have a humongous object with a few remembered sets, we simply flush these
2597       // remembered set entries into the DCQS. That will result in automatic
2598       // re-evaluation of their remembered set entries during the following evacuation
2599       // phase.
2600       if (!r->rem_set()->is_empty()) {
2601         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2602                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2603         G1CardTable* ct = g1h->card_table();
2604         HeapRegionRemSetIterator hrrs(r->rem_set());
2605         size_t card_index;
2606         while (hrrs.has_next(card_index)) {
2607           jbyte* card_ptr = (jbyte*)ct->byte_for_index(card_index);
2608           // The remembered set might contain references to already freed
2609           // regions. Filter out such entries to avoid failing card table
2610           // verification.
2611           if (g1h->is_in_closed_subset(ct->addr_for(card_ptr))) {
2612             if (*card_ptr != G1CardTable::dirty_card_val()) {
2613               *card_ptr = G1CardTable::dirty_card_val();
2614               _dcq.enqueue(card_ptr);
2615             }
2616           }
2617         }
2618         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2619                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2620                hrrs.n_yielded(), r->rem_set()->occupied());
2621         // We should only clear the card based remembered set here as we will not
2622         // implicitly rebuild anything else during eager reclaim. Note that at the moment
2623         // (and probably never) we do not enter this path if there are other kind of
2624         // remembered sets for this region.
2625         r->rem_set()->clear_locked(true /* only_cardset */);
2626         // Clear_locked() above sets the state to Empty. However we want to continue
2627         // collecting remembered set entries for humongous regions that were not
2628         // reclaimed.
2629         r->rem_set()->set_state_complete();
2630       }
2631       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2632     }
2633     _total_humongous++;
2634 
2635     return false;
2636   }
2637 
2638   size_t total_humongous() const { return _total_humongous; }
2639   size_t candidate_humongous() const { return _candidate_humongous; }
2640 
2641   void flush_rem_set_entries() { _dcq.flush(); }
2642 };
2643 
2644 void G1CollectedHeap::register_humongous_regions_with_cset() {
2645   if (!G1EagerReclaimHumongousObjects) {
2646     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2647     return;
2648   }
2649   double time = os::elapsed_counter();
2650 
2651   // Collect reclaim candidate information and register candidates with cset.
2652   RegisterHumongousWithInCSetFastTestClosure cl;
2653   heap_region_iterate(&cl);
2654 
2655   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2656   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2657                                                                   cl.total_humongous(),
2658                                                                   cl.candidate_humongous());
2659   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2660 
2661   // Finally flush all remembered set entries to re-check into the global DCQS.
2662   cl.flush_rem_set_entries();
2663 }
2664 
2665 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2666   public:
2667     bool do_heap_region(HeapRegion* hr) {
2668       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2669         hr->verify_rem_set();
2670       }
2671       return false;
2672     }
2673 };
2674 
2675 uint G1CollectedHeap::num_task_queues() const {
2676   return _task_queues->size();
2677 }
2678 
2679 #if TASKQUEUE_STATS
2680 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2681   st->print_raw_cr("GC Task Stats");
2682   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2683   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2684 }
2685 
2686 void G1CollectedHeap::print_taskqueue_stats() const {
2687   if (!log_is_enabled(Trace, gc, task, stats)) {
2688     return;
2689   }
2690   Log(gc, task, stats) log;
2691   ResourceMark rm;
2692   LogStream ls(log.trace());
2693   outputStream* st = &ls;
2694 
2695   print_taskqueue_stats_hdr(st);
2696 
2697   TaskQueueStats totals;
2698   const uint n = num_task_queues();
2699   for (uint i = 0; i < n; ++i) {
2700     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2701     totals += task_queue(i)->stats;
2702   }
2703   st->print_raw("tot "); totals.print(st); st->cr();
2704 
2705   DEBUG_ONLY(totals.verify());
2706 }
2707 
2708 void G1CollectedHeap::reset_taskqueue_stats() {
2709   const uint n = num_task_queues();
2710   for (uint i = 0; i < n; ++i) {
2711     task_queue(i)->stats.reset();
2712   }
2713 }
2714 #endif // TASKQUEUE_STATS
2715 
2716 void G1CollectedHeap::wait_for_root_region_scanning() {
2717   double scan_wait_start = os::elapsedTime();
2718   // We have to wait until the CM threads finish scanning the
2719   // root regions as it's the only way to ensure that all the
2720   // objects on them have been correctly scanned before we start
2721   // moving them during the GC.
2722   bool waited = _cm->root_regions()->wait_until_scan_finished();
2723   double wait_time_ms = 0.0;
2724   if (waited) {
2725     double scan_wait_end = os::elapsedTime();
2726     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2727   }
2728   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2729 }
2730 
2731 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2732 private:
2733   G1HRPrinter* _hr_printer;
2734 public:
2735   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2736 
2737   virtual bool do_heap_region(HeapRegion* r) {
2738     _hr_printer->cset(r);
2739     return false;
2740   }
2741 };
2742 
2743 void G1CollectedHeap::start_new_collection_set() {
2744   collection_set()->start_incremental_building();
2745 
2746   clear_cset_fast_test();
2747 
2748   guarantee(_eden.length() == 0, "eden should have been cleared");
2749   g1_policy()->transfer_survivors_to_cset(survivor());
2750 }
2751 
2752 bool
2753 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2754   assert_at_safepoint_on_vm_thread();
2755   guarantee(!is_gc_active(), "collection is not reentrant");
2756 
2757   if (GCLocker::check_active_before_gc()) {
2758     return false;
2759   }
2760 
2761   _gc_timer_stw->register_gc_start();
2762 
2763   GCIdMark gc_id_mark;
2764   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2765 
2766   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2767   ResourceMark rm;
2768 
2769   g1_policy()->note_gc_start();
2770 
2771   wait_for_root_region_scanning();
2772 
2773   print_heap_before_gc();
2774   print_heap_regions();
2775   trace_heap_before_gc(_gc_tracer_stw);
2776 
2777   _verifier->verify_region_sets_optional();
2778   _verifier->verify_dirty_young_regions();
2779 
2780   // We should not be doing initial mark unless the conc mark thread is running
2781   if (!_cm_thread->should_terminate()) {
2782     // This call will decide whether this pause is an initial-mark
2783     // pause. If it is, in_initial_mark_gc() will return true
2784     // for the duration of this pause.
2785     g1_policy()->decide_on_conc_mark_initiation();
2786   }
2787 
2788   // We do not allow initial-mark to be piggy-backed on a mixed GC.
2789   assert(!collector_state()->in_initial_mark_gc() ||
2790           collector_state()->in_young_only_phase(), "sanity");
2791 
2792   // We also do not allow mixed GCs during marking.
2793   assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity");
2794 
2795   // Record whether this pause is an initial mark. When the current
2796   // thread has completed its logging output and it's safe to signal
2797   // the CM thread, the flag's value in the policy has been reset.
2798   bool should_start_conc_mark = collector_state()->in_initial_mark_gc();
2799 
2800   // Inner scope for scope based logging, timers, and stats collection
2801   {
2802     EvacuationInfo evacuation_info;
2803 
2804     if (collector_state()->in_initial_mark_gc()) {
2805       // We are about to start a marking cycle, so we increment the
2806       // full collection counter.
2807       increment_old_marking_cycles_started();
2808       _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2809     }
2810 
2811     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2812 
2813     GCTraceCPUTime tcpu;
2814 
2815     G1HeapVerifier::G1VerifyType verify_type;
2816     FormatBuffer<> gc_string("Pause Young ");
2817     if (collector_state()->in_initial_mark_gc()) {
2818       gc_string.append("(Concurrent Start)");
2819       verify_type = G1HeapVerifier::G1VerifyConcurrentStart;
2820     } else if (collector_state()->in_young_only_phase()) {
2821       if (collector_state()->in_young_gc_before_mixed()) {
2822         gc_string.append("(Prepare Mixed)");
2823       } else {
2824         gc_string.append("(Normal)");
2825       }
2826       verify_type = G1HeapVerifier::G1VerifyYoungNormal;
2827     } else {
2828       gc_string.append("(Mixed)");
2829       verify_type = G1HeapVerifier::G1VerifyMixed;
2830     }
2831     GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2832 
2833     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2834                                                                   workers()->active_workers(),
2835                                                                   Threads::number_of_non_daemon_threads());
2836     active_workers = workers()->update_active_workers(active_workers);
2837     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2838 
2839     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2840     TraceMemoryManagerStats tms(&_memory_manager, gc_cause());
2841 
2842     G1HeapTransition heap_transition(this);
2843     size_t heap_used_bytes_before_gc = used();
2844 
2845     // Don't dynamically change the number of GC threads this early.  A value of
2846     // 0 is used to indicate serial work.  When parallel work is done,
2847     // it will be set.
2848 
2849     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2850       IsGCActiveMark x;
2851 
2852       gc_prologue(false);
2853 
2854       if (VerifyRememberedSets) {
2855         log_info(gc, verify)("[Verifying RemSets before GC]");
2856         VerifyRegionRemSetClosure v_cl;
2857         heap_region_iterate(&v_cl);
2858       }
2859 
2860       _verifier->verify_before_gc(verify_type);
2861 
2862       _verifier->check_bitmaps("GC Start");
2863 
2864 #if COMPILER2_OR_JVMCI
2865       DerivedPointerTable::clear();
2866 #endif
2867 
2868       // Please see comment in g1CollectedHeap.hpp and
2869       // G1CollectedHeap::ref_processing_init() to see how
2870       // reference processing currently works in G1.
2871 
2872       // Enable discovery in the STW reference processor
2873       _ref_processor_stw->enable_discovery();
2874 
2875       {
2876         // We want to temporarily turn off discovery by the
2877         // CM ref processor, if necessary, and turn it back on
2878         // on again later if we do. Using a scoped
2879         // NoRefDiscovery object will do this.
