1 /*
   2  * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/metadataOnStackMark.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "classfile/symbolTable.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc/g1/bufferingOopClosure.hpp"
  32 #include "gc/g1/concurrentMarkThread.inline.hpp"
  33 #include "gc/g1/g1Allocator.inline.hpp"
  34 #include "gc/g1/g1CollectedHeap.inline.hpp"
  35 #include "gc/g1/g1CollectionSet.hpp"
  36 #include "gc/g1/g1CollectorPolicy.hpp"
  37 #include "gc/g1/g1CollectorState.hpp"
  38 #include "gc/g1/g1ConcurrentRefine.hpp"
  39 #include "gc/g1/g1ConcurrentRefineThread.hpp"
  40 #include "gc/g1/g1DefaultPolicy.hpp"
  41 #include "gc/g1/g1EvacStats.inline.hpp"
  42 #include "gc/g1/g1FullCollector.hpp"
  43 #include "gc/g1/g1GCPhaseTimes.hpp"
  44 #include "gc/g1/g1HeapSizingPolicy.hpp"
  45 #include "gc/g1/g1HeapTransition.hpp"
  46 #include "gc/g1/g1HeapVerifier.hpp"
  47 #include "gc/g1/g1HotCardCache.hpp"
  48 #include "gc/g1/g1MemoryPool.hpp"
  49 #include "gc/g1/g1OopClosures.inline.hpp"
  50 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  51 #include "gc/g1/g1Policy.hpp"
  52 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  53 #include "gc/g1/g1RemSet.hpp"
  54 #include "gc/g1/g1RootClosures.hpp"
  55 #include "gc/g1/g1RootProcessor.hpp"
  56 #include "gc/g1/g1StringDedup.hpp"
  57 #include "gc/g1/g1YCTypes.hpp"
  58 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
  59 #include "gc/g1/heapRegion.inline.hpp"
  60 #include "gc/g1/heapRegionRemSet.hpp"
  61 #include "gc/g1/heapRegionSet.inline.hpp"
  62 #include "gc/g1/vm_operations_g1.hpp"
  63 #include "gc/shared/adaptiveSizePolicy.hpp"
  64 #include "gc/shared/gcHeapSummary.hpp"
  65 #include "gc/shared/gcId.hpp"
  66 #include "gc/shared/gcLocker.inline.hpp"
  67 #include "gc/shared/gcTimer.hpp"
  68 #include "gc/shared/gcTrace.hpp"
  69 #include "gc/shared/gcTraceTime.inline.hpp"
  70 #include "gc/shared/generationSpec.hpp"
  71 #include "gc/shared/isGCActiveMark.hpp"
  72 #include "gc/shared/preservedMarks.inline.hpp"
  73 #include "gc/shared/suspendibleThreadSet.hpp"
  74 #include "gc/shared/referenceProcessor.inline.hpp"
  75 #include "gc/shared/taskqueue.inline.hpp"
  76 #include "gc/shared/weakProcessor.hpp"
  77 #include "logging/log.hpp"
  78 #include "memory/allocation.hpp"
  79 #include "memory/iterator.hpp"
  80 #include "memory/resourceArea.hpp"
  81 #include "oops/oop.inline.hpp"
  82 #include "prims/resolvedMethodTable.hpp"
  83 #include "runtime/atomic.hpp"
  84 #include "runtime/init.hpp"
  85 #include "runtime/orderAccess.inline.hpp"
  86 #include "runtime/threadSMR.hpp"
  87 #include "runtime/vmThread.hpp"
  88 #include "utilities/align.hpp"
  89 #include "utilities/globalDefinitions.hpp"
  90 #include "utilities/stack.inline.hpp"
  91 
  92 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  93 
  94 // INVARIANTS/NOTES
  95 //
  96 // All allocation activity covered by the G1CollectedHeap interface is
  97 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  98 // and allocate_new_tlab, which are the "entry" points to the
  99 // allocation code from the rest of the JVM.  (Note that this does not
 100 // apply to TLAB allocation, which is not part of this interface: it
 101 // is done by clients of this interface.)
 102 
 103 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 104  private:
 105   size_t _num_dirtied;
 106   G1CollectedHeap* _g1h;
 107   G1CardTable* _g1_ct;
 108 
 109   HeapRegion* region_for_card(jbyte* card_ptr) const {
 110     return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr));
 111   }
 112 
 113   bool will_become_free(HeapRegion* hr) const {
 114     // A region will be freed by free_collection_set if the region is in the
 115     // collection set and has not had an evacuation failure.
 116     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 117   }
 118 
 119  public:
 120   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
 121     _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { }
 122 
 123   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 124     HeapRegion* hr = region_for_card(card_ptr);
 125 
 126     // Should only dirty cards in regions that won't be freed.
 127     if (!will_become_free(hr)) {
 128       *card_ptr = G1CardTable::dirty_card_val();
 129       _num_dirtied++;
 130     }
 131 
 132     return true;
 133   }
 134 
 135   size_t num_dirtied()   const { return _num_dirtied; }
 136 };
 137 
 138 
 139 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 140   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 141 }
 142 
 143 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 144   // The from card cache is not the memory that is actually committed. So we cannot
 145   // take advantage of the zero_filled parameter.
 146   reset_from_card_cache(start_idx, num_regions);
 147 }
 148 
 149 
 150 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
 151                                              MemRegion mr) {
 152   return new HeapRegion(hrs_index, bot(), mr);
 153 }
 154 
 155 // Private methods.
 156 
 157 HeapRegion*
 158 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 159   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 160   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 161     if (!_secondary_free_list.is_empty()) {
 162       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 163                                       "secondary_free_list has %u entries",
 164                                       _secondary_free_list.length());
 165       // It looks as if there are free regions available on the
 166       // secondary_free_list. Let's move them to the free_list and try
 167       // again to allocate from it.
 168       append_secondary_free_list();
 169 
 170       assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
 171              "empty we should have moved at least one entry to the free_list");
 172       HeapRegion* res = _hrm.allocate_free_region(is_old);
 173       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 174                                       "allocated " HR_FORMAT " from secondary_free_list",
 175                                       HR_FORMAT_PARAMS(res));
 176       return res;
 177     }
 178 
 179     // Wait here until we get notified either when (a) there are no
 180     // more free regions coming or (b) some regions have been moved on
 181     // the secondary_free_list.
 182     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 183   }
 184 
 185   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 186                                   "could not allocate from secondary_free_list");
 187   return NULL;
 188 }
 189 
 190 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 191   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 192          "the only time we use this to allocate a humongous region is "
 193          "when we are allocating a single humongous region");
 194 
 195   HeapRegion* res;
 196   if (G1StressConcRegionFreeing) {
 197     if (!_secondary_free_list.is_empty()) {
 198       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 199                                       "forced to look at the secondary_free_list");
 200       res = new_region_try_secondary_free_list(is_old);
 201       if (res != NULL) {
 202         return res;
 203       }
 204     }
 205   }
 206 
 207   res = _hrm.allocate_free_region(is_old);
 208 
 209   if (res == NULL) {
 210     log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 211                                     "res == NULL, trying the secondary_free_list");
 212     res = new_region_try_secondary_free_list(is_old);
 213   }
 214   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 215     // Currently, only attempts to allocate GC alloc regions set
 216     // do_expand to true. So, we should only reach here during a
 217     // safepoint. If this assumption changes we might have to
 218     // reconsider the use of _expand_heap_after_alloc_failure.
 219     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 220 
 221     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 222                               word_size * HeapWordSize);
 223 
 224     if (expand(word_size * HeapWordSize)) {
 225       // Given that expand() succeeded in expanding the heap, and we
 226       // always expand the heap by an amount aligned to the heap
 227       // region size, the free list should in theory not be empty.
 228       // In either case allocate_free_region() will check for NULL.
 229       res = _hrm.allocate_free_region(is_old);
 230     } else {
 231       _expand_heap_after_alloc_failure = false;
 232     }
 233   }
 234   return res;
 235 }
 236 
 237 HeapWord*
 238 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 239                                                            uint num_regions,
 240                                                            size_t word_size) {
 241   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 242   assert(is_humongous(word_size), "word_size should be humongous");
 243   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 244 
 245   // Index of last region in the series.
 246   uint last = first + num_regions - 1;
 247 
 248   // We need to initialize the region(s) we just discovered. This is
 249   // a bit tricky given that it can happen concurrently with
 250   // refinement threads refining cards on these regions and
 251   // potentially wanting to refine the BOT as they are scanning
 252   // those cards (this can happen shortly after a cleanup; see CR
 253   // 6991377). So we have to set up the region(s) carefully and in
 254   // a specific order.
 255 
 256   // The word size sum of all the regions we will allocate.
 257   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 258   assert(word_size <= word_size_sum, "sanity");
 259 
 260   // This will be the "starts humongous" region.
 261   HeapRegion* first_hr = region_at(first);
 262   // The header of the new object will be placed at the bottom of
 263   // the first region.
 264   HeapWord* new_obj = first_hr->bottom();
 265   // This will be the new top of the new object.
 266   HeapWord* obj_top = new_obj + word_size;
 267 
 268   // First, we need to zero the header of the space that we will be
 269   // allocating. When we update top further down, some refinement
 270   // threads might try to scan the region. By zeroing the header we
 271   // ensure that any thread that will try to scan the region will
 272   // come across the zero klass word and bail out.
 273   //
 274   // NOTE: It would not have been correct to have used
 275   // CollectedHeap::fill_with_object() and make the space look like
 276   // an int array. The thread that is doing the allocation will
 277   // later update the object header to a potentially different array
 278   // type and, for a very short period of time, the klass and length
 279   // fields will be inconsistent. This could cause a refinement
 280   // thread to calculate the object size incorrectly.
 281   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 282 
 283   // Next, pad out the unused tail of the last region with filler
 284   // objects, for improved usage accounting.
 285   // How many words we use for filler objects.
 286   size_t word_fill_size = word_size_sum - word_size;
 287 
 288   // How many words memory we "waste" which cannot hold a filler object.
 289   size_t words_not_fillable = 0;
 290 
 291   if (word_fill_size >= min_fill_size()) {
 292     fill_with_objects(obj_top, word_fill_size);
 293   } else if (word_fill_size > 0) {
 294     // We have space to fill, but we cannot fit an object there.
 295     words_not_fillable = word_fill_size;
 296     word_fill_size = 0;
 297   }
 298 
 299   // We will set up the first region as "starts humongous". This
 300   // will also update the BOT covering all the regions to reflect
 301   // that there is a single object that starts at the bottom of the
 302   // first region.
 303   first_hr->set_starts_humongous(obj_top, word_fill_size);
 304   // Then, if there are any, we will set up the "continues
 305   // humongous" regions.
 306   HeapRegion* hr = NULL;
 307   for (uint i = first + 1; i <= last; ++i) {
 308     hr = region_at(i);
 309     hr->set_continues_humongous(first_hr);
 310   }
 311 
 312   // Up to this point no concurrent thread would have been able to
 313   // do any scanning on any region in this series. All the top
 314   // fields still point to bottom, so the intersection between
 315   // [bottom,top] and [card_start,card_end] will be empty. Before we
 316   // update the top fields, we'll do a storestore to make sure that
 317   // no thread sees the update to top before the zeroing of the
 318   // object header and the BOT initialization.
 319   OrderAccess::storestore();
 320 
 321   // Now, we will update the top fields of the "continues humongous"
 322   // regions except the last one.
 323   for (uint i = first; i < last; ++i) {
 324     hr = region_at(i);
 325     hr->set_top(hr->end());
 326   }
 327 
 328   hr = region_at(last);
 329   // If we cannot fit a filler object, we must set top to the end
 330   // of the humongous object, otherwise we cannot iterate the heap
 331   // and the BOT will not be complete.
 332   hr->set_top(hr->end() - words_not_fillable);
 333 
 334   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 335          "obj_top should be in last region");
 336 
 337   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 338 
 339   assert(words_not_fillable == 0 ||
 340          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 341          "Miscalculation in humongous allocation");
 342 
 343   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 344 
 345   for (uint i = first; i <= last; ++i) {
 346     hr = region_at(i);
 347     _humongous_set.add(hr);
 348     _hr_printer.alloc(hr);
 349   }
 350 
 351   return new_obj;
 352 }
 353 
 354 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 355   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 356   return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 357 }
 358 
 359 // If could fit into free regions w/o expansion, try.
 360 // Otherwise, if can expand, do so.
 361 // Otherwise, if using ex regions might help, try with ex given back.
 362 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 363   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 364 
 365   _verifier->verify_region_sets_optional();
 366 
 367   uint first = G1_NO_HRM_INDEX;
 368   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 369 
 370   if (obj_regions == 1) {
 371     // Only one region to allocate, try to use a fast path by directly allocating
 372     // from the free lists. Do not try to expand here, we will potentially do that
 373     // later.
 374     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 375     if (hr != NULL) {
 376       first = hr->hrm_index();
 377     }
 378   } else {
 379     // We can't allocate humongous regions spanning more than one region while
 380     // cleanupComplete() is running, since some of the regions we find to be
 381     // empty might not yet be added to the free list. It is not straightforward
 382     // to know in which list they are on so that we can remove them. We only
 383     // need to do this if we need to allocate more than one region to satisfy the
 384     // current humongous allocation request. If we are only allocating one region
 385     // we use the one-region region allocation code (see above), that already
 386     // potentially waits for regions from the secondary free list.
 387     wait_while_free_regions_coming();
 388     append_secondary_free_list_if_not_empty_with_lock();
 389 
 390     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 391     // are lucky enough to find some.
 392     first = _hrm.find_contiguous_only_empty(obj_regions);
 393     if (first != G1_NO_HRM_INDEX) {
 394       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 395     }
 396   }
 397 
 398   if (first == G1_NO_HRM_INDEX) {
 399     // Policy: We could not find enough regions for the humongous object in the
 400     // free list. Look through the heap to find a mix of free and uncommitted regions.
 401     // If so, try expansion.
 402     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 403     if (first != G1_NO_HRM_INDEX) {
 404       // We found something. Make sure these regions are committed, i.e. expand
 405       // the heap. Alternatively we could do a defragmentation GC.
 406       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 407                                     word_size * HeapWordSize);
 408 
 409       _hrm.expand_at(first, obj_regions, workers());
 410       g1_policy()->record_new_heap_size(num_regions());
 411 
 412 #ifdef ASSERT
 413       for (uint i = first; i < first + obj_regions; ++i) {
 414         HeapRegion* hr = region_at(i);
 415         assert(hr->is_free(), "sanity");
 416         assert(hr->is_empty(), "sanity");
 417         assert(is_on_master_free_list(hr), "sanity");
 418       }
 419 #endif
 420       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 421     } else {
 422       // Policy: Potentially trigger a defragmentation GC.
 423     }
 424   }
 425 
 426   HeapWord* result = NULL;
 427   if (first != G1_NO_HRM_INDEX) {
 428     result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size);
 429     assert(result != NULL, "it should always return a valid result");
 430 
 431     // A successful humongous object allocation changes the used space
 432     // information of the old generation so we need to recalculate the
 433     // sizes and update the jstat counters here.
 434     g1mm()->update_sizes();
 435   }
 436 
 437   _verifier->verify_region_sets_optional();
 438 
 439   return result;
 440 }
 441 
 442 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 443   assert_heap_not_locked_and_not_at_safepoint();
 444   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 445 
 446   return attempt_allocation(word_size);
 447 }
 448 
 449 HeapWord*
 450 G1CollectedHeap::mem_allocate(size_t word_size,
 451                               bool*  gc_overhead_limit_was_exceeded) {
 452   assert_heap_not_locked_and_not_at_safepoint();
 453 
 454   if (is_humongous(word_size)) {
 455     return attempt_allocation_humongous(word_size);
 456   }
 457   return attempt_allocation(word_size);
 458 }
 459 
 460 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
 461   ResourceMark rm; // For retrieving the thread names in log messages.
 462 
 463   // Make sure you read the note in attempt_allocation_humongous().
 464 
 465   assert_heap_not_locked_and_not_at_safepoint();
 466   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 467          "be called for humongous allocation requests");
 468 
 469   // We should only get here after the first-level allocation attempt
 470   // (attempt_allocation()) failed to allocate.
 471 
 472   // We will loop until a) we manage to successfully perform the
 473   // allocation or b) we successfully schedule a collection which
 474   // fails to perform the allocation. b) is the only case when we'll
 475   // return NULL.
 476   HeapWord* result = NULL;
 477   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 478     bool should_try_gc;
 479     uint gc_count_before;
 480 
 481     {
 482       MutexLockerEx x(Heap_lock);
 483       result = _allocator->attempt_allocation_locked(word_size);
 484       if (result != NULL) {
 485         return result;
 486       }
 487 
 488       // If the GCLocker is active and we are bound for a GC, try expanding young gen.
 489       // This is different to when only GCLocker::needs_gc() is set: try to avoid
 490       // waiting because the GCLocker is active to not wait too long.
 491       if (GCLocker::is_active_and_needs_gc() && g1_policy()->can_expand_young_list()) {
 492         // No need for an ergo message here, can_expand_young_list() does this when
 493         // it returns true.
 494         result = _allocator->attempt_allocation_force(word_size);
 495         if (result != NULL) {
 496           return result;
 497         }
 498       }
 499       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 500       // the GCLocker initiated GC has been performed and then retry. This includes
 501       // the case when the GC Locker is not active but has not been performed.
 502       should_try_gc = !GCLocker::needs_gc();
 503       // Read the GC count while still holding the Heap_lock.
 504       gc_count_before = total_collections();
 505     }
 506 
 507     if (should_try_gc) {
 508       bool succeeded;
 509       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 510                                    GCCause::_g1_inc_collection_pause);
 511       if (result != NULL) {
 512         assert(succeeded, "only way to get back a non-NULL result");
 513         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 514                              Thread::current()->name(), p2i(result));
 515         return result;
 516       }
 517 
 518       if (succeeded) {
 519         // We successfully scheduled a collection which failed to allocate. No
 520         // point in trying to allocate further. We'll just return NULL.
 521         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 522                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 523         return NULL;
 524       }
 525       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
 526                            Thread::current()->name(), word_size);
 527     } else {
 528       // Failed to schedule a collection.
 529       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 530         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 531                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 532         return NULL;
 533       }
 534       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 535       // The GCLocker is either active or the GCLocker initiated
 536       // GC has not yet been performed. Stall until it is and
 537       // then retry the allocation.
 538       GCLocker::stall_until_clear();
 539       gclocker_retry_count += 1;
 540     }
 541 
 542     // We can reach here if we were unsuccessful in scheduling a
 543     // collection (because another thread beat us to it) or if we were
 544     // stalled due to the GC locker. In either can we should retry the
 545     // allocation attempt in case another thread successfully
 546     // performed a collection and reclaimed enough space. We do the
 547     // first attempt (without holding the Heap_lock) here and the
 548     // follow-on attempt will be at the start of the next loop
 549     // iteration (after taking the Heap_lock).
 550 
 551     result = _allocator->attempt_allocation(word_size);
 552     if (result != NULL) {
 553       return result;
 554     }
 555 
 556     // Give a warning if we seem to be looping forever.
 557     if ((QueuedAllocationWarningCount > 0) &&
 558         (try_count % QueuedAllocationWarningCount == 0)) {
 559       log_warning(gc, alloc)("%s:  Retried allocation %u times for " SIZE_FORMAT " words",
 560                              Thread::current()->name(), try_count, word_size);
 561     }
 562   }
 563 
 564   ShouldNotReachHere();
 565   return NULL;
 566 }
 567 
 568 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
 569   assert_at_safepoint_on_vm_thread();
 570   if (_archive_allocator == NULL) {
 571     _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
 572   }
 573 }
 574 
 575 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 576   // Allocations in archive regions cannot be of a size that would be considered
 577   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 578   // may be different at archive-restore time.
 579   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 580 }
 581 
 582 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 583   assert_at_safepoint_on_vm_thread();
 584   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 585   if (is_archive_alloc_too_large(word_size)) {
 586     return NULL;
 587   }
 588   return _archive_allocator->archive_mem_allocate(word_size);
 589 }
 590 
 591 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 592                                               size_t end_alignment_in_bytes) {
 593   assert_at_safepoint_on_vm_thread();
 594   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 595 
 596   // Call complete_archive to do the real work, filling in the MemRegion
 597   // array with the archive regions.
 598   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 599   delete _archive_allocator;
 600   _archive_allocator = NULL;
 601 }
 602 
 603 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 604   assert(ranges != NULL, "MemRegion array NULL");
 605   assert(count != 0, "No MemRegions provided");
 606   MemRegion reserved = _hrm.reserved();
 607   for (size_t i = 0; i < count; i++) {
 608     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 609       return false;
 610     }
 611   }
 612   return true;
 613 }
 614 
 615 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
 616                                             size_t count,
 617                                             bool open) {
 618   assert(!is_init_completed(), "Expect to be called at JVM init time");
 619   assert(ranges != NULL, "MemRegion array NULL");
 620   assert(count != 0, "No MemRegions provided");
 621   MutexLockerEx x(Heap_lock);
 622 
 623   MemRegion reserved = _hrm.reserved();
 624   HeapWord* prev_last_addr = NULL;
 625   HeapRegion* prev_last_region = NULL;
 626 
 627   // Temporarily disable pretouching of heap pages. This interface is used
 628   // when mmap'ing archived heap data in, so pre-touching is wasted.
 629   FlagSetting fs(AlwaysPreTouch, false);
 630 
 631   // Enable archive object checking used by G1MarkSweep. We have to let it know
 632   // about each archive range, so that objects in those ranges aren't marked.
