1 /*
   2  * Copyright (c) 2001, 2016, 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/g1Analytics.hpp"
  32 #include "gc/g1/bufferingOopClosure.hpp"
  33 #include "gc/g1/concurrentG1Refine.hpp"
  34 #include "gc/g1/concurrentG1RefineThread.hpp"
  35 #include "gc/g1/concurrentMarkThread.inline.hpp"
  36 #include "gc/g1/g1Allocator.inline.hpp"
  37 #include "gc/g1/g1CollectedHeap.inline.hpp"
  38 #include "gc/g1/g1CollectionSet.hpp"
  39 #include "gc/g1/g1CollectorPolicy.hpp"
  40 #include "gc/g1/g1CollectorState.hpp"
  41 #include "gc/g1/g1EvacStats.inline.hpp"
  42 #include "gc/g1/g1GCPhaseTimes.hpp"
  43 #include "gc/g1/g1HeapSizingPolicy.hpp"
  44 #include "gc/g1/g1HeapTransition.hpp"
  45 #include "gc/g1/g1HeapVerifier.hpp"
  46 #include "gc/g1/g1HotCardCache.hpp"
  47 #include "gc/g1/g1MarkSweep.hpp"
  48 #include "gc/g1/g1OopClosures.inline.hpp"
  49 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  50 #include "gc/g1/g1Policy.hpp"
  51 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  52 #include "gc/g1/g1RemSet.inline.hpp"
  53 #include "gc/g1/g1RootClosures.hpp"
  54 #include "gc/g1/g1RootProcessor.hpp"
  55 #include "gc/g1/g1StringDedup.hpp"
  56 #include "gc/g1/g1YCTypes.hpp"
  57 #include "gc/g1/heapRegion.inline.hpp"
  58 #include "gc/g1/heapRegionRemSet.hpp"
  59 #include "gc/g1/heapRegionSet.inline.hpp"
  60 #include "gc/g1/suspendibleThreadSet.hpp"
  61 #include "gc/g1/vm_operations_g1.hpp"
  62 #include "gc/shared/gcHeapSummary.hpp"
  63 #include "gc/shared/gcId.hpp"
  64 #include "gc/shared/gcLocker.inline.hpp"
  65 #include "gc/shared/gcTimer.hpp"
  66 #include "gc/shared/gcTrace.hpp"
  67 #include "gc/shared/gcTraceTime.inline.hpp"
  68 #include "gc/shared/generationSpec.hpp"
  69 #include "gc/shared/isGCActiveMark.hpp"
  70 #include "gc/shared/preservedMarks.inline.hpp"
  71 #include "gc/shared/referenceProcessor.inline.hpp"
  72 #include "gc/shared/taskqueue.inline.hpp"
  73 #include "logging/log.hpp"
  74 #include "memory/allocation.hpp"
  75 #include "memory/iterator.hpp"
  76 #include "memory/resourceArea.hpp"
  77 #include "oops/oop.inline.hpp"
  78 #include "runtime/atomic.inline.hpp"
  79 #include "runtime/init.hpp"
  80 #include "runtime/orderAccess.inline.hpp"
  81 #include "runtime/vmThread.hpp"
  82 #include "utilities/globalDefinitions.hpp"
  83 #include "utilities/stack.inline.hpp"
  84 
  85 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  86 
  87 // INVARIANTS/NOTES
  88 //
  89 // All allocation activity covered by the G1CollectedHeap interface is
  90 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  91 // and allocate_new_tlab, which are the "entry" points to the
  92 // allocation code from the rest of the JVM.  (Note that this does not
  93 // apply to TLAB allocation, which is not part of this interface: it
  94 // is done by clients of this interface.)
  95 
  96 // Local to this file.
  97 
  98 class RefineCardTableEntryClosure: public CardTableEntryClosure {
  99   bool _concurrent;
 100 public:
 101   RefineCardTableEntryClosure() : _concurrent(true) { }
 102 
 103   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 104     bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, NULL);
 105     // This path is executed by the concurrent refine or mutator threads,
 106     // concurrently, and so we do not care if card_ptr contains references
 107     // that point into the collection set.
 108     assert(!oops_into_cset, "should be");
 109 
 110     if (_concurrent && SuspendibleThreadSet::should_yield()) {
 111       // Caller will actually yield.
 112       return false;
 113     }
 114     // Otherwise, we finished successfully; return true.
 115     return true;
 116   }
 117 
 118   void set_concurrent(bool b) { _concurrent = b; }
 119 };
 120 
 121 
 122 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 123  private:
 124   size_t _num_dirtied;
 125   G1CollectedHeap* _g1h;
 126   G1SATBCardTableLoggingModRefBS* _g1_bs;
 127 
 128   HeapRegion* region_for_card(jbyte* card_ptr) const {
 129     return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
 130   }
 131 
 132   bool will_become_free(HeapRegion* hr) const {
 133     // A region will be freed by free_collection_set if the region is in the
 134     // collection set and has not had an evacuation failure.
 135     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 136   }
 137 
 138  public:
 139   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
 140     _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
 141 
 142   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 143     HeapRegion* hr = region_for_card(card_ptr);
 144 
 145     // Should only dirty cards in regions that won't be freed.
 146     if (!will_become_free(hr)) {
 147       *card_ptr = CardTableModRefBS::dirty_card_val();
 148       _num_dirtied++;
 149     }
 150 
 151     return true;
 152   }
 153 
 154   size_t num_dirtied()   const { return _num_dirtied; }
 155 };
 156 
 157 
 158 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 159   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 160 }
 161 
 162 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 163   // The from card cache is not the memory that is actually committed. So we cannot
 164   // take advantage of the zero_filled parameter.
 165   reset_from_card_cache(start_idx, num_regions);
 166 }
 167 
 168 // Returns true if the reference points to an object that
 169 // can move in an incremental collection.
 170 bool G1CollectedHeap::is_scavengable(const void* p) {
 171   HeapRegion* hr = heap_region_containing(p);
 172   return !hr->is_pinned();
 173 }
 174 
 175 // Private methods.
 176 
 177 HeapRegion*
 178 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 179   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 180   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 181     if (!_secondary_free_list.is_empty()) {
 182       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 183                                       "secondary_free_list has %u entries",
 184                                       _secondary_free_list.length());
 185       // It looks as if there are free regions available on the
 186       // secondary_free_list. Let's move them to the free_list and try
 187       // again to allocate from it.
 188       append_secondary_free_list();
 189 
 190       assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
 191              "empty we should have moved at least one entry to the free_list");
 192       HeapRegion* res = _hrm.allocate_free_region(is_old);
 193       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 194                                       "allocated " HR_FORMAT " from secondary_free_list",
 195                                       HR_FORMAT_PARAMS(res));
 196       return res;
 197     }
 198 
 199     // Wait here until we get notified either when (a) there are no
 200     // more free regions coming or (b) some regions have been moved on
 201     // the secondary_free_list.
 202     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 203   }
 204 
 205   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 206                                   "could not allocate from secondary_free_list");
 207   return NULL;
 208 }
 209 
 210 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 211   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 212          "the only time we use this to allocate a humongous region is "
 213          "when we are allocating a single humongous region");
 214 
 215   HeapRegion* res;
 216   if (G1StressConcRegionFreeing) {
 217     if (!_secondary_free_list.is_empty()) {
 218       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 219                                       "forced to look at the secondary_free_list");
 220       res = new_region_try_secondary_free_list(is_old);
 221       if (res != NULL) {
 222         return res;
 223       }
 224     }
 225   }
 226 
 227   res = _hrm.allocate_free_region(is_old);
 228 
 229   if (res == NULL) {
 230     log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 231                                     "res == NULL, trying the secondary_free_list");
 232     res = new_region_try_secondary_free_list(is_old);
 233   }
 234   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 235     // Currently, only attempts to allocate GC alloc regions set
 236     // do_expand to true. So, we should only reach here during a
 237     // safepoint. If this assumption changes we might have to
 238     // reconsider the use of _expand_heap_after_alloc_failure.
 239     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 240 
 241     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 242                               word_size * HeapWordSize);
 243 
 244     if (expand(word_size * HeapWordSize)) {
 245       // Given that expand() succeeded in expanding the heap, and we
 246       // always expand the heap by an amount aligned to the heap
 247       // region size, the free list should in theory not be empty.
 248       // In either case allocate_free_region() will check for NULL.
 249       res = _hrm.allocate_free_region(is_old);
 250     } else {
 251       _expand_heap_after_alloc_failure = false;
 252     }
 253   }
 254   return res;
 255 }
 256 
 257 HeapWord*
 258 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 259                                                            uint num_regions,
 260                                                            size_t word_size,
 261                                                            AllocationContext_t context) {
 262   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 263   assert(is_humongous(word_size), "word_size should be humongous");
 264   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 265 
 266   // Index of last region in the series.
 267   uint last = first + num_regions - 1;
 268 
 269   // We need to initialize the region(s) we just discovered. This is
 270   // a bit tricky given that it can happen concurrently with
 271   // refinement threads refining cards on these regions and
 272   // potentially wanting to refine the BOT as they are scanning
 273   // those cards (this can happen shortly after a cleanup; see CR
 274   // 6991377). So we have to set up the region(s) carefully and in
 275   // a specific order.
 276 
 277   // The word size sum of all the regions we will allocate.
 278   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 279   assert(word_size <= word_size_sum, "sanity");
 280 
 281   // This will be the "starts humongous" region.
 282   HeapRegion* first_hr = region_at(first);
 283   // The header of the new object will be placed at the bottom of
 284   // the first region.
 285   HeapWord* new_obj = first_hr->bottom();
 286   // This will be the new top of the new object.
 287   HeapWord* obj_top = new_obj + word_size;
 288 
 289   // First, we need to zero the header of the space that we will be
 290   // allocating. When we update top further down, some refinement
 291   // threads might try to scan the region. By zeroing the header we
 292   // ensure that any thread that will try to scan the region will
 293   // come across the zero klass word and bail out.
 294   //
 295   // NOTE: It would not have been correct to have used
 296   // CollectedHeap::fill_with_object() and make the space look like
 297   // an int array. The thread that is doing the allocation will
 298   // later update the object header to a potentially different array
 299   // type and, for a very short period of time, the klass and length
 300   // fields will be inconsistent. This could cause a refinement
 301   // thread to calculate the object size incorrectly.
 302   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 303 
 304   // How many words we use for filler objects.
 305   size_t word_fill_size = word_size_sum - word_size;
 306 
 307   // How many words memory we "waste" which cannot hold a filler object.
 308   size_t words_not_fillable = 0;
 309 
 310   if (word_fill_size >= min_fill_size()) {
 311     fill_with_objects(obj_top, word_fill_size);
 312   } else if (word_fill_size > 0) {
 313     // We have space to fill, but we cannot fit an object there.
 314     words_not_fillable = word_fill_size;
 315     word_fill_size = 0;
 316   }
 317 
 318   // We will set up the first region as "starts humongous". This
 319   // will also update the BOT covering all the regions to reflect
 320   // that there is a single object that starts at the bottom of the
 321   // first region.
 322   first_hr->set_starts_humongous(obj_top, word_fill_size);
 323   first_hr->set_allocation_context(context);
 324   // Then, if there are any, we will set up the "continues
 325   // humongous" regions.
 326   HeapRegion* hr = NULL;
 327   for (uint i = first + 1; i <= last; ++i) {
 328     hr = region_at(i);
 329     hr->set_continues_humongous(first_hr);
 330     hr->set_allocation_context(context);
 331   }
 332 
 333   // Up to this point no concurrent thread would have been able to
 334   // do any scanning on any region in this series. All the top
 335   // fields still point to bottom, so the intersection between
 336   // [bottom,top] and [card_start,card_end] will be empty. Before we
 337   // update the top fields, we'll do a storestore to make sure that
 338   // no thread sees the update to top before the zeroing of the
 339   // object header and the BOT initialization.
 340   OrderAccess::storestore();
 341 
 342   // Now, we will update the top fields of the "continues humongous"
 343   // regions except the last one.
 344   for (uint i = first; i < last; ++i) {
 345     hr = region_at(i);
 346     hr->set_top(hr->end());
 347   }
 348 
 349   hr = region_at(last);
 350   // If we cannot fit a filler object, we must set top to the end
 351   // of the humongous object, otherwise we cannot iterate the heap
 352   // and the BOT will not be complete.
 353   hr->set_top(hr->end() - words_not_fillable);
 354 
 355   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 356          "obj_top should be in last region");
 357 
 358   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 359 
 360   assert(words_not_fillable == 0 ||
 361          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 362          "Miscalculation in humongous allocation");
 363 
 364   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 365 
 366   for (uint i = first; i <= last; ++i) {
 367     hr = region_at(i);
 368     _humongous_set.add(hr);
 369     _hr_printer.alloc(hr);
 370   }
 371 
 372   return new_obj;
 373 }
 374 
 375 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 376   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 377   return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 378 }
 379 
 380 // If could fit into free regions w/o expansion, try.
 381 // Otherwise, if can expand, do so.
 382 // Otherwise, if using ex regions might help, try with ex given back.
 383 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
 384   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 385 
 386   _verifier->verify_region_sets_optional();
 387 
 388   uint first = G1_NO_HRM_INDEX;
 389   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 390 
 391   if (obj_regions == 1) {
 392     // Only one region to allocate, try to use a fast path by directly allocating
 393     // from the free lists. Do not try to expand here, we will potentially do that
 394     // later.
 395     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 396     if (hr != NULL) {
 397       first = hr->hrm_index();
 398     }
 399   } else {
 400     // We can't allocate humongous regions spanning more than one region while
 401     // cleanupComplete() is running, since some of the regions we find to be
 402     // empty might not yet be added to the free list. It is not straightforward
 403     // to know in which list they are on so that we can remove them. We only
 404     // need to do this if we need to allocate more than one region to satisfy the
 405     // current humongous allocation request. If we are only allocating one region
 406     // we use the one-region region allocation code (see above), that already
 407     // potentially waits for regions from the secondary free list.
 408     wait_while_free_regions_coming();
 409     append_secondary_free_list_if_not_empty_with_lock();
 410 
 411     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 412     // are lucky enough to find some.
 413     first = _hrm.find_contiguous_only_empty(obj_regions);
 414     if (first != G1_NO_HRM_INDEX) {
 415       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 416     }
 417   }
 418 
 419   if (first == G1_NO_HRM_INDEX) {
 420     // Policy: We could not find enough regions for the humongous object in the
 421     // free list. Look through the heap to find a mix of free and uncommitted regions.
 422     // If so, try expansion.
 423     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 424     if (first != G1_NO_HRM_INDEX) {
 425       // We found something. Make sure these regions are committed, i.e. expand
 426       // the heap. Alternatively we could do a defragmentation GC.
 427       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 428                                     word_size * HeapWordSize);
 429 
 430 
 431       _hrm.expand_at(first, obj_regions);
 432       g1_policy()->record_new_heap_size(num_regions());
 433 
 434 #ifdef ASSERT
 435       for (uint i = first; i < first + obj_regions; ++i) {
 436         HeapRegion* hr = region_at(i);
 437         assert(hr->is_free(), "sanity");
 438         assert(hr->is_empty(), "sanity");
 439         assert(is_on_master_free_list(hr), "sanity");
 440       }
 441 #endif
 442       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 443     } else {
 444       // Policy: Potentially trigger a defragmentation GC.
 445     }
 446   }
 447 
 448   HeapWord* result = NULL;
 449   if (first != G1_NO_HRM_INDEX) {
 450     result = humongous_obj_allocate_initialize_regions(first, obj_regions,
 451                                                        word_size, context);
 452     assert(result != NULL, "it should always return a valid result");
 453 
 454     // A successful humongous object allocation changes the used space
 455     // information of the old generation so we need to recalculate the
 456     // sizes and update the jstat counters here.
 457     g1mm()->update_sizes();
 458   }
 459 
 460   _verifier->verify_region_sets_optional();
 461 
 462   return result;
 463 }
 464 
 465 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 466   assert_heap_not_locked_and_not_at_safepoint();
 467   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 468 
 469   uint dummy_gc_count_before;
 470   uint dummy_gclocker_retry_count = 0;
 471   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 472 }
 473 
 474 HeapWord*
 475 G1CollectedHeap::mem_allocate(size_t word_size,
 476                               bool*  gc_overhead_limit_was_exceeded) {
 477   assert_heap_not_locked_and_not_at_safepoint();
 478 
 479   // Loop until the allocation is satisfied, or unsatisfied after GC.
 480   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 481     uint gc_count_before;
 482 
 483     HeapWord* result = NULL;
 484     if (!is_humongous(word_size)) {
 485       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 486     } else {
 487       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 488     }
 489     if (result != NULL) {
 490       return result;
 491     }
 492 
 493     // Create the garbage collection operation...
 494     VM_G1CollectForAllocation op(gc_count_before, word_size);
 495     op.set_allocation_context(AllocationContext::current());
 496 
 497     // ...and get the VM thread to execute it.
 498     VMThread::execute(&op);
 499 
 500     if (op.prologue_succeeded() && op.pause_succeeded()) {
 501       // If the operation was successful we'll return the result even
 502       // if it is NULL. If the allocation attempt failed immediately
 503       // after a Full GC, it's unlikely we'll be able to allocate now.
 504       HeapWord* result = op.result();
 505       if (result != NULL && !is_humongous(word_size)) {
 506         // Allocations that take place on VM operations do not do any
 507         // card dirtying and we have to do it here. We only have to do
 508         // this for non-humongous allocations, though.