2880         NoRefDiscovery no_cm_discovery(_ref_processor_cm);
2881 
2882         // Forget the current alloc region (we might even choose it to be part
2883         // of the collection set!).
2884         _allocator->release_mutator_alloc_region();
2885 
2886         // This timing is only used by the ergonomics to handle our pause target.
2887         // It is unclear why this should not include the full pause. We will
2888         // investigate this in CR 7178365.
2889         //
2890         // Preserving the old comment here if that helps the investigation:
2891         //
2892         // The elapsed time induced by the start time below deliberately elides
2893         // the possible verification above.
2894         double sample_start_time_sec = os::elapsedTime();
2895 
2896         g1_policy()->record_collection_pause_start(sample_start_time_sec);
2897 
2898         if (collector_state()->in_initial_mark_gc()) {
2899           concurrent_mark()->pre_initial_mark();
2900         }
2901 
2902         g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
2903 
2904         evacuation_info.set_collectionset_regions(collection_set()->region_length());
2905 
2906         // Make sure the remembered sets are up to date. This needs to be
2907         // done before register_humongous_regions_with_cset(), because the
2908         // remembered sets are used there to choose eager reclaim candidates.
2909         // If the remembered sets are not up to date we might miss some
2910         // entries that need to be handled.
2911         g1_rem_set()->cleanupHRRS();
2912 
2913         register_humongous_regions_with_cset();
2914 
2915         assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
2916 
2917         // We call this after finalize_cset() to
2918         // ensure that the CSet has been finalized.
2919         _cm->verify_no_cset_oops();
2920 
2921         if (_hr_printer.is_active()) {
2922           G1PrintCollectionSetClosure cl(&_hr_printer);
2923           _collection_set.iterate(&cl);
2924         }
2925 
2926         // Initialize the GC alloc regions.
2927         _allocator->init_gc_alloc_regions(evacuation_info);
2928 
2929         G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
2930         pre_evacuate_collection_set();
2931 
2932         // Actually do the work...
2933         evacuate_collection_set(&per_thread_states);
2934 
2935         post_evacuate_collection_set(evacuation_info, &per_thread_states);
2936 
2937         const size_t* surviving_young_words = per_thread_states.surviving_young_words();
2938         free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
2939 
2940         eagerly_reclaim_humongous_regions();
2941 
2942         record_obj_copy_mem_stats();
2943         _survivor_evac_stats.adjust_desired_plab_sz();
2944         _old_evac_stats.adjust_desired_plab_sz();
2945 
2946         double start = os::elapsedTime();
2947         start_new_collection_set();
2948         g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
2949 
2950         if (evacuation_failed()) {
2951           set_used(recalculate_used());
2952           if (_archive_allocator != NULL) {
2953             _archive_allocator->clear_used();
2954           }
2955           for (uint i = 0; i < ParallelGCThreads; i++) {
2956             if (_evacuation_failed_info_array[i].has_failed()) {
2957               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
2958             }
2959           }
2960         } else {
2961           // The "used" of the the collection set have already been subtracted
2962           // when they were freed.  Add in the bytes evacuated.
2963           increase_used(g1_policy()->bytes_copied_during_gc());
2964         }
2965 
2966         if (collector_state()->in_initial_mark_gc()) {
2967           // We have to do this before we notify the CM threads that
2968           // they can start working to make sure that all the
2969           // appropriate initialization is done on the CM object.
2970           concurrent_mark()->post_initial_mark();
2971           // Note that we don't actually trigger the CM thread at
2972           // this point. We do that later when we're sure that
2973           // the current thread has completed its logging output.
2974         }
2975 
2976         allocate_dummy_regions();
2977 
2978         _allocator->init_mutator_alloc_region();
2979 
2980         {
2981           size_t expand_bytes = _heap_sizing_policy->expansion_amount();
2982           if (expand_bytes > 0) {
2983             size_t bytes_before = capacity();
2984             // No need for an ergo logging here,
2985             // expansion_amount() does this when it returns a value > 0.
2986             double expand_ms;
2987             if (!expand(expand_bytes, _workers, &expand_ms)) {
2988               // We failed to expand the heap. Cannot do anything about it.
2989             }
2990             g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
2991           }
2992         }
2993 
2994         // We redo the verification but now wrt to the new CSet which
2995         // has just got initialized after the previous CSet was freed.
2996         _cm->verify_no_cset_oops();
2997 
2998         // This timing is only used by the ergonomics to handle our pause target.
2999         // It is unclear why this should not include the full pause. We will
3000         // investigate this in CR 7178365.
3001         double sample_end_time_sec = os::elapsedTime();
3002         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3003         size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
3004         g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3005 
3006         evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3007         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3008 
3009         if (VerifyRememberedSets) {
3010           log_info(gc, verify)("[Verifying RemSets after GC]");
3011           VerifyRegionRemSetClosure v_cl;
3012           heap_region_iterate(&v_cl);
3013         }
3014 
3015         _verifier->verify_after_gc(verify_type);
3016         _verifier->check_bitmaps("GC End");
3017 
3018         assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
3019         _ref_processor_stw->verify_no_references_recorded();
3020 
3021         // CM reference discovery will be re-enabled if necessary.
3022       }
3023 
3024 #ifdef TRACESPINNING
3025       ParallelTaskTerminator::print_termination_counts();
3026 #endif
3027 
3028       gc_epilogue(false);
3029     }
3030 
3031     // Print the remainder of the GC log output.
3032     if (evacuation_failed()) {
3033       log_info(gc)("To-space exhausted");
3034     }
3035 
3036     g1_policy()->print_phases();
3037     heap_transition.print();
3038 
3039     // It is not yet to safe to tell the concurrent mark to
3040     // start as we have some optional output below. We don't want the
3041     // output from the concurrent mark thread interfering with this
3042     // logging output either.
3043 
3044     _hrm.verify_optional();
3045     _verifier->verify_region_sets_optional();
3046 
3047     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3048     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3049 
3050     print_heap_after_gc();
3051     print_heap_regions();
3052     trace_heap_after_gc(_gc_tracer_stw);
3053 
3054     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3055     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3056     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3057     // before any GC notifications are raised.
3058     g1mm()->update_sizes();
3059 
3060     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3061     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3062     _gc_timer_stw->register_gc_end();
3063     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3064   }
3065   // It should now be safe to tell the concurrent mark thread to start
3066   // without its logging output interfering with the logging output
3067   // that came from the pause.
3068 
3069   if (should_start_conc_mark) {
3070     // CAUTION: after the doConcurrentMark() call below,
3071     // the concurrent marking thread(s) could be running
3072     // concurrently with us. Make sure that anything after
3073     // this point does not assume that we are the only GC thread
3074     // running. Note: of course, the actual marking work will
3075     // not start until the safepoint itself is released in
3076     // SuspendibleThreadSet::desynchronize().
3077     do_concurrent_mark();
3078   }
3079 
3080   return true;
3081 }
3082 
3083 void G1CollectedHeap::remove_self_forwarding_pointers() {
3084   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3085   workers()->run_task(&rsfp_task);
3086 }
3087 
3088 void G1CollectedHeap::restore_after_evac_failure() {
3089   double remove_self_forwards_start = os::elapsedTime();
3090 
3091   remove_self_forwarding_pointers();
3092   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3093   _preserved_marks_set.restore(&task_executor);
3094 
3095   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3096 }
3097 
3098 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3099   if (!_evacuation_failed) {
3100     _evacuation_failed = true;
3101   }
3102 
3103   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3104   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3105 }
3106 
3107 bool G1ParEvacuateFollowersClosure::offer_termination() {
3108   G1ParScanThreadState* const pss = par_scan_state();
3109   start_term_time();
3110   const bool res = terminator()->offer_termination();
3111   end_term_time();
3112   return res;
3113 }
3114 
3115 void G1ParEvacuateFollowersClosure::do_void() {
3116   G1ParScanThreadState* const pss = par_scan_state();
3117   pss->trim_queue();
3118   do {
3119     pss->steal_and_trim_queue(queues());
3120   } while (!offer_termination());
3121 }
3122 
3123 class G1ParTask : public AbstractGangTask {
3124 protected:
3125   G1CollectedHeap*         _g1h;
3126   G1ParScanThreadStateSet* _pss;
3127   RefToScanQueueSet*       _queues;
3128   G1RootProcessor*         _root_processor;
3129   ParallelTaskTerminator   _terminator;
3130   uint                     _n_workers;
3131 
3132 public:
3133   G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3134     : AbstractGangTask("G1 collection"),
3135       _g1h(g1h),
3136       _pss(per_thread_states),
3137       _queues(task_queues),
3138       _root_processor(root_processor),
3139       _terminator(n_workers, _queues),
3140       _n_workers(n_workers)
3141   {}
3142 
3143   void work(uint worker_id) {
3144     if (worker_id >= _n_workers) return;  // no work needed this round
3145 
3146     double start_sec = os::elapsedTime();
3147     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3148 
3149     {
3150       ResourceMark rm;
3151       HandleMark   hm;
3152 
3153       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
3154 
3155       G1ParScanThreadState*           pss = _pss->state_for_worker(worker_id);
3156       pss->set_ref_discoverer(rp);
3157 
3158       double start_strong_roots_sec = os::elapsedTime();
3159 
3160       _root_processor->evacuate_roots(pss, worker_id);
3161 
3162       // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3163       // treating the nmethods visited to act as roots for concurrent marking.
3164       // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3165       // objects copied by the current evacuation.