 633   G1ArchiveAllocator::enable_archive_object_check();
 634 
 635   // For each specified MemRegion range, allocate the corresponding G1
 636   // regions and mark them as archive regions. We expect the ranges
 637   // in ascending starting address order, without overlap.
 638   for (size_t i = 0; i < count; i++) {
 639     MemRegion curr_range = ranges[i];
 640     HeapWord* start_address = curr_range.start();
 641     size_t word_size = curr_range.word_size();
 642     HeapWord* last_address = curr_range.last();
 643     size_t commits = 0;
 644 
 645     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 646               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 647               p2i(start_address), p2i(last_address));
 648     guarantee(start_address > prev_last_addr,
 649               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 650               p2i(start_address), p2i(prev_last_addr));
 651     prev_last_addr = last_address;
 652 
 653     // Check for ranges that start in the same G1 region in which the previous
 654     // range ended, and adjust the start address so we don't try to allocate
 655     // the same region again. If the current range is entirely within that
 656     // region, skip it, just adjusting the recorded top.
 657     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 658     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 659       start_address = start_region->end();
 660       if (start_address > last_address) {
 661         increase_used(word_size * HeapWordSize);
 662         start_region->set_top(last_address + 1);
 663         continue;
 664       }
 665       start_region->set_top(start_address);
 666       curr_range = MemRegion(start_address, last_address + 1);
 667       start_region = _hrm.addr_to_region(start_address);
 668     }
 669 
 670     // Perform the actual region allocation, exiting if it fails.
 671     // Then note how much new space we have allocated.
 672     if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
 673       return false;
 674     }
 675     increase_used(word_size * HeapWordSize);
 676     if (commits != 0) {
 677       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 678                                 HeapRegion::GrainWords * HeapWordSize * commits);
 679 
 680     }
 681 
 682     // Mark each G1 region touched by the range as archive, add it to
 683     // the old set, and set top.
 684     HeapRegion* curr_region = _hrm.addr_to_region(start_address);
 685     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 686     prev_last_region = last_region;
 687 
 688     while (curr_region != NULL) {
 689       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 690              "Region already in use (index %u)", curr_region->hrm_index());
 691       if (open) {
 692         curr_region->set_open_archive();
 693       } else {
 694         curr_region->set_closed_archive();
 695       }
 696       _hr_printer.alloc(curr_region);
 697       _old_set.add(curr_region);
 698       HeapWord* top;
 699       HeapRegion* next_region;
 700       if (curr_region != last_region) {
 701         top = curr_region->end();
 702         next_region = _hrm.next_region_in_heap(curr_region);
 703       } else {
 704         top = last_address + 1;
 705         next_region = NULL;
 706       }
 707       curr_region->set_top(top);
 708       curr_region->set_first_dead(top);
 709       curr_region->set_end_of_live(top);
 710       curr_region = next_region;
 711     }
 712 
 713     // Notify mark-sweep of the archive
 714     G1ArchiveAllocator::set_range_archive(curr_range, open);
 715   }
 716   return true;
 717 }
 718 
 719 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 720   assert(!is_init_completed(), "Expect to be called at JVM init time");
 721   assert(ranges != NULL, "MemRegion array NULL");
 722   assert(count != 0, "No MemRegions provided");
 723   MemRegion reserved = _hrm.reserved();
 724   HeapWord *prev_last_addr = NULL;
 725   HeapRegion* prev_last_region = NULL;
 726 
 727   // For each MemRegion, create filler objects, if needed, in the G1 regions
 728   // that contain the address range. The address range actually within the
 729   // MemRegion will not be modified. That is assumed to have been initialized
 730   // elsewhere, probably via an mmap of archived heap data.
 731   MutexLockerEx x(Heap_lock);
 732   for (size_t i = 0; i < count; i++) {
 733     HeapWord* start_address = ranges[i].start();
 734     HeapWord* last_address = ranges[i].last();
 735 
 736     assert(reserved.contains(start_address) && reserved.contains(last_address),
 737            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 738            p2i(start_address), p2i(last_address));
 739     assert(start_address > prev_last_addr,
 740            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 741            p2i(start_address), p2i(prev_last_addr));
 742 
 743     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 744     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 745     HeapWord* bottom_address = start_region->bottom();
 746 
 747     // Check for a range beginning in the same region in which the
 748     // previous one ended.
 749     if (start_region == prev_last_region) {
 750       bottom_address = prev_last_addr + 1;
 751     }
 752 
 753     // Verify that the regions were all marked as archive regions by
 754     // alloc_archive_regions.
 755     HeapRegion* curr_region = start_region;
 756     while (curr_region != NULL) {
 757       guarantee(curr_region->is_archive(),
 758                 "Expected archive region at index %u", curr_region->hrm_index());
 759       if (curr_region != last_region) {
 760         curr_region = _hrm.next_region_in_heap(curr_region);
 761       } else {
 762         curr_region = NULL;
 763       }
 764     }
 765 
 766     prev_last_addr = last_address;
 767     prev_last_region = last_region;
 768 
 769     // Fill the memory below the allocated range with dummy object(s),
 770     // if the region bottom does not match the range start, or if the previous
 771     // range ended within the same G1 region, and there is a gap.
 772     if (start_address != bottom_address) {
 773       size_t fill_size = pointer_delta(start_address, bottom_address);
 774       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 775       increase_used(fill_size * HeapWordSize);
 776     }
 777   }
 778 }
 779 
 780 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size) {
 781   assert_heap_not_locked_and_not_at_safepoint();
 782   assert(!is_humongous(word_size), "attempt_allocation() should not "
 783          "be called for humongous allocation requests");
 784 
 785   HeapWord* result = _allocator->attempt_allocation(word_size);
 786 
 787   if (result == NULL) {
 788     result = attempt_allocation_slow(word_size);
 789   }
 790   assert_heap_not_locked();
 791   if (result != NULL) {
 792     dirty_young_block(result, word_size);
 793   }
 794   return result;
 795 }
 796 
 797 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
 798   assert(!is_init_completed(), "Expect to be called at JVM init time");
 799   assert(ranges != NULL, "MemRegion array NULL");
 800   assert(count != 0, "No MemRegions provided");
 801   MemRegion reserved = _hrm.reserved();
 802   HeapWord* prev_last_addr = NULL;
 803   HeapRegion* prev_last_region = NULL;
 804   size_t size_used = 0;
 805   size_t uncommitted_regions = 0;
 806 
 807   // For each Memregion, free the G1 regions that constitute it, and
 808   // notify mark-sweep that the range is no longer to be considered 'archive.'
 809   MutexLockerEx x(Heap_lock);
 810   for (size_t i = 0; i < count; i++) {
 811     HeapWord* start_address = ranges[i].start();
 812     HeapWord* last_address = ranges[i].last();
 813 
 814     assert(reserved.contains(start_address) && reserved.contains(last_address),
 815            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 816            p2i(start_address), p2i(last_address));
 817     assert(start_address > prev_last_addr,
 818            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 819            p2i(start_address), p2i(prev_last_addr));
 820     size_used += ranges[i].byte_size();
 821     prev_last_addr = last_address;
 822 
 823     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 824     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 825 
 826     // Check for ranges that start in the same G1 region in which the previous
 827     // range ended, and adjust the start address so we don't try to free
 828     // the same region again. If the current range is entirely within that
 829     // region, skip it.
 830     if (start_region == prev_last_region) {
 831       start_address = start_region->end();
 832       if (start_address > last_address) {
 833         continue;
 834       }
 835       start_region = _hrm.addr_to_region(start_address);
 836     }
 837     prev_last_region = last_region;
 838 
 839     // After verifying that each region was marked as an archive region by
 840     // alloc_archive_regions, set it free and empty and uncommit it.
 841     HeapRegion* curr_region = start_region;
 842     while (curr_region != NULL) {
 843       guarantee(curr_region->is_archive(),
 844                 "Expected archive region at index %u", curr_region->hrm_index());
 845       uint curr_index = curr_region->hrm_index();
 846       _old_set.remove(curr_region);
 847       curr_region->set_free();
 848       curr_region->set_top(curr_region->bottom());
 849       if (curr_region != last_region) {
 850         curr_region = _hrm.next_region_in_heap(curr_region);
 851       } else {
 852         curr_region = NULL;
 853       }
 854       _hrm.shrink_at(curr_index, 1);
 855       uncommitted_regions++;
 856     }
 857 
 858     // Notify mark-sweep that this is no longer an archive range.
 859     G1ArchiveAllocator::set_range_archive(ranges[i], false);
 860   }
 861 
 862   if (uncommitted_regions != 0) {
 863     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 864                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 865   }
 866   decrease_used(size_used);
 867 }
 868 
 869 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
 870   ResourceMark rm; // For retrieving the thread names in log messages.
 871 
 872   // The structure of this method has a lot of similarities to
 873   // attempt_allocation_slow(). The reason these two were not merged
 874   // into a single one is that such a method would require several "if
 875   // allocation is not humongous do this, otherwise do that"
 876   // conditional paths which would obscure its flow. In fact, an early
 877   // version of this code did use a unified method which was harder to
 878   // follow and, as a result, it had subtle bugs that were hard to
 879   // track down. So keeping these two methods separate allows each to
 880   // be more readable. It will be good to keep these two in sync as
 881   // much as possible.
 882 
 883   assert_heap_not_locked_and_not_at_safepoint();
 884   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 885          "should only be called for humongous allocations");
 886 
 887   // Humongous objects can exhaust the heap quickly, so we should check if we
 888   // need to start a marking cycle at each humongous object allocation. We do
 889   // the check before we do the actual allocation. The reason for doing it
 890   // before the allocation is that we avoid having to keep track of the newly
 891   // allocated memory while we do a GC.
 892   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
 893                                            word_size)) {
 894     collect(GCCause::_g1_humongous_allocation);
 895   }
 896 
 897   // We will loop until a) we manage to successfully perform the
 898   // allocation or b) we successfully schedule a collection which
 899   // fails to perform the allocation. b) is the only case when we'll
 900   // return NULL.
 901   HeapWord* result = NULL;
 902   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 903     bool should_try_gc;
 904     uint gc_count_before;
 905 
 906 
 907     {
 908       MutexLockerEx x(Heap_lock);
 909 
 910       // Given that humongous objects are not allocated in young
 911       // regions, we'll first try to do the allocation without doing a
 912       // collection hoping that there's enough space in the heap.
 913       result = humongous_obj_allocate(word_size);
 914       if (result != NULL) {
 915         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 916         g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 917         return result;
 918       }
 919 
 920       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 921       // the GCLocker initiated GC has been performed and then retry. This includes
 922       // the case when the GC Locker is not active but has not been performed.
 923       should_try_gc = !GCLocker::needs_gc();
 924       // Read the GC count while still holding the Heap_lock.
 925       gc_count_before = total_collections();
 926     }
 927 
 928     if (should_try_gc) {
 929       bool succeeded;
 930       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 931                                    GCCause::_g1_humongous_allocation);
 932       if (result != NULL) {
 933         assert(succeeded, "only way to get back a non-NULL result");
 934         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 935                              Thread::current()->name(), p2i(result));
 936         return result;
 937       }
 938 
 939       if (succeeded) {
 940         // We successfully scheduled a collection which failed to allocate. No
 941         // point in trying to allocate further. We'll just return NULL.
 942         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 943                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 944         return NULL;
 945       }
 946       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
 947                            Thread::current()->name(), word_size);
 948     } else {
 949       // Failed to schedule a collection.
 950       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 951         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 952                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 953         return NULL;
 954       }
 955       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 956       // The GCLocker is either active or the GCLocker initiated
 957       // GC has not yet been performed. Stall until it is and
 958       // then retry the allocation.
 959       GCLocker::stall_until_clear();
 960       gclocker_retry_count += 1;
 961     }
 962 
 963 
 964     // We can reach here if we were unsuccessful in scheduling a
 965     // collection (because another thread beat us to it) or if we were
 966     // stalled due to the GC locker. In either can we should retry the
 967     // allocation attempt in case another thread successfully
 968     // performed a collection and reclaimed enough space.
 969     // Humongous object allocation always needs a lock, so we wait for the retry
 970     // in the next iteration of the loop, unlike for the regular iteration case.
 971     // Give a warning if we seem to be looping forever.
 972 
 973     if ((QueuedAllocationWarningCount > 0) &&
 974         (try_count % QueuedAllocationWarningCount == 0)) {
 975       log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
 976                              Thread::current()->name(), try_count, word_size);
 977     }
 978   }
 979 
 980   ShouldNotReachHere();
 981   return NULL;
 982 }
 983 
 984 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
 985                                                            bool expect_null_mutator_alloc_region) {
 986   assert_at_safepoint_on_vm_thread();
 987   assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
 988          "the current alloc region was unexpectedly found to be non-NULL");
 989 
 990   if (!is_humongous(word_size)) {
 991     return _allocator->attempt_allocation_locked(word_size);
 992   } else {
 993     HeapWord* result = humongous_obj_allocate(word_size);
 994     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
 995       collector_state()->set_initiate_conc_mark_if_possible(true);
 996     }
 997     return result;
 998   }
 999 
1000   ShouldNotReachHere();
1001 }
1002 
1003 class PostCompactionPrinterClosure: public HeapRegionClosure {
1004 private:
1005   G1HRPrinter* _hr_printer;
1006 public:
1007   bool do_heap_region(HeapRegion* hr) {
1008     assert(!hr->is_young(), "not expecting to find young regions");
1009     _hr_printer->post_compaction(hr);
1010     return false;
1011   }
1012 
1013   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1014     : _hr_printer(hr_printer) { }
1015 };
1016 
1017 void G1CollectedHeap::print_hrm_post_compaction() {
1018   if (_hr_printer.is_active()) {
1019     PostCompactionPrinterClosure cl(hr_printer());
1020     heap_region_iterate(&cl);
1021   }
1022 }
1023 
1024 void G1CollectedHeap::abort_concurrent_cycle() {
1025   // Note: When we have a more flexible GC logging framework that
1026   // allows us to add optional attributes to a GC log record we
1027   // could consider timing and reporting how long we wait in the
1028   // following two methods.
1029   wait_while_free_regions_coming();
1030   // If we start the compaction before the CM threads finish
1031   // scanning the root regions we might trip them over as we'll
1032   // be moving objects / updating references. So let's wait until
1033   // they are done. By telling them to abort, they should complete
1034   // early.
1035   _cm->root_regions()->abort();
1036   _cm->root_regions()->wait_until_scan_finished();
1037   append_secondary_free_list_if_not_empty_with_lock();
1038 
1039   // Disable discovery and empty the discovered lists
1040   // for the CM ref processor.
1041   ref_processor_cm()->disable_discovery();
1042   ref_processor_cm()->abandon_partial_discovery();
1043   ref_processor_cm()->verify_no_references_recorded();
1044 
1045   // Abandon current iterations of concurrent marking and concurrent
1046   // refinement, if any are in progress.
1047   concurrent_mark()->abort();
1048 }
1049 
1050 void G1CollectedHeap::prepare_heap_for_full_collection() {
1051   // Make sure we'll choose a new allocation region afterwards.
1052   _allocator->release_mutator_alloc_region();
1053   _allocator->abandon_gc_alloc_regions();
1054   g1_rem_set()->cleanupHRRS();
1055 
1056   // We may have added regions to the current incremental collection
1057   // set between the last GC or pause and now. We need to clear the
1058   // incremental collection set and then start rebuilding it afresh
1059   // after this full GC.
1060   abandon_collection_set(collection_set());
1061 
1062   tear_down_region_sets(false /* free_list_only */);
1063   collector_state()->set_gcs_are_young(true);
1064 }
1065 
1066 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1067   assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1068   assert(used() == recalculate_used(), "Should be equal");
1069   _verifier->verify_region_sets_optional();
1070   _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
1071   _verifier->check_bitmaps("Full GC Start");
1072 }
1073 
1074 void G1CollectedHeap::prepare_heap_for_mutators() {
1075   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1076   ClassLoaderDataGraph::purge();
1077   MetaspaceAux::verify_metrics();
1078 
1079   // Prepare heap for normal collections.
1080   assert(num_free_regions() == 0, "we should not have added any free regions");
1081   rebuild_region_sets(false /* free_list_only */);
1082   abort_refinement();
1083   resize_if_necessary_after_full_collection();
1084 
1085   // Rebuild the strong code root lists for each region
1086   rebuild_strong_code_roots();
1087 
1088   // Start a new incremental collection set for the next pause
1089   start_new_collection_set();
1090 
1091   _allocator->init_mutator_alloc_region();
1092 
1093   // Post collection state updates.
1094   MetaspaceGC::compute_new_size();
1095 }
1096 
1097 void G1CollectedHeap::abort_refinement() {
1098   if (_hot_card_cache->use_cache()) {
1099     _hot_card_cache->reset_hot_cache();
1100   }
1101 
1102   // Discard all remembered set updates.
1103   JavaThread::dirty_card_queue_set().abandon_logs();
1104   assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1105 }
1106 
1107 void G1CollectedHeap::verify_after_full_collection() {
1108   check_gc_time_stamps();
1109   _hrm.verify_optional();
1110   _verifier->verify_region_sets_optional();
1111   _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);
1112   // Clear the previous marking bitmap, if needed for bitmap verification.
1113   // Note we cannot do this when we clear the next marking bitmap in
1114   // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1115   // objects marked during a full GC against the previous bitmap.
1116   // But we need to clear it before calling check_bitmaps below since
1117   // the full GC has compacted objects and updated TAMS but not updated
1118   // the prev bitmap.
1119   if (G1VerifyBitmaps) {
1120     GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1121     _cm->clear_prev_bitmap(workers());
1122   }
1123   _verifier->check_bitmaps("Full GC End");
1124 
1125   // At this point there should be no regions in the
1126   // entire heap tagged as young.
1127   assert(check_young_list_empty(), "young list should be empty at this point");
1128 
1129   // Note: since we've just done a full GC, concurrent
1130   // marking is no longer active. Therefore we need not
1131   // re-enable reference discovery for the CM ref processor.
1132   // That will be done at the start of the next marking cycle.
1133   // We also know that the STW processor should no longer
1134   // discover any new references.
1135   assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1136   assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1137   ref_processor_stw()->verify_no_references_recorded();
1138   ref_processor_cm()->verify_no_references_recorded();
1139 }
1140 
1141 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1142   // Post collection logging.
1143   // We should do this after we potentially resize the heap so
1144   // that all the COMMIT / UNCOMMIT events are generated before
1145   // the compaction events.
1146   print_hrm_post_compaction();
1147   heap_transition->print();
1148   print_heap_after_gc();
1149   print_heap_regions();
1150 #ifdef TRACESPINNING
1151   ParallelTaskTerminator::print_termination_counts();
1152 #endif
1153 }
1154 
1155 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1156                                          bool clear_all_soft_refs) {
1157   assert_at_safepoint_on_vm_thread();
1158 
1159   if (GCLocker::check_active_before_gc()) {
1160     // Full GC was not completed.
1161     return false;
1162   }
1163 
1164   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1165       soft_ref_policy()->should_clear_all_soft_refs();
1166 
1167   G1FullCollector collector(this, &_full_gc_memory_manager, explicit_gc, do_clear_all_soft_refs);
1168   GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1169 
1170   collector.prepare_collection();
1171   collector.collect();
1172   collector.complete_collection();
1173 
1174   // Full collection was successfully completed.
1175   return true;
1176 }
1177 
1178 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1179   // Currently, there is no facility in the do_full_collection(bool) API to notify
1180   // the caller that the collection did not succeed (e.g., because it was locked
1181   // out by the GC locker). So, right now, we'll ignore the return value.
1182   bool dummy = do_full_collection(true,                /* explicit_gc */
1183                                   clear_all_soft_refs);
1184 }
1185 
1186 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1187   // Capacity, free and used after the GC counted as full regions to
1188   // include the waste in the following calculations.
1189   const size_t capacity_after_gc = capacity();
1190   const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1191 
1192   // This is enforced in arguments.cpp.
1193   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1194          "otherwise the code below doesn't make sense");
1195 
1196   // We don't have floating point command-line arguments
1197   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1198   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1199   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1200   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1201 
1202   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1203   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1204 
1205   // We have to be careful here as these two calculations can overflow
1206   // 32-bit size_t's.
1207   double used_after_gc_d = (double) used_after_gc;
1208   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1209   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1210 
1211   // Let's make sure that they are both under the max heap size, which
1212   // by default will make them fit into a size_t.
1213   double desired_capacity_upper_bound = (double) max_heap_size;
1214   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1215                                     desired_capacity_upper_bound);
1216   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1217                                     desired_capacity_upper_bound);
1218 
1219   // We can now safely turn them into size_t's.
1220   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1221   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1222 
1223   // This assert only makes sense here, before we adjust them
1224   // with respect to the min and max heap size.
1225   assert(minimum_desired_capacity <= maximum_desired_capacity,
1226          "minimum_desired_capacity = " SIZE_FORMAT ", "
1227          "maximum_desired_capacity = " SIZE_FORMAT,
1228          minimum_desired_capacity, maximum_desired_capacity);
1229 
1230   // Should not be greater than the heap max size. No need to adjust
1231   // it with respect to the heap min size as it's a lower bound (i.e.,
1232   // we'll try to make the capacity larger than it, not smaller).
1233   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1234   // Should not be less than the heap min size. No need to adjust it
1235   // with respect to the heap max size as it's an upper bound (i.e.,
1236   // we'll try to make the capacity smaller than it, not greater).