 509         dirty_young_block(result, word_size);
 510       }
 511       return result;
 512     } else {
 513       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 514         return NULL;
 515       }
 516       assert(op.result() == NULL,
 517              "the result should be NULL if the VM op did not succeed");
 518     }
 519 
 520     // Give a warning if we seem to be looping forever.
 521     if ((QueuedAllocationWarningCount > 0) &&
 522         (try_count % QueuedAllocationWarningCount == 0)) {
 523       log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
 524     }
 525   }
 526 
 527   ShouldNotReachHere();
 528   return NULL;
 529 }
 530 
 531 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 532                                                    AllocationContext_t context,
 533                                                    uint* gc_count_before_ret,
 534                                                    uint* gclocker_retry_count_ret) {
 535   // Make sure you read the note in attempt_allocation_humongous().
 536 
 537   assert_heap_not_locked_and_not_at_safepoint();
 538   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 539          "be called for humongous allocation requests");
 540 
 541   // We should only get here after the first-level allocation attempt
 542   // (attempt_allocation()) failed to allocate.
 543 
 544   // We will loop until a) we manage to successfully perform the
 545   // allocation or b) we successfully schedule a collection which
 546   // fails to perform the allocation. b) is the only case when we'll
 547   // return NULL.
 548   HeapWord* result = NULL;
 549   for (int try_count = 1; /* we'll return */; try_count += 1) {
 550     bool should_try_gc;
 551     uint gc_count_before;
 552 
 553     {
 554       MutexLockerEx x(Heap_lock);
 555       result = _allocator->attempt_allocation_locked(word_size, context);
 556       if (result != NULL) {
 557         return result;
 558       }
 559 
 560       if (GCLocker::is_active_and_needs_gc()) {
 561         if (g1_policy()->can_expand_young_list()) {
 562           // No need for an ergo verbose message here,
 563           // can_expand_young_list() does this when it returns true.
 564           result = _allocator->attempt_allocation_force(word_size, context);
 565           if (result != NULL) {
 566             return result;
 567           }
 568         }
 569         should_try_gc = false;
 570       } else {
 571         // The GCLocker may not be active but the GCLocker initiated
 572         // GC may not yet have been performed (GCLocker::needs_gc()
 573         // returns true). In this case we do not try this GC and
 574         // wait until the GCLocker initiated GC is performed, and
 575         // then retry the allocation.
 576         if (GCLocker::needs_gc()) {
 577           should_try_gc = false;
 578         } else {
 579           // Read the GC count while still holding the Heap_lock.
 580           gc_count_before = total_collections();
 581           should_try_gc = true;
 582         }
 583       }
 584     }
 585 
 586     if (should_try_gc) {
 587       bool succeeded;
 588       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 589                                    GCCause::_g1_inc_collection_pause);
 590       if (result != NULL) {
 591         assert(succeeded, "only way to get back a non-NULL result");
 592         return result;
 593       }
 594 
 595       if (succeeded) {
 596         // If we get here we successfully scheduled a collection which
 597         // failed to allocate. No point in trying to allocate
 598         // further. We'll just return NULL.
 599         MutexLockerEx x(Heap_lock);
 600         *gc_count_before_ret = total_collections();
 601         return NULL;
 602       }
 603     } else {
 604       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 605         MutexLockerEx x(Heap_lock);
 606         *gc_count_before_ret = total_collections();
 607         return NULL;
 608       }
 609       // The GCLocker is either active or the GCLocker initiated
 610       // GC has not yet been performed. Stall until it is and
 611       // then retry the allocation.
 612       GCLocker::stall_until_clear();
 613       (*gclocker_retry_count_ret) += 1;
 614     }
 615 
 616     // We can reach here if we were unsuccessful in scheduling a
 617     // collection (because another thread beat us to it) or if we were
 618     // stalled due to the GC locker. In either can we should retry the
 619     // allocation attempt in case another thread successfully
 620     // performed a collection and reclaimed enough space. We do the
 621     // first attempt (without holding the Heap_lock) here and the
 622     // follow-on attempt will be at the start of the next loop
 623     // iteration (after taking the Heap_lock).
 624     result = _allocator->attempt_allocation(word_size, context);
 625     if (result != NULL) {
 626       return result;
 627     }
 628 
 629     // Give a warning if we seem to be looping forever.
 630     if ((QueuedAllocationWarningCount > 0) &&
 631         (try_count % QueuedAllocationWarningCount == 0)) {
 632       log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
 633                       "retries %d times", try_count);
 634     }
 635   }
 636 
 637   ShouldNotReachHere();
 638   return NULL;
 639 }
 640 
 641 void G1CollectedHeap::begin_archive_alloc_range() {
 642   assert_at_safepoint(true /* should_be_vm_thread */);
 643   if (_archive_allocator == NULL) {
 644     _archive_allocator = G1ArchiveAllocator::create_allocator(this);
 645   }
 646 }
 647 
 648 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 649   // Allocations in archive regions cannot be of a size that would be considered
 650   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 651   // may be different at archive-restore time.
 652   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 653 }
 654 
 655 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 656   assert_at_safepoint(true /* should_be_vm_thread */);
 657   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 658   if (is_archive_alloc_too_large(word_size)) {
 659     return NULL;
 660   }
 661   return _archive_allocator->archive_mem_allocate(word_size);
 662 }
 663 
 664 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 665                                               size_t end_alignment_in_bytes) {
 666   assert_at_safepoint(true /* should_be_vm_thread */);
 667   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 668 
 669   // Call complete_archive to do the real work, filling in the MemRegion
 670   // array with the archive regions.
 671   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 672   delete _archive_allocator;
 673   _archive_allocator = NULL;
 674 }
 675 
 676 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 677   assert(ranges != NULL, "MemRegion array NULL");
 678   assert(count != 0, "No MemRegions provided");
 679   MemRegion reserved = _hrm.reserved();
 680   for (size_t i = 0; i < count; i++) {
 681     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 682       return false;
 683     }
 684   }
 685   return true;
 686 }
 687 
 688 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) {
 689   assert(!is_init_completed(), "Expect to be called at JVM init time");
 690   assert(ranges != NULL, "MemRegion array NULL");
 691   assert(count != 0, "No MemRegions provided");
 692   MutexLockerEx x(Heap_lock);
 693 
 694   MemRegion reserved = _hrm.reserved();
 695   HeapWord* prev_last_addr = NULL;
 696   HeapRegion* prev_last_region = NULL;
 697 
 698   // Temporarily disable pretouching of heap pages. This interface is used
 699   // when mmap'ing archived heap data in, so pre-touching is wasted.
 700   FlagSetting fs(AlwaysPreTouch, false);
 701 
 702   // Enable archive object checking in G1MarkSweep. We have to let it know
 703   // about each archive range, so that objects in those ranges aren't marked.
 704   G1MarkSweep::enable_archive_object_check();
 705 
 706   // For each specified MemRegion range, allocate the corresponding G1
 707   // regions and mark them as archive regions. We expect the ranges in
 708   // ascending starting address order, without overlap.
 709   for (size_t i = 0; i < count; i++) {
 710     MemRegion curr_range = ranges[i];
 711     HeapWord* start_address = curr_range.start();
 712     size_t word_size = curr_range.word_size();
 713     HeapWord* last_address = curr_range.last();
 714     size_t commits = 0;
 715 
 716     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 717               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 718               p2i(start_address), p2i(last_address));
 719     guarantee(start_address > prev_last_addr,
 720               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 721               p2i(start_address), p2i(prev_last_addr));
 722     prev_last_addr = last_address;
 723 
 724     // Check for ranges that start in the same G1 region in which the previous
 725     // range ended, and adjust the start address so we don't try to allocate
 726     // the same region again. If the current range is entirely within that
 727     // region, skip it, just adjusting the recorded top.
 728     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 729     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 730       start_address = start_region->end();
 731       if (start_address > last_address) {
 732         increase_used(word_size * HeapWordSize);
 733         start_region->set_top(last_address + 1);
 734         continue;
 735       }
 736       start_region->set_top(start_address);
 737       curr_range = MemRegion(start_address, last_address + 1);
 738       start_region = _hrm.addr_to_region(start_address);
 739     }
 740 
 741     // Perform the actual region allocation, exiting if it fails.
 742     // Then note how much new space we have allocated.
 743     if (!_hrm.allocate_containing_regions(curr_range, &commits)) {
 744       return false;
 745     }
 746     increase_used(word_size * HeapWordSize);
 747     if (commits != 0) {
 748       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 749                                 HeapRegion::GrainWords * HeapWordSize * commits);
 750 
 751     }
 752 
 753     // Mark each G1 region touched by the range as archive, add it to the old set,
 754     // and set the allocation context and top.
 755     HeapRegion* curr_region = _hrm.addr_to_region(start_address);
 756     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 757     prev_last_region = last_region;
 758 
 759     while (curr_region != NULL) {
 760       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 761              "Region already in use (index %u)", curr_region->hrm_index());
 762       curr_region->set_allocation_context(AllocationContext::system());
 763       curr_region->set_archive();
 764       _hr_printer.alloc(curr_region);
 765       _old_set.add(curr_region);
 766       if (curr_region != last_region) {
 767         curr_region->set_top(curr_region->end());
 768         curr_region = _hrm.next_region_in_heap(curr_region);
 769       } else {
 770         curr_region->set_top(last_address + 1);
 771         curr_region = NULL;
 772       }
 773     }
 774 
 775     // Notify mark-sweep of the archive range.
 776     G1MarkSweep::set_range_archive(curr_range, true);
 777   }
 778   return true;
 779 }
 780 
 781 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 782   assert(!is_init_completed(), "Expect to be called at JVM init time");
 783   assert(ranges != NULL, "MemRegion array NULL");
 784   assert(count != 0, "No MemRegions provided");
 785   MemRegion reserved = _hrm.reserved();
 786   HeapWord *prev_last_addr = NULL;
 787   HeapRegion* prev_last_region = NULL;
 788 
 789   // For each MemRegion, create filler objects, if needed, in the G1 regions
 790   // that contain the address range. The address range actually within the
 791   // MemRegion will not be modified. That is assumed to have been initialized
 792   // elsewhere, probably via an mmap of archived heap data.
 793   MutexLockerEx x(Heap_lock);
 794   for (size_t i = 0; i < count; i++) {
 795     HeapWord* start_address = ranges[i].start();
 796     HeapWord* last_address = ranges[i].last();
 797 
 798     assert(reserved.contains(start_address) && reserved.contains(last_address),
 799            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 800            p2i(start_address), p2i(last_address));
 801     assert(start_address > prev_last_addr,
 802            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 803            p2i(start_address), p2i(prev_last_addr));
 804 
 805     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 806     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 807     HeapWord* bottom_address = start_region->bottom();
 808 
 809     // Check for a range beginning in the same region in which the
 810     // previous one ended.
 811     if (start_region == prev_last_region) {
 812       bottom_address = prev_last_addr + 1;
 813     }
 814 
 815     // Verify that the regions were all marked as archive regions by
 816     // alloc_archive_regions.
 817     HeapRegion* curr_region = start_region;
 818     while (curr_region != NULL) {
 819       guarantee(curr_region->is_archive(),
 820                 "Expected archive region at index %u", curr_region->hrm_index());
 821       if (curr_region != last_region) {
 822         curr_region = _hrm.next_region_in_heap(curr_region);
 823       } else {
 824         curr_region = NULL;
 825       }
 826     }
 827 
 828     prev_last_addr = last_address;
 829     prev_last_region = last_region;
 830 
 831     // Fill the memory below the allocated range with dummy object(s),
 832     // if the region bottom does not match the range start, or if the previous
 833     // range ended within the same G1 region, and there is a gap.
 834     if (start_address != bottom_address) {
 835       size_t fill_size = pointer_delta(start_address, bottom_address);
 836       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 837       increase_used(fill_size * HeapWordSize);
 838     }
 839   }
 840 }
 841 
 842 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
 843                                                      uint* gc_count_before_ret,
 844                                                      uint* gclocker_retry_count_ret) {
 845   assert_heap_not_locked_and_not_at_safepoint();
 846   assert(!is_humongous(word_size), "attempt_allocation() should not "
 847          "be called for humongous allocation requests");
 848 
 849   AllocationContext_t context = AllocationContext::current();
 850   HeapWord* result = _allocator->attempt_allocation(word_size, context);
 851 
 852   if (result == NULL) {
 853     result = attempt_allocation_slow(word_size,
 854                                      context,
 855                                      gc_count_before_ret,
 856                                      gclocker_retry_count_ret);
 857   }
 858   assert_heap_not_locked();
 859   if (result != NULL) {
 860     dirty_young_block(result, word_size);
 861   }
 862   return result;
 863 }
 864 
 865 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
 866   assert(!is_init_completed(), "Expect to be called at JVM init time");
 867   assert(ranges != NULL, "MemRegion array NULL");
 868   assert(count != 0, "No MemRegions provided");
 869   MemRegion reserved = _hrm.reserved();
 870   HeapWord* prev_last_addr = NULL;
 871   HeapRegion* prev_last_region = NULL;
 872   size_t size_used = 0;
 873   size_t uncommitted_regions = 0;
 874 
 875   // For each Memregion, free the G1 regions that constitute it, and
 876   // notify mark-sweep that the range is no longer to be considered 'archive.'
 877   MutexLockerEx x(Heap_lock);
 878   for (size_t i = 0; i < count; i++) {
 879     HeapWord* start_address = ranges[i].start();
 880     HeapWord* last_address = ranges[i].last();
 881 
 882     assert(reserved.contains(start_address) && reserved.contains(last_address),
 883            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 884            p2i(start_address), p2i(last_address));
 885     assert(start_address > prev_last_addr,
 886            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 887            p2i(start_address), p2i(prev_last_addr));
 888     size_used += ranges[i].byte_size();
 889     prev_last_addr = last_address;
 890 
 891     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 892     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 893 
 894     // Check for ranges that start in the same G1 region in which the previous
 895     // range ended, and adjust the start address so we don't try to free
 896     // the same region again. If the current range is entirely within that
 897     // region, skip it.
 898     if (start_region == prev_last_region) {
 899       start_address = start_region->end();
 900       if (start_address > last_address) {
 901         continue;
 902       }
 903       start_region = _hrm.addr_to_region(start_address);
 904     }
 905     prev_last_region = last_region;
 906 
 907     // After verifying that each region was marked as an archive region by
 908     // alloc_archive_regions, set it free and empty and uncommit it.
 909     HeapRegion* curr_region = start_region;
 910     while (curr_region != NULL) {
 911       guarantee(curr_region->is_archive(),
 912                 "Expected archive region at index %u", curr_region->hrm_index());
 913       uint curr_index = curr_region->hrm_index();
 914       _old_set.remove(curr_region);
 915       curr_region->set_free();
 916       curr_region->set_top(curr_region->bottom());
 917       if (curr_region != last_region) {
 918         curr_region = _hrm.next_region_in_heap(curr_region);
 919       } else {
 920         curr_region = NULL;
 921       }
 922       _hrm.shrink_at(curr_index, 1);
 923       uncommitted_regions++;
 924     }
 925 
 926     // Notify mark-sweep that this is no longer an archive range.
 927     G1MarkSweep::set_range_archive(ranges[i], false);
 928   }
 929 
 930   if (uncommitted_regions != 0) {
 931     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 932                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 933   }
 934   decrease_used(size_used);
 935 }
 936 
 937 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
 938                                                         uint* gc_count_before_ret,
 939                                                         uint* gclocker_retry_count_ret) {
 940   // The structure of this method has a lot of similarities to
 941   // attempt_allocation_slow(). The reason these two were not merged
 942   // into a single one is that such a method would require several "if
 943   // allocation is not humongous do this, otherwise do that"
 944   // conditional paths which would obscure its flow. In fact, an early
 945   // version of this code did use a unified method which was harder to
 946   // follow and, as a result, it had subtle bugs that were hard to
 947   // track down. So keeping these two methods separate allows each to
 948   // be more readable. It will be good to keep these two in sync as
 949   // much as possible.
 950 
 951   assert_heap_not_locked_and_not_at_safepoint();
 952   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 953          "should only be called for humongous allocations");
 954 
 955   // Humongous objects can exhaust the heap quickly, so we should check if we
 956   // need to start a marking cycle at each humongous object allocation. We do
 957   // the check before we do the actual allocation. The reason for doing it
 958   // before the allocation is that we avoid having to keep track of the newly
 959   // allocated memory while we do a GC.
 960   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
 961                                            word_size)) {
 962     collect(GCCause::_g1_humongous_allocation);
 963   }
 964 
 965   // We will loop until a) we manage to successfully perform the
 966   // allocation or b) we successfully schedule a collection which
 967   // fails to perform the allocation. b) is the only case when we'll
 968   // return NULL.
 969   HeapWord* result = NULL;
 970   for (int try_count = 1; /* we'll return */; try_count += 1) {
 971     bool should_try_gc;
 972     uint gc_count_before;
 973 
 974     {
 975       MutexLockerEx x(Heap_lock);
 976 
 977       // Given that humongous objects are not allocated in young
 978       // regions, we'll first try to do the allocation without doing a
 979       // collection hoping that there's enough space in the heap.
 980       result = humongous_obj_allocate(word_size, AllocationContext::current());
 981       if (result != NULL) {
 982         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 983         g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 984         return result;
 985       }
 986 
 987       if (GCLocker::is_active_and_needs_gc()) {
 988         should_try_gc = false;
 989       } else {
 990          // The GCLocker may not be active but the GCLocker initiated
 991         // GC may not yet have been performed (GCLocker::needs_gc()
 992         // returns true). In this case we do not try this GC and
 993         // wait until the GCLocker initiated GC is performed, and
 994         // then retry the allocation.