3166       _g1h->g1_rem_set()->oops_into_collection_set_do(pss, worker_id);
3167 
3168       double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3169 
3170       double term_sec = 0.0;
3171       size_t evac_term_attempts = 0;
3172       {
3173         double start = os::elapsedTime();
3174         G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3175         evac.do_void();
3176 
3177         evac_term_attempts = evac.term_attempts();
3178         term_sec = evac.term_time();
3179         double elapsed_sec = os::elapsedTime() - start;
3180 
3181         G1GCPhaseTimes* p = _g1h->g1_policy()->phase_times();
3182         p->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3183         p->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3184         p->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3185       }
3186 
3187       assert(pss->queue_is_empty(), "should be empty");
3188 
3189       if (log_is_enabled(Debug, gc, task, stats)) {
3190         MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3191         size_t lab_waste;
3192         size_t lab_undo_waste;
3193         pss->waste(lab_waste, lab_undo_waste);
3194         _g1h->print_termination_stats(worker_id,
3195                                       (os::elapsedTime() - start_sec) * 1000.0,   /* elapsed time */
3196                                       strong_roots_sec * 1000.0,                  /* strong roots time */
3197                                       term_sec * 1000.0,                          /* evac term time */
3198                                       evac_term_attempts,                         /* evac term attempts */
3199                                       lab_waste,                                  /* alloc buffer waste */
3200                                       lab_undo_waste                              /* undo waste */
3201                                       );
3202       }
3203 
3204       // Close the inner scope so that the ResourceMark and HandleMark
3205       // destructors are executed here and are included as part of the
3206       // "GC Worker Time".
3207     }
3208     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3209   }
3210 };
3211 
3212 void G1CollectedHeap::print_termination_stats_hdr() {
3213   log_debug(gc, task, stats)("GC Termination Stats");
3214   log_debug(gc, task, stats)("     elapsed  --strong roots-- -------termination------- ------waste (KiB)------");
3215   log_debug(gc, task, stats)("thr     ms        ms      %%        ms      %%    attempts  total   alloc    undo");
3216   log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3217 }
3218 
3219 void G1CollectedHeap::print_termination_stats(uint worker_id,
3220                                               double elapsed_ms,
3221                                               double strong_roots_ms,
3222                                               double term_ms,
3223                                               size_t term_attempts,
3224                                               size_t alloc_buffer_waste,
3225                                               size_t undo_waste) const {
3226   log_debug(gc, task, stats)
3227               ("%3d %9.2f %9.2f %6.2f "
3228                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3229                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3230                worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3231                term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3232                (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3233                alloc_buffer_waste * HeapWordSize / K,
3234                undo_waste * HeapWordSize / K);
3235 }
3236 
3237 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3238 private:
3239   BoolObjectClosure* _is_alive;
3240   G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3241   OopStorage::ParState<false /* concurrent */, false /* const */> _par_state_string;
3242 
3243   int _initial_string_table_size;
3244   int _initial_symbol_table_size;
3245 
3246   bool  _process_strings;
3247   int _strings_processed;
3248   int _strings_removed;
3249 
3250   bool  _process_symbols;
3251   int _symbols_processed;
3252   int _symbols_removed;
3253 
3254   bool _process_string_dedup;
3255 
3256 public:
3257   G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3258     AbstractGangTask("String/Symbol Unlinking"),
3259     _is_alive(is_alive),
3260     _dedup_closure(is_alive, NULL, false),
3261     _par_state_string(StringTable::weak_storage()),
3262     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3263     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3264     _process_string_dedup(process_string_dedup) {
3265 
3266     _initial_string_table_size = (int) StringTable::the_table()->table_size();
3267     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3268     if (process_symbols) {
3269       SymbolTable::clear_parallel_claimed_index();
3270     }
3271     if (process_strings) {
3272       StringTable::reset_dead_counter();
3273     }
3274   }
3275 
3276   ~G1StringAndSymbolCleaningTask() {
3277     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3278               "claim value %d after unlink less than initial symbol table size %d",
3279               SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3280 
3281     log_info(gc, stringtable)(
3282         "Cleaned string and symbol table, "
3283         "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3284         "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3285         strings_processed(), strings_removed(),
3286         symbols_processed(), symbols_removed());
3287     if (_process_strings) {
3288       StringTable::finish_dead_counter();
3289     }
3290   }
3291 
3292   void work(uint worker_id) {
3293     int strings_processed = 0;
3294     int strings_removed = 0;
3295     int symbols_processed = 0;
3296     int symbols_removed = 0;
3297     if (_process_strings) {
3298       StringTable::possibly_parallel_unlink(&_par_state_string, _is_alive, &strings_processed, &strings_removed);
3299       Atomic::add(strings_processed, &_strings_processed);
3300       Atomic::add(strings_removed, &_strings_removed);
3301     }
3302     if (_process_symbols) {
3303       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3304       Atomic::add(symbols_processed, &_symbols_processed);
3305       Atomic::add(symbols_removed, &_symbols_removed);
3306     }
3307     if (_process_string_dedup) {
3308       G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3309     }
3310   }
3311 
3312   size_t strings_processed() const { return (size_t)_strings_processed; }
3313   size_t strings_removed()   const { return (size_t)_strings_removed; }
3314 
3315   size_t symbols_processed() const { return (size_t)_symbols_processed; }
3316   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
3317 };
3318 
3319 class G1CodeCacheUnloadingTask {
3320 private:
3321   static Monitor* _lock;
3322 
3323   BoolObjectClosure* const _is_alive;
3324   const bool               _unloading_occurred;
3325   const uint               _num_workers;
3326 
3327   // Variables used to claim nmethods.
3328   CompiledMethod* _first_nmethod;
3329   CompiledMethod* volatile _claimed_nmethod;
3330 
3331   // The list of nmethods that need to be processed by the second pass.
3332   CompiledMethod* volatile _postponed_list;
3333   volatile uint            _num_entered_barrier;
3334 
3335  public:
3336   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3337       _is_alive(is_alive),
3338       _unloading_occurred(unloading_occurred),
3339       _num_workers(num_workers),
3340       _first_nmethod(NULL),
3341       _claimed_nmethod(NULL),
3342       _postponed_list(NULL),
3343       _num_entered_barrier(0)
3344   {
3345     CompiledMethod::increase_unloading_clock();
3346     // Get first alive nmethod
3347     CompiledMethodIterator iter = CompiledMethodIterator();
3348     if(iter.next_alive()) {
3349       _first_nmethod = iter.method();
3350     }
3351     _claimed_nmethod = _first_nmethod;
3352   }
3353 
3354   ~G1CodeCacheUnloadingTask() {
3355     CodeCache::verify_clean_inline_caches();
3356 
3357     CodeCache::set_needs_cache_clean(false);
3358     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3359 
3360     CodeCache::verify_icholder_relocations();
3361   }
3362 
3363  private:
3364   void add_to_postponed_list(CompiledMethod* nm) {
3365       CompiledMethod* old;
3366       do {
3367         old = _postponed_list;
3368         nm->set_unloading_next(old);
3369       } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
3370   }
3371 
3372   void clean_nmethod(CompiledMethod* nm) {
3373     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3374 
3375     if (postponed) {
3376       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3377       add_to_postponed_list(nm);
3378     }
3379 
3380     // Mark that this nmethod has been cleaned/unloaded.
3381     // After this call, it will be safe to ask if this nmethod was unloaded or not.
3382     nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3383   }
3384 
3385   void clean_nmethod_postponed(CompiledMethod* nm) {
3386     nm->do_unloading_parallel_postponed();
3387   }
3388 
3389   static const int MaxClaimNmethods = 16;
3390 
3391   void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3392     CompiledMethod* first;
3393     CompiledMethodIterator last;
3394 
3395     do {
3396       *num_claimed_nmethods = 0;
3397 
3398       first = _claimed_nmethod;
3399       last = CompiledMethodIterator(first);
3400 
3401       if (first != NULL) {
3402 
3403         for (int i = 0; i < MaxClaimNmethods; i++) {
3404           if (!last.next_alive()) {
3405             break;
3406           }
3407           claimed_nmethods[i] = last.method();
3408           (*num_claimed_nmethods)++;
3409         }
3410       }
3411 
3412     } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
3413   }
3414 
3415   CompiledMethod* claim_postponed_nmethod() {
3416     CompiledMethod* claim;
3417     CompiledMethod* next;
3418 
3419     do {
3420       claim = _postponed_list;
3421       if (claim == NULL) {
3422         return NULL;
3423       }
3424 
3425       next = claim->unloading_next();
3426 
3427     } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
3428 
3429     return claim;
3430   }
3431 
3432  public:
3433   // Mark that we're done with the first pass of nmethod cleaning.
3434   void barrier_mark(uint worker_id) {
3435     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3436     _num_entered_barrier++;
3437     if (_num_entered_barrier == _num_workers) {
3438       ml.notify_all();
3439     }
3440   }
3441 
3442   // See if we have to wait for the other workers to
3443   // finish their first-pass nmethod cleaning work.
3444   void barrier_wait(uint worker_id) {
3445     if (_num_entered_barrier < _num_workers) {
3446       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3447       while (_num_entered_barrier < _num_workers) {
3448           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3449       }
3450     }
3451   }
3452 
3453   // Cleaning and unloading of nmethods. Some work has to be postponed
3454   // to the second pass, when we know which nmethods survive.
3455   void work_first_pass(uint worker_id) {
3456     // The first nmethods is claimed by the first worker.
3457     if (worker_id == 0 && _first_nmethod != NULL) {
3458       clean_nmethod(_first_nmethod);
3459       _first_nmethod = NULL;
3460     }
3461 
3462     int num_claimed_nmethods;
3463     CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3464 
3465     while (true) {
3466       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3467 
3468       if (num_claimed_nmethods == 0) {
3469         break;
3470       }
3471 
3472       for (int i = 0; i < num_claimed_nmethods; i++) {
3473         clean_nmethod(claimed_nmethods[i]);
3474       }
3475     }
3476   }
3477 
3478   void work_second_pass(uint worker_id) {
3479     CompiledMethod* nm;
3480     // Take care of postponed nmethods.