1237   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1238 
1239   if (capacity_after_gc < minimum_desired_capacity) {
1240     // Don't expand unless it's significant
1241     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1242 
1243     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1244                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1245                               "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1246                               capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1247 
1248     expand(expand_bytes, _workers);
1249 
1250     // No expansion, now see if we want to shrink
1251   } else if (capacity_after_gc > maximum_desired_capacity) {
1252     // Capacity too large, compute shrinking size
1253     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1254 
1255     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1256                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1257                               "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1258                               capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1259 
1260     shrink(shrink_bytes);
1261   }
1262 }
1263 
1264 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1265                                                             bool do_gc,
1266                                                             bool clear_all_soft_refs,
1267                                                             bool expect_null_mutator_alloc_region,
1268                                                             bool* gc_succeeded) {
1269   *gc_succeeded = true;
1270   // Let's attempt the allocation first.
1271   HeapWord* result =
1272     attempt_allocation_at_safepoint(word_size,
1273                                     expect_null_mutator_alloc_region);
1274   if (result != NULL) {
1275     return result;
1276   }
1277 
1278   // In a G1 heap, we're supposed to keep allocation from failing by
1279   // incremental pauses.  Therefore, at least for now, we'll favor
1280   // expansion over collection.  (This might change in the future if we can
1281   // do something smarter than full collection to satisfy a failed alloc.)
1282   result = expand_and_allocate(word_size);
1283   if (result != NULL) {
1284     return result;
1285   }
1286 
1287   if (do_gc) {
1288     // Expansion didn't work, we'll try to do a Full GC.
1289     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1290                                        clear_all_soft_refs);
1291   }
1292 
1293   return NULL;
1294 }
1295 
1296 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1297                                                      bool* succeeded) {
1298   assert_at_safepoint_on_vm_thread();
1299 
1300   // Attempts to allocate followed by Full GC.
1301   HeapWord* result =
1302     satisfy_failed_allocation_helper(word_size,
1303                                      true,  /* do_gc */
1304                                      false, /* clear_all_soft_refs */
1305                                      false, /* expect_null_mutator_alloc_region */
1306                                      succeeded);
1307 
1308   if (result != NULL || !*succeeded) {
1309     return result;
1310   }
1311 
1312   // Attempts to allocate followed by Full GC that will collect all soft references.
1313   result = satisfy_failed_allocation_helper(word_size,
1314                                             true, /* do_gc */
1315                                             true, /* clear_all_soft_refs */
1316                                             true, /* expect_null_mutator_alloc_region */
1317                                             succeeded);
1318 
1319   if (result != NULL || !*succeeded) {
1320     return result;
1321   }
1322 
1323   // Attempts to allocate, no GC
1324   result = satisfy_failed_allocation_helper(word_size,
1325                                             false, /* do_gc */
1326                                             false, /* clear_all_soft_refs */
1327                                             true,  /* expect_null_mutator_alloc_region */
1328                                             succeeded);
1329 
1330   if (result != NULL) {
1331     return result;
1332   }
1333 
1334   assert(!soft_ref_policy()->should_clear_all_soft_refs(),
1335          "Flag should have been handled and cleared prior to this point");
1336 
1337   // What else?  We might try synchronous finalization later.  If the total
1338   // space available is large enough for the allocation, then a more
1339   // complete compaction phase than we've tried so far might be
1340   // appropriate.
1341   return NULL;
1342 }
1343 
1344 // Attempting to expand the heap sufficiently
1345 // to support an allocation of the given "word_size".  If
1346 // successful, perform the allocation and return the address of the
1347 // allocated block, or else "NULL".
1348 
1349 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1350   assert_at_safepoint_on_vm_thread();
1351 
1352   _verifier->verify_region_sets_optional();
1353 
1354   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1355   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1356                             word_size * HeapWordSize);
1357 
1358 
1359   if (expand(expand_bytes, _workers)) {
1360     _hrm.verify_optional();
1361     _verifier->verify_region_sets_optional();
1362     return attempt_allocation_at_safepoint(word_size,
1363                                            false /* expect_null_mutator_alloc_region */);
1364   }
1365   return NULL;
1366 }
1367 
1368 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1369   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1370   aligned_expand_bytes = align_up(aligned_expand_bytes,
1371                                        HeapRegion::GrainBytes);
1372 
1373   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1374                             expand_bytes, aligned_expand_bytes);
1375 
1376   if (is_maximal_no_gc()) {
1377     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1378     return false;
1379   }
1380 
1381   double expand_heap_start_time_sec = os::elapsedTime();
1382   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1383   assert(regions_to_expand > 0, "Must expand by at least one region");
1384 
1385   uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1386   if (expand_time_ms != NULL) {
1387     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1388   }
1389 
1390   if (expanded_by > 0) {
1391     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1392     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1393     g1_policy()->record_new_heap_size(num_regions());
1394   } else {
1395     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1396 
1397     // The expansion of the virtual storage space was unsuccessful.
1398     // Let's see if it was because we ran out of swap.
1399     if (G1ExitOnExpansionFailure &&
1400         _hrm.available() >= regions_to_expand) {
1401       // We had head room...
1402       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1403     }
1404   }
1405   return regions_to_expand > 0;
1406 }
1407 
1408 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1409   size_t aligned_shrink_bytes =
1410     ReservedSpace::page_align_size_down(shrink_bytes);
1411   aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1412                                          HeapRegion::GrainBytes);
1413   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1414 
1415   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1416   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1417 
1418 
1419   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",
1420                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1421   if (num_regions_removed > 0) {
1422     g1_policy()->record_new_heap_size(num_regions());
1423   } else {
1424     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1425   }
1426 }
1427 
1428 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1429   _verifier->verify_region_sets_optional();
1430 
1431   // We should only reach here at the end of a Full GC which means we
1432   // should not not be holding to any GC alloc regions. The method
1433   // below will make sure of that and do any remaining clean up.
1434   _allocator->abandon_gc_alloc_regions();
1435 
1436   // Instead of tearing down / rebuilding the free lists here, we
1437   // could instead use the remove_all_pending() method on free_list to
1438   // remove only the ones that we need to remove.
1439   tear_down_region_sets(true /* free_list_only */);
1440   shrink_helper(shrink_bytes);
1441   rebuild_region_sets(true /* free_list_only */);
1442 
1443   _hrm.verify_optional();
1444   _verifier->verify_region_sets_optional();
1445 }
1446 
1447 // Public methods.
1448 
1449 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1450   CollectedHeap(),
1451   _young_gen_sampling_thread(NULL),
1452   _collector_policy(collector_policy),
1453   _soft_ref_policy(),
1454   _card_table(NULL),
1455   _memory_manager("G1 Young Generation", "end of minor GC"),
1456   _full_gc_memory_manager("G1 Old Generation", "end of major GC"),
1457   _eden_pool(NULL),
1458   _survivor_pool(NULL),
1459   _old_pool(NULL),
1460   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1461   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1462   _g1_policy(new G1DefaultPolicy(_gc_timer_stw)),
1463   _collection_set(this, _g1_policy),
1464   _dirty_card_queue_set(false),
1465   _is_alive_closure_cm(this),
1466   _is_alive_closure_stw(this),
1467   _ref_processor_cm(NULL),
1468   _ref_processor_stw(NULL),
1469   _bot(NULL),
1470   _hot_card_cache(NULL),
1471   _g1_rem_set(NULL),
1472   _cr(NULL),
1473   _g1mm(NULL),
1474   _preserved_marks_set(true /* in_c_heap */),
1475   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1476   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1477   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1478   _humongous_reclaim_candidates(),
1479   _has_humongous_reclaim_candidates(false),
1480   _archive_allocator(NULL),
1481   _free_regions_coming(false),
1482   _gc_time_stamp(0),
1483   _summary_bytes_used(0),
1484   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1485   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1486   _expand_heap_after_alloc_failure(true),
1487   _old_marking_cycles_started(0),
1488   _old_marking_cycles_completed(0),
1489   _in_cset_fast_test() {
1490 
1491   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1492                           /* are_GC_task_threads */true,
1493                           /* are_ConcurrentGC_threads */false);
1494   _workers->initialize_workers();
1495   _verifier = new G1HeapVerifier(this);
1496 
1497   _allocator = new G1DefaultAllocator(this);
1498 
1499   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1500 
1501   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1502 
1503   // Override the default _filler_array_max_size so that no humongous filler
1504   // objects are created.
1505   _filler_array_max_size = _humongous_object_threshold_in_words;
1506 
1507   uint n_queues = ParallelGCThreads;
1508   _task_queues = new RefToScanQueueSet(n_queues);
1509 
1510   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1511 
1512   for (uint i = 0; i < n_queues; i++) {
1513     RefToScanQueue* q = new RefToScanQueue();
1514     q->initialize();
1515     _task_queues->register_queue(i, q);
1516     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1517   }
1518 
1519   // Initialize the G1EvacuationFailureALot counters and flags.
1520   NOT_PRODUCT(reset_evacuation_should_fail();)
1521 
1522   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1523 }
1524 
1525 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1526                                                                  size_t size,
1527                                                                  size_t translation_factor) {
1528   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1529   // Allocate a new reserved space, preferring to use large pages.
1530   ReservedSpace rs(size, preferred_page_size);
1531   G1RegionToSpaceMapper* result  =
1532     G1RegionToSpaceMapper::create_mapper(rs,
1533                                          size,
1534                                          rs.alignment(),
1535                                          HeapRegion::GrainBytes,
1536                                          translation_factor,
1537                                          mtGC);
1538 
1539   os::trace_page_sizes_for_requested_size(description,
1540                                           size,
1541                                           preferred_page_size,
1542                                           rs.alignment(),
1543                                           rs.base(),
1544                                           rs.size());
1545 
1546   return result;
1547 }
1548 
1549 jint G1CollectedHeap::initialize_concurrent_refinement() {
1550   jint ecode = JNI_OK;
1551   _cr = G1ConcurrentRefine::create(&ecode);
1552   return ecode;
1553 }
1554 
1555 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1556   _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1557   if (_young_gen_sampling_thread->osthread() == NULL) {
1558     vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1559     return JNI_ENOMEM;
1560   }
1561   return JNI_OK;
1562 }
1563 
1564 jint G1CollectedHeap::initialize() {
1565   os::enable_vtime();
1566 
1567   // Necessary to satisfy locking discipline assertions.
1568 
1569   MutexLocker x(Heap_lock);
1570 
1571   // While there are no constraints in the GC code that HeapWordSize
1572   // be any particular value, there are multiple other areas in the
1573   // system which believe this to be true (e.g. oop->object_size in some
1574   // cases incorrectly returns the size in wordSize units rather than
1575   // HeapWordSize).
1576   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1577 
1578   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1579   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1580   size_t heap_alignment = collector_policy()->heap_alignment();
1581 
1582   // Ensure that the sizes are properly aligned.
1583   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1584   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1585   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1586 
1587   // Reserve the maximum.
1588 
1589   // When compressed oops are enabled, the preferred heap base
1590   // is calculated by subtracting the requested size from the
1591   // 32Gb boundary and using the result as the base address for
1592   // heap reservation. If the requested size is not aligned to
1593   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1594   // into the ReservedHeapSpace constructor) then the actual
1595   // base of the reserved heap may end up differing from the
1596   // address that was requested (i.e. the preferred heap base).
1597   // If this happens then we could end up using a non-optimal
1598   // compressed oops mode.
1599 
1600   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1601                                                  heap_alignment);
1602 
1603   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1604 
1605   // Create the barrier set for the entire reserved region.
1606   G1CardTable* ct = new G1CardTable(reserved_region());
1607   ct->initialize();
1608   G1BarrierSet* bs = new G1BarrierSet(ct);
1609   bs->initialize();
1610   assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1611   set_barrier_set(bs);
1612   _card_table = ct;
1613 
1614   // Create the hot card cache.
1615   _hot_card_cache = new G1HotCardCache(this);
1616 
1617   // Carve out the G1 part of the heap.
1618   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1619   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1620   G1RegionToSpaceMapper* heap_storage =
1621     G1RegionToSpaceMapper::create_mapper(g1_rs,
1622                                          g1_rs.size(),
1623                                          page_size,
1624                                          HeapRegion::GrainBytes,
1625                                          1,
1626                                          mtJavaHeap);
1627   os::trace_page_sizes("Heap",
1628                        collector_policy()->min_heap_byte_size(),
1629                        max_byte_size,
1630                        page_size,
1631                        heap_rs.base(),
1632                        heap_rs.size());
1633   heap_storage->set_mapping_changed_listener(&_listener);
1634 
1635   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1636   G1RegionToSpaceMapper* bot_storage =
1637     create_aux_memory_mapper("Block Offset Table",
1638                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1639                              G1BlockOffsetTable::heap_map_factor());
1640 
1641   G1RegionToSpaceMapper* cardtable_storage =
1642     create_aux_memory_mapper("Card Table",
1643                              G1CardTable::compute_size(g1_rs.size() / HeapWordSize),
1644                              G1CardTable::heap_map_factor());
1645 
1646   G1RegionToSpaceMapper* card_counts_storage =
1647     create_aux_memory_mapper("Card Counts Table",
1648                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1649                              G1CardCounts::heap_map_factor());
1650 
1651   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1652   G1RegionToSpaceMapper* prev_bitmap_storage =
1653     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1654   G1RegionToSpaceMapper* next_bitmap_storage =
1655     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1656 
1657   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1658   _card_table->initialize(cardtable_storage);
1659   // Do later initialization work for concurrent refinement.
1660   _hot_card_cache->initialize(card_counts_storage);
1661 
1662   // 6843694 - ensure that the maximum region index can fit
1663   // in the remembered set structures.
1664   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1665   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1666 
1667   // Also create a G1 rem set.
1668   _g1_rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
1669   _g1_rem_set->initialize(max_capacity(), max_regions());
1670 
1671   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1672   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1673   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1674             "too many cards per region");
1675 
1676   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1677 
1678   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1679 
1680   {
1681     HeapWord* start = _hrm.reserved().start();
1682     HeapWord* end = _hrm.reserved().end();
1683     size_t granularity = HeapRegion::GrainBytes;
1684 
1685     _in_cset_fast_test.initialize(start, end, granularity);
1686     _humongous_reclaim_candidates.initialize(start, end, granularity);
1687   }
1688 
1689   // Create the G1ConcurrentMark data structure and thread.
1690   // (Must do this late, so that "max_regions" is defined.)
1691   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1692   if (_cm == NULL || !_cm->completed_initialization()) {
1693     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1694     return JNI_ENOMEM;
1695   }
1696   _cmThread = _cm->cm_thread();
1697 
1698   // Now expand into the initial heap size.
1699   if (!expand(init_byte_size, _workers)) {
1700     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1701     return JNI_ENOMEM;
1702   }
1703 
1704   // Perform any initialization actions delegated to the policy.
1705   g1_policy()->init(this, &_collection_set);
1706 
1707   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1708                                                SATB_Q_FL_lock,
1709                                                G1SATBProcessCompletedThreshold,
1710                                                Shared_SATB_Q_lock);
1711 
1712   jint ecode = initialize_concurrent_refinement();
1713   if (ecode != JNI_OK) {
1714     return ecode;
1715   }
1716 
1717   ecode = initialize_young_gen_sampling_thread();
1718   if (ecode != JNI_OK) {
1719     return ecode;
1720   }
1721 
1722   JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1723                                                 DirtyCardQ_FL_lock,
1724                                                 (int)concurrent_refine()->yellow_zone(),
1725                                                 (int)concurrent_refine()->red_zone(),
1726                                                 Shared_DirtyCardQ_lock,
1727                                                 NULL,  // fl_owner
1728                                                 true); // init_free_ids
1729 
1730   dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1731                                     DirtyCardQ_FL_lock,
1732                                     -1, // never trigger processing
1733                                     -1, // no limit on length
1734                                     Shared_DirtyCardQ_lock,
1735                                     &JavaThread::dirty_card_queue_set());
1736 
1737   // Here we allocate the dummy HeapRegion that is required by the
1738   // G1AllocRegion class.
1739   HeapRegion* dummy_region = _hrm.get_dummy_region();
1740 
1741   // We'll re-use the same region whether the alloc region will
1742   // require BOT updates or not and, if it doesn't, then a non-young
1743   // region will complain that it cannot support allocations without
1744   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1745   dummy_region->set_eden();
1746   // Make sure it's full.
1747   dummy_region->set_top(dummy_region->end());
1748   G1AllocRegion::setup(this, dummy_region);
1749 
1750   _allocator->init_mutator_alloc_region();
1751 
1752   // Do create of the monitoring and management support so that
1753   // values in the heap have been properly initialized.
1754   _g1mm = new G1MonitoringSupport(this);
1755 
1756   G1StringDedup::initialize();
1757 
1758   _preserved_marks_set.init(ParallelGCThreads);
1759 
1760   _collection_set.initialize(max_regions());
1761 
1762   return JNI_OK;
1763 }
1764 
1765 void G1CollectedHeap::initialize_serviceability() {
1766   _eden_pool = new G1EdenPool(this);
1767   _survivor_pool = new G1SurvivorPool(this);
1768   _old_pool = new G1OldGenPool(this);
1769 
1770   _full_gc_memory_manager.add_pool(_eden_pool);
1771   _full_gc_memory_manager.add_pool(_survivor_pool);
1772   _full_gc_memory_manager.add_pool(_old_pool);
1773 
1774   _memory_manager.add_pool(_eden_pool);
1775   _memory_manager.add_pool(_survivor_pool);
1776 
1777 }
1778 
1779 void G1CollectedHeap::stop() {
1780   // Stop all concurrent threads. We do this to make sure these threads
1781   // do not continue to execute and access resources (e.g. logging)
1782   // that are destroyed during shutdown.
1783   _cr->stop();
1784   _young_gen_sampling_thread->stop();
1785   _cmThread->stop();
1786   if (G1StringDedup::is_enabled()) {
1787     G1StringDedup::stop();
1788   }
1789 }
1790 
1791 void G1CollectedHeap::safepoint_synchronize_begin() {
1792   SuspendibleThreadSet::synchronize();
1793 }
1794 
1795 void G1CollectedHeap::safepoint_synchronize_end() {
1796   SuspendibleThreadSet::desynchronize();
1797 }
1798 
1799 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1800   return HeapRegion::max_region_size();
1801 }
1802 
1803 void G1CollectedHeap::post_initialize() {
1804   CollectedHeap::post_initialize();
1805   ref_processing_init();
1806 }
1807 
1808 void G1CollectedHeap::ref_processing_init() {
1809   // Reference processing in G1 currently works as follows:
1810   //
1811   // * There are two reference processor instances. One is
1812   //   used to record and process discovered references
1813   //   during concurrent marking; the other is used to
1814   //   record and process references during STW pauses
1815   //   (both full and incremental).
1816   // * Both ref processors need to 'span' the entire heap as
1817   //   the regions in the collection set may be dotted around.
1818   //
1819   // * For the concurrent marking ref processor:
1820   //   * Reference discovery is enabled at initial marking.
1821   //   * Reference discovery is disabled and the discovered
1822   //     references processed etc during remarking.
1823   //   * Reference discovery is MT (see below).
1824   //   * Reference discovery requires a barrier (see below).
1825   //   * Reference processing may or may not be MT
1826   //     (depending on the value of ParallelRefProcEnabled
1827   //     and ParallelGCThreads).
1828   //   * A full GC disables reference discovery by the CM
1829   //     ref processor and abandons any entries on it's
1830   //     discovered lists.
1831   //
1832   // * For the STW processor:
1833   //   * Non MT discovery is enabled at the start of a full GC.
1834   //   * Processing and enqueueing during a full GC is non-MT.
1835   //   * During a full GC, references are processed after marking.
1836   //
1837   //   * Discovery (may or may not be MT) is enabled at the start
1838   //     of an incremental evacuation pause.
1839   //   * References are processed near the end of a STW evacuation pause.
1840   //   * For both types of GC:
1841   //     * Discovery is atomic - i.e. not concurrent.
1842   //     * Reference discovery will not need a barrier.
1843 
1844   MemRegion mr = reserved_region();
1845 
1846   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1847 
1848   // Concurrent Mark ref processor
1849   _ref_processor_cm =
1850     new ReferenceProcessor(mr,    // span
1851                            mt_processing,
1852                                 // mt processing
1853                            ParallelGCThreads,
1854                                 // degree of mt processing
1855                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
1856                                 // mt discovery
1857                            MAX2(ParallelGCThreads, ConcGCThreads),
1858                                 // degree of mt discovery
1859                            false,
1860                                 // Reference discovery is not atomic
1861                            &_is_alive_closure_cm);
1862                                 // is alive closure
1863                                 // (for efficiency/performance)
1864 
1865   // STW ref processor
1866   _ref_processor_stw =
1867     new ReferenceProcessor(mr,    // span
1868                            mt_processing,
1869                                 // mt processing
1870                            ParallelGCThreads,
1871                                 // degree of mt processing
1872                            (ParallelGCThreads > 1),
1873                                 // mt discovery
1874                            ParallelGCThreads,
1875                                 // degree of mt discovery
1876                            true,
1877                                 // Reference discovery is atomic
1878                            &_is_alive_closure_stw);
1879                                 // is alive closure
1880                                 // (for efficiency/performance)
1881 }
1882 
1883 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1884   return _collector_policy;
1885 }
1886 
1887 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
1888   return &_soft_ref_policy;
1889 }
1890 
1891 size_t G1CollectedHeap::capacity() const {
1892   return _hrm.length() * HeapRegion::GrainBytes;
1893 }
1894 
1895 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1896   return _hrm.total_free_bytes();
1897 }
1898 
1899 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
1900   hr->reset_gc_time_stamp();
1901 }
1902 
1903 #ifndef PRODUCT
1904 
1905 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
1906 private:
1907   unsigned _gc_time_stamp;
1908   bool _failures;
1909 
1910 public:
1911   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
1912     _gc_time_stamp(gc_time_stamp), _failures(false) { }
1913 
1914   virtual bool do_heap_region(HeapRegion* hr) {
1915     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
1916     if (_gc_time_stamp != region_gc_time_stamp) {
1917       log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
1918                             region_gc_time_stamp, _gc_time_stamp);
1919       _failures = true;
1920     }
1921     return false;
1922   }
1923 
1924   bool failures() { return _failures; }
1925 };
1926 
1927 void G1CollectedHeap::check_gc_time_stamps() {
1928   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
1929   heap_region_iterate(&cl);
1930   guarantee(!cl.failures(), "all GC time stamps should have been reset");
1931 }
1932 #endif // PRODUCT
1933 
1934 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
1935   _hot_card_cache->drain(cl, worker_i);
1936 }
1937 
1938 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
1939   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1940   size_t n_completed_buffers = 0;
1941   while (dcqs.apply_closure_during_gc(cl, worker_i)) {
1942     n_completed_buffers++;
1943   }
1944   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
1945   dcqs.clear_n_completed_buffers();
1946   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
1947 }
1948 
1949 // Computes the sum of the storage used by the various regions.