 995         if (GCLocker::needs_gc()) {
 996           should_try_gc = false;
 997         } else {
 998           // Read the GC count while still holding the Heap_lock.
 999           gc_count_before = total_collections();
1000           should_try_gc = true;
1001         }
1002       }
1003     }
1004 
1005     if (should_try_gc) {
1006       // If we failed to allocate the humongous object, we should try to
1007       // do a collection pause (if we're allowed) in case it reclaims
1008       // enough space for the allocation to succeed after the pause.
1009 
1010       bool succeeded;
1011       result = do_collection_pause(word_size, gc_count_before, &succeeded,
1012                                    GCCause::_g1_humongous_allocation);
1013       if (result != NULL) {
1014         assert(succeeded, "only way to get back a non-NULL result");
1015         return result;
1016       }
1017 
1018       if (succeeded) {
1019         // If we get here we successfully scheduled a collection which
1020         // failed to allocate. No point in trying to allocate
1021         // further. We'll just return NULL.
1022         MutexLockerEx x(Heap_lock);
1023         *gc_count_before_ret = total_collections();
1024         return NULL;
1025       }
1026     } else {
1027       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1028         MutexLockerEx x(Heap_lock);
1029         *gc_count_before_ret = total_collections();
1030         return NULL;
1031       }
1032       // The GCLocker is either active or the GCLocker initiated
1033       // GC has not yet been performed. Stall until it is and
1034       // then retry the allocation.
1035       GCLocker::stall_until_clear();
1036       (*gclocker_retry_count_ret) += 1;
1037     }
1038 
1039     // We can reach here if we were unsuccessful in scheduling a
1040     // collection (because another thread beat us to it) or if we were
1041     // stalled due to the GC locker. In either can we should retry the
1042     // allocation attempt in case another thread successfully
1043     // performed a collection and reclaimed enough space.  Give a
1044     // warning if we seem to be looping forever.
1045 
1046     if ((QueuedAllocationWarningCount > 0) &&
1047         (try_count % QueuedAllocationWarningCount == 0)) {
1048       log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
1049                       "retries %d times", try_count);
1050     }
1051   }
1052 
1053   ShouldNotReachHere();
1054   return NULL;
1055 }
1056 
1057 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1058                                                            AllocationContext_t context,
1059                                                            bool expect_null_mutator_alloc_region) {
1060   assert_at_safepoint(true /* should_be_vm_thread */);
1061   assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1062          "the current alloc region was unexpectedly found to be non-NULL");
1063 
1064   if (!is_humongous(word_size)) {
1065     return _allocator->attempt_allocation_locked(word_size, context);
1066   } else {
1067     HeapWord* result = humongous_obj_allocate(word_size, context);
1068     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1069       collector_state()->set_initiate_conc_mark_if_possible(true);
1070     }
1071     return result;
1072   }
1073 
1074   ShouldNotReachHere();
1075 }
1076 
1077 class PostMCRemSetClearClosure: public HeapRegionClosure {
1078   G1CollectedHeap* _g1h;
1079   ModRefBarrierSet* _mr_bs;
1080 public:
1081   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1082     _g1h(g1h), _mr_bs(mr_bs) {}
1083 
1084   bool doHeapRegion(HeapRegion* r) {
1085     HeapRegionRemSet* hrrs = r->rem_set();
1086 
1087     _g1h->reset_gc_time_stamps(r);
1088 
1089     if (r->is_continues_humongous()) {
1090       // We'll assert that the strong code root list and RSet is empty
1091       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1092       assert(hrrs->occupied() == 0, "RSet should be empty");
1093     } else {
1094       hrrs->clear();
1095     }
1096     // You might think here that we could clear just the cards
1097     // corresponding to the used region.  But no: if we leave a dirty card
1098     // in a region we might allocate into, then it would prevent that card
1099     // from being enqueued, and cause it to be missed.
1100     // Re: the performance cost: we shouldn't be doing full GC anyway!
1101     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1102 
1103     return false;
1104   }
1105 };
1106 
1107 void G1CollectedHeap::clear_rsets_post_compaction() {
1108   PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1109   heap_region_iterate(&rs_clear);
1110 }
1111 
1112 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1113   G1CollectedHeap*   _g1h;
1114   UpdateRSOopClosure _cl;
1115 public:
1116   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) :
1117     _cl(g1->g1_rem_set(), worker_i),
1118     _g1h(g1)
1119   { }
1120 
1121   bool doHeapRegion(HeapRegion* r) {
1122     if (!r->is_continues_humongous()) {
1123       _cl.set_from(r);
1124       r->oop_iterate(&_cl);
1125     }
1126     return false;
1127   }
1128 };
1129 
1130 class ParRebuildRSTask: public AbstractGangTask {
1131   G1CollectedHeap* _g1;
1132   HeapRegionClaimer _hrclaimer;
1133 
1134 public:
1135   ParRebuildRSTask(G1CollectedHeap* g1) :
1136       AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {}
1137 
1138   void work(uint worker_id) {
1139     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1140     _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer);
1141   }
1142 };
1143 
1144 class PostCompactionPrinterClosure: public HeapRegionClosure {
1145 private:
1146   G1HRPrinter* _hr_printer;
1147 public:
1148   bool doHeapRegion(HeapRegion* hr) {
1149     assert(!hr->is_young(), "not expecting to find young regions");
1150     _hr_printer->post_compaction(hr);
1151     return false;
1152   }
1153 
1154   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1155     : _hr_printer(hr_printer) { }
1156 };
1157 
1158 void G1CollectedHeap::print_hrm_post_compaction() {
1159   if (_hr_printer.is_active()) {
1160     PostCompactionPrinterClosure cl(hr_printer());
1161     heap_region_iterate(&cl);
1162   }
1163 
1164 }
1165 
1166 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1167                                          bool clear_all_soft_refs) {
1168   assert_at_safepoint(true /* should_be_vm_thread */);
1169 
1170   if (GCLocker::check_active_before_gc()) {
1171     return false;
1172   }
1173 
1174   STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1175   gc_timer->register_gc_start();
1176 
1177   SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1178   GCIdMark gc_id_mark;
1179   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1180 
1181   SvcGCMarker sgcm(SvcGCMarker::FULL);
1182   ResourceMark rm;
1183 
1184   print_heap_before_gc();
1185   print_heap_regions();
1186   trace_heap_before_gc(gc_tracer);
1187 
1188   size_t metadata_prev_used = MetaspaceAux::used_bytes();
1189 
1190   _verifier->verify_region_sets_optional();
1191 
1192   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1193                            collector_policy()->should_clear_all_soft_refs();
1194 
1195   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1196 
1197   {
1198     IsGCActiveMark x;
1199 
1200     // Timing
1201     assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1202     GCTraceCPUTime tcpu;
1203 
1204     {
1205       GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1206       TraceCollectorStats tcs(g1mm()->full_collection_counters());
1207       TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1208 
1209       G1HeapTransition heap_transition(this);
1210       g1_policy()->record_full_collection_start();
1211 
1212       // Note: When we have a more flexible GC logging framework that
1213       // allows us to add optional attributes to a GC log record we
1214       // could consider timing and reporting how long we wait in the
1215       // following two methods.
1216       wait_while_free_regions_coming();
1217       // If we start the compaction before the CM threads finish
1218       // scanning the root regions we might trip them over as we'll
1219       // be moving objects / updating references. So let's wait until
1220       // they are done. By telling them to abort, they should complete
1221       // early.
1222       _cm->root_regions()->abort();
1223       _cm->root_regions()->wait_until_scan_finished();
1224       append_secondary_free_list_if_not_empty_with_lock();
1225 
1226       gc_prologue(true);
1227       increment_total_collections(true /* full gc */);
1228       increment_old_marking_cycles_started();
1229 
1230       assert(used() == recalculate_used(), "Should be equal");
1231 
1232       _verifier->verify_before_gc();
1233 
1234       _verifier->check_bitmaps("Full GC Start");
1235       pre_full_gc_dump(gc_timer);
1236 
1237 #if defined(COMPILER2) || INCLUDE_JVMCI
1238       DerivedPointerTable::clear();
1239 #endif
1240 
1241       // Disable discovery and empty the discovered lists
1242       // for the CM ref processor.
1243       ref_processor_cm()->disable_discovery();
1244       ref_processor_cm()->abandon_partial_discovery();
1245       ref_processor_cm()->verify_no_references_recorded();
1246 
1247       // Abandon current iterations of concurrent marking and concurrent
1248       // refinement, if any are in progress.
1249       concurrent_mark()->abort();
1250 
1251       // Make sure we'll choose a new allocation region afterwards.
1252       _allocator->release_mutator_alloc_region();
1253       _allocator->abandon_gc_alloc_regions();
1254       g1_rem_set()->cleanupHRRS();
1255 
1256       // We may have added regions to the current incremental collection
1257       // set between the last GC or pause and now. We need to clear the
1258       // incremental collection set and then start rebuilding it afresh
1259       // after this full GC.
1260       abandon_collection_set(collection_set());
1261 
1262       tear_down_region_sets(false /* free_list_only */);
1263       collector_state()->set_gcs_are_young(true);
1264 
1265       // See the comments in g1CollectedHeap.hpp and
1266       // G1CollectedHeap::ref_processing_init() about
1267       // how reference processing currently works in G1.
1268 
1269       // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1270       ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1271 
1272       // Temporarily clear the STW ref processor's _is_alive_non_header field.
1273       ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1274 
1275       ref_processor_stw()->enable_discovery();
1276       ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1277 
1278       // Do collection work
1279       {
1280         HandleMark hm;  // Discard invalid handles created during gc
1281         G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1282       }
1283 
1284       assert(num_free_regions() == 0, "we should not have added any free regions");
1285       rebuild_region_sets(false /* free_list_only */);
1286 
1287       // Enqueue any discovered reference objects that have
1288       // not been removed from the discovered lists.
1289       ref_processor_stw()->enqueue_discovered_references();
1290 
1291 #if defined(COMPILER2) || INCLUDE_JVMCI
1292       DerivedPointerTable::update_pointers();
1293 #endif
1294 
1295       MemoryService::track_memory_usage();
1296 
1297       assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1298       ref_processor_stw()->verify_no_references_recorded();
1299 
1300       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1301       ClassLoaderDataGraph::purge();
1302       MetaspaceAux::verify_metrics();
1303 
1304       // Note: since we've just done a full GC, concurrent
1305       // marking is no longer active. Therefore we need not
1306       // re-enable reference discovery for the CM ref processor.
1307       // That will be done at the start of the next marking cycle.
1308       assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1309       ref_processor_cm()->verify_no_references_recorded();
1310 
1311       reset_gc_time_stamp();
1312       // Since everything potentially moved, we will clear all remembered
1313       // sets, and clear all cards.  Later we will rebuild remembered
1314       // sets. We will also reset the GC time stamps of the regions.
1315       clear_rsets_post_compaction();
1316       check_gc_time_stamps();
1317 
1318       resize_if_necessary_after_full_collection();
1319 
1320       // We should do this after we potentially resize the heap so
1321       // that all the COMMIT / UNCOMMIT events are generated before
1322       // the compaction events.
1323       print_hrm_post_compaction();
1324 
1325       if (_hot_card_cache->use_cache()) {
1326         _hot_card_cache->reset_card_counts();
1327         _hot_card_cache->reset_hot_cache();
1328       }
1329 
1330       // Rebuild remembered sets of all regions.
1331       uint n_workers =
1332         AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1333                                                 workers()->active_workers(),
1334                                                 Threads::number_of_non_daemon_threads());
1335       workers()->update_active_workers(n_workers);
1336 
1337       ParRebuildRSTask rebuild_rs_task(this);
1338       workers()->run_task(&rebuild_rs_task);
1339 
1340       // Rebuild the strong code root lists for each region
1341       rebuild_strong_code_roots();
1342 
1343       if (true) { // FIXME
1344         MetaspaceGC::compute_new_size();
1345       }
1346 
1347 #ifdef TRACESPINNING
1348       ParallelTaskTerminator::print_termination_counts();
1349 #endif
1350 
1351       // Discard all rset updates
1352       JavaThread::dirty_card_queue_set().abandon_logs();
1353       assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1354 
1355       // At this point there should be no regions in the
1356       // entire heap tagged as young.
1357       assert(check_young_list_empty(), "young list should be empty at this point");
1358 
1359       // Update the number of full collections that have been completed.
1360       increment_old_marking_cycles_completed(false /* concurrent */);
1361 
1362       _hrm.verify_optional();
1363       _verifier->verify_region_sets_optional();
1364 
1365       _verifier->verify_after_gc();
1366 
1367       // Clear the previous marking bitmap, if needed for bitmap verification.
1368       // Note we cannot do this when we clear the next marking bitmap in
1369       // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1370       // objects marked during a full GC against the previous bitmap.
1371       // But we need to clear it before calling check_bitmaps below since
1372       // the full GC has compacted objects and updated TAMS but not updated
1373       // the prev bitmap.
1374       if (G1VerifyBitmaps) {
1375         GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1376         _cm->clear_prev_bitmap(workers());
1377       }
1378       _verifier->check_bitmaps("Full GC End");
1379 
1380       // Start a new incremental collection set for the next pause
1381       collection_set()->start_incremental_building();
1382 
1383       clear_cset_fast_test();
1384 
1385       _allocator->init_mutator_alloc_region();
1386 
1387       g1_policy()->record_full_collection_end();
1388 
1389       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1390       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1391       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1392       // before any GC notifications are raised.
1393       g1mm()->update_sizes();
1394 
1395       gc_epilogue(true);
1396 
1397       heap_transition.print();
1398 
1399       print_heap_after_gc();
1400       print_heap_regions();
1401       trace_heap_after_gc(gc_tracer);
1402 
1403       post_full_gc_dump(gc_timer);
1404     }
1405 
1406     gc_timer->register_gc_end();
1407     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1408   }
1409 
1410   return true;
1411 }
1412 
1413 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1414   // Currently, there is no facility in the do_full_collection(bool) API to notify
1415   // the caller that the collection did not succeed (e.g., because it was locked
1416   // out by the GC locker). So, right now, we'll ignore the return value.
1417   bool dummy = do_full_collection(true,                /* explicit_gc */
1418                                   clear_all_soft_refs);
1419 }
1420 
1421 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1422   // Include bytes that will be pre-allocated to support collections, as "used".
1423   const size_t used_after_gc = used();
1424   const size_t capacity_after_gc = capacity();
1425   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1426 
1427   // This is enforced in arguments.cpp.
1428   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1429          "otherwise the code below doesn't make sense");
1430 
1431   // We don't have floating point command-line arguments
1432   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1433   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1434   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1435   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1436 
1437   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1438   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1439 
1440   // We have to be careful here as these two calculations can overflow
1441   // 32-bit size_t's.
1442   double used_after_gc_d = (double) used_after_gc;
1443   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1444   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1445 
1446   // Let's make sure that they are both under the max heap size, which
1447   // by default will make them fit into a size_t.
1448   double desired_capacity_upper_bound = (double) max_heap_size;
1449   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1450                                     desired_capacity_upper_bound);
1451   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1452                                     desired_capacity_upper_bound);
1453 
1454   // We can now safely turn them into size_t's.
1455   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1456   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1457 
1458   // This assert only makes sense here, before we adjust them
1459   // with respect to the min and max heap size.
1460   assert(minimum_desired_capacity <= maximum_desired_capacity,
1461          "minimum_desired_capacity = " SIZE_FORMAT ", "
1462          "maximum_desired_capacity = " SIZE_FORMAT,
1463          minimum_desired_capacity, maximum_desired_capacity);
1464 
1465   // Should not be greater than the heap max size. No need to adjust
1466   // it with respect to the heap min size as it's a lower bound (i.e.,
1467   // we'll try to make the capacity larger than it, not smaller).
1468   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1469   // Should not be less than the heap min size. No need to adjust it
1470   // with respect to the heap max size as it's an upper bound (i.e.,
1471   // we'll try to make the capacity smaller than it, not greater).
1472   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1473 
1474   if (capacity_after_gc < minimum_desired_capacity) {
1475     // Don't expand unless it's significant
1476     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1477 
1478     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1479                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1480                               capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1481 
1482     expand(expand_bytes);
1483 
1484     // No expansion, now see if we want to shrink
1485   } else if (capacity_after_gc > maximum_desired_capacity) {
1486     // Capacity too large, compute shrinking size
1487     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1488 
1489     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1490                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1491                               capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1492 
1493     shrink(shrink_bytes);
1494   }
1495 }
1496 
1497 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1498                                                             AllocationContext_t context,
1499                                                             bool do_gc,
1500                                                             bool clear_all_soft_refs,
1501                                                             bool expect_null_mutator_alloc_region,
1502                                                             bool* gc_succeeded) {
1503   *gc_succeeded = true;
1504   // Let's attempt the allocation first.
1505   HeapWord* result =
1506     attempt_allocation_at_safepoint(word_size,
1507                                     context,
1508                                     expect_null_mutator_alloc_region);
1509   if (result != NULL) {
1510     assert(*gc_succeeded, "sanity");
1511     return result;
1512   }
1513 
1514   // In a G1 heap, we're supposed to keep allocation from failing by
1515   // incremental pauses.  Therefore, at least for now, we'll favor
1516   // expansion over collection.  (This might change in the future if we can
1517   // do something smarter than full collection to satisfy a failed alloc.)
1518   result = expand_and_allocate(word_size, context);
1519   if (result != NULL) {
1520     assert(*gc_succeeded, "sanity");
1521     return result;
1522   }
1523 
1524   if (do_gc) {
1525     // Expansion didn't work, we'll try to do a Full GC.