3481     while ((nm = claim_postponed_nmethod()) != NULL) {
3482       clean_nmethod_postponed(nm);
3483     }
3484   }
3485 };
3486 
3487 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3488 
3489 class G1KlassCleaningTask : public StackObj {
3490   volatile int                            _clean_klass_tree_claimed;
3491   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3492 
3493  public:
3494   G1KlassCleaningTask() :
3495       _clean_klass_tree_claimed(0),
3496       _klass_iterator() {
3497   }
3498 
3499  private:
3500   bool claim_clean_klass_tree_task() {
3501     if (_clean_klass_tree_claimed) {
3502       return false;
3503     }
3504 
3505     return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0;
3506   }
3507 
3508   InstanceKlass* claim_next_klass() {
3509     Klass* klass;
3510     do {
3511       klass =_klass_iterator.next_klass();
3512     } while (klass != NULL && !klass->is_instance_klass());
3513 
3514     // this can be null so don't call InstanceKlass::cast
3515     return static_cast<InstanceKlass*>(klass);
3516   }
3517 
3518 public:
3519 
3520   void clean_klass(InstanceKlass* ik) {
3521     ik->clean_weak_instanceklass_links();
3522   }
3523 
3524   void work() {
3525     ResourceMark rm;
3526 
3527     // One worker will clean the subklass/sibling klass tree.
3528     if (claim_clean_klass_tree_task()) {
3529       Klass::clean_subklass_tree();
3530     }
3531 
3532     // All workers will help cleaning the classes,
3533     InstanceKlass* klass;
3534     while ((klass = claim_next_klass()) != NULL) {
3535       clean_klass(klass);
3536     }
3537   }
3538 };
3539 
3540 class G1ResolvedMethodCleaningTask : public StackObj {
3541   volatile int       _resolved_method_task_claimed;
3542 public:
3543   G1ResolvedMethodCleaningTask() :
3544       _resolved_method_task_claimed(0) {}
3545 
3546   bool claim_resolved_method_task() {
3547     if (_resolved_method_task_claimed) {
3548       return false;
3549     }
3550     return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0;
3551   }
3552 
3553   // These aren't big, one thread can do it all.
3554   void work() {
3555     if (claim_resolved_method_task()) {
3556       ResolvedMethodTable::unlink();
3557     }
3558   }
3559 };
3560 
3561 
3562 // To minimize the remark pause times, the tasks below are done in parallel.
3563 class G1ParallelCleaningTask : public AbstractGangTask {
3564 private:
3565   bool                          _unloading_occurred;
3566   G1StringAndSymbolCleaningTask _string_symbol_task;
3567   G1CodeCacheUnloadingTask      _code_cache_task;
3568   G1KlassCleaningTask           _klass_cleaning_task;
3569   G1ResolvedMethodCleaningTask  _resolved_method_cleaning_task;
3570 
3571 public:
3572   // The constructor is run in the VMThread.
3573   G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3574       AbstractGangTask("Parallel Cleaning"),
3575       _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3576       _code_cache_task(num_workers, is_alive, unloading_occurred),
3577       _klass_cleaning_task(),
3578       _unloading_occurred(unloading_occurred),
3579       _resolved_method_cleaning_task() {
3580   }
3581 
3582   // The parallel work done by all worker threads.
3583   void work(uint worker_id) {
3584     // Do first pass of code cache cleaning.
3585     _code_cache_task.work_first_pass(worker_id);
3586 
3587     // Let the threads mark that the first pass is done.
3588     _code_cache_task.barrier_mark(worker_id);
3589 
3590     // Clean the Strings and Symbols.
3591     _string_symbol_task.work(worker_id);
3592 
3593     // Clean unreferenced things in the ResolvedMethodTable
3594     _resolved_method_cleaning_task.work();
3595 
3596     // Wait for all workers to finish the first code cache cleaning pass.
3597     _code_cache_task.barrier_wait(worker_id);
3598 
3599     // Do the second code cache cleaning work, which realize on
3600     // the liveness information gathered during the first pass.
3601     _code_cache_task.work_second_pass(worker_id);
3602 
3603     // Clean all klasses that were not unloaded.
3604     // The weak metadata in klass doesn't need to be
3605     // processed if there was no unloading.
3606     if (_unloading_occurred) {
3607       _klass_cleaning_task.work();
3608     }
3609   }
3610 };
3611 
3612 
3613 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3614                                         bool class_unloading_occurred) {
3615   uint n_workers = workers()->active_workers();
3616 
3617   G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3618   workers()->run_task(&g1_unlink_task);
3619 }
3620 
3621 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3622                                        bool process_strings,
3623                                        bool process_symbols,
3624                                        bool process_string_dedup) {
3625   if (!process_strings && !process_symbols && !process_string_dedup) {
3626     // Nothing to clean.
3627     return;
3628   }
3629 
3630   G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3631   workers()->run_task(&g1_unlink_task);
3632 
3633 }
3634 
3635 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3636  private:
3637   DirtyCardQueueSet* _queue;
3638   G1CollectedHeap* _g1h;
3639  public:
3640   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3641     _queue(queue), _g1h(g1h) { }
3642 
3643   virtual void work(uint worker_id) {
3644     G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3645     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3646 
3647     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3648     _queue->par_apply_closure_to_all_completed_buffers(&cl);
3649 
3650     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3651   }
3652 };
3653 
3654 void G1CollectedHeap::redirty_logged_cards() {
3655   double redirty_logged_cards_start = os::elapsedTime();
3656 
3657   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3658   dirty_card_queue_set().reset_for_par_iteration();
3659   workers()->run_task(&redirty_task);
3660 
3661   DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set();
3662   dcq.merge_bufferlists(&dirty_card_queue_set());
3663   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3664 
3665   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3666 }
3667 
3668 // Weak Reference Processing support
3669 
3670 bool G1STWIsAliveClosure::do_object_b(oop p) {
3671   // An object is reachable if it is outside the collection set,
3672   // or is inside and copied.
3673   return !_g1h->is_in_cset(p) || p->is_forwarded();
3674 }
3675 
3676 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) {
3677   assert(obj != NULL, "must not be NULL");
3678   assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj));
3679   // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below
3680   // may falsely indicate that this is not the case here: however the collection set only
3681   // contains old regions when concurrent mark is not running.
3682   return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor();
3683 }
3684 
3685 // Non Copying Keep Alive closure
3686 class G1KeepAliveClosure: public OopClosure {
3687   G1CollectedHeap*_g1h;
3688 public:
3689   G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {}
3690   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3691   void do_oop(oop* p) {
3692     oop obj = *p;
3693     assert(obj != NULL, "the caller should have filtered out NULL values");
3694 
3695     const InCSetState cset_state =_g1h->in_cset_state(obj);
3696     if (!cset_state.is_in_cset_or_humongous()) {
3697       return;
3698     }
3699     if (cset_state.is_in_cset()) {
3700       assert( obj->is_forwarded(), "invariant" );
3701       *p = obj->forwardee();
3702     } else {
3703       assert(!obj->is_forwarded(), "invariant" );
3704       assert(cset_state.is_humongous(),
3705              "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3706      _g1h->set_humongous_is_live(obj);
3707     }
3708   }
3709 };
3710 
3711 // Copying Keep Alive closure - can be called from both
3712 // serial and parallel code as long as different worker
3713 // threads utilize different G1ParScanThreadState instances
3714 // and different queues.
3715 
3716 class G1CopyingKeepAliveClosure: public OopClosure {
3717   G1CollectedHeap*         _g1h;
3718   OopClosure*              _copy_non_heap_obj_cl;
3719   G1ParScanThreadState*    _par_scan_state;
3720 
3721 public:
3722   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3723                             OopClosure* non_heap_obj_cl,
3724                             G1ParScanThreadState* pss):
3725     _g1h(g1h),
3726     _copy_non_heap_obj_cl(non_heap_obj_cl),
3727     _par_scan_state(pss)
3728   {}
3729 
3730   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3731   virtual void do_oop(      oop* p) { do_oop_work(p); }
3732 
3733   template <class T> void do_oop_work(T* p) {
3734     oop obj = RawAccess<>::oop_load(p);
3735 
3736     if (_g1h->is_in_cset_or_humongous(obj)) {
3737       // If the referent object has been forwarded (either copied
3738       // to a new location or to itself in the event of an
3739       // evacuation failure) then we need to update the reference
3740       // field and, if both reference and referent are in the G1
3741       // heap, update the RSet for the referent.
3742       //
3743       // If the referent has not been forwarded then we have to keep
3744       // it alive by policy. Therefore we have copy the referent.
3745       //
3746       // If the reference field is in the G1 heap then we can push
3747       // on the PSS queue. When the queue is drained (after each
3748       // phase of reference processing) the object and it's followers
3749       // will be copied, the reference field set to point to the
3750       // new location, and the RSet updated. Otherwise we need to
3751       // use the the non-heap or metadata closures directly to copy
3752       // the referent object and update the pointer, while avoiding
3753       // updating the RSet.
3754 
3755       if (_g1h->is_in_g1_reserved(p)) {
3756         _par_scan_state->push_on_queue(p);
3757       } else {
3758         assert(!Metaspace::contains((const void*)p),
3759                "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3760         _copy_non_heap_obj_cl->do_oop(p);
3761       }
3762     }
3763   }
3764 };
3765 
3766 // Serial drain queue closure. Called as the 'complete_gc'
3767 // closure for each discovered list in some of the
3768 // reference processing phases.