1950 size_t G1CollectedHeap::used() const {
1951   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1952   if (_archive_allocator != NULL) {
1953     result += _archive_allocator->used();
1954   }
1955   return result;
1956 }
1957 
1958 size_t G1CollectedHeap::used_unlocked() const {
1959   return _summary_bytes_used;
1960 }
1961 
1962 class SumUsedClosure: public HeapRegionClosure {
1963   size_t _used;
1964 public:
1965   SumUsedClosure() : _used(0) {}
1966   bool do_heap_region(HeapRegion* r) {
1967     _used += r->used();
1968     return false;
1969   }
1970   size_t result() { return _used; }
1971 };
1972 
1973 size_t G1CollectedHeap::recalculate_used() const {
1974   double recalculate_used_start = os::elapsedTime();
1975 
1976   SumUsedClosure blk;
1977   heap_region_iterate(&blk);
1978 
1979   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
1980   return blk.result();
1981 }
1982 
1983 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
1984   switch (cause) {
1985     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
1986     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
1987     case GCCause::_wb_conc_mark:                        return true;
1988     default :                                           return false;
1989   }
1990 }
1991 
1992 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
1993   switch (cause) {
1994     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
1995     case GCCause::_g1_humongous_allocation: return true;
1996     default:                                return is_user_requested_concurrent_full_gc(cause);
1997   }
1998 }
1999 
2000 #ifndef PRODUCT
2001 void G1CollectedHeap::allocate_dummy_regions() {
2002   // Let's fill up most of the region
2003   size_t word_size = HeapRegion::GrainWords - 1024;
2004   // And as a result the region we'll allocate will be humongous.
2005   guarantee(is_humongous(word_size), "sanity");
2006 
2007   // _filler_array_max_size is set to humongous object threshold
2008   // but temporarily change it to use CollectedHeap::fill_with_object().
2009   SizeTFlagSetting fs(_filler_array_max_size, word_size);
2010 
2011   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2012     // Let's use the existing mechanism for the allocation
2013     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2014     if (dummy_obj != NULL) {
2015       MemRegion mr(dummy_obj, word_size);
2016       CollectedHeap::fill_with_object(mr);
2017     } else {
2018       // If we can't allocate once, we probably cannot allocate
2019       // again. Let's get out of the loop.
2020       break;
2021     }
2022   }
2023 }
2024 #endif // !PRODUCT
2025 
2026 void G1CollectedHeap::increment_old_marking_cycles_started() {
2027   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2028          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2029          "Wrong marking cycle count (started: %d, completed: %d)",
2030          _old_marking_cycles_started, _old_marking_cycles_completed);
2031 
2032   _old_marking_cycles_started++;
2033 }
2034 
2035 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2036   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2037 
2038   // We assume that if concurrent == true, then the caller is a
2039   // concurrent thread that was joined the Suspendible Thread
2040   // Set. If there's ever a cheap way to check this, we should add an
2041   // assert here.
2042 
2043   // Given that this method is called at the end of a Full GC or of a
2044   // concurrent cycle, and those can be nested (i.e., a Full GC can
2045   // interrupt a concurrent cycle), the number of full collections
2046   // completed should be either one (in the case where there was no
2047   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2048   // behind the number of full collections started.
2049 
2050   // This is the case for the inner caller, i.e. a Full GC.
2051   assert(concurrent ||
2052          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2053          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2054          "for inner caller (Full GC): _old_marking_cycles_started = %u "
2055          "is inconsistent with _old_marking_cycles_completed = %u",
2056          _old_marking_cycles_started, _old_marking_cycles_completed);
2057 
2058   // This is the case for the outer caller, i.e. the concurrent cycle.
2059   assert(!concurrent ||
2060          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2061          "for outer caller (concurrent cycle): "
2062          "_old_marking_cycles_started = %u "
2063          "is inconsistent with _old_marking_cycles_completed = %u",
2064          _old_marking_cycles_started, _old_marking_cycles_completed);
2065 
2066   _old_marking_cycles_completed += 1;
2067 
2068   // We need to clear the "in_progress" flag in the CM thread before
2069   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2070   // is set) so that if a waiter requests another System.gc() it doesn't
2071   // incorrectly see that a marking cycle is still in progress.
2072   if (concurrent) {
2073     _cmThread->set_idle();
2074   }
2075 
2076   // This notify_all() will ensure that a thread that called
2077   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2078   // and it's waiting for a full GC to finish will be woken up. It is
2079   // waiting in VM_G1CollectForAllocation::doit_epilogue().
2080   FullGCCount_lock->notify_all();
2081 }
2082 
2083 void G1CollectedHeap::collect(GCCause::Cause cause) {
2084   assert_heap_not_locked();
2085 
2086   uint gc_count_before;
2087   uint old_marking_count_before;
2088   uint full_gc_count_before;
2089   bool retry_gc;
2090 
2091   do {
2092     retry_gc = false;
2093 
2094     {
2095       MutexLocker ml(Heap_lock);
2096 
2097       // Read the GC count while holding the Heap_lock
2098       gc_count_before = total_collections();
2099       full_gc_count_before = total_full_collections();
2100       old_marking_count_before = _old_marking_cycles_started;
2101     }
2102 
2103     if (should_do_concurrent_full_gc(cause)) {
2104       // Schedule an initial-mark evacuation pause that will start a
2105       // concurrent cycle. We're setting word_size to 0 which means that
2106       // we are not requesting a post-GC allocation.
2107       VM_G1CollectForAllocation op(0,     /* word_size */
2108                                    gc_count_before,
2109                                    cause,
2110                                    true,  /* should_initiate_conc_mark */
2111                                    g1_policy()->max_pause_time_ms());
2112       VMThread::execute(&op);
2113       if (!op.pause_succeeded()) {
2114         if (old_marking_count_before == _old_marking_cycles_started) {
2115           retry_gc = op.should_retry_gc();
2116         } else {
2117           // A Full GC happened while we were trying to schedule the
2118           // initial-mark GC. No point in starting a new cycle given
2119           // that the whole heap was collected anyway.
2120         }
2121 
2122         if (retry_gc) {
2123           if (GCLocker::is_active_and_needs_gc()) {
2124             GCLocker::stall_until_clear();
2125           }
2126         }
2127       }
2128     } else {
2129       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2130           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2131 
2132         // Schedule a standard evacuation pause. We're setting word_size
2133         // to 0 which means that we are not requesting a post-GC allocation.
2134         VM_G1CollectForAllocation op(0,     /* word_size */
2135                                      gc_count_before,
2136                                      cause,
2137                                      false, /* should_initiate_conc_mark */
2138                                      g1_policy()->max_pause_time_ms());
2139         VMThread::execute(&op);
2140       } else {
2141         // Schedule a Full GC.
2142         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2143         VMThread::execute(&op);
2144       }
2145     }
2146   } while (retry_gc);
2147 }
2148 
2149 bool G1CollectedHeap::is_in(const void* p) const {
2150   if (_hrm.reserved().contains(p)) {
2151     // Given that we know that p is in the reserved space,
2152     // heap_region_containing() should successfully
2153     // return the containing region.
2154     HeapRegion* hr = heap_region_containing(p);
2155     return hr->is_in(p);
2156   } else {
2157     return false;
2158   }
2159 }
2160 
2161 #ifdef ASSERT
2162 bool G1CollectedHeap::is_in_exact(const void* p) const {
2163   bool contains = reserved_region().contains(p);
2164   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2165   if (contains && available) {
2166     return true;
2167   } else {
2168     return false;
2169   }
2170 }
2171 #endif
2172 
2173 // Iteration functions.
2174 
2175 // Iterates an ObjectClosure over all objects within a HeapRegion.
2176 
2177 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2178   ObjectClosure* _cl;
2179 public:
2180   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2181   bool do_heap_region(HeapRegion* r) {
2182     if (!r->is_continues_humongous()) {
2183       r->object_iterate(_cl);
2184     }
2185     return false;
2186   }
2187 };
2188 
2189 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2190   IterateObjectClosureRegionClosure blk(cl);
2191   heap_region_iterate(&blk);
2192 }
2193 
2194 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2195   _hrm.iterate(cl);
2196 }
2197 
2198 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2199                                                                  HeapRegionClaimer *hrclaimer,
2200                                                                  uint worker_id) const {
2201   _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2202 }
2203 
2204 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2205                                                          HeapRegionClaimer *hrclaimer) const {
2206   _hrm.par_iterate(cl, hrclaimer, 0);
2207 }
2208 
2209 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2210   _collection_set.iterate(cl);
2211 }
2212 
2213 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2214   _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2215 }
2216 
2217 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2218   HeapRegion* hr = heap_region_containing(addr);
2219   return hr->block_start(addr);
2220 }
2221 
2222 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2223   HeapRegion* hr = heap_region_containing(addr);
2224   return hr->block_size(addr);
2225 }
2226 
2227 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2228   HeapRegion* hr = heap_region_containing(addr);
2229   return hr->block_is_obj(addr);
2230 }
2231 
2232 bool G1CollectedHeap::supports_tlab_allocation() const {
2233   return true;
2234 }
2235 
2236 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2237   return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2238 }
2239 
2240 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2241   return _eden.length() * HeapRegion::GrainBytes;
2242 }
2243 
2244 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2245 // must be equal to the humongous object limit.
2246 size_t G1CollectedHeap::max_tlab_size() const {
2247   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2248 }
2249 
2250 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2251   return _allocator->unsafe_max_tlab_alloc();
2252 }
2253 
2254 size_t G1CollectedHeap::max_capacity() const {
2255   return _hrm.reserved().byte_size();
2256 }
2257 
2258 jlong G1CollectedHeap::millis_since_last_gc() {
2259   // See the notes in GenCollectedHeap::millis_since_last_gc()
2260   // for more information about the implementation.
2261   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2262     _g1_policy->collection_pause_end_millis();
2263   if (ret_val < 0) {
2264     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2265       ". returning zero instead.", ret_val);
2266     return 0;
2267   }
2268   return ret_val;
2269 }
2270 
2271 void G1CollectedHeap::prepare_for_verify() {
2272   _verifier->prepare_for_verify();
2273 }
2274 
2275 void G1CollectedHeap::verify(VerifyOption vo) {
2276   _verifier->verify(vo);
2277 }
2278 
2279 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2280   return true;
2281 }
2282 
2283 const char* const* G1CollectedHeap::concurrent_phases() const {
2284   return _cmThread->concurrent_phases();
2285 }
2286 
2287 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2288   return _cmThread->request_concurrent_phase(phase);
2289 }
2290 
2291 class PrintRegionClosure: public HeapRegionClosure {
2292   outputStream* _st;
2293 public:
2294   PrintRegionClosure(outputStream* st) : _st(st) {}
2295   bool do_heap_region(HeapRegion* r) {
2296     r->print_on(_st);
2297     return false;
2298   }
2299 };
2300 
2301 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2302                                        const HeapRegion* hr,
2303                                        const VerifyOption vo) const {
2304   switch (vo) {
2305   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2306   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2307   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2308   default:                            ShouldNotReachHere();
2309   }
2310   return false; // keep some compilers happy
2311 }
2312 
2313 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2314                                        const VerifyOption vo) const {
2315   switch (vo) {
2316   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2317   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2318   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2319   default:                            ShouldNotReachHere();
2320   }
2321   return false; // keep some compilers happy
2322 }
2323 
2324 void G1CollectedHeap::print_heap_regions() const {
2325   LogTarget(Trace, gc, heap, region) lt;
2326   if (lt.is_enabled()) {
2327     LogStream ls(lt);
2328     print_regions_on(&ls);
2329   }
2330 }
2331 
2332 void G1CollectedHeap::print_on(outputStream* st) const {
2333   st->print(" %-20s", "garbage-first heap");
2334   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2335             capacity()/K, used_unlocked()/K);
2336   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2337             p2i(_hrm.reserved().start()),
2338             p2i(_hrm.reserved().end()));
2339   st->cr();
2340   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2341   uint young_regions = young_regions_count();
2342   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2343             (size_t) young_regions * HeapRegion::GrainBytes / K);
2344   uint survivor_regions = survivor_regions_count();
2345   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2346             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2347   st->cr();
2348   MetaspaceAux::print_on(st);
2349 }
2350 
2351 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2352   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2353                "HS=humongous(starts), HC=humongous(continues), "
2354                "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2355                "TAMS=top-at-mark-start (previous, next)");
2356   PrintRegionClosure blk(st);
2357   heap_region_iterate(&blk);
2358 }
2359 
2360 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2361   print_on(st);
2362 
2363   // Print the per-region information.
2364   print_regions_on(st);
2365 }
2366 
2367 void G1CollectedHeap::print_on_error(outputStream* st) const {
2368   this->CollectedHeap::print_on_error(st);
2369 
2370   if (_cm != NULL) {
2371     st->cr();
2372     _cm->print_on_error(st);
2373   }
2374 }
2375 
2376 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2377   workers()->print_worker_threads_on(st);
2378   _cmThread->print_on(st);
2379   st->cr();
2380   _cm->print_worker_threads_on(st);
2381   _cr->print_threads_on(st);
2382   _young_gen_sampling_thread->print_on(st);
2383   if (G1StringDedup::is_enabled()) {
2384     G1StringDedup::print_worker_threads_on(st);
2385   }
2386 }
2387 
2388 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2389   workers()->threads_do(tc);
2390   tc->do_thread(_cmThread);
2391   _cm->threads_do(tc);
2392   _cr->threads_do(tc);
2393   tc->do_thread(_young_gen_sampling_thread);
2394   if (G1StringDedup::is_enabled()) {
2395     G1StringDedup::threads_do(tc);
2396   }
2397 }
2398 
2399 void G1CollectedHeap::print_tracing_info() const {
2400   g1_rem_set()->print_summary_info();
2401   concurrent_mark()->print_summary_info();
2402 }
2403 
2404 #ifndef PRODUCT
2405 // Helpful for debugging RSet issues.
2406 
2407 class PrintRSetsClosure : public HeapRegionClosure {
2408 private:
2409   const char* _msg;
2410   size_t _occupied_sum;
2411 
2412 public:
2413   bool do_heap_region(HeapRegion* r) {
2414     HeapRegionRemSet* hrrs = r->rem_set();
2415     size_t occupied = hrrs->occupied();
2416     _occupied_sum += occupied;
2417 
2418     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2419     if (occupied == 0) {
2420       tty->print_cr("  RSet is empty");
2421     } else {
2422       hrrs->print();
2423     }
2424     tty->print_cr("----------");
2425     return false;
2426   }
2427 
2428   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2429     tty->cr();
2430     tty->print_cr("========================================");
2431     tty->print_cr("%s", msg);
2432     tty->cr();
2433   }
2434 
2435   ~PrintRSetsClosure() {
2436     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2437     tty->print_cr("========================================");
2438     tty->cr();
2439   }
2440 };
2441 
2442 void G1CollectedHeap::print_cset_rsets() {
2443   PrintRSetsClosure cl("Printing CSet RSets");
2444   collection_set_iterate(&cl);
2445 }
2446 
2447 void G1CollectedHeap::print_all_rsets() {
2448   PrintRSetsClosure cl("Printing All RSets");;
2449   heap_region_iterate(&cl);
2450 }
2451 #endif // PRODUCT
2452 
2453 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2454 
2455   size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2456   size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2457   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2458 
2459   size_t eden_capacity_bytes =
2460     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2461 
2462   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2463   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2464                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2465 }
2466 
2467 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2468   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2469                        stats->unused(), stats->used(), stats->region_end_waste(),
2470                        stats->regions_filled(), stats->direct_allocated(),
2471                        stats->failure_used(), stats->failure_waste());
2472 }
2473 
2474 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2475   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2476   gc_tracer->report_gc_heap_summary(when, heap_summary);
2477 
2478   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2479   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2480 }
2481 
2482 G1CollectedHeap* G1CollectedHeap::heap() {
2483   CollectedHeap* heap = Universe::heap();
2484   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2485   assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2486   return (G1CollectedHeap*)heap;
2487 }
2488 
2489 void G1CollectedHeap::gc_prologue(bool full) {
2490   // always_do_update_barrier = false;
2491   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2492 
2493   // This summary needs to be printed before incrementing total collections.
2494   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2495 
2496   // Update common counters.
2497   increment_total_collections(full /* full gc */);
2498   if (full) {
2499     increment_old_marking_cycles_started();
2500     reset_gc_time_stamp();
2501   } else {
2502     increment_gc_time_stamp();
2503   }
2504 
2505   // Fill TLAB's and such
2506   double start = os::elapsedTime();
2507   accumulate_statistics_all_tlabs();
2508   ensure_parsability(true);
2509   g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2510 }
2511 
2512 void G1CollectedHeap::gc_epilogue(bool full) {
2513   // Update common counters.
2514   if (full) {
2515     // Update the number of full collections that have been completed.
2516     increment_old_marking_cycles_completed(false /* concurrent */);
2517   }
2518 
2519   // We are at the end of the GC. Total collections has already been increased.
2520   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2521 
2522   // FIXME: what is this about?
2523   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2524   // is set.
2525 #if COMPILER2_OR_JVMCI
2526   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2527 #endif
2528   // always_do_update_barrier = true;
2529 
2530   double start = os::elapsedTime();
2531   resize_all_tlabs();
2532   g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2533 
2534   MemoryService::track_memory_usage();
2535   // We have just completed a GC. Update the soft reference
2536   // policy with the new heap occupancy
2537   Universe::update_heap_info_at_gc();
2538 }
2539 
2540 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2541                                                uint gc_count_before,
2542                                                bool* succeeded,
2543                                                GCCause::Cause gc_cause) {
2544   assert_heap_not_locked_and_not_at_safepoint();
2545   VM_G1CollectForAllocation op(word_size,
2546                                gc_count_before,
2547                                gc_cause,
2548                                false, /* should_initiate_conc_mark */
2549                                g1_policy()->max_pause_time_ms());
2550   VMThread::execute(&op);
2551 
2552   HeapWord* result = op.result();
2553   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2554   assert(result == NULL || ret_succeeded,
2555          "the result should be NULL if the VM did not succeed");
2556   *succeeded = ret_succeeded;
2557 
2558   assert_heap_not_locked();
2559   return result;
2560 }
2561 
2562 void
2563 G1CollectedHeap::doConcurrentMark() {
2564   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2565   if (!_cmThread->in_progress()) {
2566     _cmThread->set_started();
2567     CGC_lock->notify();
2568   }
2569 }
2570 
2571 size_t G1CollectedHeap::pending_card_num() {
2572   size_t extra_cards = 0;
2573   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) {
2574     DirtyCardQueue& dcq = curr->dirty_card_queue();
2575     extra_cards += dcq.size();
2576   }
2577   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2578   size_t buffer_size = dcqs.buffer_size();
2579   size_t buffer_num = dcqs.completed_buffers_num();
2580 
2581   return buffer_size * buffer_num + extra_cards;
2582 }
2583 
2584 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2585  private:
2586   size_t _total_humongous;
2587   size_t _candidate_humongous;
2588 
2589   DirtyCardQueue _dcq;
2590 
2591   // We don't nominate objects with many remembered set entries, on
2592   // the assumption that such objects are likely still live.
2593   bool is_remset_small(HeapRegion* region) const {
2594     HeapRegionRemSet* const rset = region->rem_set();
2595     return G1EagerReclaimHumongousObjectsWithStaleRefs
2596       ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2597       : rset->is_empty();
2598   }
2599 
2600   bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2601     assert(region->is_starts_humongous(), "Must start a humongous object");
2602 
2603     oop obj = oop(region->bottom());
2604 
2605     // Dead objects cannot be eager reclaim candidates. Due to class
2606     // unloading it is unsafe to query their classes so we return early.
2607     if (heap->is_obj_dead(obj, region)) {
2608       return false;
2609     }
2610 
2611     // Candidate selection must satisfy the following constraints
2612     // while concurrent marking is in progress:
2613     //
2614     // * In order to maintain SATB invariants, an object must not be
2615     // reclaimed if it was allocated before the start of marking and
2616     // has not had its references scanned.  Such an object must have
2617     // its references (including type metadata) scanned to ensure no
2618     // live objects are missed by the marking process.  Objects
2619     // allocated after the start of concurrent marking don't need to
2620     // be scanned.