1526     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1527                                        clear_all_soft_refs);
1528   }
1529 
1530   return NULL;
1531 }
1532 
1533 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1534                                                      AllocationContext_t context,
1535                                                      bool* succeeded) {
1536   assert_at_safepoint(true /* should_be_vm_thread */);
1537 
1538   // Attempts to allocate followed by Full GC.
1539   HeapWord* result =
1540     satisfy_failed_allocation_helper(word_size,
1541                                      context,
1542                                      true,  /* do_gc */
1543                                      false, /* clear_all_soft_refs */
1544                                      false, /* expect_null_mutator_alloc_region */
1545                                      succeeded);
1546 
1547   if (result != NULL || !*succeeded) {
1548     return result;
1549   }
1550 
1551   // Attempts to allocate followed by Full GC that will collect all soft references.
1552   result = satisfy_failed_allocation_helper(word_size,
1553                                             context,
1554                                             true, /* do_gc */
1555                                             true, /* clear_all_soft_refs */
1556                                             true, /* expect_null_mutator_alloc_region */
1557                                             succeeded);
1558 
1559   if (result != NULL || !*succeeded) {
1560     return result;
1561   }
1562 
1563   // Attempts to allocate, no GC
1564   result = satisfy_failed_allocation_helper(word_size,
1565                                             context,
1566                                             false, /* do_gc */
1567                                             false, /* clear_all_soft_refs */
1568                                             true,  /* expect_null_mutator_alloc_region */
1569                                             succeeded);
1570 
1571   if (result != NULL) {
1572     assert(*succeeded, "sanity");
1573     return result;
1574   }
1575 
1576   assert(!collector_policy()->should_clear_all_soft_refs(),
1577          "Flag should have been handled and cleared prior to this point");
1578 
1579   // What else?  We might try synchronous finalization later.  If the total
1580   // space available is large enough for the allocation, then a more
1581   // complete compaction phase than we've tried so far might be
1582   // appropriate.
1583   assert(*succeeded, "sanity");
1584   return NULL;
1585 }
1586 
1587 // Attempting to expand the heap sufficiently
1588 // to support an allocation of the given "word_size".  If
1589 // successful, perform the allocation and return the address of the
1590 // allocated block, or else "NULL".
1591 
1592 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1593   assert_at_safepoint(true /* should_be_vm_thread */);
1594 
1595   _verifier->verify_region_sets_optional();
1596 
1597   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1598   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1599                             word_size * HeapWordSize);
1600 
1601 
1602   if (expand(expand_bytes)) {
1603     _hrm.verify_optional();
1604     _verifier->verify_region_sets_optional();
1605     return attempt_allocation_at_safepoint(word_size,
1606                                            context,
1607                                            false /* expect_null_mutator_alloc_region */);
1608   }
1609   return NULL;
1610 }
1611 
1612 bool G1CollectedHeap::expand(size_t expand_bytes, double* expand_time_ms) {
1613   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1614   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1615                                        HeapRegion::GrainBytes);
1616 
1617   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount:" SIZE_FORMAT "B expansion amount:" SIZE_FORMAT "B",
1618                             expand_bytes, aligned_expand_bytes);
1619 
1620   if (is_maximal_no_gc()) {
1621     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1622     return false;
1623   }
1624 
1625   double expand_heap_start_time_sec = os::elapsedTime();
1626   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1627   assert(regions_to_expand > 0, "Must expand by at least one region");
1628 
1629   uint expanded_by = _hrm.expand_by(regions_to_expand);
1630   if (expand_time_ms != NULL) {
1631     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1632   }
1633 
1634   if (expanded_by > 0) {
1635     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1636     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1637     g1_policy()->record_new_heap_size(num_regions());
1638   } else {
1639     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1640 
1641     // The expansion of the virtual storage space was unsuccessful.
1642     // Let's see if it was because we ran out of swap.
1643     if (G1ExitOnExpansionFailure &&
1644         _hrm.available() >= regions_to_expand) {
1645       // We had head room...
1646       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1647     }
1648   }
1649   return regions_to_expand > 0;
1650 }
1651 
1652 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1653   size_t aligned_shrink_bytes =
1654     ReservedSpace::page_align_size_down(shrink_bytes);
1655   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1656                                          HeapRegion::GrainBytes);
1657   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1658 
1659   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1660   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1661 
1662 
1663   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",
1664                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1665   if (num_regions_removed > 0) {
1666     g1_policy()->record_new_heap_size(num_regions());
1667   } else {
1668     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1669   }
1670 }
1671 
1672 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1673   _verifier->verify_region_sets_optional();
1674 
1675   // We should only reach here at the end of a Full GC which means we
1676   // should not not be holding to any GC alloc regions. The method
1677   // below will make sure of that and do any remaining clean up.
1678   _allocator->abandon_gc_alloc_regions();
1679 
1680   // Instead of tearing down / rebuilding the free lists here, we
1681   // could instead use the remove_all_pending() method on free_list to
1682   // remove only the ones that we need to remove.
1683   tear_down_region_sets(true /* free_list_only */);
1684   shrink_helper(shrink_bytes);
1685   rebuild_region_sets(true /* free_list_only */);
1686 
1687   _hrm.verify_optional();
1688   _verifier->verify_region_sets_optional();
1689 }
1690 
1691 // Public methods.
1692 
1693 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1694   CollectedHeap(),
1695   _collector_policy(collector_policy),
1696   _g1_policy(create_g1_policy()),
1697   _collection_set(this, _g1_policy),
1698   _dirty_card_queue_set(false),
1699   _is_alive_closure_cm(this),
1700   _is_alive_closure_stw(this),
1701   _ref_processor_cm(NULL),
1702   _ref_processor_stw(NULL),
1703   _bot(NULL),
1704   _hot_card_cache(NULL),
1705   _g1_rem_set(NULL),
1706   _cg1r(NULL),
1707   _g1mm(NULL),
1708   _refine_cte_cl(NULL),
1709   _preserved_marks_set(true /* in_c_heap */),
1710   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1711   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1712   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1713   _humongous_reclaim_candidates(),
1714   _has_humongous_reclaim_candidates(false),
1715   _archive_allocator(NULL),
1716   _free_regions_coming(false),
1717   _gc_time_stamp(0),
1718   _summary_bytes_used(0),
1719   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1720   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1721   _expand_heap_after_alloc_failure(true),
1722   _old_marking_cycles_started(0),
1723   _old_marking_cycles_completed(0),
1724   _in_cset_fast_test(),
1725   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1726   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()) {
1727 
1728   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1729                           /* are_GC_task_threads */true,
1730                           /* are_ConcurrentGC_threads */false);
1731   _workers->initialize_workers();
1732   _verifier = new G1HeapVerifier(this);
1733 
1734   _allocator = G1Allocator::create_allocator(this);
1735 
1736   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1737 
1738   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1739 
1740   // Override the default _filler_array_max_size so that no humongous filler
1741   // objects are created.
1742   _filler_array_max_size = _humongous_object_threshold_in_words;
1743 
1744   uint n_queues = ParallelGCThreads;
1745   _task_queues = new RefToScanQueueSet(n_queues);
1746 
1747   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1748 
1749   for (uint i = 0; i < n_queues; i++) {
1750     RefToScanQueue* q = new RefToScanQueue();
1751     q->initialize();
1752     _task_queues->register_queue(i, q);
1753     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1754   }
1755 
1756   // Initialize the G1EvacuationFailureALot counters and flags.
1757   NOT_PRODUCT(reset_evacuation_should_fail();)
1758 
1759   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1760 }
1761 
1762 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1763                                                                  size_t size,
1764                                                                  size_t translation_factor) {
1765   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1766   // Allocate a new reserved space, preferring to use large pages.
1767   ReservedSpace rs(size, preferred_page_size);
1768   G1RegionToSpaceMapper* result  =
1769     G1RegionToSpaceMapper::create_mapper(rs,
1770                                          size,
1771                                          rs.alignment(),
1772                                          HeapRegion::GrainBytes,
1773                                          translation_factor,
1774                                          mtGC);
1775 
1776   os::trace_page_sizes_for_requested_size(description,
1777                                           size,
1778                                           preferred_page_size,
1779                                           rs.alignment(),
1780                                           rs.base(),
1781                                           rs.size());
1782 
1783   return result;
1784 }
1785 
1786 jint G1CollectedHeap::initialize() {
1787   CollectedHeap::pre_initialize();
1788   os::enable_vtime();
1789 
1790   // Necessary to satisfy locking discipline assertions.
1791 
1792   MutexLocker x(Heap_lock);
1793 
1794   // While there are no constraints in the GC code that HeapWordSize
1795   // be any particular value, there are multiple other areas in the
1796   // system which believe this to be true (e.g. oop->object_size in some
1797   // cases incorrectly returns the size in wordSize units rather than
1798   // HeapWordSize).
1799   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1800 
1801   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1802   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1803   size_t heap_alignment = collector_policy()->heap_alignment();
1804 
1805   // Ensure that the sizes are properly aligned.
1806   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1807   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1808   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1809 
1810   _refine_cte_cl = new RefineCardTableEntryClosure();
1811 
1812   jint ecode = JNI_OK;
1813   _cg1r = ConcurrentG1Refine::create(_refine_cte_cl, &ecode);
1814   if (_cg1r == NULL) {
1815     return ecode;
1816   }
1817 
1818   // Reserve the maximum.
1819 
1820   // When compressed oops are enabled, the preferred heap base
1821   // is calculated by subtracting the requested size from the
1822   // 32Gb boundary and using the result as the base address for
1823   // heap reservation. If the requested size is not aligned to
1824   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1825   // into the ReservedHeapSpace constructor) then the actual
1826   // base of the reserved heap may end up differing from the
1827   // address that was requested (i.e. the preferred heap base).
1828   // If this happens then we could end up using a non-optimal
1829   // compressed oops mode.
1830 
1831   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1832                                                  heap_alignment);
1833 
1834   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1835 
1836   // Create the barrier set for the entire reserved region.
1837   G1SATBCardTableLoggingModRefBS* bs
1838     = new G1SATBCardTableLoggingModRefBS(reserved_region());
1839   bs->initialize();
1840   assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1841   set_barrier_set(bs);
1842 
1843   // Create the hot card cache.
1844   _hot_card_cache = new G1HotCardCache(this);
1845 
1846   // Also create a G1 rem set.
1847   _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache);
1848 
1849   // Carve out the G1 part of the heap.
1850   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1851   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1852   G1RegionToSpaceMapper* heap_storage =
1853     G1RegionToSpaceMapper::create_mapper(g1_rs,
1854                                          g1_rs.size(),
1855                                          page_size,
1856                                          HeapRegion::GrainBytes,
1857                                          1,
1858                                          mtJavaHeap);
1859   os::trace_page_sizes("Heap",
1860                        collector_policy()->min_heap_byte_size(),
1861                        max_byte_size,
1862                        page_size,
1863                        heap_rs.base(),
1864                        heap_rs.size());
1865   heap_storage->set_mapping_changed_listener(&_listener);
1866 
1867   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1868   G1RegionToSpaceMapper* bot_storage =
1869     create_aux_memory_mapper("Block Offset Table",
1870                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1871                              G1BlockOffsetTable::heap_map_factor());
1872 
1873   ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1874   G1RegionToSpaceMapper* cardtable_storage =
1875     create_aux_memory_mapper("Card Table",
1876                              G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1877                              G1SATBCardTableLoggingModRefBS::heap_map_factor());
1878 
1879   G1RegionToSpaceMapper* card_counts_storage =
1880     create_aux_memory_mapper("Card Counts Table",
1881                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1882                              G1CardCounts::heap_map_factor());
1883 
1884   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1885   G1RegionToSpaceMapper* prev_bitmap_storage =
1886     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1887   G1RegionToSpaceMapper* next_bitmap_storage =
1888     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1889 
1890   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1891   g1_barrier_set()->initialize(cardtable_storage);
1892   // Do later initialization work for concurrent refinement.
1893   _hot_card_cache->initialize(card_counts_storage);
1894 
1895   // 6843694 - ensure that the maximum region index can fit
1896   // in the remembered set structures.
1897   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1898   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1899 
1900   g1_rem_set()->initialize(max_capacity(), max_regions());
1901 
1902   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1903   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1904   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1905             "too many cards per region");
1906 
1907   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1908 
1909   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1910 
1911   {
1912     HeapWord* start = _hrm.reserved().start();
1913     HeapWord* end = _hrm.reserved().end();
1914     size_t granularity = HeapRegion::GrainBytes;
1915 
1916     _in_cset_fast_test.initialize(start, end, granularity);
1917     _humongous_reclaim_candidates.initialize(start, end, granularity);
1918   }
1919 
1920   // Create the G1ConcurrentMark data structure and thread.
1921   // (Must do this late, so that "max_regions" is defined.)
1922   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1923   if (_cm == NULL || !_cm->completed_initialization()) {
1924     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1925     return JNI_ENOMEM;
1926   }
1927   _cmThread = _cm->cmThread();
1928 
1929   // Now expand into the initial heap size.
1930   if (!expand(init_byte_size)) {
1931     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1932     return JNI_ENOMEM;
1933   }
1934 
1935   // Perform any initialization actions delegated to the policy.
1936   g1_policy()->init(this, &_collection_set);
1937 
1938   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1939                                                SATB_Q_FL_lock,
1940                                                G1SATBProcessCompletedThreshold,
1941                                                Shared_SATB_Q_lock);
1942 
1943   JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
1944                                                 DirtyCardQ_CBL_mon,
1945                                                 DirtyCardQ_FL_lock,
1946                                                 (int)concurrent_g1_refine()->yellow_zone(),
1947                                                 (int)concurrent_g1_refine()->red_zone(),
1948                                                 Shared_DirtyCardQ_lock,
1949                                                 NULL,  // fl_owner
1950                                                 true); // init_free_ids
1951 
1952   dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
1953                                     DirtyCardQ_CBL_mon,
1954                                     DirtyCardQ_FL_lock,
1955                                     -1, // never trigger processing
1956                                     -1, // no limit on length
1957                                     Shared_DirtyCardQ_lock,
1958                                     &JavaThread::dirty_card_queue_set());
1959 
1960   // Here we allocate the dummy HeapRegion that is required by the
1961   // G1AllocRegion class.
1962   HeapRegion* dummy_region = _hrm.get_dummy_region();
1963 
1964   // We'll re-use the same region whether the alloc region will
1965   // require BOT updates or not and, if it doesn't, then a non-young
1966   // region will complain that it cannot support allocations without
1967   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1968   dummy_region->set_eden();
1969   // Make sure it's full.
1970   dummy_region->set_top(dummy_region->end());
1971   G1AllocRegion::setup(this, dummy_region);
1972 
1973   _allocator->init_mutator_alloc_region();
1974 
1975   // Do create of the monitoring and management support so that
1976   // values in the heap have been properly initialized.
1977   _g1mm = new G1MonitoringSupport(this);
1978 
1979   G1StringDedup::initialize();
1980 
1981   _preserved_marks_set.init(ParallelGCThreads);
1982 
1983   _collection_set.initialize(max_regions());
1984 
1985   return JNI_OK;
1986 }
1987 
1988 void G1CollectedHeap::stop() {
1989   // Stop all concurrent threads. We do this to make sure these threads
1990   // do not continue to execute and access resources (e.g. logging)
1991   // that are destroyed during shutdown.
1992   _cg1r->stop();
1993   _cmThread->stop();
1994   if (G1StringDedup::is_enabled()) {
1995     G1StringDedup::stop();
1996   }
1997 }
1998 
1999 void G1CollectedHeap::post_initialize() {
2000   ref_processing_init();
2001 }
2002 
2003 void G1CollectedHeap::ref_processing_init() {
2004   // Reference processing in G1 currently works as follows:
2005   //
2006   // * There are two reference processor instances. One is
2007   //   used to record and process discovered references
2008   //   during concurrent marking; the other is used to
2009   //   record and process references during STW pauses
2010   //   (both full and incremental).
2011   // * Both ref processors need to 'span' the entire heap as
2012   //   the regions in the collection set may be dotted around.
2013   //
2014   // * For the concurrent marking ref processor:
2015   //   * Reference discovery is enabled at initial marking.
2016   //   * Reference discovery is disabled and the discovered
2017   //     references processed etc during remarking.
2018   //   * Reference discovery is MT (see below).
2019   //   * Reference discovery requires a barrier (see below).
2020   //   * Reference processing may or may not be MT
2021   //     (depending on the value of ParallelRefProcEnabled
2022   //     and ParallelGCThreads).
2023   //   * A full GC disables reference discovery by the CM
2024   //     ref processor and abandons any entries on it's
2025   //     discovered lists.
2026   //
2027   // * For the STW processor:
2028   //   * Non MT discovery is enabled at the start of a full GC.
2029   //   * Processing and enqueueing during a full GC is non-MT.
2030   //   * During a full GC, references are processed after marking.
2031   //
2032   //   * Discovery (may or may not be MT) is enabled at the start
2033   //     of an incremental evacuation pause.
2034   //   * References are processed near the end of a STW evacuation pause.
2035   //   * For both types of GC:
2036   //     * Discovery is atomic - i.e. not concurrent.
2037   //     * Reference discovery will not need a barrier.