3769 
3770 class G1STWDrainQueueClosure: public VoidClosure {
3771 protected:
3772   G1CollectedHeap* _g1h;
3773   G1ParScanThreadState* _par_scan_state;
3774 
3775   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3776 
3777 public:
3778   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3779     _g1h(g1h),
3780     _par_scan_state(pss)
3781   { }
3782 
3783   void do_void() {
3784     G1ParScanThreadState* const pss = par_scan_state();
3785     pss->trim_queue();
3786   }
3787 };
3788 
3789 // Parallel Reference Processing closures
3790 
3791 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3792 // processing during G1 evacuation pauses.
3793 
3794 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3795 private:
3796   G1CollectedHeap*          _g1h;
3797   G1ParScanThreadStateSet*  _pss;
3798   RefToScanQueueSet*        _queues;
3799   WorkGang*                 _workers;
3800 
3801 public:
3802   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3803                            G1ParScanThreadStateSet* per_thread_states,
3804                            WorkGang* workers,
3805                            RefToScanQueueSet *task_queues) :
3806     _g1h(g1h),
3807     _pss(per_thread_states),
3808     _queues(task_queues),
3809     _workers(workers)
3810   {
3811     g1h->ref_processor_stw()->set_active_mt_degree(workers->active_workers());
3812   }
3813 
3814   // Executes the given task using concurrent marking worker threads.
3815   virtual void execute(ProcessTask& task, uint ergo_workers);
3816 };
3817 
3818 // Gang task for possibly parallel reference processing
3819 
3820 class G1STWRefProcTaskProxy: public AbstractGangTask {
3821   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3822   ProcessTask&     _proc_task;
3823   G1CollectedHeap* _g1h;
3824   G1ParScanThreadStateSet* _pss;
3825   RefToScanQueueSet* _task_queues;
3826   ParallelTaskTerminator* _terminator;
3827 
3828 public:
3829   G1STWRefProcTaskProxy(ProcessTask& proc_task,
3830                         G1CollectedHeap* g1h,
3831                         G1ParScanThreadStateSet* per_thread_states,
3832                         RefToScanQueueSet *task_queues,
3833                         ParallelTaskTerminator* terminator) :
3834     AbstractGangTask("Process reference objects in parallel"),
3835     _proc_task(proc_task),
3836     _g1h(g1h),
3837     _pss(per_thread_states),
3838     _task_queues(task_queues),
3839     _terminator(terminator)
3840   {}
3841 
3842   virtual void work(uint worker_id) {
3843     // The reference processing task executed by a single worker.
3844     ResourceMark rm;
3845     HandleMark   hm;
3846 
3847     G1STWIsAliveClosure is_alive(_g1h);
3848 
3849     G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3850     pss->set_ref_discoverer(NULL);
3851 
3852     // Keep alive closure.
3853     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
3854 
3855     // Complete GC closure
3856     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
3857 
3858     // Call the reference processing task's work routine.
3859     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3860 
3861     // Note we cannot assert that the refs array is empty here as not all
3862     // of the processing tasks (specifically phase2 - pp2_work) execute
3863     // the complete_gc closure (which ordinarily would drain the queue) so
3864     // the queue may not be empty.
3865   }
3866 };
3867 
3868 // Driver routine for parallel reference processing.
3869 // Creates an instance of the ref processing gang
3870 // task and has the worker threads execute it.
3871 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) {
3872   assert(_workers != NULL, "Need parallel worker threads.");
3873 
3874   assert(_workers->active_workers() >= ergo_workers,
3875          "Ergonomically chosen workers (%u) should be less than or equal to active workers (%u)",
3876          ergo_workers, _workers->active_workers());
3877   ParallelTaskTerminator terminator(ergo_workers, _queues);
3878   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
3879 
3880   _workers->run_task(&proc_task_proxy, ergo_workers);
3881 }
3882 
3883 // End of weak reference support closures
3884 
3885 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
3886   double ref_proc_start = os::elapsedTime();
3887 
3888   ReferenceProcessor* rp = _ref_processor_stw;
3889   assert(rp->discovery_enabled(), "should have been enabled");
3890 
3891   // Closure to test whether a referent is alive.
3892   G1STWIsAliveClosure is_alive(this);
3893 
3894   // Even when parallel reference processing is enabled, the processing
3895   // of JNI refs is serial and performed serially by the current thread
3896   // rather than by a worker. The following PSS will be used for processing
3897   // JNI refs.
3898 
3899   // Use only a single queue for this PSS.
3900   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
3901   pss->set_ref_discoverer(NULL);
3902   assert(pss->queue_is_empty(), "pre-condition");
3903 
3904   // Keep alive closure.
3905   G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
3906 
3907   // Serial Complete GC closure
3908   G1STWDrainQueueClosure drain_queue(this, pss);
3909 
3910   // Setup the soft refs policy...
3911   rp->setup_policy(false);
3912 
3913   ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
3914 
3915   ReferenceProcessorStats stats;
3916   if (!rp->processing_is_mt()) {
3917     // Serial reference processing...
3918     stats = rp->process_discovered_references(&is_alive,
3919                                               &keep_alive,
3920                                               &drain_queue,
3921                                               NULL,
3922                                               pt);
3923   } else {
3924     uint no_of_gc_workers = workers()->active_workers();
3925 
3926     // Parallel reference processing
3927     assert(no_of_gc_workers <= rp->max_num_queues(),
3928            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
3929            no_of_gc_workers,  rp->max_num_queues());
3930 
3931     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues);
3932     stats = rp->process_discovered_references(&is_alive,
3933                                               &keep_alive,
3934                                               &drain_queue,
3935                                               &par_task_executor,
3936                                               pt);
3937   }
3938 
3939   _gc_tracer_stw->report_gc_reference_stats(stats);
3940 
3941   // We have completed copying any necessary live referent objects.
3942   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
3943 
3944   make_pending_list_reachable();
3945 
3946   rp->verify_no_references_recorded();
3947 
3948   double ref_proc_time = os::elapsedTime() - ref_proc_start;
3949   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
3950 }
3951 
3952 void G1CollectedHeap::make_pending_list_reachable() {
3953   if (collector_state()->in_initial_mark_gc()) {
3954     oop pll_head = Universe::reference_pending_list();
3955     if (pll_head != NULL) {
3956       // Any valid worker id is fine here as we are in the VM thread and single-threaded.
3957       _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head);
3958     }
3959   }
3960 }
3961 
3962 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
3963   double merge_pss_time_start = os::elapsedTime();
3964   per_thread_states->flush();
3965   g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
3966 }
3967 
3968 void G1CollectedHeap::pre_evacuate_collection_set() {
3969   _expand_heap_after_alloc_failure = true;
3970   _evacuation_failed = false;
3971 
3972   // Disable the hot card cache.
3973   _hot_card_cache->reset_hot_cache_claimed_index();
3974   _hot_card_cache->set_use_cache(false);
3975 
3976   g1_rem_set()->prepare_for_oops_into_collection_set_do();
3977   _preserved_marks_set.assert_empty();
3978 
3979   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
3980 
3981   // InitialMark needs claim bits to keep track of the marked-through CLDs.
3982   if (collector_state()->in_initial_mark_gc()) {
3983     double start_clear_claimed_marks = os::elapsedTime();
3984 
3985     ClassLoaderDataGraph::clear_claimed_marks();
3986 
3987     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
3988     phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
3989   }
3990 }
3991 
3992 void G1CollectedHeap::evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3993   // Should G1EvacuationFailureALot be in effect for this GC?
3994   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
3995 
3996   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
3997 
3998   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
3999 
4000   double start_par_time_sec = os::elapsedTime();
4001   double end_par_time_sec;
4002 
4003   {
4004     const uint n_workers = workers()->active_workers();
4005     G1RootProcessor root_processor(this, n_workers);
4006     G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4007 
4008     print_termination_stats_hdr();
4009 
4010     workers()->run_task(&g1_par_task);
4011     end_par_time_sec = os::elapsedTime();
4012 
4013     // Closing the inner scope will execute the destructor
4014     // for the G1RootProcessor object. We record the current
4015     // elapsed time before closing the scope so that time
4016     // taken for the destructor is NOT included in the
4017     // reported parallel time.
4018   }
4019 
4020   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4021   phase_times->record_par_time(par_time_ms);
4022 
4023   double code_root_fixup_time_ms =
4024         (os::elapsedTime() - end_par_time_sec) * 1000.0;
4025   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4026 }
4027 
4028 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4029   // Also cleans the card table from temporary duplicate detection information used
4030   // during UpdateRS/ScanRS.
4031   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4032 
4033   // Process any discovered reference objects - we have
4034   // to do this _before_ we retire the GC alloc regions
4035   // as we may have to copy some 'reachable' referent
4036   // objects (and their reachable sub-graphs) that were
4037   // not copied during the pause.
4038   process_discovered_references(per_thread_states);
4039 
4040   // FIXME
4041   // CM's reference processing also cleans up the string and symbol tables.
4042   // Should we do that here also? We could, but it is a serial operation
4043   // and could significantly increase the pause time.
4044 
4045   G1STWIsAliveClosure is_alive(this);
4046   G1KeepAliveClosure keep_alive(this);
4047 
4048   {
4049     double start = os::elapsedTime();
4050 
4051     WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
4052 
4053     double time_ms = (os::elapsedTime() - start) * 1000.0;
4054     g1_policy()->phase_times()->record_weak_ref_proc_time(time_ms);
4055   }
4056 
4057   if (G1StringDedup::is_enabled()) {
4058     double fixup_start = os::elapsedTime();
4059 
4060     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4061 
4062     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4063     g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4064   }
4065 
4066   if (evacuation_failed()) {
4067     restore_after_evac_failure();
4068 
4069     // Reset the G1EvacuationFailureALot counters and flags
4070     // Note: the values are reset only when an actual
4071     // evacuation failure occurs.