2621     //
2622     // * An object must not be reclaimed if it is on the concurrent
2623     // mark stack.  Objects allocated after the start of concurrent
2624     // marking are never pushed on the mark stack.
2625     //
2626     // Nominating only objects allocated after the start of concurrent
2627     // marking is sufficient to meet both constraints.  This may miss
2628     // some objects that satisfy the constraints, but the marking data
2629     // structures don't support efficiently performing the needed
2630     // additional tests or scrubbing of the mark stack.
2631     //
2632     // However, we presently only nominate is_typeArray() objects.
2633     // A humongous object containing references induces remembered
2634     // set entries on other regions.  In order to reclaim such an
2635     // object, those remembered sets would need to be cleaned up.
2636     //
2637     // We also treat is_typeArray() objects specially, allowing them
2638     // to be reclaimed even if allocated before the start of
2639     // concurrent mark.  For this we rely on mark stack insertion to
2640     // exclude is_typeArray() objects, preventing reclaiming an object
2641     // that is in the mark stack.  We also rely on the metadata for
2642     // such objects to be built-in and so ensured to be kept live.
2643     // Frequent allocation and drop of large binary blobs is an
2644     // important use case for eager reclaim, and this special handling
2645     // may reduce needed headroom.
2646 
2647     return obj->is_typeArray() && is_remset_small(region);
2648   }
2649 
2650  public:
2651   RegisterHumongousWithInCSetFastTestClosure()
2652   : _total_humongous(0),
2653     _candidate_humongous(0),
2654     _dcq(&JavaThread::dirty_card_queue_set()) {
2655   }
2656 
2657   virtual bool do_heap_region(HeapRegion* r) {
2658     if (!r->is_starts_humongous()) {
2659       return false;
2660     }
2661     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2662 
2663     bool is_candidate = humongous_region_is_candidate(g1h, r);
2664     uint rindex = r->hrm_index();
2665     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2666     if (is_candidate) {
2667       _candidate_humongous++;
2668       g1h->register_humongous_region_with_cset(rindex);
2669       // Is_candidate already filters out humongous object with large remembered sets.
2670       // If we have a humongous object with a few remembered sets, we simply flush these
2671       // remembered set entries into the DCQS. That will result in automatic
2672       // re-evaluation of their remembered set entries during the following evacuation
2673       // phase.
2674       if (!r->rem_set()->is_empty()) {
2675         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2676                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2677         G1CardTable* ct = g1h->card_table();
2678         HeapRegionRemSetIterator hrrs(r->rem_set());
2679         size_t card_index;
2680         while (hrrs.has_next(card_index)) {
2681           jbyte* card_ptr = (jbyte*)ct->byte_for_index(card_index);
2682           // The remembered set might contain references to already freed
2683           // regions. Filter out such entries to avoid failing card table
2684           // verification.
2685           if (g1h->is_in_closed_subset(ct->addr_for(card_ptr))) {
2686             if (*card_ptr != G1CardTable::dirty_card_val()) {
2687               *card_ptr = G1CardTable::dirty_card_val();
2688               _dcq.enqueue(card_ptr);
2689             }
2690           }
2691         }
2692         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2693                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2694                hrrs.n_yielded(), r->rem_set()->occupied());
2695         r->rem_set()->clear_locked();
2696       }
2697       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2698     }
2699     _total_humongous++;
2700 
2701     return false;
2702   }
2703 
2704   size_t total_humongous() const { return _total_humongous; }
2705   size_t candidate_humongous() const { return _candidate_humongous; }
2706 
2707   void flush_rem_set_entries() { _dcq.flush(); }
2708 };
2709 
2710 void G1CollectedHeap::register_humongous_regions_with_cset() {
2711   if (!G1EagerReclaimHumongousObjects) {
2712     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2713     return;
2714   }
2715   double time = os::elapsed_counter();
2716 
2717   // Collect reclaim candidate information and register candidates with cset.
2718   RegisterHumongousWithInCSetFastTestClosure cl;
2719   heap_region_iterate(&cl);
2720 
2721   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2722   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2723                                                                   cl.total_humongous(),
2724                                                                   cl.candidate_humongous());
2725   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2726 
2727   // Finally flush all remembered set entries to re-check into the global DCQS.
2728   cl.flush_rem_set_entries();
2729 }
2730 
2731 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2732   public:
2733     bool do_heap_region(HeapRegion* hr) {
2734       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2735         hr->verify_rem_set();
2736       }
2737       return false;
2738     }
2739 };
2740 
2741 uint G1CollectedHeap::num_task_queues() const {
2742   return _task_queues->size();
2743 }
2744 
2745 #if TASKQUEUE_STATS
2746 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2747   st->print_raw_cr("GC Task Stats");
2748   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2749   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2750 }
2751 
2752 void G1CollectedHeap::print_taskqueue_stats() const {
2753   if (!log_is_enabled(Trace, gc, task, stats)) {
2754     return;
2755   }
2756   Log(gc, task, stats) log;
2757   ResourceMark rm;
2758   LogStream ls(log.trace());
2759   outputStream* st = &ls;
2760 
2761   print_taskqueue_stats_hdr(st);
2762 
2763   TaskQueueStats totals;
2764   const uint n = num_task_queues();
2765   for (uint i = 0; i < n; ++i) {
2766     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2767     totals += task_queue(i)->stats;
2768   }
2769   st->print_raw("tot "); totals.print(st); st->cr();
2770 
2771   DEBUG_ONLY(totals.verify());
2772 }
2773 
2774 void G1CollectedHeap::reset_taskqueue_stats() {
2775   const uint n = num_task_queues();
2776   for (uint i = 0; i < n; ++i) {
2777     task_queue(i)->stats.reset();
2778   }
2779 }
2780 #endif // TASKQUEUE_STATS
2781 
2782 void G1CollectedHeap::wait_for_root_region_scanning() {
2783   double scan_wait_start = os::elapsedTime();
2784   // We have to wait until the CM threads finish scanning the
2785   // root regions as it's the only way to ensure that all the
2786   // objects on them have been correctly scanned before we start
2787   // moving them during the GC.
2788   bool waited = _cm->root_regions()->wait_until_scan_finished();
2789   double wait_time_ms = 0.0;
2790   if (waited) {
2791     double scan_wait_end = os::elapsedTime();
2792     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2793   }
2794   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2795 }
2796 
2797 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2798 private:
2799   G1HRPrinter* _hr_printer;
2800 public:
2801   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2802 
2803   virtual bool do_heap_region(HeapRegion* r) {
2804     _hr_printer->cset(r);
2805     return false;
2806   }
2807 };
2808 
2809 void G1CollectedHeap::start_new_collection_set() {
2810   collection_set()->start_incremental_building();
2811 
2812   clear_cset_fast_test();
2813 
2814   guarantee(_eden.length() == 0, "eden should have been cleared");
2815   g1_policy()->transfer_survivors_to_cset(survivor());
2816 }
2817 
2818 bool
2819 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2820   assert_at_safepoint_on_vm_thread();
2821   guarantee(!is_gc_active(), "collection is not reentrant");
2822 
2823   if (GCLocker::check_active_before_gc()) {
2824     return false;
2825   }
2826 
2827   _gc_timer_stw->register_gc_start();
2828 
2829   GCIdMark gc_id_mark;
2830   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2831 
2832   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2833   ResourceMark rm;
2834 
2835   g1_policy()->note_gc_start();
2836 
2837   wait_for_root_region_scanning();
2838 
2839   print_heap_before_gc();
2840   print_heap_regions();
2841   trace_heap_before_gc(_gc_tracer_stw);
2842 
2843   _verifier->verify_region_sets_optional();
2844   _verifier->verify_dirty_young_regions();
2845 
2846   // We should not be doing initial mark unless the conc mark thread is running
2847   if (!_cmThread->should_terminate()) {
2848     // This call will decide whether this pause is an initial-mark
2849     // pause. If it is, during_initial_mark_pause() will return true
2850     // for the duration of this pause.
2851     g1_policy()->decide_on_conc_mark_initiation();
2852   }
2853 
2854   // We do not allow initial-mark to be piggy-backed on a mixed GC.
2855   assert(!collector_state()->during_initial_mark_pause() ||
2856           collector_state()->gcs_are_young(), "sanity");
2857 
2858   // We also do not allow mixed GCs during marking.
2859   assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
2860 
2861   // Record whether this pause is an initial mark. When the current
2862   // thread has completed its logging output and it's safe to signal
2863   // the CM thread, the flag's value in the policy has been reset.
2864   bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
2865 
2866   // Inner scope for scope based logging, timers, and stats collection
2867   {
2868     EvacuationInfo evacuation_info;
2869 
2870     if (collector_state()->during_initial_mark_pause()) {
2871       // We are about to start a marking cycle, so we increment the
2872       // full collection counter.
2873       increment_old_marking_cycles_started();
2874       _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2875     }
2876 
2877     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2878 
2879     GCTraceCPUTime tcpu;
2880 
2881     G1HeapVerifier::G1VerifyType verify_type;
2882     FormatBuffer<> gc_string("Pause ");
2883     if (collector_state()->during_initial_mark_pause()) {
2884       gc_string.append("Initial Mark");
2885       verify_type = G1HeapVerifier::G1VerifyInitialMark;
2886     } else if (collector_state()->gcs_are_young()) {
2887       gc_string.append("Young");
2888       verify_type = G1HeapVerifier::G1VerifyYoungOnly;
2889     } else {
2890       gc_string.append("Mixed");
2891       verify_type = G1HeapVerifier::G1VerifyMixed;
2892     }
2893     GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2894 
2895     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2896                                                                   workers()->active_workers(),
2897                                                                   Threads::number_of_non_daemon_threads());
2898     workers()->update_active_workers(active_workers);
2899     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2900 
2901     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2902     TraceMemoryManagerStats tms(&_memory_manager, gc_cause());
2903 
2904     // If the secondary_free_list is not empty, append it to the
2905     // free_list. No need to wait for the cleanup operation to finish;
2906     // the region allocation code will check the secondary_free_list
2907     // and wait if necessary. If the G1StressConcRegionFreeing flag is
2908     // set, skip this step so that the region allocation code has to
2909     // get entries from the secondary_free_list.
2910     if (!G1StressConcRegionFreeing) {
2911       append_secondary_free_list_if_not_empty_with_lock();
2912     }
2913 
2914     G1HeapTransition heap_transition(this);
2915     size_t heap_used_bytes_before_gc = used();
2916 
2917     // Don't dynamically change the number of GC threads this early.  A value of
2918     // 0 is used to indicate serial work.  When parallel work is done,
2919     // it will be set.
2920 
2921     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2922       IsGCActiveMark x;
2923 
2924       gc_prologue(false);
2925 
2926       if (VerifyRememberedSets) {
2927         log_info(gc, verify)("[Verifying RemSets before GC]");
2928         VerifyRegionRemSetClosure v_cl;
2929         heap_region_iterate(&v_cl);
2930       }
2931 
2932       _verifier->verify_before_gc(verify_type);
2933 
2934       _verifier->check_bitmaps("GC Start");
2935 
2936 #if COMPILER2_OR_JVMCI
2937       DerivedPointerTable::clear();
2938 #endif
2939 
2940       // Please see comment in g1CollectedHeap.hpp and
2941       // G1CollectedHeap::ref_processing_init() to see how
2942       // reference processing currently works in G1.
2943 
2944       // Enable discovery in the STW reference processor
2945       if (g1_policy()->should_process_references()) {
2946         ref_processor_stw()->enable_discovery();
2947       } else {
2948         ref_processor_stw()->disable_discovery();
2949       }
2950 
2951       {
2952         // We want to temporarily turn off discovery by the
2953         // CM ref processor, if necessary, and turn it back on
2954         // on again later if we do. Using a scoped
2955         // NoRefDiscovery object will do this.
2956         NoRefDiscovery no_cm_discovery(ref_processor_cm());
2957 
2958         // Forget the current alloc region (we might even choose it to be part
2959         // of the collection set!).
2960         _allocator->release_mutator_alloc_region();
2961 
2962         // This timing is only used by the ergonomics to handle our pause target.
2963         // It is unclear why this should not include the full pause. We will
2964         // investigate this in CR 7178365.
2965         //
2966         // Preserving the old comment here if that helps the investigation:
2967         //
2968         // The elapsed time induced by the start time below deliberately elides
2969         // the possible verification above.
2970         double sample_start_time_sec = os::elapsedTime();
2971 
2972         g1_policy()->record_collection_pause_start(sample_start_time_sec);
2973 
2974         if (collector_state()->during_initial_mark_pause()) {
2975           concurrent_mark()->checkpoint_roots_initial_pre();
2976         }
2977 
2978         g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
2979 
2980         evacuation_info.set_collectionset_regions(collection_set()->region_length());
2981 
2982         // Make sure the remembered sets are up to date. This needs to be
2983         // done before register_humongous_regions_with_cset(), because the
2984         // remembered sets are used there to choose eager reclaim candidates.
2985         // If the remembered sets are not up to date we might miss some
2986         // entries that need to be handled.
2987         g1_rem_set()->cleanupHRRS();
2988 
2989         register_humongous_regions_with_cset();
2990 
2991         assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
2992 
2993         // We call this after finalize_cset() to
2994         // ensure that the CSet has been finalized.
2995         _cm->verify_no_cset_oops();
2996 
2997         if (_hr_printer.is_active()) {
2998           G1PrintCollectionSetClosure cl(&_hr_printer);
2999           _collection_set.iterate(&cl);
3000         }
3001 
3002         // Initialize the GC alloc regions.
3003         _allocator->init_gc_alloc_regions(evacuation_info);
3004 
3005         G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3006         pre_evacuate_collection_set();
3007 
3008         // Actually do the work...
3009         evacuate_collection_set(&per_thread_states);
3010 
3011         post_evacuate_collection_set(evacuation_info, &per_thread_states);
3012 
3013         const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3014         free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
3015 
3016         eagerly_reclaim_humongous_regions();
3017 
3018         record_obj_copy_mem_stats();
3019         _survivor_evac_stats.adjust_desired_plab_sz();
3020         _old_evac_stats.adjust_desired_plab_sz();
3021 
3022         double start = os::elapsedTime();
3023         start_new_collection_set();
3024         g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
3025 
3026         if (evacuation_failed()) {
3027           set_used(recalculate_used());
3028           if (_archive_allocator != NULL) {
3029             _archive_allocator->clear_used();
3030           }
3031           for (uint i = 0; i < ParallelGCThreads; i++) {
3032             if (_evacuation_failed_info_array[i].has_failed()) {
3033               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3034             }
3035           }
3036         } else {
3037           // The "used" of the the collection set have already been subtracted
3038           // when they were freed.  Add in the bytes evacuated.
3039           increase_used(g1_policy()->bytes_copied_during_gc());
3040         }
3041 
3042         if (collector_state()->during_initial_mark_pause()) {
3043           // We have to do this before we notify the CM threads that
3044           // they can start working to make sure that all the
3045           // appropriate initialization is done on the CM object.
3046           concurrent_mark()->checkpoint_roots_initial_post();
3047           collector_state()->set_mark_in_progress(true);
3048           // Note that we don't actually trigger the CM thread at
3049           // this point. We do that later when we're sure that
3050           // the current thread has completed its logging output.
3051         }
3052 
3053         allocate_dummy_regions();
3054 
3055         _allocator->init_mutator_alloc_region();
3056 
3057         {
3058           size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3059           if (expand_bytes > 0) {
3060             size_t bytes_before = capacity();
3061             // No need for an ergo logging here,
3062             // expansion_amount() does this when it returns a value > 0.
3063             double expand_ms;
3064             if (!expand(expand_bytes, _workers, &expand_ms)) {
3065               // We failed to expand the heap. Cannot do anything about it.
3066             }
3067             g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3068           }
3069         }
3070 
3071         // We redo the verification but now wrt to the new CSet which
3072         // has just got initialized after the previous CSet was freed.
3073         _cm->verify_no_cset_oops();
3074 
3075         // This timing is only used by the ergonomics to handle our pause target.
3076         // It is unclear why this should not include the full pause. We will
3077         // investigate this in CR 7178365.
3078         double sample_end_time_sec = os::elapsedTime();
3079         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3080         size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
3081         g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3082 
3083         evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3084         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3085 
3086         if (VerifyRememberedSets) {
3087           log_info(gc, verify)("[Verifying RemSets after GC]");
3088           VerifyRegionRemSetClosure v_cl;
3089           heap_region_iterate(&v_cl);
3090         }
3091 
3092         _verifier->verify_after_gc(verify_type);
3093         _verifier->check_bitmaps("GC End");
3094 
3095         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3096         ref_processor_stw()->verify_no_references_recorded();
3097 
3098         // CM reference discovery will be re-enabled if necessary.
3099       }
3100 
3101 #ifdef TRACESPINNING
3102       ParallelTaskTerminator::print_termination_counts();
3103 #endif
3104 
3105       gc_epilogue(false);
3106     }
3107 
3108     // Print the remainder of the GC log output.
3109     if (evacuation_failed()) {
3110       log_info(gc)("To-space exhausted");
3111     }
3112 
3113     g1_policy()->print_phases();
3114     heap_transition.print();
3115 
3116     // It is not yet to safe to tell the concurrent mark to
3117     // start as we have some optional output below. We don't want the
3118     // output from the concurrent mark thread interfering with this
3119     // logging output either.
3120 
3121     _hrm.verify_optional();
3122     _verifier->verify_region_sets_optional();
3123 
3124     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3125     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3126 
3127     print_heap_after_gc();
3128     print_heap_regions();
3129     trace_heap_after_gc(_gc_tracer_stw);
3130 
3131     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3132     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3133     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3134     // before any GC notifications are raised.
3135     g1mm()->update_sizes();
3136 
3137     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3138     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3139     _gc_timer_stw->register_gc_end();
3140     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3141   }
3142   // It should now be safe to tell the concurrent mark thread to start
3143   // without its logging output interfering with the logging output
3144   // that came from the pause.
3145 
3146   if (should_start_conc_mark) {
3147     // CAUTION: after the doConcurrentMark() call below,
3148     // the concurrent marking thread(s) could be running
3149     // concurrently with us. Make sure that anything after
3150     // this point does not assume that we are the only GC thread
3151     // running. Note: of course, the actual marking work will
3152     // not start until the safepoint itself is released in
3153     // SuspendibleThreadSet::desynchronize().
3154     doConcurrentMark();
3155   }
3156 
3157   return true;
3158 }
3159 
3160 void G1CollectedHeap::remove_self_forwarding_pointers() {
3161   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3162   workers()->run_task(&rsfp_task);
3163 }
3164 
3165 void G1CollectedHeap::restore_after_evac_failure() {
3166   double remove_self_forwards_start = os::elapsedTime();
3167 
3168   remove_self_forwarding_pointers();
3169   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3170   _preserved_marks_set.restore(&task_executor);
3171 
3172   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3173 }
3174 
3175 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3176   if (!_evacuation_failed) {
3177     _evacuation_failed = true;
3178   }
3179 
3180   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3181   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3182 }
3183 
3184 bool G1ParEvacuateFollowersClosure::offer_termination() {
3185   G1ParScanThreadState* const pss = par_scan_state();
3186   start_term_time();
3187   const bool res = terminator()->offer_termination();
3188   end_term_time();
3189   return res;
3190 }
3191 
3192 void G1ParEvacuateFollowersClosure::do_void() {
3193   G1ParScanThreadState* const pss = par_scan_state();
3194   pss->trim_queue();
3195   do {
3196     pss->steal_and_trim_queue(queues());
3197   } while (!offer_termination());
3198 }
3199 
3200 class G1ParTask : public AbstractGangTask {
3201 protected:
3202   G1CollectedHeap*         _g1h;
3203   G1ParScanThreadStateSet* _pss;
3204   RefToScanQueueSet*       _queues;
3205   G1RootProcessor*         _root_processor;
3206   ParallelTaskTerminator   _terminator;
3207   uint                     _n_workers;
3208 
3209 public:
3210   G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3211     : AbstractGangTask("G1 collection"),
3212       _g1h(g1h),
3213       _pss(per_thread_states),
3214       _queues(task_queues),
3215       _root_processor(root_processor),
3216       _terminator(n_workers, _queues),
3217       _n_workers(n_workers)
3218   {}
3219 
3220   void work(uint worker_id) {
3221     if (worker_id >= _n_workers) return;  // no work needed this round
3222 
3223     double start_sec = os::elapsedTime();
3224     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3225 
3226     {
3227       ResourceMark rm;
3228       HandleMark   hm;
3229 
3230       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
3231 
3232       G1ParScanThreadState*           pss = _pss->state_for_worker(worker_id);
3233       pss->set_ref_processor(rp);
3234 
3235       double start_strong_roots_sec = os::elapsedTime();
3236 
3237       _root_processor->evacuate_roots(pss->closures(), worker_id);
3238 
3239       // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3240       // treating the nmethods visited to act as roots for concurrent marking.
3241       // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3242       // objects copied by the current evacuation.