2038 
2039   MemRegion mr = reserved_region();
2040 
2041   // Concurrent Mark ref processor
2042   _ref_processor_cm =
2043     new ReferenceProcessor(mr,    // span
2044                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2045                                 // mt processing
2046                            ParallelGCThreads,
2047                                 // degree of mt processing
2048                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2049                                 // mt discovery
2050                            MAX2(ParallelGCThreads, ConcGCThreads),
2051                                 // degree of mt discovery
2052                            false,
2053                                 // Reference discovery is not atomic
2054                            &_is_alive_closure_cm);
2055                                 // is alive closure
2056                                 // (for efficiency/performance)
2057 
2058   // STW ref processor
2059   _ref_processor_stw =
2060     new ReferenceProcessor(mr,    // span
2061                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2062                                 // mt processing
2063                            ParallelGCThreads,
2064                                 // degree of mt processing
2065                            (ParallelGCThreads > 1),
2066                                 // mt discovery
2067                            ParallelGCThreads,
2068                                 // degree of mt discovery
2069                            true,
2070                                 // Reference discovery is atomic
2071                            &_is_alive_closure_stw);
2072                                 // is alive closure
2073                                 // (for efficiency/performance)
2074 }
2075 
2076 CollectorPolicy* G1CollectedHeap::collector_policy() const {
2077   return _collector_policy;
2078 }
2079 
2080 size_t G1CollectedHeap::capacity() const {
2081   return _hrm.length() * HeapRegion::GrainBytes;
2082 }
2083 
2084 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2085   hr->reset_gc_time_stamp();
2086 }
2087 
2088 #ifndef PRODUCT
2089 
2090 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2091 private:
2092   unsigned _gc_time_stamp;
2093   bool _failures;
2094 
2095 public:
2096   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2097     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2098 
2099   virtual bool doHeapRegion(HeapRegion* hr) {
2100     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2101     if (_gc_time_stamp != region_gc_time_stamp) {
2102       log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
2103                             region_gc_time_stamp, _gc_time_stamp);
2104       _failures = true;
2105     }
2106     return false;
2107   }
2108 
2109   bool failures() { return _failures; }
2110 };
2111 
2112 void G1CollectedHeap::check_gc_time_stamps() {
2113   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2114   heap_region_iterate(&cl);
2115   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2116 }
2117 #endif // PRODUCT
2118 
2119 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
2120   _hot_card_cache->drain(cl, worker_i);
2121 }
2122 
2123 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
2124   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2125   size_t n_completed_buffers = 0;
2126   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2127     n_completed_buffers++;
2128   }
2129   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2130   dcqs.clear_n_completed_buffers();
2131   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2132 }
2133 
2134 // Computes the sum of the storage used by the various regions.
2135 size_t G1CollectedHeap::used() const {
2136   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
2137   if (_archive_allocator != NULL) {
2138     result += _archive_allocator->used();
2139   }
2140   return result;
2141 }
2142 
2143 size_t G1CollectedHeap::used_unlocked() const {
2144   return _summary_bytes_used;
2145 }
2146 
2147 class SumUsedClosure: public HeapRegionClosure {
2148   size_t _used;
2149 public:
2150   SumUsedClosure() : _used(0) {}
2151   bool doHeapRegion(HeapRegion* r) {
2152     _used += r->used();
2153     return false;
2154   }
2155   size_t result() { return _used; }
2156 };
2157 
2158 size_t G1CollectedHeap::recalculate_used() const {
2159   double recalculate_used_start = os::elapsedTime();
2160 
2161   SumUsedClosure blk;
2162   heap_region_iterate(&blk);
2163 
2164   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2165   return blk.result();
2166 }
2167 
2168 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2169   switch (cause) {
2170     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
2171     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
2172     case GCCause::_update_allocation_context_stats_inc: return true;
2173     case GCCause::_wb_conc_mark:                        return true;
2174     default :                                           return false;
2175   }
2176 }
2177 
2178 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2179   switch (cause) {
2180     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2181     case GCCause::_g1_humongous_allocation: return true;
2182     default:                                return is_user_requested_concurrent_full_gc(cause);
2183   }
2184 }
2185 
2186 #ifndef PRODUCT
2187 void G1CollectedHeap::allocate_dummy_regions() {
2188   // Let's fill up most of the region
2189   size_t word_size = HeapRegion::GrainWords - 1024;
2190   // And as a result the region we'll allocate will be humongous.
2191   guarantee(is_humongous(word_size), "sanity");
2192 
2193   // _filler_array_max_size is set to humongous object threshold
2194   // but temporarily change it to use CollectedHeap::fill_with_object().
2195   SizeTFlagSetting fs(_filler_array_max_size, word_size);
2196 
2197   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2198     // Let's use the existing mechanism for the allocation
2199     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2200                                                  AllocationContext::system());
2201     if (dummy_obj != NULL) {
2202       MemRegion mr(dummy_obj, word_size);
2203       CollectedHeap::fill_with_object(mr);
2204     } else {
2205       // If we can't allocate once, we probably cannot allocate
2206       // again. Let's get out of the loop.
2207       break;
2208     }
2209   }
2210 }
2211 #endif // !PRODUCT
2212 
2213 void G1CollectedHeap::increment_old_marking_cycles_started() {
2214   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2215          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2216          "Wrong marking cycle count (started: %d, completed: %d)",
2217          _old_marking_cycles_started, _old_marking_cycles_completed);
2218 
2219   _old_marking_cycles_started++;
2220 }
2221 
2222 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2223   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2224 
2225   // We assume that if concurrent == true, then the caller is a
2226   // concurrent thread that was joined the Suspendible Thread
2227   // Set. If there's ever a cheap way to check this, we should add an
2228   // assert here.
2229 
2230   // Given that this method is called at the end of a Full GC or of a
2231   // concurrent cycle, and those can be nested (i.e., a Full GC can
2232   // interrupt a concurrent cycle), the number of full collections
2233   // completed should be either one (in the case where there was no
2234   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2235   // behind the number of full collections started.
2236 
2237   // This is the case for the inner caller, i.e. a Full GC.
2238   assert(concurrent ||
2239          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2240          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2241          "for inner caller (Full GC): _old_marking_cycles_started = %u "
2242          "is inconsistent with _old_marking_cycles_completed = %u",
2243          _old_marking_cycles_started, _old_marking_cycles_completed);
2244 
2245   // This is the case for the outer caller, i.e. the concurrent cycle.
2246   assert(!concurrent ||
2247          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2248          "for outer caller (concurrent cycle): "
2249          "_old_marking_cycles_started = %u "
2250          "is inconsistent with _old_marking_cycles_completed = %u",
2251          _old_marking_cycles_started, _old_marking_cycles_completed);
2252 
2253   _old_marking_cycles_completed += 1;
2254 
2255   // We need to clear the "in_progress" flag in the CM thread before
2256   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2257   // is set) so that if a waiter requests another System.gc() it doesn't
2258   // incorrectly see that a marking cycle is still in progress.
2259   if (concurrent) {
2260     _cmThread->set_idle();
2261   }
2262 
2263   // This notify_all() will ensure that a thread that called
2264   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2265   // and it's waiting for a full GC to finish will be woken up. It is
2266   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2267   FullGCCount_lock->notify_all();
2268 }
2269 
2270 void G1CollectedHeap::collect(GCCause::Cause cause) {
2271   assert_heap_not_locked();
2272 
2273   uint gc_count_before;
2274   uint old_marking_count_before;
2275   uint full_gc_count_before;
2276   bool retry_gc;
2277 
2278   do {
2279     retry_gc = false;
2280 
2281     {
2282       MutexLocker ml(Heap_lock);
2283 
2284       // Read the GC count while holding the Heap_lock
2285       gc_count_before = total_collections();
2286       full_gc_count_before = total_full_collections();
2287       old_marking_count_before = _old_marking_cycles_started;
2288     }
2289 
2290     if (should_do_concurrent_full_gc(cause)) {
2291       // Schedule an initial-mark evacuation pause that will start a
2292       // concurrent cycle. We're setting word_size to 0 which means that
2293       // we are not requesting a post-GC allocation.
2294       VM_G1IncCollectionPause op(gc_count_before,
2295                                  0,     /* word_size */
2296                                  true,  /* should_initiate_conc_mark */
2297                                  g1_policy()->max_pause_time_ms(),
2298                                  cause);
2299       op.set_allocation_context(AllocationContext::current());
2300 
2301       VMThread::execute(&op);
2302       if (!op.pause_succeeded()) {
2303         if (old_marking_count_before == _old_marking_cycles_started) {
2304           retry_gc = op.should_retry_gc();
2305         } else {
2306           // A Full GC happened while we were trying to schedule the
2307           // initial-mark GC. No point in starting a new cycle given
2308           // that the whole heap was collected anyway.
2309         }
2310 
2311         if (retry_gc) {
2312           if (GCLocker::is_active_and_needs_gc()) {
2313             GCLocker::stall_until_clear();
2314           }
2315         }
2316       }
2317     } else {
2318       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2319           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2320 
2321         // Schedule a standard evacuation pause. We're setting word_size
2322         // to 0 which means that we are not requesting a post-GC allocation.
2323         VM_G1IncCollectionPause op(gc_count_before,
2324                                    0,     /* word_size */
2325                                    false, /* should_initiate_conc_mark */
2326                                    g1_policy()->max_pause_time_ms(),
2327                                    cause);
2328         VMThread::execute(&op);
2329       } else {
2330         // Schedule a Full GC.
2331         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2332         VMThread::execute(&op);
2333       }
2334     }
2335   } while (retry_gc);
2336 }
2337 
2338 bool G1CollectedHeap::is_in(const void* p) const {
2339   if (_hrm.reserved().contains(p)) {
2340     // Given that we know that p is in the reserved space,
2341     // heap_region_containing() should successfully
2342     // return the containing region.
2343     HeapRegion* hr = heap_region_containing(p);
2344     return hr->is_in(p);
2345   } else {
2346     return false;
2347   }
2348 }
2349 
2350 #ifdef ASSERT
2351 bool G1CollectedHeap::is_in_exact(const void* p) const {
2352   bool contains = reserved_region().contains(p);
2353   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2354   if (contains && available) {
2355     return true;
2356   } else {
2357     return false;
2358   }
2359 }
2360 #endif
2361 
2362 bool G1CollectedHeap::obj_in_cs(oop obj) {
2363   HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj);
2364   return r != NULL && r->in_collection_set();
2365 }
2366 
2367 // Iteration functions.
2368 
2369 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2370 
2371 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2372   ExtendedOopClosure* _cl;
2373 public:
2374   IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2375   bool doHeapRegion(HeapRegion* r) {
2376     if (!r->is_continues_humongous()) {
2377       r->oop_iterate(_cl);
2378     }
2379     return false;
2380   }
2381 };
2382 
2383 // Iterates an ObjectClosure over all objects within a HeapRegion.
2384 
2385 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2386   ObjectClosure* _cl;
2387 public:
2388   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2389   bool doHeapRegion(HeapRegion* r) {
2390     if (!r->is_continues_humongous()) {
2391       r->object_iterate(_cl);
2392     }
2393     return false;
2394   }
2395 };
2396 
2397 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2398   IterateObjectClosureRegionClosure blk(cl);
2399   heap_region_iterate(&blk);
2400 }
2401 
2402 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2403   _hrm.iterate(cl);
2404 }
2405 
2406 void
2407 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2408                                          uint worker_id,
2409                                          HeapRegionClaimer *hrclaimer,
2410                                          bool concurrent) const {
2411   _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent);
2412 }
2413 
2414 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2415   _collection_set.iterate(cl);
2416 }
2417 
2418 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2419   _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2420 }
2421 
2422 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2423   HeapRegion* result = _hrm.next_region_in_heap(from);
2424   while (result != NULL && result->is_pinned()) {
2425     result = _hrm.next_region_in_heap(result);
2426   }
2427   return result;
2428 }
2429 
2430 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2431   HeapRegion* hr = heap_region_containing(addr);
2432   return hr->block_start(addr);
2433 }
2434 
2435 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2436   HeapRegion* hr = heap_region_containing(addr);
2437   return hr->block_size(addr);
2438 }
2439 
2440 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2441   HeapRegion* hr = heap_region_containing(addr);
2442   return hr->block_is_obj(addr);
2443 }
2444 
2445 bool G1CollectedHeap::supports_tlab_allocation() const {
2446   return true;
2447 }
2448 
2449 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2450   return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2451 }
2452 
2453 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2454   return _eden.length() * HeapRegion::GrainBytes;
2455 }
2456 
2457 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2458 // must be equal to the humongous object limit.
2459 size_t G1CollectedHeap::max_tlab_size() const {
2460   return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment);
2461 }
2462 
2463 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2464   AllocationContext_t context = AllocationContext::current();
2465   return _allocator->unsafe_max_tlab_alloc(context);
2466 }
2467 
2468 size_t G1CollectedHeap::max_capacity() const {
2469   return _hrm.reserved().byte_size();
2470 }
2471 
2472 jlong G1CollectedHeap::millis_since_last_gc() {
2473   jlong now = os::elapsed_counter() / NANOSECS_PER_MILLISEC;
2474   const G1Analytics* analytics = _g1_policy->analytics();
2475   double last = analytics->last_known_gc_end_time_sec();
2476   jlong ret_val = now - (last * 1000);
2477   if (ret_val < 0) {
2478     // See the notes in GenCollectedHeap::millis_since_last_gc()
2479     // for more information about the implementation.
2480     log_warning(gc)("Detected clock going backwards. "
2481       "Milliseconds since last GC would be " JLONG_FORMAT
2482       ". returning zero instead.", ret_val);
2483     return 0;
2484   }
2485   return ret_val;
2486 }
2487 
2488 void G1CollectedHeap::prepare_for_verify() {
2489   _verifier->prepare_for_verify();
2490 }
2491 
2492 void G1CollectedHeap::verify(VerifyOption vo) {
2493   _verifier->verify(vo);
2494 }
2495 
2496 class PrintRegionClosure: public HeapRegionClosure {
2497   outputStream* _st;
2498 public:
2499   PrintRegionClosure(outputStream* st) : _st(st) {}
2500   bool doHeapRegion(HeapRegion* r) {
2501     r->print_on(_st);
2502     return false;
2503   }
2504 };
2505 
2506 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2507                                        const HeapRegion* hr,
2508                                        const VerifyOption vo) const {
2509   switch (vo) {
2510   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2511   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2512   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked() && !hr->is_archive();
2513   default:                            ShouldNotReachHere();
2514   }
2515   return false; // keep some compilers happy
2516 }
2517 
2518 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2519                                        const VerifyOption vo) const {
2520   switch (vo) {
2521   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2522   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2523   case VerifyOption_G1UseMarkWord: {
2524     HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj);
2525     return !obj->is_gc_marked() && !hr->is_archive();
2526   }
2527   default:                            ShouldNotReachHere();
2528   }
2529   return false; // keep some compilers happy
2530 }
2531 
2532 void G1CollectedHeap::print_heap_regions() const {
2533   Log(gc, heap, region) log;
2534   if (log.is_trace()) {
2535     ResourceMark rm;
2536     print_regions_on(log.trace_stream());
2537   }
2538 }
2539 
2540 void G1CollectedHeap::print_on(outputStream* st) const {
2541   st->print(" %-20s", "garbage-first heap");
2542   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2543             capacity()/K, used_unlocked()/K);
2544   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
2545             p2i(_hrm.reserved().start()),
2546             p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords),
2547             p2i(_hrm.reserved().end()));
2548   st->cr();
2549   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2550   uint young_regions = young_regions_count();
2551   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2552             (size_t) young_regions * HeapRegion::GrainBytes / K);
2553   uint survivor_regions = survivor_regions_count();
2554   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2555             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2556   st->cr();
2557   MetaspaceAux::print_on(st);
2558 }
2559 
2560 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2561   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2562                "HS=humongous(starts), HC=humongous(continues), "
2563                "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2564                "AC=allocation context, "
2565                "TAMS=top-at-mark-start (previous, next)");
2566   PrintRegionClosure blk(st);
2567   heap_region_iterate(&blk);
2568 }
2569 
2570 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2571   print_on(st);
2572 
2573   // Print the per-region information.
2574   print_regions_on(st);
2575 }
2576 
2577 void G1CollectedHeap::print_on_error(outputStream* st) const {
2578   this->CollectedHeap::print_on_error(st);
2579 
2580   if (_cm != NULL) {
2581     st->cr();
2582     _cm->print_on_error(st);
2583   }
2584 }
2585 
2586 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2587   workers()->print_worker_threads_on(st);
2588   _cmThread->print_on(st);
2589   st->cr();
2590   _cm->print_worker_threads_on(st);
2591   _cg1r->print_worker_threads_on(st); // also prints the sample thread
2592   if (G1StringDedup::is_enabled()) {
2593     G1StringDedup::print_worker_threads_on(st);
2594   }
2595 }
2596 
2597 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2598   workers()->threads_do(tc);
2599   tc->do_thread(_cmThread);
2600   _cm->threads_do(tc);
2601   _cg1r->threads_do(tc); // also iterates over the sample thread
2602   if (G1StringDedup::is_enabled()) {
2603     G1StringDedup::threads_do(tc);
2604   }
2605 }
2606 
2607 void G1CollectedHeap::print_tracing_info() const {
2608   g1_rem_set()->print_summary_info();
2609   concurrent_mark()->print_summary_info();
2610 }
2611 
2612 #ifndef PRODUCT
2613 // Helpful for debugging RSet issues.