4072     NOT_PRODUCT(reset_evacuation_should_fail();)
4073   }
4074 
4075   _preserved_marks_set.assert_empty();
4076 
4077   _allocator->release_gc_alloc_regions(evacuation_info);
4078 
4079   merge_per_thread_state_info(per_thread_states);
4080 
4081   // Reset and re-enable the hot card cache.
4082   // Note the counts for the cards in the regions in the
4083   // collection set are reset when the collection set is freed.
4084   _hot_card_cache->reset_hot_cache();
4085   _hot_card_cache->set_use_cache(true);
4086 
4087   purge_code_root_memory();
4088 
4089   redirty_logged_cards();
4090 #if COMPILER2_OR_JVMCI
4091   double start = os::elapsedTime();
4092   DerivedPointerTable::update_pointers();
4093   g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4094 #endif
4095   g1_policy()->print_age_table();
4096 }
4097 
4098 void G1CollectedHeap::record_obj_copy_mem_stats() {
4099   g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4100 
4101   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4102                                                create_g1_evac_summary(&_old_evac_stats));
4103 }
4104 
4105 void G1CollectedHeap::free_region(HeapRegion* hr,
4106                                   FreeRegionList* free_list,
4107                                   bool skip_remset,
4108                                   bool skip_hot_card_cache,
4109                                   bool locked) {
4110   assert(!hr->is_free(), "the region should not be free");
4111   assert(!hr->is_empty(), "the region should not be empty");
4112   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4113   assert(free_list != NULL, "pre-condition");
4114 
4115   if (G1VerifyBitmaps) {
4116     MemRegion mr(hr->bottom(), hr->end());
4117     concurrent_mark()->clear_range_in_prev_bitmap(mr);
4118   }
4119 
4120   // Clear the card counts for this region.
4121   // Note: we only need to do this if the region is not young
4122   // (since we don't refine cards in young regions).
4123   if (!skip_hot_card_cache && !hr->is_young()) {
4124     _hot_card_cache->reset_card_counts(hr);
4125   }
4126   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4127   _g1_policy->remset_tracker()->update_at_free(hr);
4128   free_list->add_ordered(hr);
4129 }
4130 
4131 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4132                                             FreeRegionList* free_list) {
4133   assert(hr->is_humongous(), "this is only for humongous regions");
4134   assert(free_list != NULL, "pre-condition");
4135   hr->clear_humongous();
4136   free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */);
4137 }
4138 
4139 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4140                                            const uint humongous_regions_removed) {
4141   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4142     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4143     _old_set.bulk_remove(old_regions_removed);
4144     _humongous_set.bulk_remove(humongous_regions_removed);
4145   }
4146 
4147 }
4148 
4149 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4150   assert(list != NULL, "list can't be null");
4151   if (!list->is_empty()) {
4152     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4153     _hrm.insert_list_into_free_list(list);
4154   }
4155 }
4156 
4157 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4158   decrease_used(bytes);
4159 }
4160 
4161 class G1FreeCollectionSetTask : public AbstractGangTask {
4162 private:
4163 
4164   // Closure applied to all regions in the collection set to do work that needs to
4165   // be done serially in a single thread.
4166   class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4167   private:
4168     EvacuationInfo* _evacuation_info;
4169     const size_t* _surviving_young_words;
4170 
4171     // Bytes used in successfully evacuated regions before the evacuation.
4172     size_t _before_used_bytes;
4173     // Bytes used in unsucessfully evacuated regions before the evacuation
4174     size_t _after_used_bytes;
4175 
4176     size_t _bytes_allocated_in_old_since_last_gc;
4177 
4178     size_t _failure_used_words;
4179     size_t _failure_waste_words;
4180 
4181     FreeRegionList _local_free_list;
4182   public:
4183     G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4184       HeapRegionClosure(),
4185       _evacuation_info(evacuation_info),
4186       _surviving_young_words(surviving_young_words),
4187       _before_used_bytes(0),
4188       _after_used_bytes(0),
4189       _bytes_allocated_in_old_since_last_gc(0),
4190       _failure_used_words(0),
4191       _failure_waste_words(0),
4192       _local_free_list("Local Region List for CSet Freeing") {
4193     }
4194 
4195     virtual bool do_heap_region(HeapRegion* r) {
4196       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4197 
4198       assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4199       g1h->clear_in_cset(r);
4200 
4201       if (r->is_young()) {
4202         assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4203                "Young index %d is wrong for region %u of type %s with %u young regions",
4204                r->young_index_in_cset(),
4205                r->hrm_index(),
4206                r->get_type_str(),
4207                g1h->collection_set()->young_region_length());
4208         size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4209         r->record_surv_words_in_group(words_survived);
4210       }
4211 
4212       if (!r->evacuation_failed()) {
4213         assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4214         _before_used_bytes += r->used();
4215         g1h->free_region(r,
4216                          &_local_free_list,
4217                          true, /* skip_remset */
4218                          true, /* skip_hot_card_cache */
4219                          true  /* locked */);
4220       } else {
4221         r->uninstall_surv_rate_group();
4222         r->set_young_index_in_cset(-1);
4223         r->set_evacuation_failed(false);
4224         // When moving a young gen region to old gen, we "allocate" that whole region
4225         // there. This is in addition to any already evacuated objects. Notify the
4226         // policy about that.
4227         // Old gen regions do not cause an additional allocation: both the objects
4228         // still in the region and the ones already moved are accounted for elsewhere.
4229         if (r->is_young()) {
4230           _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4231         }
4232         // The region is now considered to be old.
4233         r->set_old();
4234         // Do some allocation statistics accounting. Regions that failed evacuation
4235         // are always made old, so there is no need to update anything in the young
4236         // gen statistics, but we need to update old gen statistics.
4237         size_t used_words = r->marked_bytes() / HeapWordSize;
4238 
4239         _failure_used_words += used_words;
4240         _failure_waste_words += HeapRegion::GrainWords - used_words;
4241 
4242         g1h->old_set_add(r);
4243         _after_used_bytes += r->used();
4244       }
4245       return false;
4246     }
4247 
4248     void complete_work() {
4249       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4250 
4251       _evacuation_info->set_regions_freed(_local_free_list.length());
4252       _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4253 
4254       g1h->prepend_to_freelist(&_local_free_list);
4255       g1h->decrement_summary_bytes(_before_used_bytes);
4256 
4257       G1Policy* policy = g1h->g1_policy();
4258       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4259 
4260       g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4261     }
4262   };
4263 
4264   G1CollectionSet* _collection_set;
4265   G1SerialFreeCollectionSetClosure _cl;
4266   const size_t* _surviving_young_words;
4267 
4268   size_t _rs_lengths;
4269 
4270   volatile jint _serial_work_claim;
4271 
4272   struct WorkItem {
4273     uint region_idx;
4274     bool is_young;
4275     bool evacuation_failed;
4276 
4277     WorkItem(HeapRegion* r) {
4278       region_idx = r->hrm_index();
4279       is_young = r->is_young();
4280       evacuation_failed = r->evacuation_failed();
4281     }
4282   };
4283 
4284   volatile size_t _parallel_work_claim;
4285   size_t _num_work_items;
4286   WorkItem* _work_items;
4287 
4288   void do_serial_work() {
4289     // Need to grab the lock to be allowed to modify the old region list.
4290     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4291     _collection_set->iterate(&_cl);
4292   }
4293 
4294   void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4295     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4296 
4297     HeapRegion* r = g1h->region_at(region_idx);
4298     assert(!g1h->is_on_master_free_list(r), "sanity");
4299 
4300     Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4301 
4302     if (!is_young) {
4303       g1h->_hot_card_cache->reset_card_counts(r);
4304     }
4305 
4306     if (!evacuation_failed) {
4307       r->rem_set()->clear_locked();
4308     }
4309   }
4310 
4311   class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4312   private:
4313     size_t _cur_idx;
4314     WorkItem* _work_items;
4315   public:
4316     G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4317 
4318     virtual bool do_heap_region(HeapRegion* r) {
4319       _work_items[_cur_idx++] = WorkItem(r);
4320       return false;
4321     }
4322   };
4323 
4324   void prepare_work() {
4325     G1PrepareFreeCollectionSetClosure cl(_work_items);
4326     _collection_set->iterate(&cl);
4327   }
4328 
4329   void complete_work() {
4330     _cl.complete_work();
4331 
4332     G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4333     policy->record_max_rs_lengths(_rs_lengths);
4334     policy->cset_regions_freed();
4335   }
4336 public:
4337   G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4338     AbstractGangTask("G1 Free Collection Set"),
4339     _cl(evacuation_info, surviving_young_words),
4340     _collection_set(collection_set),
4341     _surviving_young_words(surviving_young_words),
4342     _serial_work_claim(0),
4343     _rs_lengths(0),
4344     _parallel_work_claim(0),
4345     _num_work_items(collection_set->region_length()),
4346     _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4347     prepare_work();
4348   }
4349 
4350   ~G1FreeCollectionSetTask() {
4351     complete_work();
4352     FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4353   }
4354 
4355   // Chunk size for work distribution. The chosen value has been determined experimentally
4356   // to be a good tradeoff between overhead and achievable parallelism.
4357   static uint chunk_size() { return 32; }
4358 
4359   virtual void work(uint worker_id) {
4360     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4361 
4362     // Claim serial work.
4363     if (_serial_work_claim == 0) {
4364       jint value = Atomic::add(1, &_serial_work_claim) - 1;
4365       if (value == 0) {
4366         double serial_time = os::elapsedTime();
4367         do_serial_work();
4368         timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4369       }
4370     }
4371 
4372     // Start parallel work.