3243       _g1h->g1_rem_set()->oops_into_collection_set_do(pss,
3244                                                       pss->closures()->weak_codeblobs(),
3245                                                       worker_id);
3246 
3247       double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3248 
3249       double term_sec = 0.0;
3250       size_t evac_term_attempts = 0;
3251       {
3252         double start = os::elapsedTime();
3253         G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3254         evac.do_void();
3255 
3256         evac_term_attempts = evac.term_attempts();
3257         term_sec = evac.term_time();
3258         double elapsed_sec = os::elapsedTime() - start;
3259         _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3260         _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3261         _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3262       }
3263 
3264       assert(pss->queue_is_empty(), "should be empty");
3265 
3266       if (log_is_enabled(Debug, gc, task, stats)) {
3267         MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3268         size_t lab_waste;
3269         size_t lab_undo_waste;
3270         pss->waste(lab_waste, lab_undo_waste);
3271         _g1h->print_termination_stats(worker_id,
3272                                       (os::elapsedTime() - start_sec) * 1000.0,   /* elapsed time */
3273                                       strong_roots_sec * 1000.0,                  /* strong roots time */
3274                                       term_sec * 1000.0,                          /* evac term time */
3275                                       evac_term_attempts,                         /* evac term attempts */
3276                                       lab_waste,                                  /* alloc buffer waste */
3277                                       lab_undo_waste                              /* undo waste */
3278                                       );
3279       }
3280 
3281       // Close the inner scope so that the ResourceMark and HandleMark
3282       // destructors are executed here and are included as part of the
3283       // "GC Worker Time".
3284     }
3285     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3286   }
3287 };
3288 
3289 void G1CollectedHeap::print_termination_stats_hdr() {
3290   log_debug(gc, task, stats)("GC Termination Stats");
3291   log_debug(gc, task, stats)("     elapsed  --strong roots-- -------termination------- ------waste (KiB)------");
3292   log_debug(gc, task, stats)("thr     ms        ms      %%        ms      %%    attempts  total   alloc    undo");
3293   log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3294 }
3295 
3296 void G1CollectedHeap::print_termination_stats(uint worker_id,
3297                                               double elapsed_ms,
3298                                               double strong_roots_ms,
3299                                               double term_ms,
3300                                               size_t term_attempts,
3301                                               size_t alloc_buffer_waste,
3302                                               size_t undo_waste) const {
3303   log_debug(gc, task, stats)
3304               ("%3d %9.2f %9.2f %6.2f "
3305                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3306                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3307                worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3308                term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3309                (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3310                alloc_buffer_waste * HeapWordSize / K,
3311                undo_waste * HeapWordSize / K);
3312 }
3313 
3314 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3315 private:
3316   BoolObjectClosure* _is_alive;
3317   G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3318 
3319   int _initial_string_table_size;
3320   int _initial_symbol_table_size;
3321 
3322   bool  _process_strings;
3323   int _strings_processed;
3324   int _strings_removed;
3325 
3326   bool  _process_symbols;
3327   int _symbols_processed;
3328   int _symbols_removed;
3329 
3330   bool _process_string_dedup;
3331 
3332 public:
3333   G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3334     AbstractGangTask("String/Symbol Unlinking"),
3335     _is_alive(is_alive),
3336     _dedup_closure(is_alive, NULL, false),
3337     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3338     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3339     _process_string_dedup(process_string_dedup) {
3340 
3341     _initial_string_table_size = StringTable::the_table()->table_size();
3342     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3343     if (process_strings) {
3344       StringTable::clear_parallel_claimed_index();
3345     }
3346     if (process_symbols) {
3347       SymbolTable::clear_parallel_claimed_index();
3348     }
3349   }
3350 
3351   ~G1StringAndSymbolCleaningTask() {
3352     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3353               "claim value %d after unlink less than initial string table size %d",
3354               StringTable::parallel_claimed_index(), _initial_string_table_size);
3355     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3356               "claim value %d after unlink less than initial symbol table size %d",
3357               SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3358 
3359     log_info(gc, stringtable)(
3360         "Cleaned string and symbol table, "
3361         "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3362         "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3363         strings_processed(), strings_removed(),
3364         symbols_processed(), symbols_removed());
3365   }
3366 
3367   void work(uint worker_id) {
3368     int strings_processed = 0;
3369     int strings_removed = 0;
3370     int symbols_processed = 0;
3371     int symbols_removed = 0;
3372     if (_process_strings) {
3373       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3374       Atomic::add(strings_processed, &_strings_processed);
3375       Atomic::add(strings_removed, &_strings_removed);
3376     }
3377     if (_process_symbols) {
3378       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3379       Atomic::add(symbols_processed, &_symbols_processed);
3380       Atomic::add(symbols_removed, &_symbols_removed);
3381     }
3382     if (_process_string_dedup) {
3383       G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3384     }
3385   }
3386 
3387   size_t strings_processed() const { return (size_t)_strings_processed; }
3388   size_t strings_removed()   const { return (size_t)_strings_removed; }
3389 
3390   size_t symbols_processed() const { return (size_t)_symbols_processed; }
3391   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
3392 };
3393 
3394 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3395 private:
3396   static Monitor* _lock;
3397 
3398   BoolObjectClosure* const _is_alive;
3399   const bool               _unloading_occurred;
3400   const uint               _num_workers;
3401 
3402   // Variables used to claim nmethods.
3403   CompiledMethod* _first_nmethod;
3404   CompiledMethod* volatile _claimed_nmethod;
3405 
3406   // The list of nmethods that need to be processed by the second pass.
3407   CompiledMethod* volatile _postponed_list;
3408   volatile uint            _num_entered_barrier;
3409 
3410  public:
3411   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3412       _is_alive(is_alive),
3413       _unloading_occurred(unloading_occurred),
3414       _num_workers(num_workers),
3415       _first_nmethod(NULL),
3416       _claimed_nmethod(NULL),
3417       _postponed_list(NULL),
3418       _num_entered_barrier(0)
3419   {
3420     CompiledMethod::increase_unloading_clock();
3421     // Get first alive nmethod
3422     CompiledMethodIterator iter = CompiledMethodIterator();
3423     if(iter.next_alive()) {
3424       _first_nmethod = iter.method();
3425     }
3426     _claimed_nmethod = _first_nmethod;
3427   }
3428 
3429   ~G1CodeCacheUnloadingTask() {
3430     CodeCache::verify_clean_inline_caches();
3431 
3432     CodeCache::set_needs_cache_clean(false);
3433     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3434 
3435     CodeCache::verify_icholder_relocations();
3436   }
3437 
3438  private:
3439   void add_to_postponed_list(CompiledMethod* nm) {
3440       CompiledMethod* old;
3441       do {
3442         old = _postponed_list;
3443         nm->set_unloading_next(old);
3444       } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
3445   }
3446 
3447   void clean_nmethod(CompiledMethod* nm) {
3448     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3449 
3450     if (postponed) {
3451       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3452       add_to_postponed_list(nm);
3453     }
3454 
3455     // Mark that this thread has been cleaned/unloaded.
3456     // After this call, it will be safe to ask if this nmethod was unloaded or not.
3457     nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3458   }
3459 
3460   void clean_nmethod_postponed(CompiledMethod* nm) {
3461     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3462   }
3463 
3464   static const int MaxClaimNmethods = 16;
3465 
3466   void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3467     CompiledMethod* first;
3468     CompiledMethodIterator last;
3469 
3470     do {
3471       *num_claimed_nmethods = 0;
3472 
3473       first = _claimed_nmethod;
3474       last = CompiledMethodIterator(first);
3475 
3476       if (first != NULL) {
3477 
3478         for (int i = 0; i < MaxClaimNmethods; i++) {
3479           if (!last.next_alive()) {
3480             break;
3481           }
3482           claimed_nmethods[i] = last.method();
3483           (*num_claimed_nmethods)++;
3484         }
3485       }
3486 
3487     } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
3488   }
3489 
3490   CompiledMethod* claim_postponed_nmethod() {
3491     CompiledMethod* claim;
3492     CompiledMethod* next;
3493 
3494     do {
3495       claim = _postponed_list;
3496       if (claim == NULL) {
3497         return NULL;
3498       }
3499 
3500       next = claim->unloading_next();
3501 
3502     } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
3503 
3504     return claim;
3505   }
3506 
3507  public:
3508   // Mark that we're done with the first pass of nmethod cleaning.
3509   void barrier_mark(uint worker_id) {
3510     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3511     _num_entered_barrier++;
3512     if (_num_entered_barrier == _num_workers) {
3513       ml.notify_all();
3514     }
3515   }
3516 
3517   // See if we have to wait for the other workers to
3518   // finish their first-pass nmethod cleaning work.
3519   void barrier_wait(uint worker_id) {
3520     if (_num_entered_barrier < _num_workers) {
3521       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3522       while (_num_entered_barrier < _num_workers) {
3523           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3524       }
3525     }
3526   }
3527 
3528   // Cleaning and unloading of nmethods. Some work has to be postponed
3529   // to the second pass, when we know which nmethods survive.
3530   void work_first_pass(uint worker_id) {
3531     // The first nmethods is claimed by the first worker.
3532     if (worker_id == 0 && _first_nmethod != NULL) {
3533       clean_nmethod(_first_nmethod);
3534       _first_nmethod = NULL;
3535     }
3536 
3537     int num_claimed_nmethods;
3538     CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3539 
3540     while (true) {
3541       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3542 
3543       if (num_claimed_nmethods == 0) {
3544         break;
3545       }
3546 
3547       for (int i = 0; i < num_claimed_nmethods; i++) {
3548         clean_nmethod(claimed_nmethods[i]);
3549       }
3550     }
3551   }
3552 
3553   void work_second_pass(uint worker_id) {
3554     CompiledMethod* nm;
3555     // Take care of postponed nmethods.
3556     while ((nm = claim_postponed_nmethod()) != NULL) {
3557       clean_nmethod_postponed(nm);
3558     }
3559   }
3560 };
3561 
3562 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3563 
3564 class G1KlassCleaningTask : public StackObj {
3565   BoolObjectClosure*                      _is_alive;
3566   volatile int                            _clean_klass_tree_claimed;
3567   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3568 
3569  public:
3570   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3571       _is_alive(is_alive),
3572       _clean_klass_tree_claimed(0),
3573       _klass_iterator() {
3574   }
3575 
3576  private:
3577   bool claim_clean_klass_tree_task() {
3578     if (_clean_klass_tree_claimed) {
3579       return false;
3580     }
3581 
3582     return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0;
3583   }
3584 
3585   InstanceKlass* claim_next_klass() {
3586     Klass* klass;
3587     do {
3588       klass =_klass_iterator.next_klass();
3589     } while (klass != NULL && !klass->is_instance_klass());
3590 
3591     // this can be null so don't call InstanceKlass::cast
3592     return static_cast<InstanceKlass*>(klass);
3593   }
3594 
3595 public:
3596 
3597   void clean_klass(InstanceKlass* ik) {
3598     ik->clean_weak_instanceklass_links(_is_alive);
3599   }
3600 
3601   void work() {
3602     ResourceMark rm;
3603 
3604     // One worker will clean the subklass/sibling klass tree.
3605     if (claim_clean_klass_tree_task()) {
3606       Klass::clean_subklass_tree(_is_alive);
3607     }
3608 
3609     // All workers will help cleaning the classes,
3610     InstanceKlass* klass;
3611     while ((klass = claim_next_klass()) != NULL) {
3612       clean_klass(klass);
3613     }
3614   }
3615 };
3616 
3617 class G1ResolvedMethodCleaningTask : public StackObj {
3618   BoolObjectClosure* _is_alive;
3619   volatile int       _resolved_method_task_claimed;
3620 public:
3621   G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) :
3622       _is_alive(is_alive), _resolved_method_task_claimed(0) {}
3623 
3624   bool claim_resolved_method_task() {
3625     if (_resolved_method_task_claimed) {
3626       return false;
3627     }
3628     return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0;
3629   }
3630 
3631   // These aren't big, one thread can do it all.
3632   void work() {
3633     if (claim_resolved_method_task()) {
3634       ResolvedMethodTable::unlink(_is_alive);
3635     }
3636   }
3637 };
3638 
3639 
3640 // To minimize the remark pause times, the tasks below are done in parallel.
3641 class G1ParallelCleaningTask : public AbstractGangTask {
3642 private:
3643   G1StringAndSymbolCleaningTask _string_symbol_task;
3644   G1CodeCacheUnloadingTask      _code_cache_task;
3645   G1KlassCleaningTask           _klass_cleaning_task;
3646   G1ResolvedMethodCleaningTask  _resolved_method_cleaning_task;
3647 
3648 public:
3649   // The constructor is run in the VMThread.
3650   G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3651       AbstractGangTask("Parallel Cleaning"),
3652       _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3653       _code_cache_task(num_workers, is_alive, unloading_occurred),
3654       _klass_cleaning_task(is_alive),
3655       _resolved_method_cleaning_task(is_alive) {
3656   }
3657 
3658   // The parallel work done by all worker threads.
3659   void work(uint worker_id) {
3660     // Do first pass of code cache cleaning.
3661     _code_cache_task.work_first_pass(worker_id);
3662 
3663     // Let the threads mark that the first pass is done.
3664     _code_cache_task.barrier_mark(worker_id);
3665 
3666     // Clean the Strings and Symbols.
3667     _string_symbol_task.work(worker_id);
3668 
3669     // Clean unreferenced things in the ResolvedMethodTable
3670     _resolved_method_cleaning_task.work();
3671 
3672     // Wait for all workers to finish the first code cache cleaning pass.
3673     _code_cache_task.barrier_wait(worker_id);
3674 
3675     // Do the second code cache cleaning work, which realize on
3676     // the liveness information gathered during the first pass.
3677     _code_cache_task.work_second_pass(worker_id);
3678 
3679     // Clean all klasses that were not unloaded.
3680     _klass_cleaning_task.work();
3681   }
3682 };
3683 
3684 
3685 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3686                                         bool class_unloading_occurred) {
3687   uint n_workers = workers()->active_workers();
3688 
3689   G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3690   workers()->run_task(&g1_unlink_task);
3691 }
3692 
3693 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3694                                        bool process_strings,
3695                                        bool process_symbols,
3696                                        bool process_string_dedup) {
3697   if (!process_strings && !process_symbols && !process_string_dedup) {
3698     // Nothing to clean.
3699     return;
3700   }
3701 
3702   G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3703   workers()->run_task(&g1_unlink_task);
3704 
3705 }
3706 
3707 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3708  private:
3709   DirtyCardQueueSet* _queue;
3710   G1CollectedHeap* _g1h;
3711  public:
3712   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3713     _queue(queue), _g1h(g1h) { }
3714 
3715   virtual void work(uint worker_id) {
3716     G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3717     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3718 
3719     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3720     _queue->par_apply_closure_to_all_completed_buffers(&cl);
3721 
3722     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3723   }
3724 };
3725 
3726 void G1CollectedHeap::redirty_logged_cards() {
3727   double redirty_logged_cards_start = os::elapsedTime();
3728 
3729   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3730   dirty_card_queue_set().reset_for_par_iteration();
3731   workers()->run_task(&redirty_task);
3732 
3733   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
3734   dcq.merge_bufferlists(&dirty_card_queue_set());
3735   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3736 
3737   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3738 }
3739 
3740 // Weak Reference Processing support
3741 
3742 // An always "is_alive" closure that is used to preserve referents.
3743 // If the object is non-null then it's alive.  Used in the preservation
3744 // of referent objects that are pointed to by reference objects
3745 // discovered by the CM ref processor.
3746 class G1AlwaysAliveClosure: public BoolObjectClosure {
3747   G1CollectedHeap* _g1;
3748 public:
3749   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3750   bool do_object_b(oop p) {
3751     if (p != NULL) {
3752       return true;
3753     }
3754     return false;
3755   }
3756 };
3757 
3758 bool G1STWIsAliveClosure::do_object_b(oop p) {
3759   // An object is reachable if it is outside the collection set,
3760   // or is inside and copied.
3761   return !_g1->is_in_cset(p) || p->is_forwarded();
3762 }
3763 
3764 // Non Copying Keep Alive closure
3765 class G1KeepAliveClosure: public OopClosure {
3766   G1CollectedHeap* _g1;
3767 public:
3768   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3769   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3770   void do_oop(oop* p) {
3771     oop obj = *p;
3772     assert(obj != NULL, "the caller should have filtered out NULL values");
3773 
3774     const InCSetState cset_state = _g1->in_cset_state(obj);
3775     if (!cset_state.is_in_cset_or_humongous()) {
3776       return;
3777     }
3778     if (cset_state.is_in_cset()) {
3779       assert( obj->is_forwarded(), "invariant" );
3780       *p = obj->forwardee();
3781     } else {
3782       assert(!obj->is_forwarded(), "invariant" );
3783       assert(cset_state.is_humongous(),
3784              "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3785       _g1->set_humongous_is_live(obj);
3786     }
3787   }
3788 };
3789 
3790 // Copying Keep Alive closure - can be called from both
3791 // serial and parallel code as long as different worker
3792 // threads utilize different G1ParScanThreadState instances
3793 // and different queues.
3794 
3795 class G1CopyingKeepAliveClosure: public OopClosure {
3796   G1CollectedHeap*         _g1h;
3797   OopClosure*              _copy_non_heap_obj_cl;
3798   G1ParScanThreadState*    _par_scan_state;
3799 
3800 public:
3801   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3802                             OopClosure* non_heap_obj_cl,
3803                             G1ParScanThreadState* pss):
3804     _g1h(g1h),
3805     _copy_non_heap_obj_cl(non_heap_obj_cl),
3806     _par_scan_state(pss)
3807   {}
3808 
3809   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3810   virtual void do_oop(      oop* p) { do_oop_work(p); }
3811 
3812   template <class T> void do_oop_work(T* p) {
3813     oop obj = oopDesc::load_decode_heap_oop(p);
3814 
3815     if (_g1h->is_in_cset_or_humongous(obj)) {
3816       // If the referent object has been forwarded (either copied
3817       // to a new location or to itself in the event of an
3818       // evacuation failure) then we need to update the reference
3819       // field and, if both reference and referent are in the G1
3820       // heap, update the RSet for the referent.
3821       //
3822       // If the referent has not been forwarded then we have to keep
3823       // it alive by policy. Therefore we have copy the referent.
3824       //
3825       // If the reference field is in the G1 heap then we can push
3826       // on the PSS queue. When the queue is drained (after each
3827       // phase of reference processing) the object and it's followers
3828       // will be copied, the reference field set to point to the
3829       // new location, and the RSet updated. Otherwise we need to
3830       // use the the non-heap or metadata closures directly to copy
3831       // the referent object and update the pointer, while avoiding
3832       // updating the RSet.
3833 
3834       if (_g1h->is_in_g1_reserved(p)) {
3835         _par_scan_state->push_on_queue(p);
3836       } else {
3837         assert(!Metaspace::contains((const void*)p),
3838                "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3839         _copy_non_heap_obj_cl->do_oop(p);
3840       }
3841     }
3842   }
3843 };
3844 
3845 // Serial drain queue closure. Called as the 'complete_gc'
3846 // closure for each discovered list in some of the
3847 // reference processing phases.
3848 
3849 class G1STWDrainQueueClosure: public VoidClosure {
3850 protected:
3851   G1CollectedHeap* _g1h;
3852   G1ParScanThreadState* _par_scan_state;
3853 
3854   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3855 
3856 public:
3857   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3858     _g1h(g1h),
3859     _par_scan_state(pss)
3860   { }
3861 
3862   void do_void() {
3863     G1ParScanThreadState* const pss = par_scan_state();
3864     pss->trim_queue();
3865   }
3866 };
3867 
3868 // Parallel Reference Processing closures
3869 
3870 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3871 // processing during G1 evacuation pauses.
3872 
3873 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3874 private:
3875   G1CollectedHeap*          _g1h;
3876   G1ParScanThreadStateSet*  _pss;
3877   RefToScanQueueSet*        _queues;
3878   WorkGang*                 _workers;
3879   uint                      _active_workers;
3880 
3881 public:
3882   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3883                            G1ParScanThreadStateSet* per_thread_states,
3884                            WorkGang* workers,
3885                            RefToScanQueueSet *task_queues,
3886                            uint n_workers) :
3887     _g1h(g1h),
3888     _pss(per_thread_states),
3889     _queues(task_queues),
3890     _workers(workers),
3891     _active_workers(n_workers)
3892   {
3893     g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
3894   }
3895 
3896   // Executes the given task using concurrent marking worker threads.
3897   virtual void execute(ProcessTask& task);
3898   virtual void execute(EnqueueTask& task);
3899 };
3900 
3901 // Gang task for possibly parallel reference processing
3902 
3903 class G1STWRefProcTaskProxy: public AbstractGangTask {
3904   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3905   ProcessTask&     _proc_task;
3906   G1CollectedHeap* _g1h;
3907   G1ParScanThreadStateSet* _pss;
3908   RefToScanQueueSet* _task_queues;
3909   ParallelTaskTerminator* _terminator;
3910 
3911 public:
3912   G1STWRefProcTaskProxy(ProcessTask& proc_task,
3913                         G1CollectedHeap* g1h,
3914                         G1ParScanThreadStateSet* per_thread_states,
3915                         RefToScanQueueSet *task_queues,
3916                         ParallelTaskTerminator* terminator) :
3917     AbstractGangTask("Process reference objects in parallel"),
3918     _proc_task(proc_task),
3919     _g1h(g1h),
3920     _pss(per_thread_states),
3921     _task_queues(task_queues),
3922     _terminator(terminator)
3923   {}
3924 
3925   virtual void work(uint worker_id) {
3926     // The reference processing task executed by a single worker.
3927     ResourceMark rm;
3928     HandleMark   hm;
3929 
3930     G1STWIsAliveClosure is_alive(_g1h);
3931 
3932     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
3933     pss->set_ref_processor(NULL);
3934 
3935     // Keep alive closure.