2614 
2615 class PrintRSetsClosure : public HeapRegionClosure {
2616 private:
2617   const char* _msg;
2618   size_t _occupied_sum;
2619 
2620 public:
2621   bool doHeapRegion(HeapRegion* r) {
2622     HeapRegionRemSet* hrrs = r->rem_set();
2623     size_t occupied = hrrs->occupied();
2624     _occupied_sum += occupied;
2625 
2626     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2627     if (occupied == 0) {
2628       tty->print_cr("  RSet is empty");
2629     } else {
2630       hrrs->print();
2631     }
2632     tty->print_cr("----------");
2633     return false;
2634   }
2635 
2636   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2637     tty->cr();
2638     tty->print_cr("========================================");
2639     tty->print_cr("%s", msg);
2640     tty->cr();
2641   }
2642 
2643   ~PrintRSetsClosure() {
2644     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2645     tty->print_cr("========================================");
2646     tty->cr();
2647   }
2648 };
2649 
2650 void G1CollectedHeap::print_cset_rsets() {
2651   PrintRSetsClosure cl("Printing CSet RSets");
2652   collection_set_iterate(&cl);
2653 }
2654 
2655 void G1CollectedHeap::print_all_rsets() {
2656   PrintRSetsClosure cl("Printing All RSets");;
2657   heap_region_iterate(&cl);
2658 }
2659 #endif // PRODUCT
2660 
2661 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2662 
2663   size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2664   size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2665   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2666 
2667   size_t eden_capacity_bytes =
2668     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2669 
2670   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2671   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2672                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2673 }
2674 
2675 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2676   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2677                        stats->unused(), stats->used(), stats->region_end_waste(),
2678                        stats->regions_filled(), stats->direct_allocated(),
2679                        stats->failure_used(), stats->failure_waste());
2680 }
2681 
2682 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2683   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2684   gc_tracer->report_gc_heap_summary(when, heap_summary);
2685 
2686   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2687   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2688 }
2689 
2690 G1CollectedHeap* G1CollectedHeap::heap() {
2691   CollectedHeap* heap = GC::gc()->heap();
2692   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2693   assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2694   return (G1CollectedHeap*)heap;
2695 }
2696 
2697 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
2698   // always_do_update_barrier = false;
2699   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2700   // Fill TLAB's and such
2701   accumulate_statistics_all_tlabs();
2702   ensure_parsability(true);
2703 
2704   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2705 }
2706 
2707 void G1CollectedHeap::gc_epilogue(bool full) {
2708   // we are at the end of the GC. Total collections has already been increased.
2709   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2710 
2711   // FIXME: what is this about?
2712   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2713   // is set.
2714 #if defined(COMPILER2) || INCLUDE_JVMCI
2715   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2716 #endif
2717   // always_do_update_barrier = true;
2718 
2719   resize_all_tlabs();
2720   allocation_context_stats().update(full);
2721 
2722   // We have just completed a GC. Update the soft reference
2723   // policy with the new heap occupancy
2724   Universe::update_heap_info_at_gc();
2725 }
2726 
2727 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2728                                                uint gc_count_before,
2729                                                bool* succeeded,
2730                                                GCCause::Cause gc_cause) {
2731   assert_heap_not_locked_and_not_at_safepoint();
2732   VM_G1IncCollectionPause op(gc_count_before,
2733                              word_size,
2734                              false, /* should_initiate_conc_mark */
2735                              g1_policy()->max_pause_time_ms(),
2736                              gc_cause);
2737 
2738   op.set_allocation_context(AllocationContext::current());
2739   VMThread::execute(&op);
2740 
2741   HeapWord* result = op.result();
2742   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2743   assert(result == NULL || ret_succeeded,
2744          "the result should be NULL if the VM did not succeed");
2745   *succeeded = ret_succeeded;
2746 
2747   assert_heap_not_locked();
2748   return result;
2749 }
2750 
2751 void
2752 G1CollectedHeap::doConcurrentMark() {
2753   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2754   if (!_cmThread->in_progress()) {
2755     _cmThread->set_started();
2756     CGC_lock->notify();
2757   }
2758 }
2759 
2760 size_t G1CollectedHeap::pending_card_num() {
2761   size_t extra_cards = 0;
2762   JavaThread *curr = Threads::first();
2763   while (curr != NULL) {
2764     DirtyCardQueue& dcq = curr->dirty_card_queue();
2765     extra_cards += dcq.size();
2766     curr = curr->next();
2767   }
2768   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2769   size_t buffer_size = dcqs.buffer_size();
2770   size_t buffer_num = dcqs.completed_buffers_num();
2771 
2772   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
2773   // in bytes - not the number of 'entries'. We need to convert
2774   // into a number of cards.
2775   return (buffer_size * buffer_num + extra_cards) / oopSize;
2776 }
2777 
2778 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2779  private:
2780   size_t _total_humongous;
2781   size_t _candidate_humongous;
2782 
2783   DirtyCardQueue _dcq;
2784 
2785   // We don't nominate objects with many remembered set entries, on
2786   // the assumption that such objects are likely still live.
2787   bool is_remset_small(HeapRegion* region) const {
2788     HeapRegionRemSet* const rset = region->rem_set();
2789     return G1EagerReclaimHumongousObjectsWithStaleRefs
2790       ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2791       : rset->is_empty();
2792   }
2793 
2794   bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2795     assert(region->is_starts_humongous(), "Must start a humongous object");
2796 
2797     oop obj = oop(region->bottom());
2798 
2799     // Dead objects cannot be eager reclaim candidates. Due to class
2800     // unloading it is unsafe to query their classes so we return early.
2801     if (heap->is_obj_dead(obj, region)) {
2802       return false;
2803     }
2804 
2805     // Candidate selection must satisfy the following constraints
2806     // while concurrent marking is in progress:
2807     //
2808     // * In order to maintain SATB invariants, an object must not be
2809     // reclaimed if it was allocated before the start of marking and
2810     // has not had its references scanned.  Such an object must have
2811     // its references (including type metadata) scanned to ensure no
2812     // live objects are missed by the marking process.  Objects
2813     // allocated after the start of concurrent marking don't need to
2814     // be scanned.
2815     //
2816     // * An object must not be reclaimed if it is on the concurrent
2817     // mark stack.  Objects allocated after the start of concurrent
2818     // marking are never pushed on the mark stack.
2819     //
2820     // Nominating only objects allocated after the start of concurrent
2821     // marking is sufficient to meet both constraints.  This may miss
2822     // some objects that satisfy the constraints, but the marking data
2823     // structures don't support efficiently performing the needed
2824     // additional tests or scrubbing of the mark stack.
2825     //
2826     // However, we presently only nominate is_typeArray() objects.
2827     // A humongous object containing references induces remembered
2828     // set entries on other regions.  In order to reclaim such an
2829     // object, those remembered sets would need to be cleaned up.
2830     //
2831     // We also treat is_typeArray() objects specially, allowing them
2832     // to be reclaimed even if allocated before the start of
2833     // concurrent mark.  For this we rely on mark stack insertion to
2834     // exclude is_typeArray() objects, preventing reclaiming an object
2835     // that is in the mark stack.  We also rely on the metadata for
2836     // such objects to be built-in and so ensured to be kept live.
2837     // Frequent allocation and drop of large binary blobs is an
2838     // important use case for eager reclaim, and this special handling
2839     // may reduce needed headroom.
2840 
2841     return obj->is_typeArray() && is_remset_small(region);
2842   }
2843 
2844  public:
2845   RegisterHumongousWithInCSetFastTestClosure()
2846   : _total_humongous(0),
2847     _candidate_humongous(0),
2848     _dcq(&JavaThread::dirty_card_queue_set()) {
2849   }
2850 
2851   virtual bool doHeapRegion(HeapRegion* r) {
2852     if (!r->is_starts_humongous()) {
2853       return false;
2854     }
2855     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2856 
2857     bool is_candidate = humongous_region_is_candidate(g1h, r);
2858     uint rindex = r->hrm_index();
2859     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2860     if (is_candidate) {
2861       _candidate_humongous++;
2862       g1h->register_humongous_region_with_cset(rindex);
2863       // Is_candidate already filters out humongous object with large remembered sets.
2864       // If we have a humongous object with a few remembered sets, we simply flush these
2865       // remembered set entries into the DCQS. That will result in automatic
2866       // re-evaluation of their remembered set entries during the following evacuation
2867       // phase.
2868       if (!r->rem_set()->is_empty()) {
2869         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2870                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2871         G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
2872         HeapRegionRemSetIterator hrrs(r->rem_set());
2873         size_t card_index;
2874         while (hrrs.has_next(card_index)) {
2875           jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
2876           // The remembered set might contain references to already freed
2877           // regions. Filter out such entries to avoid failing card table
2878           // verification.
2879           if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
2880             if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
2881               *card_ptr = CardTableModRefBS::dirty_card_val();
2882               _dcq.enqueue(card_ptr);
2883             }
2884           }
2885         }
2886         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2887                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2888                hrrs.n_yielded(), r->rem_set()->occupied());
2889         r->rem_set()->clear_locked();
2890       }
2891       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2892     }
2893     _total_humongous++;
2894 
2895     return false;
2896   }
2897 
2898   size_t total_humongous() const { return _total_humongous; }
2899   size_t candidate_humongous() const { return _candidate_humongous; }
2900 
2901   void flush_rem_set_entries() { _dcq.flush(); }
2902 };
2903 
2904 void G1CollectedHeap::register_humongous_regions_with_cset() {
2905   if (!G1EagerReclaimHumongousObjects) {
2906     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2907     return;
2908   }
2909   double time = os::elapsed_counter();
2910 
2911   // Collect reclaim candidate information and register candidates with cset.
2912   RegisterHumongousWithInCSetFastTestClosure cl;
2913   heap_region_iterate(&cl);
2914 
2915   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2916   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2917                                                                   cl.total_humongous(),
2918                                                                   cl.candidate_humongous());
2919   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2920 
2921   // Finally flush all remembered set entries to re-check into the global DCQS.
2922   cl.flush_rem_set_entries();
2923 }
2924 
2925 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2926   public:
2927     bool doHeapRegion(HeapRegion* hr) {
2928       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2929         hr->verify_rem_set();
2930       }
2931       return false;
2932     }
2933 };
2934 
2935 uint G1CollectedHeap::num_task_queues() const {
2936   return _task_queues->size();
2937 }
2938 
2939 #if TASKQUEUE_STATS
2940 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2941   st->print_raw_cr("GC Task Stats");
2942   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2943   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2944 }
2945 
2946 void G1CollectedHeap::print_taskqueue_stats() const {
2947   if (!log_is_enabled(Trace, gc, task, stats)) {
2948     return;
2949   }
2950   Log(gc, task, stats) log;
2951   ResourceMark rm;
2952   outputStream* st = log.trace_stream();
2953 
2954   print_taskqueue_stats_hdr(st);
2955 
2956   TaskQueueStats totals;
2957   const uint n = num_task_queues();
2958   for (uint i = 0; i < n; ++i) {
2959     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2960     totals += task_queue(i)->stats;
2961   }
2962   st->print_raw("tot "); totals.print(st); st->cr();
2963 
2964   DEBUG_ONLY(totals.verify());
2965 }
2966 
2967 void G1CollectedHeap::reset_taskqueue_stats() {
2968   const uint n = num_task_queues();
2969   for (uint i = 0; i < n; ++i) {
2970     task_queue(i)->stats.reset();
2971   }
2972 }
2973 #endif // TASKQUEUE_STATS
2974 
2975 void G1CollectedHeap::wait_for_root_region_scanning() {
2976   double scan_wait_start = os::elapsedTime();
2977   // We have to wait until the CM threads finish scanning the
2978   // root regions as it's the only way to ensure that all the
2979   // objects on them have been correctly scanned before we start
2980   // moving them during the GC.
2981   bool waited = _cm->root_regions()->wait_until_scan_finished();
2982   double wait_time_ms = 0.0;
2983   if (waited) {
2984     double scan_wait_end = os::elapsedTime();
2985     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2986   }
2987   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2988 }
2989 
2990 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2991 private:
2992   G1HRPrinter* _hr_printer;
2993 public:
2994   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2995 
2996   virtual bool doHeapRegion(HeapRegion* r) {
2997     _hr_printer->cset(r);
2998     return false;
2999   }
3000 };
3001 
3002 bool
3003 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3004   assert_at_safepoint(true /* should_be_vm_thread */);
3005   guarantee(!is_gc_active(), "collection is not reentrant");
3006 
3007   if (GCLocker::check_active_before_gc()) {
3008     return false;
3009   }
3010 
3011   _gc_timer_stw->register_gc_start();
3012 
3013   GCIdMark gc_id_mark;
3014   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3015 
3016   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3017   ResourceMark rm;
3018 
3019   g1_policy()->note_gc_start();
3020 
3021   wait_for_root_region_scanning();
3022 
3023   print_heap_before_gc();
3024   print_heap_regions();
3025   trace_heap_before_gc(_gc_tracer_stw);
3026 
3027   _verifier->verify_region_sets_optional();
3028   _verifier->verify_dirty_young_regions();
3029 
3030   // We should not be doing initial mark unless the conc mark thread is running
3031   if (!_cmThread->should_terminate()) {
3032     // This call will decide whether this pause is an initial-mark
3033     // pause. If it is, during_initial_mark_pause() will return true
3034     // for the duration of this pause.
3035     g1_policy()->decide_on_conc_mark_initiation();
3036   }
3037 
3038   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3039   assert(!collector_state()->during_initial_mark_pause() ||
3040           collector_state()->gcs_are_young(), "sanity");
3041 
3042   // We also do not allow mixed GCs during marking.
3043   assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
3044 
3045   // Record whether this pause is an initial mark. When the current
3046   // thread has completed its logging output and it's safe to signal
3047   // the CM thread, the flag's value in the policy has been reset.
3048   bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
3049 
3050   // Inner scope for scope based logging, timers, and stats collection
3051   {
3052     EvacuationInfo evacuation_info;
3053 
3054     if (collector_state()->during_initial_mark_pause()) {
3055       // We are about to start a marking cycle, so we increment the
3056       // full collection counter.
3057       increment_old_marking_cycles_started();
3058       _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
3059     }
3060 
3061     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
3062 
3063     GCTraceCPUTime tcpu;
3064 
3065     FormatBuffer<> gc_string("Pause ");
3066     if (collector_state()->during_initial_mark_pause()) {
3067       gc_string.append("Initial Mark");
3068     } else if (collector_state()->gcs_are_young()) {
3069       gc_string.append("Young");
3070     } else {
3071       gc_string.append("Mixed");
3072     }
3073     GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
3074 
3075     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
3076                                                                   workers()->active_workers(),
3077                                                                   Threads::number_of_non_daemon_threads());
3078     workers()->update_active_workers(active_workers);
3079 
3080     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3081     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3082 
3083     // If the secondary_free_list is not empty, append it to the
3084     // free_list. No need to wait for the cleanup operation to finish;
3085     // the region allocation code will check the secondary_free_list
3086     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3087     // set, skip this step so that the region allocation code has to
3088     // get entries from the secondary_free_list.
3089     if (!G1StressConcRegionFreeing) {
3090       append_secondary_free_list_if_not_empty_with_lock();
3091     }
3092 
3093     G1HeapTransition heap_transition(this);
3094     size_t heap_used_bytes_before_gc = used();
3095 
3096     // Don't dynamically change the number of GC threads this early.  A value of
3097     // 0 is used to indicate serial work.  When parallel work is done,
3098     // it will be set.
3099 
3100     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3101       IsGCActiveMark x;
3102 
3103       gc_prologue(false);
3104       increment_total_collections(false /* full gc */);
3105       increment_gc_time_stamp();
3106 
3107       if (VerifyRememberedSets) {
3108         log_info(gc, verify)("[Verifying RemSets before GC]");
3109         VerifyRegionRemSetClosure v_cl;
3110         heap_region_iterate(&v_cl);
3111       }
3112 
3113       _verifier->verify_before_gc();
3114 
3115       _verifier->check_bitmaps("GC Start");
3116 
3117 #if defined(COMPILER2) || INCLUDE_JVMCI
3118       DerivedPointerTable::clear();
3119 #endif
3120 
3121       // Please see comment in g1CollectedHeap.hpp and
3122       // G1CollectedHeap::ref_processing_init() to see how
3123       // reference processing currently works in G1.
3124 
3125       // Enable discovery in the STW reference processor
3126       if (g1_policy()->should_process_references()) {
3127         ref_processor_stw()->enable_discovery();
3128       } else {
3129         ref_processor_stw()->disable_discovery();
3130       }
3131 
3132       {
3133         // We want to temporarily turn off discovery by the
3134         // CM ref processor, if necessary, and turn it back on
3135         // on again later if we do. Using a scoped
3136         // NoRefDiscovery object will do this.
3137         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3138 
3139         // Forget the current alloc region (we might even choose it to be part
3140         // of the collection set!).
3141         _allocator->release_mutator_alloc_region();
3142 
3143         // This timing is only used by the ergonomics to handle our pause target.
3144         // It is unclear why this should not include the full pause. We will
3145         // investigate this in CR 7178365.
3146         //
3147         // Preserving the old comment here if that helps the investigation:
3148         //
3149         // The elapsed time induced by the start time below deliberately elides
3150         // the possible verification above.
3151         double sample_start_time_sec = os::elapsedTime();
3152 
3153         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3154 
3155         if (collector_state()->during_initial_mark_pause()) {
3156           concurrent_mark()->checkpointRootsInitialPre();
3157         }
3158 
3159         g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
3160 
3161         evacuation_info.set_collectionset_regions(collection_set()->region_length());
3162 
3163         // Make sure the remembered sets are up to date. This needs to be
3164         // done before register_humongous_regions_with_cset(), because the
3165         // remembered sets are used there to choose eager reclaim candidates.
3166         // If the remembered sets are not up to date we might miss some
3167         // entries that need to be handled.
3168         g1_rem_set()->cleanupHRRS();
3169 
3170         register_humongous_regions_with_cset();
3171 
3172         assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3173 
3174         _cm->note_start_of_gc();
3175         // We call this after finalize_cset() to
3176         // ensure that the CSet has been finalized.