4373     double young_time = 0.0;
4374     bool has_young_time = false;
4375     double non_young_time = 0.0;
4376     bool has_non_young_time = false;
4377 
4378     while (true) {
4379       size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4380       size_t cur = end - chunk_size();
4381 
4382       if (cur >= _num_work_items) {
4383         break;
4384       }
4385 
4386       double start_time = os::elapsedTime();
4387 
4388       end = MIN2(end, _num_work_items);
4389 
4390       for (; cur < end; cur++) {
4391         bool is_young = _work_items[cur].is_young;
4392 
4393         do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4394 
4395         double end_time = os::elapsedTime();
4396         double time_taken = end_time - start_time;
4397         if (is_young) {
4398           young_time += time_taken;
4399           has_young_time = true;
4400         } else {
4401           non_young_time += time_taken;
4402           has_non_young_time = true;
4403         }
4404         start_time = end_time;
4405       }
4406     }
4407 
4408     if (has_young_time) {
4409       timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4410     }
4411     if (has_non_young_time) {
4412       timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, non_young_time);
4413     }
4414   }
4415 };
4416 
4417 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4418   _eden.clear();
4419 
4420   double free_cset_start_time = os::elapsedTime();
4421 
4422   {
4423     uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4424     uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4425 
4426     G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4427 
4428     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4429                         cl.name(),
4430                         num_workers,
4431                         _collection_set.region_length());
4432     workers()->run_task(&cl, num_workers);
4433   }
4434   g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4435 
4436   collection_set->clear();
4437 }
4438 
4439 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4440  private:
4441   FreeRegionList* _free_region_list;
4442   HeapRegionSet* _proxy_set;
4443   uint _humongous_objects_reclaimed;
4444   uint _humongous_regions_reclaimed;
4445   size_t _freed_bytes;
4446  public:
4447 
4448   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4449     _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4450   }
4451 
4452   virtual bool do_heap_region(HeapRegion* r) {
4453     if (!r->is_starts_humongous()) {
4454       return false;
4455     }
4456 
4457     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4458 
4459     oop obj = (oop)r->bottom();
4460     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4461 
4462     // The following checks whether the humongous object is live are sufficient.
4463     // The main additional check (in addition to having a reference from the roots
4464     // or the young gen) is whether the humongous object has a remembered set entry.
4465     //
4466     // A humongous object cannot be live if there is no remembered set for it
4467     // because:
4468     // - there can be no references from within humongous starts regions referencing
4469     // the object because we never allocate other objects into them.
4470     // (I.e. there are no intra-region references that may be missed by the
4471     // remembered set)
4472     // - as soon there is a remembered set entry to the humongous starts region
4473     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4474     // until the end of a concurrent mark.
4475     //
4476     // It is not required to check whether the object has been found dead by marking
4477     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4478     // all objects allocated during that time are considered live.
4479     // SATB marking is even more conservative than the remembered set.
4480     // So if at this point in the collection there is no remembered set entry,
4481     // nobody has a reference to it.
4482     // At the start of collection we flush all refinement logs, and remembered sets
4483     // are completely up-to-date wrt to references to the humongous object.
4484     //
4485     // Other implementation considerations:
4486     // - never consider object arrays at this time because they would pose
4487     // considerable effort for cleaning up the the remembered sets. This is
4488     // required because stale remembered sets might reference locations that
4489     // are currently allocated into.
4490     uint region_idx = r->hrm_index();
4491     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4492         !r->rem_set()->is_empty()) {
4493       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",
4494                                region_idx,
4495                                (size_t)obj->size() * HeapWordSize,
4496                                p2i(r->bottom()),
4497                                r->rem_set()->occupied(),
4498                                r->rem_set()->strong_code_roots_list_length(),
4499                                next_bitmap->is_marked(r->bottom()),
4500                                g1h->is_humongous_reclaim_candidate(region_idx),
4501                                obj->is_typeArray()
4502                               );
4503       return false;
4504     }
4505 
4506     guarantee(obj->is_typeArray(),
4507               "Only eagerly reclaiming type arrays is supported, but the object "
4508               PTR_FORMAT " is not.", p2i(r->bottom()));
4509 
4510     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",
4511                              region_idx,
4512                              (size_t)obj->size() * HeapWordSize,
4513                              p2i(r->bottom()),
4514                              r->rem_set()->occupied(),
4515                              r->rem_set()->strong_code_roots_list_length(),
4516                              next_bitmap->is_marked(r->bottom()),
4517                              g1h->is_humongous_reclaim_candidate(region_idx),
4518                              obj->is_typeArray()
4519                             );
4520 
4521     G1ConcurrentMark* const cm = g1h->concurrent_mark();
4522     cm->humongous_object_eagerly_reclaimed(r);
4523     assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj),
4524            "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s",
4525            region_idx,
4526            BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)),
4527            BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj)));
4528     _humongous_objects_reclaimed++;
4529     do {
4530       HeapRegion* next = g1h->next_region_in_humongous(r);
4531       _freed_bytes += r->used();
4532       r->set_containing_set(NULL);
4533       _humongous_regions_reclaimed++;
4534       g1h->free_humongous_region(r, _free_region_list);
4535       r = next;
4536     } while (r != NULL);
4537 
4538     return false;
4539   }
4540 
4541   uint humongous_objects_reclaimed() {
4542     return _humongous_objects_reclaimed;
4543   }
4544 
4545   uint humongous_regions_reclaimed() {
4546     return _humongous_regions_reclaimed;
4547   }
4548 
4549   size_t bytes_freed() const {
4550     return _freed_bytes;
4551   }
4552 };
4553 
4554 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4555   assert_at_safepoint_on_vm_thread();
4556 
4557   if (!G1EagerReclaimHumongousObjects ||
4558       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4559     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4560     return;
4561   }
4562 
4563   double start_time = os::elapsedTime();
4564 
4565   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4566 
4567   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4568   heap_region_iterate(&cl);
4569 
4570   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4571 
4572   G1HRPrinter* hrp = hr_printer();
4573   if (hrp->is_active()) {
4574     FreeRegionListIterator iter(&local_cleanup_list);
4575     while (iter.more_available()) {
4576       HeapRegion* hr = iter.get_next();
4577       hrp->cleanup(hr);
4578     }
4579   }
4580 
4581   prepend_to_freelist(&local_cleanup_list);
4582   decrement_summary_bytes(cl.bytes_freed());
4583 
4584   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4585                                                                     cl.humongous_objects_reclaimed());
4586 }
4587 
4588 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4589 public:
4590   virtual bool do_heap_region(HeapRegion* r) {
4591     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4592     G1CollectedHeap::heap()->clear_in_cset(r);
4593     r->set_young_index_in_cset(-1);
4594     return false;
4595   }
4596 };
4597 
4598 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4599   G1AbandonCollectionSetClosure cl;
4600   collection_set->iterate(&cl);
4601 
4602   collection_set->clear();
4603   collection_set->stop_incremental_building();
4604 }
4605 
4606 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4607   return _allocator->is_retained_old_region(hr);
4608 }
4609 
4610 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4611   _eden.add(hr);
4612   _g1_policy->set_region_eden(hr);
4613 }
4614 
4615 #ifdef ASSERT
4616 
4617 class NoYoungRegionsClosure: public HeapRegionClosure {
4618 private:
4619   bool _success;
4620 public:
4621   NoYoungRegionsClosure() : _success(true) { }
4622   bool do_heap_region(HeapRegion* r) {
4623     if (r->is_young()) {
4624       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4625                             p2i(r->bottom()), p2i(r->end()));
4626       _success = false;
4627     }
4628     return false;
4629   }
4630   bool success() { return _success; }
4631 };
4632 
4633 bool G1CollectedHeap::check_young_list_empty() {
4634   bool ret = (young_regions_count() == 0);
4635 
4636   NoYoungRegionsClosure closure;
4637   heap_region_iterate(&closure);
4638   ret = ret && closure.success();
4639 
4640   return ret;
4641 }
4642 
4643 #endif // ASSERT
4644 
4645 class TearDownRegionSetsClosure : public HeapRegionClosure {
4646 private:
4647   HeapRegionSet *_old_set;
4648 
4649 public:
4650   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
4651 
4652   bool do_heap_region(HeapRegion* r) {
4653     if (r->is_old()) {
4654       _old_set->remove(r);
4655     } else if(r->is_young()) {
4656       r->uninstall_surv_rate_group();
4657     } else {
4658       // We ignore free regions, we'll empty the free list afterwards.
4659       // We ignore humongous regions, we're not tearing down the
4660       // humongous regions set.
4661       assert(r->is_free() || r->is_humongous(),
4662              "it cannot be another type");
4663     }
4664     return false;
4665   }
4666 
4667   ~TearDownRegionSetsClosure() {
4668     assert(_old_set->is_empty(), "post-condition");
4669   }
4670 };
4671 
4672 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
4673   assert_at_safepoint_on_vm_thread();
4674 
4675   if (!free_list_only) {
4676     TearDownRegionSetsClosure cl(&_old_set);
4677     heap_region_iterate(&cl);
4678 
4679     // Note that emptying the _young_list is postponed and instead done as
4680     // the first step when rebuilding the regions sets again. The reason for
4681     // this is that during a full GC string deduplication needs to know if
4682     // a collected region was young or old when the full GC was initiated.