3936     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
3937 
3938     // Complete GC closure
3939     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
3940 
3941     // Call the reference processing task's work routine.
3942     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3943 
3944     // Note we cannot assert that the refs array is empty here as not all
3945     // of the processing tasks (specifically phase2 - pp2_work) execute
3946     // the complete_gc closure (which ordinarily would drain the queue) so
3947     // the queue may not be empty.
3948   }
3949 };
3950 
3951 // Driver routine for parallel reference processing.
3952 // Creates an instance of the ref processing gang
3953 // task and has the worker threads execute it.
3954 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
3955   assert(_workers != NULL, "Need parallel worker threads.");
3956 
3957   ParallelTaskTerminator terminator(_active_workers, _queues);
3958   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
3959 
3960   _workers->run_task(&proc_task_proxy);
3961 }
3962 
3963 // Gang task for parallel reference enqueueing.
3964 
3965 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
3966   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
3967   EnqueueTask& _enq_task;
3968 
3969 public:
3970   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
3971     AbstractGangTask("Enqueue reference objects in parallel"),
3972     _enq_task(enq_task)
3973   { }
3974 
3975   virtual void work(uint worker_id) {
3976     _enq_task.work(worker_id);
3977   }
3978 };
3979 
3980 // Driver routine for parallel reference enqueueing.
3981 // Creates an instance of the ref enqueueing gang
3982 // task and has the worker threads execute it.
3983 
3984 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
3985   assert(_workers != NULL, "Need parallel worker threads.");
3986 
3987   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
3988 
3989   _workers->run_task(&enq_task_proxy);
3990 }
3991 
3992 // End of weak reference support closures
3993 
3994 // Abstract task used to preserve (i.e. copy) any referent objects
3995 // that are in the collection set and are pointed to by reference
3996 // objects discovered by the CM ref processor.
3997 
3998 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
3999 protected:
4000   G1CollectedHeap*         _g1h;
4001   G1ParScanThreadStateSet* _pss;
4002   RefToScanQueueSet*       _queues;
4003   ParallelTaskTerminator   _terminator;
4004   uint                     _n_workers;
4005 
4006 public:
4007   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4008     AbstractGangTask("ParPreserveCMReferents"),
4009     _g1h(g1h),
4010     _pss(per_thread_states),
4011     _queues(task_queues),
4012     _terminator(workers, _queues),
4013     _n_workers(workers)
4014   {
4015     g1h->ref_processor_cm()->set_active_mt_degree(workers);
4016   }
4017 
4018   void work(uint worker_id) {
4019     G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4020 
4021     ResourceMark rm;
4022     HandleMark   hm;
4023 
4024     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4025     pss->set_ref_processor(NULL);
4026     assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4027 
4028     // Is alive closure
4029     G1AlwaysAliveClosure always_alive(_g1h);
4030 
4031     // Copying keep alive closure. Applied to referent objects that need
4032     // to be copied.
4033     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4034 
4035     ReferenceProcessor* rp = _g1h->ref_processor_cm();
4036 
4037     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4038     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4039 
4040     // limit is set using max_num_q() - which was set using ParallelGCThreads.
4041     // So this must be true - but assert just in case someone decides to
4042     // change the worker ids.
4043     assert(worker_id < limit, "sanity");
4044     assert(!rp->discovery_is_atomic(), "check this code");
4045 
4046     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4047     for (uint idx = worker_id; idx < limit; idx += stride) {
4048       DiscoveredList& ref_list = rp->discovered_refs()[idx];
4049 
4050       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4051       while (iter.has_next()) {
4052         // Since discovery is not atomic for the CM ref processor, we
4053         // can see some null referent objects.
4054         iter.load_ptrs(DEBUG_ONLY(true));
4055         oop ref = iter.obj();
4056 
4057         // This will filter nulls.
4058         if (iter.is_referent_alive()) {
4059           iter.make_referent_alive();
4060         }
4061         iter.move_to_next();
4062       }
4063     }
4064 
4065     // Drain the queue - which may cause stealing
4066     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4067     drain_queue.do_void();
4068     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4069     assert(pss->queue_is_empty(), "should be");
4070   }
4071 };
4072 
4073 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4074   // Any reference objects, in the collection set, that were 'discovered'
4075   // by the CM ref processor should have already been copied (either by
4076   // applying the external root copy closure to the discovered lists, or
4077   // by following an RSet entry).
4078   //
4079   // But some of the referents, that are in the collection set, that these
4080   // reference objects point to may not have been copied: the STW ref
4081   // processor would have seen that the reference object had already
4082   // been 'discovered' and would have skipped discovering the reference,
4083   // but would not have treated the reference object as a regular oop.
4084   // As a result the copy closure would not have been applied to the
4085   // referent object.
4086   //
4087   // We need to explicitly copy these referent objects - the references
4088   // will be processed at the end of remarking.
4089   //
4090   // We also need to do this copying before we process the reference
4091   // objects discovered by the STW ref processor in case one of these
4092   // referents points to another object which is also referenced by an
4093   // object discovered by the STW ref processor.
4094   double preserve_cm_referents_time = 0.0;
4095 
4096   // To avoid spawning task when there is no work to do, check that
4097   // a concurrent cycle is active and that some references have been
4098   // discovered.
4099   if (concurrent_mark()->cm_thread()->during_cycle() &&
4100       ref_processor_cm()->has_discovered_references()) {
4101     double preserve_cm_referents_start = os::elapsedTime();
4102     uint no_of_gc_workers = workers()->active_workers();
4103     G1ParPreserveCMReferentsTask keep_cm_referents(this,
4104                                                    per_thread_states,
4105                                                    no_of_gc_workers,
4106                                                    _task_queues);
4107     workers()->run_task(&keep_cm_referents);
4108     preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4109   }
4110 
4111   g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4112 }
4113 
4114 // Weak Reference processing during an evacuation pause (part 1).
4115 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4116   double ref_proc_start = os::elapsedTime();
4117 
4118   ReferenceProcessor* rp = _ref_processor_stw;
4119   assert(rp->discovery_enabled(), "should have been enabled");
4120 
4121   // Closure to test whether a referent is alive.
4122   G1STWIsAliveClosure is_alive(this);
4123 
4124   // Even when parallel reference processing is enabled, the processing
4125   // of JNI refs is serial and performed serially by the current thread
4126   // rather than by a worker. The following PSS will be used for processing
4127   // JNI refs.
4128 
4129   // Use only a single queue for this PSS.
4130   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
4131   pss->set_ref_processor(NULL);
4132   assert(pss->queue_is_empty(), "pre-condition");
4133 
4134   // Keep alive closure.
4135   G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4136 
4137   // Serial Complete GC closure
4138   G1STWDrainQueueClosure drain_queue(this, pss);
4139 
4140   // Setup the soft refs policy...
4141   rp->setup_policy(false);
4142 
4143   ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4144 
4145   ReferenceProcessorStats stats;
4146   if (!rp->processing_is_mt()) {
4147     // Serial reference processing...
4148     stats = rp->process_discovered_references(&is_alive,
4149                                               &keep_alive,
4150                                               &drain_queue,
4151                                               NULL,
4152                                               pt);
4153   } else {
4154     uint no_of_gc_workers = workers()->active_workers();
4155 
4156     // Parallel reference processing
4157     assert(no_of_gc_workers <= rp->max_num_q(),
4158            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4159            no_of_gc_workers,  rp->max_num_q());
4160 
4161     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4162     stats = rp->process_discovered_references(&is_alive,
4163                                               &keep_alive,
4164                                               &drain_queue,
4165                                               &par_task_executor,
4166                                               pt);
4167   }
4168 
4169   _gc_tracer_stw->report_gc_reference_stats(stats);
4170 
4171   // We have completed copying any necessary live referent objects.
4172   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4173 
4174   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4175   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4176 }
4177 
4178 // Weak Reference processing during an evacuation pause (part 2).
4179 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4180   double ref_enq_start = os::elapsedTime();
4181 
4182   ReferenceProcessor* rp = _ref_processor_stw;
4183   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4184 
4185   ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4186 
4187   // Now enqueue any remaining on the discovered lists on to
4188   // the pending list.
4189   if (!rp->processing_is_mt()) {
4190     // Serial reference processing...
4191     rp->enqueue_discovered_references(NULL, pt);
4192   } else {
4193     // Parallel reference enqueueing
4194 
4195     uint n_workers = workers()->active_workers();
4196 
4197     assert(n_workers <= rp->max_num_q(),
4198            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4199            n_workers,  rp->max_num_q());
4200 
4201     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4202     rp->enqueue_discovered_references(&par_task_executor, pt);
4203   }
4204 
4205   rp->verify_no_references_recorded();
4206   assert(!rp->discovery_enabled(), "should have been disabled");
4207 
4208   // If during an initial mark pause we install a pending list head which is not otherwise reachable
4209   // ensure that it is marked in the bitmap for concurrent marking to discover.
4210   if (collector_state()->during_initial_mark_pause()) {
4211     oop pll_head = Universe::reference_pending_list();
4212     if (pll_head != NULL) {
4213       _cm->mark_in_next_bitmap(pll_head);
4214     }
4215   }
4216 
4217   // FIXME
4218   // CM's reference processing also cleans up the string and symbol tables.
4219   // Should we do that here also? We could, but it is a serial operation
4220   // and could significantly increase the pause time.
4221 
4222   double ref_enq_time = os::elapsedTime() - ref_enq_start;
4223   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4224 }
4225 
4226 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4227   double merge_pss_time_start = os::elapsedTime();
4228   per_thread_states->flush();
4229   g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4230 }
4231 
4232 void G1CollectedHeap::pre_evacuate_collection_set() {
4233   _expand_heap_after_alloc_failure = true;
4234   _evacuation_failed = false;
4235 
4236   // Disable the hot card cache.
4237   _hot_card_cache->reset_hot_cache_claimed_index();
4238   _hot_card_cache->set_use_cache(false);
4239 
4240   g1_rem_set()->prepare_for_oops_into_collection_set_do();
4241   _preserved_marks_set.assert_empty();
4242 
4243   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4244 
4245   // InitialMark needs claim bits to keep track of the marked-through CLDs.
4246   if (collector_state()->during_initial_mark_pause()) {
4247     double start_clear_claimed_marks = os::elapsedTime();
4248 
4249     ClassLoaderDataGraph::clear_claimed_marks();
4250 
4251     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
4252     phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
4253   }
4254 }
4255 
4256 void G1CollectedHeap::evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states) {
4257   // Should G1EvacuationFailureALot be in effect for this GC?
4258   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4259 
4260   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4261 
4262   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4263 
4264   double start_par_time_sec = os::elapsedTime();
4265   double end_par_time_sec;
4266 
4267   {
4268     const uint n_workers = workers()->active_workers();
4269     G1RootProcessor root_processor(this, n_workers);
4270     G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4271 
4272     print_termination_stats_hdr();
4273 
4274     workers()->run_task(&g1_par_task);
4275     end_par_time_sec = os::elapsedTime();
4276 
4277     // Closing the inner scope will execute the destructor
4278     // for the G1RootProcessor object. We record the current
4279     // elapsed time before closing the scope so that time
4280     // taken for the destructor is NOT included in the
4281     // reported parallel time.
4282   }
4283 
4284   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4285   phase_times->record_par_time(par_time_ms);
4286 
4287   double code_root_fixup_time_ms =
4288         (os::elapsedTime() - end_par_time_sec) * 1000.0;
4289   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4290 }
4291 
4292 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4293   // Process any discovered reference objects - we have
4294   // to do this _before_ we retire the GC alloc regions
4295   // as we may have to copy some 'reachable' referent
4296   // objects (and their reachable sub-graphs) that were
4297   // not copied during the pause.
4298   if (g1_policy()->should_process_references()) {
4299     preserve_cm_referents(per_thread_states);
4300     process_discovered_references(per_thread_states);
4301   } else {
4302     ref_processor_stw()->verify_no_references_recorded();
4303   }
4304 
4305   G1STWIsAliveClosure is_alive(this);
4306   G1KeepAliveClosure keep_alive(this);
4307 
4308   {
4309     double start = os::elapsedTime();
4310 
4311     WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
4312 
4313     double time_ms = (os::elapsedTime() - start) * 1000.0;
4314     g1_policy()->phase_times()->record_ref_proc_time(time_ms);
4315   }
4316 
4317   if (G1StringDedup::is_enabled()) {
4318     double fixup_start = os::elapsedTime();
4319 
4320     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4321 
4322     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4323     g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4324   }
4325 
4326   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4327 
4328   if (evacuation_failed()) {
4329     restore_after_evac_failure();
4330 
4331     // Reset the G1EvacuationFailureALot counters and flags
4332     // Note: the values are reset only when an actual
4333     // evacuation failure occurs.
4334     NOT_PRODUCT(reset_evacuation_should_fail();)
4335   }
4336 
4337   _preserved_marks_set.assert_empty();
4338 
4339   // Enqueue any remaining references remaining on the STW
4340   // reference processor's discovered lists. We need to do
4341   // this after the card table is cleaned (and verified) as
4342   // the act of enqueueing entries on to the pending list
4343   // will log these updates (and dirty their associated
4344   // cards). We need these updates logged to update any
4345   // RSets.
4346   if (g1_policy()->should_process_references()) {
4347     enqueue_discovered_references(per_thread_states);
4348   } else {
4349     g1_policy()->phase_times()->record_ref_enq_time(0);
4350   }
4351 
4352   _allocator->release_gc_alloc_regions(evacuation_info);
4353 
4354   merge_per_thread_state_info(per_thread_states);
4355 
4356   // Reset and re-enable the hot card cache.
4357   // Note the counts for the cards in the regions in the
4358   // collection set are reset when the collection set is freed.
4359   _hot_card_cache->reset_hot_cache();
4360   _hot_card_cache->set_use_cache(true);
4361 
4362   purge_code_root_memory();
4363 
4364   redirty_logged_cards();
4365 #if COMPILER2_OR_JVMCI
4366   double start = os::elapsedTime();
4367   DerivedPointerTable::update_pointers();
4368   g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4369 #endif
4370   g1_policy()->print_age_table();
4371 }
4372 
4373 void G1CollectedHeap::record_obj_copy_mem_stats() {
4374   g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4375 
4376   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4377                                                create_g1_evac_summary(&_old_evac_stats));
4378 }
4379 
4380 void G1CollectedHeap::free_region(HeapRegion* hr,
4381                                   FreeRegionList* free_list,
4382                                   bool skip_remset,
4383                                   bool skip_hot_card_cache,
4384                                   bool locked) {
4385   assert(!hr->is_free(), "the region should not be free");
4386   assert(!hr->is_empty(), "the region should not be empty");
4387   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4388   assert(free_list != NULL, "pre-condition");
4389 
4390   if (G1VerifyBitmaps) {
4391     MemRegion mr(hr->bottom(), hr->end());
4392     concurrent_mark()->clear_range_in_prev_bitmap(mr);
4393   }
4394 
4395   // Clear the card counts for this region.
4396   // Note: we only need to do this if the region is not young
4397   // (since we don't refine cards in young regions).
4398   if (!skip_hot_card_cache && !hr->is_young()) {
4399     _hot_card_cache->reset_card_counts(hr);
4400   }
4401   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4402   free_list->add_ordered(hr);
4403 }
4404 
4405 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4406                                             FreeRegionList* free_list,
4407                                             bool skip_remset) {
4408   assert(hr->is_humongous(), "this is only for humongous regions");
4409   assert(free_list != NULL, "pre-condition");
4410   hr->clear_humongous();
4411   free_region(hr, free_list, skip_remset);
4412 }
4413 
4414 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4415                                            const uint humongous_regions_removed) {
4416   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4417     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4418     _old_set.bulk_remove(old_regions_removed);
4419     _humongous_set.bulk_remove(humongous_regions_removed);
4420   }
4421 
4422 }
4423 
4424 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4425   assert(list != NULL, "list can't be null");
4426   if (!list->is_empty()) {
4427     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4428     _hrm.insert_list_into_free_list(list);
4429   }
4430 }
4431 
4432 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4433   decrease_used(bytes);
4434 }
4435 
4436 class G1ParScrubRemSetTask: public AbstractGangTask {
4437 protected:
4438   G1RemSet* _g1rs;
4439   HeapRegionClaimer _hrclaimer;
4440 
4441 public:
4442   G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
4443     AbstractGangTask("G1 ScrubRS"),
4444     _g1rs(g1_rs),
4445     _hrclaimer(num_workers) {
4446   }
4447 
4448   void work(uint worker_id) {
4449     _g1rs->scrub(worker_id, &_hrclaimer);
4450   }
4451 };
4452 
4453 void G1CollectedHeap::scrub_rem_set() {
4454   uint num_workers = workers()->active_workers();
4455   G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
4456   workers()->run_task(&g1_par_scrub_rs_task);
4457 }
4458 
4459 class G1FreeCollectionSetTask : public AbstractGangTask {
4460 private:
4461 
4462   // Closure applied to all regions in the collection set to do work that needs to
4463   // be done serially in a single thread.
4464   class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4465   private:
4466     EvacuationInfo* _evacuation_info;
4467     const size_t* _surviving_young_words;
4468 
4469     // Bytes used in successfully evacuated regions before the evacuation.
4470     size_t _before_used_bytes;
4471     // Bytes used in unsucessfully evacuated regions before the evacuation
4472     size_t _after_used_bytes;
4473 
4474     size_t _bytes_allocated_in_old_since_last_gc;
4475 
4476     size_t _failure_used_words;
4477     size_t _failure_waste_words;
4478 
4479     FreeRegionList _local_free_list;
4480   public:
4481     G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4482       HeapRegionClosure(),
4483       _evacuation_info(evacuation_info),
4484       _surviving_young_words(surviving_young_words),
4485       _before_used_bytes(0),
4486       _after_used_bytes(0),
4487       _bytes_allocated_in_old_since_last_gc(0),
4488       _failure_used_words(0),
4489       _failure_waste_words(0),
4490       _local_free_list("Local Region List for CSet Freeing") {
4491     }
4492 
4493     virtual bool do_heap_region(HeapRegion* r) {
4494       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4495 
4496       assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4497       g1h->clear_in_cset(r);
4498 
4499       if (r->is_young()) {
4500         assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4501                "Young index %d is wrong for region %u of type %s with %u young regions",
4502                r->young_index_in_cset(),
4503                r->hrm_index(),
4504                r->get_type_str(),
4505                g1h->collection_set()->young_region_length());
4506         size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4507         r->record_surv_words_in_group(words_survived);
4508       }
4509 
4510       if (!r->evacuation_failed()) {
4511         assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4512         _before_used_bytes += r->used();
4513         g1h->free_region(r,
4514                          &_local_free_list,
4515                          true, /* skip_remset */
4516                          true, /* skip_hot_card_cache */
4517                          true  /* locked */);
4518       } else {
4519         r->uninstall_surv_rate_group();
4520         r->set_young_index_in_cset(-1);
4521         r->set_evacuation_failed(false);
4522         // When moving a young gen region to old gen, we "allocate" that whole region
4523         // there. This is in addition to any already evacuated objects. Notify the
4524         // policy about that.
4525         // Old gen regions do not cause an additional allocation: both the objects
4526         // still in the region and the ones already moved are accounted for elsewhere.
4527         if (r->is_young()) {
4528           _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4529         }
4530         // The region is now considered to be old.
4531         r->set_old();
4532         // Do some allocation statistics accounting. Regions that failed evacuation
4533         // are always made old, so there is no need to update anything in the young
4534         // gen statistics, but we need to update old gen statistics.
4535         size_t used_words = r->marked_bytes() / HeapWordSize;
4536 
4537         _failure_used_words += used_words;
4538         _failure_waste_words += HeapRegion::GrainWords - used_words;
4539 
4540         g1h->old_set_add(r);
4541         _after_used_bytes += r->used();
4542       }
4543       return false;
4544     }
4545 
4546     void complete_work() {
4547       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4548 
4549       _evacuation_info->set_regions_freed(_local_free_list.length());
4550       _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4551 
4552       g1h->prepend_to_freelist(&_local_free_list);
4553       g1h->decrement_summary_bytes(_before_used_bytes);
4554 
4555       G1Policy* policy = g1h->g1_policy();
4556       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4557 
4558       g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4559     }
4560   };
4561 
4562   G1CollectionSet* _collection_set;
4563   G1SerialFreeCollectionSetClosure _cl;
4564   const size_t* _surviving_young_words;
4565 
4566   size_t _rs_lengths;
4567 
4568   volatile jint _serial_work_claim;
4569 
4570   struct WorkItem {
4571     uint region_idx;
4572     bool is_young;
4573     bool evacuation_failed;
4574 
4575     WorkItem(HeapRegion* r) {
4576       region_idx = r->hrm_index();
4577       is_young = r->is_young();
4578       evacuation_failed = r->evacuation_failed();
4579     }
4580   };
4581 
4582   volatile size_t _parallel_work_claim;
4583   size_t _num_work_items;
4584   WorkItem* _work_items;
4585 
4586   void do_serial_work() {
4587     // Need to grab the lock to be allowed to modify the old region list.