3177         _cm->verify_no_cset_oops();
3178 
3179         if (_hr_printer.is_active()) {
3180           G1PrintCollectionSetClosure cl(&_hr_printer);
3181           _collection_set.iterate(&cl);
3182         }
3183 
3184         // Initialize the GC alloc regions.
3185         _allocator->init_gc_alloc_regions(evacuation_info);
3186 
3187         G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3188         pre_evacuate_collection_set();
3189 
3190         // Actually do the work...
3191         evacuate_collection_set(evacuation_info, &per_thread_states);
3192 
3193         post_evacuate_collection_set(evacuation_info, &per_thread_states);
3194 
3195         const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3196         free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
3197 
3198         eagerly_reclaim_humongous_regions();
3199 
3200         record_obj_copy_mem_stats();
3201         _survivor_evac_stats.adjust_desired_plab_sz();
3202         _old_evac_stats.adjust_desired_plab_sz();
3203 
3204         // Start a new incremental collection set for the next pause.
3205         collection_set()->start_incremental_building();
3206 
3207         clear_cset_fast_test();
3208 
3209         guarantee(_eden.length() == 0, "eden should have been cleared");
3210         g1_policy()->transfer_survivors_to_cset(survivor());
3211 
3212         if (evacuation_failed()) {
3213           set_used(recalculate_used());
3214           if (_archive_allocator != NULL) {
3215             _archive_allocator->clear_used();
3216           }
3217           for (uint i = 0; i < ParallelGCThreads; i++) {
3218             if (_evacuation_failed_info_array[i].has_failed()) {
3219               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3220             }
3221           }
3222         } else {
3223           // The "used" of the the collection set have already been subtracted
3224           // when they were freed.  Add in the bytes evacuated.
3225           increase_used(g1_policy()->bytes_copied_during_gc());
3226         }
3227 
3228         if (collector_state()->during_initial_mark_pause()) {
3229           // We have to do this before we notify the CM threads that
3230           // they can start working to make sure that all the
3231           // appropriate initialization is done on the CM object.
3232           concurrent_mark()->checkpointRootsInitialPost();
3233           collector_state()->set_mark_in_progress(true);
3234           // Note that we don't actually trigger the CM thread at
3235           // this point. We do that later when we're sure that
3236           // the current thread has completed its logging output.
3237         }
3238 
3239         allocate_dummy_regions();
3240 
3241         _allocator->init_mutator_alloc_region();
3242 
3243         {
3244           size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3245           if (expand_bytes > 0) {
3246             size_t bytes_before = capacity();
3247             // No need for an ergo logging here,
3248             // expansion_amount() does this when it returns a value > 0.
3249             double expand_ms;
3250             if (!expand(expand_bytes, &expand_ms)) {
3251               // We failed to expand the heap. Cannot do anything about it.
3252             }
3253             g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3254           }
3255         }
3256 
3257         // We redo the verification but now wrt to the new CSet which
3258         // has just got initialized after the previous CSet was freed.
3259         _cm->verify_no_cset_oops();
3260         _cm->note_end_of_gc();
3261 
3262         // This timing is only used by the ergonomics to handle our pause target.
3263         // It is unclear why this should not include the full pause. We will
3264         // investigate this in CR 7178365.
3265         double sample_end_time_sec = os::elapsedTime();
3266         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3267         size_t total_cards_scanned = per_thread_states.total_cards_scanned();
3268         g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3269 
3270         evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3271         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3272 
3273         MemoryService::track_memory_usage();
3274 
3275         // In prepare_for_verify() below we'll need to scan the deferred
3276         // update buffers to bring the RSets up-to-date if
3277         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3278         // the update buffers we'll probably need to scan cards on the
3279         // regions we just allocated to (i.e., the GC alloc
3280         // regions). However, during the last GC we called
3281         // set_saved_mark() on all the GC alloc regions, so card
3282         // scanning might skip the [saved_mark_word()...top()] area of
3283         // those regions (i.e., the area we allocated objects into
3284         // during the last GC). But it shouldn't. Given that
3285         // saved_mark_word() is conditional on whether the GC time stamp
3286         // on the region is current or not, by incrementing the GC time
3287         // stamp here we invalidate all the GC time stamps on all the
3288         // regions and saved_mark_word() will simply return top() for
3289         // all the regions. This is a nicer way of ensuring this rather
3290         // than iterating over the regions and fixing them. In fact, the
3291         // GC time stamp increment here also ensures that
3292         // saved_mark_word() will return top() between pauses, i.e.,
3293         // during concurrent refinement. So we don't need the
3294         // is_gc_active() check to decided which top to use when
3295         // scanning cards (see CR 7039627).
3296         increment_gc_time_stamp();
3297 
3298         if (VerifyRememberedSets) {
3299           log_info(gc, verify)("[Verifying RemSets after GC]");
3300           VerifyRegionRemSetClosure v_cl;
3301           heap_region_iterate(&v_cl);
3302         }
3303 
3304         _verifier->verify_after_gc();
3305         _verifier->check_bitmaps("GC End");
3306 
3307         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3308         ref_processor_stw()->verify_no_references_recorded();
3309 
3310         // CM reference discovery will be re-enabled if necessary.
3311       }
3312 
3313 #ifdef TRACESPINNING
3314       ParallelTaskTerminator::print_termination_counts();
3315 #endif
3316 
3317       gc_epilogue(false);
3318     }
3319 
3320     // Print the remainder of the GC log output.
3321     if (evacuation_failed()) {
3322       log_info(gc)("To-space exhausted");
3323     }
3324 
3325     g1_policy()->print_phases();
3326     heap_transition.print();
3327 
3328     // It is not yet to safe to tell the concurrent mark to
3329     // start as we have some optional output below. We don't want the
3330     // output from the concurrent mark thread interfering with this
3331     // logging output either.
3332 
3333     _hrm.verify_optional();
3334     _verifier->verify_region_sets_optional();
3335 
3336     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3337     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3338 
3339     print_heap_after_gc();
3340     print_heap_regions();
3341     trace_heap_after_gc(_gc_tracer_stw);
3342 
3343     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3344     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3345     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3346     // before any GC notifications are raised.
3347     g1mm()->update_sizes();
3348 
3349     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3350     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3351     _gc_timer_stw->register_gc_end();
3352     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3353   }
3354   // It should now be safe to tell the concurrent mark thread to start
3355   // without its logging output interfering with the logging output
3356   // that came from the pause.
3357 
3358   if (should_start_conc_mark) {
3359     // CAUTION: after the doConcurrentMark() call below,
3360     // the concurrent marking thread(s) could be running
3361     // concurrently with us. Make sure that anything after
3362     // this point does not assume that we are the only GC thread
3363     // running. Note: of course, the actual marking work will
3364     // not start until the safepoint itself is released in
3365     // SuspendibleThreadSet::desynchronize().
3366     doConcurrentMark();
3367   }
3368 
3369   return true;
3370 }
3371 
3372 void G1CollectedHeap::remove_self_forwarding_pointers() {
3373   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3374   workers()->run_task(&rsfp_task);
3375 }
3376 
3377 void G1CollectedHeap::restore_after_evac_failure() {
3378   double remove_self_forwards_start = os::elapsedTime();
3379 
3380   remove_self_forwarding_pointers();
3381   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3382   _preserved_marks_set.restore(&task_executor);
3383 
3384   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3385 }
3386 
3387 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3388   if (!_evacuation_failed) {
3389     _evacuation_failed = true;
3390   }
3391 
3392   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3393   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3394 }
3395 
3396 bool G1ParEvacuateFollowersClosure::offer_termination() {
3397   G1ParScanThreadState* const pss = par_scan_state();
3398   start_term_time();
3399   const bool res = terminator()->offer_termination();
3400   end_term_time();
3401   return res;
3402 }
3403 
3404 void G1ParEvacuateFollowersClosure::do_void() {
3405   G1ParScanThreadState* const pss = par_scan_state();
3406   pss->trim_queue();
3407   do {
3408     pss->steal_and_trim_queue(queues());
3409   } while (!offer_termination());
3410 }
3411 
3412 class G1ParTask : public AbstractGangTask {
3413 protected:
3414   G1CollectedHeap*         _g1h;
3415   G1ParScanThreadStateSet* _pss;
3416   RefToScanQueueSet*       _queues;
3417   G1RootProcessor*         _root_processor;
3418   ParallelTaskTerminator   _terminator;
3419   uint                     _n_workers;
3420 
3421 public:
3422   G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3423     : AbstractGangTask("G1 collection"),
3424       _g1h(g1h),
3425       _pss(per_thread_states),
3426       _queues(task_queues),
3427       _root_processor(root_processor),
3428       _terminator(n_workers, _queues),
3429       _n_workers(n_workers)
3430   {}
3431 
3432   void work(uint worker_id) {
3433     if (worker_id >= _n_workers) return;  // no work needed this round
3434 
3435     double start_sec = os::elapsedTime();
3436     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3437 
3438     {
3439       ResourceMark rm;
3440       HandleMark   hm;
3441 
3442       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
3443 
3444       G1ParScanThreadState*           pss = _pss->state_for_worker(worker_id);
3445       pss->set_ref_processor(rp);
3446 
3447       double start_strong_roots_sec = os::elapsedTime();
3448 
3449       _root_processor->evacuate_roots(pss->closures(), worker_id);
3450 
3451       G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss);
3452 
3453       // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3454       // treating the nmethods visited to act as roots for concurrent marking.
3455       // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3456       // objects copied by the current evacuation.
3457       size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl,
3458                                                                              pss->closures()->weak_codeblobs(),
3459                                                                              worker_id);
3460 
3461       _pss->add_cards_scanned(worker_id, cards_scanned);
3462 
3463       double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3464 
3465       double term_sec = 0.0;
3466       size_t evac_term_attempts = 0;
3467       {
3468         double start = os::elapsedTime();
3469         G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3470         evac.do_void();
3471 
3472         evac_term_attempts = evac.term_attempts();
3473         term_sec = evac.term_time();
3474         double elapsed_sec = os::elapsedTime() - start;
3475         _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3476         _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3477         _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3478       }
3479 
3480       assert(pss->queue_is_empty(), "should be empty");
3481 
3482       if (log_is_enabled(Debug, gc, task, stats)) {
3483         MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3484         size_t lab_waste;
3485         size_t lab_undo_waste;
3486         pss->waste(lab_waste, lab_undo_waste);
3487         _g1h->print_termination_stats(worker_id,
3488                                       (os::elapsedTime() - start_sec) * 1000.0,   /* elapsed time */
3489                                       strong_roots_sec * 1000.0,                  /* strong roots time */
3490                                       term_sec * 1000.0,                          /* evac term time */
3491                                       evac_term_attempts,                         /* evac term attempts */
3492                                       lab_waste,                                  /* alloc buffer waste */
3493                                       lab_undo_waste                              /* undo waste */
3494                                       );
3495       }
3496 
3497       // Close the inner scope so that the ResourceMark and HandleMark
3498       // destructors are executed here and are included as part of the
3499       // "GC Worker Time".
3500     }
3501     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3502   }
3503 };
3504 
3505 void G1CollectedHeap::print_termination_stats_hdr() {
3506   log_debug(gc, task, stats)("GC Termination Stats");
3507   log_debug(gc, task, stats)("     elapsed  --strong roots-- -------termination------- ------waste (KiB)------");
3508   log_debug(gc, task, stats)("thr     ms        ms      %%        ms      %%    attempts  total   alloc    undo");
3509   log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3510 }
3511 
3512 void G1CollectedHeap::print_termination_stats(uint worker_id,
3513                                               double elapsed_ms,
3514                                               double strong_roots_ms,
3515                                               double term_ms,
3516                                               size_t term_attempts,
3517                                               size_t alloc_buffer_waste,
3518                                               size_t undo_waste) const {
3519   log_debug(gc, task, stats)
3520               ("%3d %9.2f %9.2f %6.2f "
3521                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3522                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3523                worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3524                term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3525                (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3526                alloc_buffer_waste * HeapWordSize / K,
3527                undo_waste * HeapWordSize / K);
3528 }
3529 
3530 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
3531 private:
3532   BoolObjectClosure* _is_alive;
3533   int _initial_string_table_size;
3534   int _initial_symbol_table_size;
3535 
3536   bool  _process_strings;
3537   int _strings_processed;
3538   int _strings_removed;
3539 
3540   bool  _process_symbols;
3541   int _symbols_processed;
3542   int _symbols_removed;
3543 
3544 public:
3545   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
3546     AbstractGangTask("String/Symbol Unlinking"),
3547     _is_alive(is_alive),
3548     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3549     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
3550 
3551     _initial_string_table_size = StringTable::the_table()->table_size();
3552     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3553     if (process_strings) {
3554       StringTable::clear_parallel_claimed_index();
3555     }
3556     if (process_symbols) {
3557       SymbolTable::clear_parallel_claimed_index();
3558     }
3559   }
3560 
3561   ~G1StringSymbolTableUnlinkTask() {
3562     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3563               "claim value %d after unlink less than initial string table size %d",
3564               StringTable::parallel_claimed_index(), _initial_string_table_size);
3565     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3566               "claim value %d after unlink less than initial symbol table size %d",
3567               SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3568 
3569     log_info(gc, stringtable)(
3570         "Cleaned string and symbol table, "
3571         "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3572         "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3573         strings_processed(), strings_removed(),
3574         symbols_processed(), symbols_removed());
3575   }
3576 
3577   void work(uint worker_id) {
3578     int strings_processed = 0;
3579     int strings_removed = 0;
3580     int symbols_processed = 0;
3581     int symbols_removed = 0;
3582     if (_process_strings) {
3583       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3584       Atomic::add(strings_processed, &_strings_processed);
3585       Atomic::add(strings_removed, &_strings_removed);
3586     }
3587     if (_process_symbols) {
3588       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3589       Atomic::add(symbols_processed, &_symbols_processed);
3590       Atomic::add(symbols_removed, &_symbols_removed);
3591     }
3592   }
3593 
3594   size_t strings_processed() const { return (size_t)_strings_processed; }
3595   size_t strings_removed()   const { return (size_t)_strings_removed; }
3596 
3597   size_t symbols_processed() const { return (size_t)_symbols_processed; }
3598   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
3599 };
3600 
3601 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3602 private:
3603   static Monitor* _lock;
3604 
3605   BoolObjectClosure* const _is_alive;
3606   const bool               _unloading_occurred;
3607   const uint               _num_workers;
3608 
3609   // Variables used to claim nmethods.
3610   CompiledMethod* _first_nmethod;
3611   volatile CompiledMethod* _claimed_nmethod;
3612 
3613   // The list of nmethods that need to be processed by the second pass.
3614   volatile CompiledMethod* _postponed_list;
3615   volatile uint            _num_entered_barrier;
3616 
3617  public:
3618   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3619       _is_alive(is_alive),
3620       _unloading_occurred(unloading_occurred),
3621       _num_workers(num_workers),
3622       _first_nmethod(NULL),
3623       _claimed_nmethod(NULL),
3624       _postponed_list(NULL),
3625       _num_entered_barrier(0)
3626   {
3627     CompiledMethod::increase_unloading_clock();
3628     // Get first alive nmethod
3629     CompiledMethodIterator iter = CompiledMethodIterator();
3630     if(iter.next_alive()) {
3631       _first_nmethod = iter.method();
3632     }
3633     _claimed_nmethod = (volatile CompiledMethod*)_first_nmethod;
3634   }
3635 
3636   ~G1CodeCacheUnloadingTask() {
3637     CodeCache::verify_clean_inline_caches();
3638 
3639     CodeCache::set_needs_cache_clean(false);
3640     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3641 
3642     CodeCache::verify_icholder_relocations();
3643   }
3644 
3645  private:
3646   void add_to_postponed_list(CompiledMethod* nm) {
3647       CompiledMethod* old;
3648       do {
3649         old = (CompiledMethod*)_postponed_list;
3650         nm->set_unloading_next(old);
3651       } while ((CompiledMethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
3652   }
3653 
3654   void clean_nmethod(CompiledMethod* nm) {
3655     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3656 
3657     if (postponed) {
3658       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3659       add_to_postponed_list(nm);
3660     }
3661 
3662     // Mark that this thread has been cleaned/unloaded.
3663     // After this call, it will be safe to ask if this nmethod was unloaded or not.
3664     nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3665   }
3666 
3667   void clean_nmethod_postponed(CompiledMethod* nm) {
3668     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3669   }
3670 
3671   static const int MaxClaimNmethods = 16;
3672 
3673   void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3674     CompiledMethod* first;
3675     CompiledMethodIterator last;
3676 
3677     do {
3678       *num_claimed_nmethods = 0;
3679 
3680       first = (CompiledMethod*)_claimed_nmethod;
3681       last = CompiledMethodIterator(first);
3682 
3683       if (first != NULL) {
3684 
3685         for (int i = 0; i < MaxClaimNmethods; i++) {
3686           if (!last.next_alive()) {
3687             break;
3688           }
3689           claimed_nmethods[i] = last.method();
3690           (*num_claimed_nmethods)++;
3691         }
3692       }
3693 
3694     } while ((CompiledMethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
3695   }
3696 
3697   CompiledMethod* claim_postponed_nmethod() {
3698     CompiledMethod* claim;
3699     CompiledMethod* next;
3700 
3701     do {
3702       claim = (CompiledMethod*)_postponed_list;
3703       if (claim == NULL) {
3704         return NULL;
3705       }
3706 
3707       next = claim->unloading_next();
3708 
3709     } while ((CompiledMethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
3710 
3711     return claim;
3712   }
3713 
3714  public:
3715   // Mark that we're done with the first pass of nmethod cleaning.