4683   }
4684   _hrm.remove_all_free_regions();
4685 }
4686 
4687 void G1CollectedHeap::increase_used(size_t bytes) {
4688   _summary_bytes_used += bytes;
4689 }
4690 
4691 void G1CollectedHeap::decrease_used(size_t bytes) {
4692   assert(_summary_bytes_used >= bytes,
4693          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
4694          _summary_bytes_used, bytes);
4695   _summary_bytes_used -= bytes;
4696 }
4697 
4698 void G1CollectedHeap::set_used(size_t bytes) {
4699   _summary_bytes_used = bytes;
4700 }
4701 
4702 class RebuildRegionSetsClosure : public HeapRegionClosure {
4703 private:
4704   bool            _free_list_only;
4705   HeapRegionSet*   _old_set;
4706   HeapRegionManager*   _hrm;
4707   size_t          _total_used;
4708 
4709 public:
4710   RebuildRegionSetsClosure(bool free_list_only,
4711                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
4712     _free_list_only(free_list_only),
4713     _old_set(old_set), _hrm(hrm), _total_used(0) {
4714     assert(_hrm->num_free_regions() == 0, "pre-condition");
4715     if (!free_list_only) {
4716       assert(_old_set->is_empty(), "pre-condition");
4717     }
4718   }
4719 
4720   bool do_heap_region(HeapRegion* r) {
4721     // After full GC, no region should have a remembered set.
4722     r->rem_set()->clear(true);
4723     if (r->is_empty()) {
4724       // Add free regions to the free list
4725       r->set_free();
4726       _hrm->insert_into_free_list(r);
4727     } else if (!_free_list_only) {
4728 
4729       if (r->is_humongous()) {
4730         // We ignore humongous regions. We left the humongous set unchanged.
4731       } else {
4732         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
4733         // We now move all (non-humongous, non-old) regions to old gen, and register them as such.
4734         r->move_to_old();
4735         _old_set->add(r);
4736       }
4737       _total_used += r->used();
4738     }
4739 
4740     return false;
4741   }
4742 
4743   size_t total_used() {
4744     return _total_used;
4745   }
4746 };
4747 
4748 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
4749   assert_at_safepoint_on_vm_thread();
4750 
4751   if (!free_list_only) {
4752     _eden.clear();
4753     _survivor.clear();
4754   }
4755 
4756   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
4757   heap_region_iterate(&cl);
4758 
4759   if (!free_list_only) {
4760     set_used(cl.total_used());
4761     if (_archive_allocator != NULL) {
4762       _archive_allocator->clear_used();
4763     }
4764   }
4765   assert(used_unlocked() == recalculate_used(),
4766          "inconsistent used_unlocked(), "
4767          "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
4768          used_unlocked(), recalculate_used());
4769 }
4770 
4771 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
4772   HeapRegion* hr = heap_region_containing(p);
4773   return hr->is_in(p);
4774 }
4775 
4776 // Methods for the mutator alloc region
4777 
4778 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
4779                                                       bool force) {
4780   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4781   bool should_allocate = g1_policy()->should_allocate_mutator_region();
4782   if (force || should_allocate) {
4783     HeapRegion* new_alloc_region = new_region(word_size,
4784                                               false /* is_old */,
4785                                               false /* do_expand */);
4786     if (new_alloc_region != NULL) {
4787       set_region_short_lived_locked(new_alloc_region);
4788       _hr_printer.alloc(new_alloc_region, !should_allocate);
4789       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
4790       _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region);
4791       return new_alloc_region;
4792     }
4793   }
4794   return NULL;
4795 }
4796 
4797 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
4798                                                   size_t allocated_bytes) {
4799   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4800   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
4801 
4802   collection_set()->add_eden_region(alloc_region);
4803   increase_used(allocated_bytes);
4804   _hr_printer.retire(alloc_region);
4805   // We update the eden sizes here, when the region is retired,
4806   // instead of when it's allocated, since this is the point that its
4807   // used space has been recored in _summary_bytes_used.
4808   g1mm()->update_eden_size();
4809 }
4810 
4811 // Methods for the GC alloc regions
4812 
4813 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
4814   if (dest.is_old()) {
4815     return true;
4816   } else {
4817     return survivor_regions_count() < g1_policy()->max_survivor_regions();
4818   }
4819 }
4820 
4821 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
4822   assert(FreeList_lock->owned_by_self(), "pre-condition");
4823 
4824   if (!has_more_regions(dest)) {
4825     return NULL;
4826   }
4827 
4828   const bool is_survivor = dest.is_young();
4829 
4830   HeapRegion* new_alloc_region = new_region(word_size,
4831                                             !is_survivor,
4832                                             true /* do_expand */);
4833   if (new_alloc_region != NULL) {
4834     if (is_survivor) {
4835       new_alloc_region->set_survivor();
4836       _survivor.add(new_alloc_region);
4837       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
4838     } else {
4839       new_alloc_region->set_old();
4840       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
4841     }
4842     _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region);
4843     _hr_printer.alloc(new_alloc_region);
4844     bool during_im = collector_state()->in_initial_mark_gc();
4845     new_alloc_region->note_start_of_copying(during_im);
4846     return new_alloc_region;
4847   }
4848   return NULL;
4849 }
4850 
4851 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
4852                                              size_t allocated_bytes,
4853                                              InCSetState dest) {
4854   bool during_im = collector_state()->in_initial_mark_gc();
4855   alloc_region->note_end_of_copying(during_im);
4856   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
4857   if (dest.is_old()) {
4858     _old_set.add(alloc_region);
4859   }
4860   _hr_printer.retire(alloc_region);
4861 }
4862 
4863 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
4864   bool expanded = false;
4865   uint index = _hrm.find_highest_free(&expanded);
4866 
4867   if (index != G1_NO_HRM_INDEX) {
4868     if (expanded) {
4869       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
4870                                 HeapRegion::GrainWords * HeapWordSize);
4871     }
4872     _hrm.allocate_free_regions_starting_at(index, 1);
4873     return region_at(index);
4874   }
4875   return NULL;
4876 }
4877 
4878 // Optimized nmethod scanning
4879 
4880 class RegisterNMethodOopClosure: public OopClosure {
4881   G1CollectedHeap* _g1h;
4882   nmethod* _nm;
4883 
4884   template <class T> void do_oop_work(T* p) {
4885     T heap_oop = RawAccess<>::oop_load(p);
4886     if (!CompressedOops::is_null(heap_oop)) {
4887       oop obj = CompressedOops::decode_not_null(heap_oop);
4888       HeapRegion* hr = _g1h->heap_region_containing(obj);
4889       assert(!hr->is_continues_humongous(),
4890              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4891              " starting at " HR_FORMAT,
4892              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4893 
4894       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
4895       hr->add_strong_code_root_locked(_nm);
4896     }
4897   }
4898 
4899 public:
4900   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4901     _g1h(g1h), _nm(nm) {}
4902 
4903   void do_oop(oop* p)       { do_oop_work(p); }
4904   void do_oop(narrowOop* p) { do_oop_work(p); }
4905 };
4906 
4907 class UnregisterNMethodOopClosure: public OopClosure {
4908   G1CollectedHeap* _g1h;
4909   nmethod* _nm;
4910 
4911   template <class T> void do_oop_work(T* p) {
4912     T heap_oop = RawAccess<>::oop_load(p);
4913     if (!CompressedOops::is_null(heap_oop)) {
4914       oop obj = CompressedOops::decode_not_null(heap_oop);
4915       HeapRegion* hr = _g1h->heap_region_containing(obj);
4916       assert(!hr->is_continues_humongous(),
4917              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4918              " starting at " HR_FORMAT,
4919              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4920 
4921       hr->remove_strong_code_root(_nm);
4922     }
4923   }
4924 
4925 public:
4926   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4927     _g1h(g1h), _nm(nm) {}
4928 
4929   void do_oop(oop* p)       { do_oop_work(p); }
4930   void do_oop(narrowOop* p) { do_oop_work(p); }
4931 };
4932 
4933 // Returns true if the reference points to an object that
4934 // can move in an incremental collection.
4935 bool G1CollectedHeap::is_scavengable(oop obj) {
4936   HeapRegion* hr = heap_region_containing(obj);
4937   return !hr->is_pinned();
4938 }
4939 
4940 void G1CollectedHeap::register_nmethod(nmethod* nm) {
4941   guarantee(nm != NULL, "sanity");
4942   RegisterNMethodOopClosure reg_cl(this, nm);
4943   nm->oops_do(&reg_cl);
4944 }
4945 
4946 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
4947   guarantee(nm != NULL, "sanity");
4948   UnregisterNMethodOopClosure reg_cl(this, nm);
4949   nm->oops_do(&reg_cl, true);
4950 }
4951 
4952 void G1CollectedHeap::purge_code_root_memory() {
4953   double purge_start = os::elapsedTime();
4954   G1CodeRootSet::purge();
4955   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
4956   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
4957 }
4958 
4959 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
4960   G1CollectedHeap* _g1h;
4961 
4962 public:
4963   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
4964     _g1h(g1h) {}
4965 
4966   void do_code_blob(CodeBlob* cb) {
4967     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
4968     if (nm == NULL) {
4969       return;
4970     }
4971 
4972     if (ScavengeRootsInCode) {
4973       _g1h->register_nmethod(nm);
4974     }
4975   }
4976 };
4977 
4978 void G1CollectedHeap::rebuild_strong_code_roots() {
4979   RebuildStrongCodeRootClosure blob_cl(this);
4980   CodeCache::blobs_do(&blob_cl);
4981 }
4982 
4983 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
4984   GrowableArray<GCMemoryManager*> memory_managers(2);
4985   memory_managers.append(&_memory_manager);
4986   memory_managers.append(&_full_gc_memory_manager);
4987   return memory_managers;
4988 }
4989 
4990 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
4991   GrowableArray<MemoryPool*> memory_pools(3);
4992   memory_pools.append(_eden_pool);
4993   memory_pools.append(_survivor_pool);
4994   memory_pools.append(_old_pool);
4995   return memory_pools;
4996 }
--- EOF ---