4588     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4589     _collection_set->iterate(&_cl);
4590   }
4591 
4592   void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4593     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4594 
4595     HeapRegion* r = g1h->region_at(region_idx);
4596     assert(!g1h->is_on_master_free_list(r), "sanity");
4597 
4598     Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4599 
4600     if (!is_young) {
4601       g1h->_hot_card_cache->reset_card_counts(r);
4602     }
4603 
4604     if (!evacuation_failed) {
4605       r->rem_set()->clear_locked();
4606     }
4607   }
4608 
4609   class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4610   private:
4611     size_t _cur_idx;
4612     WorkItem* _work_items;
4613   public:
4614     G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4615 
4616     virtual bool do_heap_region(HeapRegion* r) {
4617       _work_items[_cur_idx++] = WorkItem(r);
4618       return false;
4619     }
4620   };
4621 
4622   void prepare_work() {
4623     G1PrepareFreeCollectionSetClosure cl(_work_items);
4624     _collection_set->iterate(&cl);
4625   }
4626 
4627   void complete_work() {
4628     _cl.complete_work();
4629 
4630     G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4631     policy->record_max_rs_lengths(_rs_lengths);
4632     policy->cset_regions_freed();
4633   }
4634 public:
4635   G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4636     AbstractGangTask("G1 Free Collection Set"),
4637     _cl(evacuation_info, surviving_young_words),
4638     _collection_set(collection_set),
4639     _surviving_young_words(surviving_young_words),
4640     _serial_work_claim(0),
4641     _rs_lengths(0),
4642     _parallel_work_claim(0),
4643     _num_work_items(collection_set->region_length()),
4644     _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4645     prepare_work();
4646   }
4647 
4648   ~G1FreeCollectionSetTask() {
4649     complete_work();
4650     FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4651   }
4652 
4653   // Chunk size for work distribution. The chosen value has been determined experimentally
4654   // to be a good tradeoff between overhead and achievable parallelism.
4655   static uint chunk_size() { return 32; }
4656 
4657   virtual void work(uint worker_id) {
4658     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4659 
4660     // Claim serial work.
4661     if (_serial_work_claim == 0) {
4662       jint value = Atomic::add(1, &_serial_work_claim) - 1;
4663       if (value == 0) {
4664         double serial_time = os::elapsedTime();
4665         do_serial_work();
4666         timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4667       }
4668     }
4669 
4670     // Start parallel work.
4671     double young_time = 0.0;
4672     bool has_young_time = false;
4673     double non_young_time = 0.0;
4674     bool has_non_young_time = false;
4675 
4676     while (true) {
4677       size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4678       size_t cur = end - chunk_size();
4679 
4680       if (cur >= _num_work_items) {
4681         break;
4682       }
4683 
4684       double start_time = os::elapsedTime();
4685 
4686       end = MIN2(end, _num_work_items);
4687 
4688       for (; cur < end; cur++) {
4689         bool is_young = _work_items[cur].is_young;
4690 
4691         do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4692 
4693         double end_time = os::elapsedTime();
4694         double time_taken = end_time - start_time;
4695         if (is_young) {
4696           young_time += time_taken;
4697           has_young_time = true;
4698         } else {
4699           non_young_time += time_taken;
4700           has_non_young_time = true;
4701         }
4702         start_time = end_time;
4703       }
4704     }
4705 
4706     if (has_young_time) {
4707       timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4708     }
4709     if (has_non_young_time) {
4710       timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, non_young_time);
4711     }
4712   }
4713 };
4714 
4715 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4716   _eden.clear();
4717 
4718   double free_cset_start_time = os::elapsedTime();
4719 
4720   {
4721     uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4722     uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4723 
4724     G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4725 
4726     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4727                         cl.name(),
4728                         num_workers,
4729                         _collection_set.region_length());
4730     workers()->run_task(&cl, num_workers);
4731   }
4732   g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4733 
4734   collection_set->clear();
4735 }
4736 
4737 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4738  private:
4739   FreeRegionList* _free_region_list;
4740   HeapRegionSet* _proxy_set;
4741   uint _humongous_objects_reclaimed;
4742   uint _humongous_regions_reclaimed;
4743   size_t _freed_bytes;
4744  public:
4745 
4746   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4747     _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4748   }
4749 
4750   virtual bool do_heap_region(HeapRegion* r) {
4751     if (!r->is_starts_humongous()) {
4752       return false;
4753     }
4754 
4755     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4756 
4757     oop obj = (oop)r->bottom();
4758     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4759 
4760     // The following checks whether the humongous object is live are sufficient.
4761     // The main additional check (in addition to having a reference from the roots
4762     // or the young gen) is whether the humongous object has a remembered set entry.
4763     //
4764     // A humongous object cannot be live if there is no remembered set for it
4765     // because:
4766     // - there can be no references from within humongous starts regions referencing
4767     // the object because we never allocate other objects into them.
4768     // (I.e. there are no intra-region references that may be missed by the
4769     // remembered set)
4770     // - as soon there is a remembered set entry to the humongous starts region
4771     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4772     // until the end of a concurrent mark.
4773     //
4774     // It is not required to check whether the object has been found dead by marking
4775     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4776     // all objects allocated during that time are considered live.
4777     // SATB marking is even more conservative than the remembered set.
4778     // So if at this point in the collection there is no remembered set entry,
4779     // nobody has a reference to it.
4780     // At the start of collection we flush all refinement logs, and remembered sets
4781     // are completely up-to-date wrt to references to the humongous object.
4782     //
4783     // Other implementation considerations:
4784     // - never consider object arrays at this time because they would pose
4785     // considerable effort for cleaning up the the remembered sets. This is
4786     // required because stale remembered sets might reference locations that
4787     // are currently allocated into.
4788     uint region_idx = r->hrm_index();
4789     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4790         !r->rem_set()->is_empty()) {
4791       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",
4792                                region_idx,
4793                                (size_t)obj->size() * HeapWordSize,
4794                                p2i(r->bottom()),
4795                                r->rem_set()->occupied(),
4796                                r->rem_set()->strong_code_roots_list_length(),
4797                                next_bitmap->is_marked(r->bottom()),
4798                                g1h->is_humongous_reclaim_candidate(region_idx),
4799                                obj->is_typeArray()
4800                               );
4801       return false;
4802     }
4803 
4804     guarantee(obj->is_typeArray(),
4805               "Only eagerly reclaiming type arrays is supported, but the object "
4806               PTR_FORMAT " is not.", p2i(r->bottom()));
4807 
4808     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",
4809                              region_idx,
4810                              (size_t)obj->size() * HeapWordSize,
4811                              p2i(r->bottom()),
4812                              r->rem_set()->occupied(),
4813                              r->rem_set()->strong_code_roots_list_length(),
4814                              next_bitmap->is_marked(r->bottom()),
4815                              g1h->is_humongous_reclaim_candidate(region_idx),
4816                              obj->is_typeArray()
4817                             );
4818 
4819     // Need to clear mark bit of the humongous object if already set.
4820     if (next_bitmap->is_marked(r->bottom())) {
4821       next_bitmap->clear(r->bottom());
4822     }
4823     _humongous_objects_reclaimed++;
4824     do {
4825       HeapRegion* next = g1h->next_region_in_humongous(r);
4826       _freed_bytes += r->used();
4827       r->set_containing_set(NULL);
4828       _humongous_regions_reclaimed++;
4829       g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ );
4830       r = next;
4831     } while (r != NULL);
4832 
4833     return false;
4834   }
4835 
4836   uint humongous_objects_reclaimed() {
4837     return _humongous_objects_reclaimed;
4838   }
4839 
4840   uint humongous_regions_reclaimed() {
4841     return _humongous_regions_reclaimed;
4842   }
4843 
4844   size_t bytes_freed() const {
4845     return _freed_bytes;
4846   }
4847 };
4848 
4849 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4850   assert_at_safepoint_on_vm_thread();
4851 
4852   if (!G1EagerReclaimHumongousObjects ||
4853       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4854     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4855     return;
4856   }
4857 
4858   double start_time = os::elapsedTime();
4859 
4860   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4861 
4862   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4863   heap_region_iterate(&cl);
4864 
4865   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4866 
4867   G1HRPrinter* hrp = hr_printer();
4868   if (hrp->is_active()) {
4869     FreeRegionListIterator iter(&local_cleanup_list);
4870     while (iter.more_available()) {
4871       HeapRegion* hr = iter.get_next();
4872       hrp->cleanup(hr);
4873     }
4874   }
4875 
4876   prepend_to_freelist(&local_cleanup_list);
4877   decrement_summary_bytes(cl.bytes_freed());
4878 
4879   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4880                                                                     cl.humongous_objects_reclaimed());
4881 }
4882 
4883 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4884 public:
4885   virtual bool do_heap_region(HeapRegion* r) {
4886     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4887     G1CollectedHeap::heap()->clear_in_cset(r);
4888     r->set_young_index_in_cset(-1);
4889     return false;
4890   }
4891 };
4892 
4893 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4894   G1AbandonCollectionSetClosure cl;
4895   collection_set->iterate(&cl);
4896 
4897   collection_set->clear();
4898   collection_set->stop_incremental_building();
4899 }
4900 
4901 void G1CollectedHeap::set_free_regions_coming() {
4902   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
4903 
4904   assert(!free_regions_coming(), "pre-condition");
4905   _free_regions_coming = true;
4906 }
4907 
4908 void G1CollectedHeap::reset_free_regions_coming() {
4909   assert(free_regions_coming(), "pre-condition");
4910 
4911   {
4912     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4913     _free_regions_coming = false;
4914     SecondaryFreeList_lock->notify_all();
4915   }
4916 
4917   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
4918 }
4919 
4920 void G1CollectedHeap::wait_while_free_regions_coming() {
4921   // Most of the time we won't have to wait, so let's do a quick test
4922   // first before we take the lock.
4923   if (!free_regions_coming()) {
4924     return;
4925   }
4926 
4927   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
4928 
4929   {
4930     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4931     while (free_regions_coming()) {
4932       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
4933     }
4934   }
4935 
4936   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
4937 }
4938 
4939 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4940   return _allocator->is_retained_old_region(hr);
4941 }
4942 
4943 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4944   _eden.add(hr);
4945   _g1_policy->set_region_eden(hr);
4946 }
4947 
4948 #ifdef ASSERT
4949 
4950 class NoYoungRegionsClosure: public HeapRegionClosure {
4951 private:
4952   bool _success;
4953 public:
4954   NoYoungRegionsClosure() : _success(true) { }
4955   bool do_heap_region(HeapRegion* r) {
4956     if (r->is_young()) {
4957       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4958                             p2i(r->bottom()), p2i(r->end()));
4959       _success = false;
4960     }
4961     return false;
4962   }
4963   bool success() { return _success; }
4964 };
4965 
4966 bool G1CollectedHeap::check_young_list_empty() {
4967   bool ret = (young_regions_count() == 0);
4968 
4969   NoYoungRegionsClosure closure;
4970   heap_region_iterate(&closure);
4971   ret = ret && closure.success();
4972 
4973   return ret;
4974 }
4975 
4976 #endif // ASSERT
4977 
4978 class TearDownRegionSetsClosure : public HeapRegionClosure {
4979 private:
4980   HeapRegionSet *_old_set;
4981 
4982 public:
4983   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
4984 
4985   bool do_heap_region(HeapRegion* r) {
4986     if (r->is_old()) {
4987       _old_set->remove(r);
4988     } else if(r->is_young()) {
4989       r->uninstall_surv_rate_group();
4990     } else {
4991       // We ignore free regions, we'll empty the free list afterwards.
4992       // We ignore humongous regions, we're not tearing down the
4993       // humongous regions set.
4994       assert(r->is_free() || r->is_humongous(),
4995              "it cannot be another type");
4996     }
4997     return false;
4998   }
4999 
5000   ~TearDownRegionSetsClosure() {
5001     assert(_old_set->is_empty(), "post-condition");
5002   }
5003 };
5004 
5005 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5006   assert_at_safepoint_on_vm_thread();
5007 
5008   if (!free_list_only) {
5009     TearDownRegionSetsClosure cl(&_old_set);
5010     heap_region_iterate(&cl);
5011 
5012     // Note that emptying the _young_list is postponed and instead done as
5013     // the first step when rebuilding the regions sets again. The reason for
5014     // this is that during a full GC string deduplication needs to know if
5015     // a collected region was young or old when the full GC was initiated.
5016   }
5017   _hrm.remove_all_free_regions();
5018 }
5019 
5020 void G1CollectedHeap::increase_used(size_t bytes) {
5021   _summary_bytes_used += bytes;
5022 }
5023 
5024 void G1CollectedHeap::decrease_used(size_t bytes) {
5025   assert(_summary_bytes_used >= bytes,
5026          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5027          _summary_bytes_used, bytes);
5028   _summary_bytes_used -= bytes;
5029 }
5030 
5031 void G1CollectedHeap::set_used(size_t bytes) {
5032   _summary_bytes_used = bytes;
5033 }
5034 
5035 class RebuildRegionSetsClosure : public HeapRegionClosure {
5036 private:
5037   bool            _free_list_only;
5038   HeapRegionSet*   _old_set;
5039   HeapRegionManager*   _hrm;
5040   size_t          _total_used;
5041 
5042 public:
5043   RebuildRegionSetsClosure(bool free_list_only,
5044                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
5045     _free_list_only(free_list_only),
5046     _old_set(old_set), _hrm(hrm), _total_used(0) {
5047     assert(_hrm->num_free_regions() == 0, "pre-condition");
5048     if (!free_list_only) {
5049       assert(_old_set->is_empty(), "pre-condition");
5050     }
5051   }
5052 
5053   bool do_heap_region(HeapRegion* r) {
5054     if (r->is_empty()) {
5055       // Add free regions to the free list
5056       r->set_free();
5057       _hrm->insert_into_free_list(r);
5058     } else if (!_free_list_only) {
5059 
5060       if (r->is_humongous()) {
5061         // We ignore humongous regions. We left the humongous set unchanged.
5062       } else {
5063         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
5064         // We now move all (non-humongous, non-old) regions to old gen, and register them as such.
5065         r->move_to_old();
5066         _old_set->add(r);
5067       }
5068       _total_used += r->used();
5069     }
5070 
5071     return false;
5072   }
5073 
5074   size_t total_used() {
5075     return _total_used;
5076   }
5077 };
5078 
5079 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5080   assert_at_safepoint_on_vm_thread();
5081 
5082   if (!free_list_only) {
5083     _eden.clear();
5084     _survivor.clear();
5085   }
5086 
5087   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5088   heap_region_iterate(&cl);
5089 
5090   if (!free_list_only) {
5091     set_used(cl.total_used());
5092     if (_archive_allocator != NULL) {
5093       _archive_allocator->clear_used();
5094     }
5095   }
5096   assert(used_unlocked() == recalculate_used(),
5097          "inconsistent used_unlocked(), "
5098          "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5099          used_unlocked(), recalculate_used());
5100 }
5101 
5102 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5103   HeapRegion* hr = heap_region_containing(p);
5104   return hr->is_in(p);
5105 }
5106 
5107 // Methods for the mutator alloc region
5108 
5109 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5110                                                       bool force) {
5111   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5112   bool should_allocate = g1_policy()->should_allocate_mutator_region();
5113   if (force || should_allocate) {
5114     HeapRegion* new_alloc_region = new_region(word_size,
5115                                               false /* is_old */,
5116                                               false /* do_expand */);
5117     if (new_alloc_region != NULL) {
5118       set_region_short_lived_locked(new_alloc_region);
5119       _hr_printer.alloc(new_alloc_region, !should_allocate);
5120       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5121       return new_alloc_region;
5122     }
5123   }
5124   return NULL;
5125 }
5126 
5127 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5128                                                   size_t allocated_bytes) {
5129   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5130   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5131 
5132   collection_set()->add_eden_region(alloc_region);
5133   increase_used(allocated_bytes);
5134   _hr_printer.retire(alloc_region);
5135   // We update the eden sizes here, when the region is retired,
5136   // instead of when it's allocated, since this is the point that its
5137   // used space has been recored in _summary_bytes_used.
5138   g1mm()->update_eden_size();
5139 }
5140 
5141 // Methods for the GC alloc regions
5142 
5143 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
5144   if (dest.is_old()) {
5145     return true;
5146   } else {
5147     return survivor_regions_count() < g1_policy()->max_survivor_regions();
5148   }
5149 }
5150 
5151 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
5152   assert(FreeList_lock->owned_by_self(), "pre-condition");
5153 
5154   if (!has_more_regions(dest)) {
5155     return NULL;
5156   }
5157 
5158   const bool is_survivor = dest.is_young();
5159 
5160   HeapRegion* new_alloc_region = new_region(word_size,
5161                                             !is_survivor,
5162                                             true /* do_expand */);
5163   if (new_alloc_region != NULL) {
5164     // We really only need to do this for old regions given that we
5165     // should never scan survivors. But it doesn't hurt to do it
5166     // for survivors too.
5167     new_alloc_region->record_timestamp();
5168     if (is_survivor) {
5169       new_alloc_region->set_survivor();
5170       _survivor.add(new_alloc_region);
5171       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5172     } else {
5173       new_alloc_region->set_old();
5174       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5175     }
5176     _hr_printer.alloc(new_alloc_region);
5177     bool during_im = collector_state()->during_initial_mark_pause();
5178     new_alloc_region->note_start_of_copying(during_im);
5179     return new_alloc_region;
5180   }
5181   return NULL;
5182 }
5183 
5184 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5185                                              size_t allocated_bytes,
5186                                              InCSetState dest) {
5187   bool during_im = collector_state()->during_initial_mark_pause();
5188   alloc_region->note_end_of_copying(during_im);
5189   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5190   if (dest.is_old()) {
5191     _old_set.add(alloc_region);
5192   }
5193   _hr_printer.retire(alloc_region);
5194 }
5195 
5196 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5197   bool expanded = false;
5198   uint index = _hrm.find_highest_free(&expanded);
5199 
5200   if (index != G1_NO_HRM_INDEX) {
5201     if (expanded) {
5202       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5203                                 HeapRegion::GrainWords * HeapWordSize);
5204     }
5205     _hrm.allocate_free_regions_starting_at(index, 1);
5206     return region_at(index);
5207   }
5208   return NULL;
5209 }
5210 
5211 // Optimized nmethod scanning
5212 
5213 class RegisterNMethodOopClosure: public OopClosure {
5214   G1CollectedHeap* _g1h;
5215   nmethod* _nm;
5216 
5217   template <class T> void do_oop_work(T* p) {
5218     T heap_oop = oopDesc::load_heap_oop(p);
5219     if (!oopDesc::is_null(heap_oop)) {
5220       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5221       HeapRegion* hr = _g1h->heap_region_containing(obj);
5222       assert(!hr->is_continues_humongous(),
5223              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5224              " starting at " HR_FORMAT,
5225              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5226 
5227       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5228       hr->add_strong_code_root_locked(_nm);
5229     }
5230   }
5231 
5232 public:
5233   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5234     _g1h(g1h), _nm(nm) {}
5235 
5236   void do_oop(oop* p)       { do_oop_work(p); }
5237   void do_oop(narrowOop* p) { do_oop_work(p); }
5238 };
5239 
5240 class UnregisterNMethodOopClosure: public OopClosure {
5241   G1CollectedHeap* _g1h;
5242   nmethod* _nm;
5243 
5244   template <class T> void do_oop_work(T* p) {
5245     T heap_oop = oopDesc::load_heap_oop(p);
5246     if (!oopDesc::is_null(heap_oop)) {
5247       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5248       HeapRegion* hr = _g1h->heap_region_containing(obj);
5249       assert(!hr->is_continues_humongous(),
5250              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5251              " starting at " HR_FORMAT,
5252              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5253 
5254       hr->remove_strong_code_root(_nm);
5255     }
5256   }
5257 
5258 public:
5259   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5260     _g1h(g1h), _nm(nm) {}
5261 
5262   void do_oop(oop* p)       { do_oop_work(p); }
5263   void do_oop(narrowOop* p) { do_oop_work(p); }
5264 };
5265 
5266 // Returns true if the reference points to an object that
5267 // can move in an incremental collection.
5268 bool G1CollectedHeap::is_scavengable(oop obj) {
5269   HeapRegion* hr = heap_region_containing(obj);
5270   return !hr->is_pinned();
5271 }
5272 
5273 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5274   guarantee(nm != NULL, "sanity");
5275   RegisterNMethodOopClosure reg_cl(this, nm);
5276   nm->oops_do(&reg_cl);
5277 }
5278 
5279 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5280   guarantee(nm != NULL, "sanity");
5281   UnregisterNMethodOopClosure reg_cl(this, nm);
5282   nm->oops_do(&reg_cl, true);
5283 }
5284 
5285 void G1CollectedHeap::purge_code_root_memory() {
5286   double purge_start = os::elapsedTime();
5287   G1CodeRootSet::purge();
5288   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5289   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5290 }
5291 
5292 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5293   G1CollectedHeap* _g1h;
5294 
5295 public:
5296   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5297     _g1h(g1h) {}
5298 
5299   void do_code_blob(CodeBlob* cb) {
5300     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5301     if (nm == NULL) {
5302       return;
5303     }
5304 
5305     if (ScavengeRootsInCode) {
5306       _g1h->register_nmethod(nm);
5307     }
5308   }
5309 };
5310 
5311 void G1CollectedHeap::rebuild_strong_code_roots() {
5312   RebuildStrongCodeRootClosure blob_cl(this);
5313   CodeCache::blobs_do(&blob_cl);
5314 }
5315 
5316 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
5317   GrowableArray<GCMemoryManager*> memory_managers(2);
5318   memory_managers.append(&_memory_manager);
5319   memory_managers.append(&_full_gc_memory_manager);
5320   return memory_managers;
5321 }
5322 
5323 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
5324   GrowableArray<MemoryPool*> memory_pools(3);
5325   memory_pools.append(_eden_pool);
5326   memory_pools.append(_survivor_pool);
5327   memory_pools.append(_old_pool);
5328   return memory_pools;
5329 }