3716   void barrier_mark(uint worker_id) {
3717     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3718     _num_entered_barrier++;
3719     if (_num_entered_barrier == _num_workers) {
3720       ml.notify_all();
3721     }
3722   }
3723 
3724   // See if we have to wait for the other workers to
3725   // finish their first-pass nmethod cleaning work.
3726   void barrier_wait(uint worker_id) {
3727     if (_num_entered_barrier < _num_workers) {
3728       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3729       while (_num_entered_barrier < _num_workers) {
3730           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3731       }
3732     }
3733   }
3734 
3735   // Cleaning and unloading of nmethods. Some work has to be postponed
3736   // to the second pass, when we know which nmethods survive.
3737   void work_first_pass(uint worker_id) {
3738     // The first nmethods is claimed by the first worker.
3739     if (worker_id == 0 && _first_nmethod != NULL) {
3740       clean_nmethod(_first_nmethod);
3741       _first_nmethod = NULL;
3742     }
3743 
3744     int num_claimed_nmethods;
3745     CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3746 
3747     while (true) {
3748       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3749 
3750       if (num_claimed_nmethods == 0) {
3751         break;
3752       }
3753 
3754       for (int i = 0; i < num_claimed_nmethods; i++) {
3755         clean_nmethod(claimed_nmethods[i]);
3756       }
3757     }
3758   }
3759 
3760   void work_second_pass(uint worker_id) {
3761     CompiledMethod* nm;
3762     // Take care of postponed nmethods.
3763     while ((nm = claim_postponed_nmethod()) != NULL) {
3764       clean_nmethod_postponed(nm);
3765     }
3766   }
3767 };
3768 
3769 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3770 
3771 class G1KlassCleaningTask : public StackObj {
3772   BoolObjectClosure*                      _is_alive;
3773   volatile jint                           _clean_klass_tree_claimed;
3774   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3775 
3776  public:
3777   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3778       _is_alive(is_alive),
3779       _clean_klass_tree_claimed(0),
3780       _klass_iterator() {
3781   }
3782 
3783  private:
3784   bool claim_clean_klass_tree_task() {
3785     if (_clean_klass_tree_claimed) {
3786       return false;
3787     }
3788 
3789     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
3790   }
3791 
3792   InstanceKlass* claim_next_klass() {
3793     Klass* klass;
3794     do {
3795       klass =_klass_iterator.next_klass();
3796     } while (klass != NULL && !klass->is_instance_klass());
3797 
3798     // this can be null so don't call InstanceKlass::cast
3799     return static_cast<InstanceKlass*>(klass);
3800   }
3801 
3802 public:
3803 
3804   void clean_klass(InstanceKlass* ik) {
3805     ik->clean_weak_instanceklass_links(_is_alive);
3806   }
3807 
3808   void work() {
3809     ResourceMark rm;
3810 
3811     // One worker will clean the subklass/sibling klass tree.
3812     if (claim_clean_klass_tree_task()) {
3813       Klass::clean_subklass_tree(_is_alive);
3814     }
3815 
3816     // All workers will help cleaning the classes,
3817     InstanceKlass* klass;
3818     while ((klass = claim_next_klass()) != NULL) {
3819       clean_klass(klass);
3820     }
3821   }
3822 };
3823 
3824 // To minimize the remark pause times, the tasks below are done in parallel.
3825 class G1ParallelCleaningTask : public AbstractGangTask {
3826 private:
3827   G1StringSymbolTableUnlinkTask _string_symbol_task;
3828   G1CodeCacheUnloadingTask      _code_cache_task;
3829   G1KlassCleaningTask           _klass_cleaning_task;
3830 
3831 public:
3832   // The constructor is run in the VMThread.
3833   G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
3834       AbstractGangTask("Parallel Cleaning"),
3835       _string_symbol_task(is_alive, process_strings, process_symbols),
3836       _code_cache_task(num_workers, is_alive, unloading_occurred),
3837       _klass_cleaning_task(is_alive) {
3838   }
3839 
3840   // The parallel work done by all worker threads.
3841   void work(uint worker_id) {
3842     // Do first pass of code cache cleaning.
3843     _code_cache_task.work_first_pass(worker_id);
3844 
3845     // Let the threads mark that the first pass is done.
3846     _code_cache_task.barrier_mark(worker_id);
3847 
3848     // Clean the Strings and Symbols.
3849     _string_symbol_task.work(worker_id);
3850 
3851     // Wait for all workers to finish the first code cache cleaning pass.
3852     _code_cache_task.barrier_wait(worker_id);
3853 
3854     // Do the second code cache cleaning work, which realize on
3855     // the liveness information gathered during the first pass.
3856     _code_cache_task.work_second_pass(worker_id);
3857 
3858     // Clean all klasses that were not unloaded.
3859     _klass_cleaning_task.work();
3860   }
3861 };
3862 
3863 
3864 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
3865                                         bool process_strings,
3866                                         bool process_symbols,
3867                                         bool class_unloading_occurred) {
3868   uint n_workers = workers()->active_workers();
3869 
3870   G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
3871                                         n_workers, class_unloading_occurred);
3872   workers()->run_task(&g1_unlink_task);
3873 }
3874 
3875 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
3876                                                      bool process_strings, bool process_symbols) {
3877   { // Timing scope
3878     G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
3879     workers()->run_task(&g1_unlink_task);
3880   }
3881 }
3882 
3883 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3884  private:
3885   DirtyCardQueueSet* _queue;
3886   G1CollectedHeap* _g1h;
3887  public:
3888   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3889     _queue(queue), _g1h(g1h) { }
3890 
3891   virtual void work(uint worker_id) {
3892     G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3893     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3894 
3895     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3896     _queue->par_apply_closure_to_all_completed_buffers(&cl);
3897 
3898     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3899   }
3900 };
3901 
3902 void G1CollectedHeap::redirty_logged_cards() {
3903   double redirty_logged_cards_start = os::elapsedTime();
3904 
3905   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3906   dirty_card_queue_set().reset_for_par_iteration();
3907   workers()->run_task(&redirty_task);
3908 
3909   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
3910   dcq.merge_bufferlists(&dirty_card_queue_set());
3911   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3912 
3913   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3914 }
3915 
3916 // Weak Reference Processing support
3917 
3918 // An always "is_alive" closure that is used to preserve referents.
3919 // If the object is non-null then it's alive.  Used in the preservation
3920 // of referent objects that are pointed to by reference objects
3921 // discovered by the CM ref processor.
3922 class G1AlwaysAliveClosure: public BoolObjectClosure {
3923   G1CollectedHeap* _g1;
3924 public:
3925   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3926   bool do_object_b(oop p) {
3927     if (p != NULL) {
3928       return true;
3929     }
3930     return false;
3931   }
3932 };
3933 
3934 bool G1STWIsAliveClosure::do_object_b(oop p) {
3935   // An object is reachable if it is outside the collection set,
3936   // or is inside and copied.
3937   return !_g1->is_in_cset(p) || p->is_forwarded();
3938 }
3939 
3940 // Non Copying Keep Alive closure
3941 class G1KeepAliveClosure: public OopClosure {
3942   G1CollectedHeap* _g1;
3943 public:
3944   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3945   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3946   void do_oop(oop* p) {
3947     oop obj = *p;
3948     assert(obj != NULL, "the caller should have filtered out NULL values");
3949 
3950     const InCSetState cset_state = _g1->in_cset_state(obj);
3951     if (!cset_state.is_in_cset_or_humongous()) {
3952       return;
3953     }
3954     if (cset_state.is_in_cset()) {
3955       assert( obj->is_forwarded(), "invariant" );
3956       *p = obj->forwardee();
3957     } else {
3958       assert(!obj->is_forwarded(), "invariant" );
3959       assert(cset_state.is_humongous(),
3960              "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3961       _g1->set_humongous_is_live(obj);
3962     }
3963   }
3964 };
3965 
3966 // Copying Keep Alive closure - can be called from both
3967 // serial and parallel code as long as different worker
3968 // threads utilize different G1ParScanThreadState instances
3969 // and different queues.
3970 
3971 class G1CopyingKeepAliveClosure: public OopClosure {
3972   G1CollectedHeap*         _g1h;
3973   OopClosure*              _copy_non_heap_obj_cl;
3974   G1ParScanThreadState*    _par_scan_state;
3975 
3976 public:
3977   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3978                             OopClosure* non_heap_obj_cl,
3979                             G1ParScanThreadState* pss):
3980     _g1h(g1h),
3981     _copy_non_heap_obj_cl(non_heap_obj_cl),
3982     _par_scan_state(pss)
3983   {}
3984 
3985   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3986   virtual void do_oop(      oop* p) { do_oop_work(p); }
3987 
3988   template <class T> void do_oop_work(T* p) {
3989     oop obj = oopDesc::load_decode_heap_oop(p);
3990 
3991     if (_g1h->is_in_cset_or_humongous(obj)) {
3992       // If the referent object has been forwarded (either copied
3993       // to a new location or to itself in the event of an
3994       // evacuation failure) then we need to update the reference
3995       // field and, if both reference and referent are in the G1
3996       // heap, update the RSet for the referent.
3997       //
3998       // If the referent has not been forwarded then we have to keep
3999       // it alive by policy. Therefore we have copy the referent.
4000       //
4001       // If the reference field is in the G1 heap then we can push
4002       // on the PSS queue. When the queue is drained (after each
4003       // phase of reference processing) the object and it's followers
4004       // will be copied, the reference field set to point to the
4005       // new location, and the RSet updated. Otherwise we need to
4006       // use the the non-heap or metadata closures directly to copy
4007       // the referent object and update the pointer, while avoiding
4008       // updating the RSet.
4009 
4010       if (_g1h->is_in_g1_reserved(p)) {
4011         _par_scan_state->push_on_queue(p);
4012       } else {
4013         assert(!Metaspace::contains((const void*)p),
4014                "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
4015         _copy_non_heap_obj_cl->do_oop(p);
4016       }
4017     }
4018   }
4019 };
4020 
4021 // Serial drain queue closure. Called as the 'complete_gc'
4022 // closure for each discovered list in some of the
4023 // reference processing phases.
4024 
4025 class G1STWDrainQueueClosure: public VoidClosure {
4026 protected:
4027   G1CollectedHeap* _g1h;
4028   G1ParScanThreadState* _par_scan_state;
4029 
4030   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4031 
4032 public:
4033   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
4034     _g1h(g1h),
4035     _par_scan_state(pss)
4036   { }
4037 
4038   void do_void() {
4039     G1ParScanThreadState* const pss = par_scan_state();
4040     pss->trim_queue();
4041   }
4042 };
4043 
4044 // Parallel Reference Processing closures
4045 
4046 // Implementation of AbstractRefProcTaskExecutor for parallel reference
4047 // processing during G1 evacuation pauses.
4048 
4049 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
4050 private:
4051   G1CollectedHeap*          _g1h;
4052   G1ParScanThreadStateSet*  _pss;
4053   RefToScanQueueSet*        _queues;
4054   WorkGang*                 _workers;
4055   uint                      _active_workers;
4056 
4057 public:
4058   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
4059                            G1ParScanThreadStateSet* per_thread_states,
4060                            WorkGang* workers,
4061                            RefToScanQueueSet *task_queues,
4062                            uint n_workers) :
4063     _g1h(g1h),
4064     _pss(per_thread_states),
4065     _queues(task_queues),
4066     _workers(workers),
4067     _active_workers(n_workers)
4068   {
4069     g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
4070   }
4071 
4072   // Executes the given task using concurrent marking worker threads.
4073   virtual void execute(ProcessTask& task);
4074   virtual void execute(EnqueueTask& task);
4075 };
4076 
4077 // Gang task for possibly parallel reference processing
4078 
4079 class G1STWRefProcTaskProxy: public AbstractGangTask {
4080   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
4081   ProcessTask&     _proc_task;
4082   G1CollectedHeap* _g1h;
4083   G1ParScanThreadStateSet* _pss;
4084   RefToScanQueueSet* _task_queues;
4085   ParallelTaskTerminator* _terminator;
4086 
4087 public:
4088   G1STWRefProcTaskProxy(ProcessTask& proc_task,
4089                         G1CollectedHeap* g1h,
4090                         G1ParScanThreadStateSet* per_thread_states,
4091                         RefToScanQueueSet *task_queues,
4092                         ParallelTaskTerminator* terminator) :
4093     AbstractGangTask("Process reference objects in parallel"),
4094     _proc_task(proc_task),
4095     _g1h(g1h),
4096     _pss(per_thread_states),
4097     _task_queues(task_queues),
4098     _terminator(terminator)
4099   {}
4100 
4101   virtual void work(uint worker_id) {
4102     // The reference processing task executed by a single worker.
4103     ResourceMark rm;
4104     HandleMark   hm;
4105 
4106     G1STWIsAliveClosure is_alive(_g1h);
4107 
4108     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4109     pss->set_ref_processor(NULL);
4110 
4111     // Keep alive closure.
4112     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4113 
4114     // Complete GC closure
4115     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
4116 
4117     // Call the reference processing task's work routine.
4118     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
4119 
4120     // Note we cannot assert that the refs array is empty here as not all
4121     // of the processing tasks (specifically phase2 - pp2_work) execute
4122     // the complete_gc closure (which ordinarily would drain the queue) so
4123     // the queue may not be empty.
4124   }
4125 };
4126 
4127 // Driver routine for parallel reference processing.
4128 // Creates an instance of the ref processing gang
4129 // task and has the worker threads execute it.
4130 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4131   assert(_workers != NULL, "Need parallel worker threads.");
4132 
4133   ParallelTaskTerminator terminator(_active_workers, _queues);
4134   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4135 
4136   _workers->run_task(&proc_task_proxy);
4137 }
4138 
4139 // Gang task for parallel reference enqueueing.
4140 
4141 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4142   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4143   EnqueueTask& _enq_task;
4144 
4145 public:
4146   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4147     AbstractGangTask("Enqueue reference objects in parallel"),
4148     _enq_task(enq_task)
4149   { }
4150 
4151   virtual void work(uint worker_id) {
4152     _enq_task.work(worker_id);
4153   }
4154 };
4155 
4156 // Driver routine for parallel reference enqueueing.
4157 // Creates an instance of the ref enqueueing gang
4158 // task and has the worker threads execute it.
4159 
4160 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4161   assert(_workers != NULL, "Need parallel worker threads.");
4162 
4163   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4164 
4165   _workers->run_task(&enq_task_proxy);
4166 }
4167 
4168 // End of weak reference support closures
4169 
4170 // Abstract task used to preserve (i.e. copy) any referent objects
4171 // that are in the collection set and are pointed to by reference
4172 // objects discovered by the CM ref processor.
4173 
4174 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4175 protected:
4176   G1CollectedHeap*         _g1h;
4177   G1ParScanThreadStateSet* _pss;
4178   RefToScanQueueSet*       _queues;
4179   ParallelTaskTerminator   _terminator;
4180   uint                     _n_workers;
4181 
4182 public:
4183   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4184     AbstractGangTask("ParPreserveCMReferents"),
4185     _g1h(g1h),
4186     _pss(per_thread_states),
4187     _queues(task_queues),
4188     _terminator(workers, _queues),
4189     _n_workers(workers)
4190   {
4191     g1h->ref_processor_cm()->set_active_mt_degree(workers);
4192   }
4193 
4194   void work(uint worker_id) {
4195     G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4196 
4197     ResourceMark rm;
4198     HandleMark   hm;
4199 
4200     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4201     pss->set_ref_processor(NULL);
4202     assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4203 
4204     // Is alive closure
4205     G1AlwaysAliveClosure always_alive(_g1h);
4206 
4207     // Copying keep alive closure. Applied to referent objects that need
4208     // to be copied.
4209     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4210 
4211     ReferenceProcessor* rp = _g1h->ref_processor_cm();
4212 
4213     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4214     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4215 
4216     // limit is set using max_num_q() - which was set using ParallelGCThreads.
4217     // So this must be true - but assert just in case someone decides to
4218     // change the worker ids.
4219     assert(worker_id < limit, "sanity");
4220     assert(!rp->discovery_is_atomic(), "check this code");
4221 
4222     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4223     for (uint idx = worker_id; idx < limit; idx += stride) {
4224       DiscoveredList& ref_list = rp->discovered_refs()[idx];
4225 
4226       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4227       while (iter.has_next()) {
4228         // Since discovery is not atomic for the CM ref processor, we
4229         // can see some null referent objects.
4230         iter.load_ptrs(DEBUG_ONLY(true));
4231         oop ref = iter.obj();
4232 
4233         // This will filter nulls.
4234         if (iter.is_referent_alive()) {
4235           iter.make_referent_alive();
4236         }
4237         iter.move_to_next();
4238       }
4239     }
4240 
4241     // Drain the queue - which may cause stealing
4242     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4243     drain_queue.do_void();
4244     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4245     assert(pss->queue_is_empty(), "should be");
4246   }
4247 };
4248 
4249 void G1CollectedHeap::process_weak_jni_handles() {
4250   double ref_proc_start = os::elapsedTime();
4251 
4252   G1STWIsAliveClosure is_alive(this);
4253   G1KeepAliveClosure keep_alive(this);
4254   JNIHandles::weak_oops_do(&is_alive, &keep_alive);
4255 
4256   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4257   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4258 }
4259 
4260 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4261   // Any reference objects, in the collection set, that were 'discovered'
4262   // by the CM ref processor should have already been copied (either by
4263   // applying the external root copy closure to the discovered lists, or
4264   // by following an RSet entry).
4265   //
4266   // But some of the referents, that are in the collection set, that these
4267   // reference objects point to may not have been copied: the STW ref
4268   // processor would have seen that the reference object had already
4269   // been 'discovered' and would have skipped discovering the reference,
4270   // but would not have treated the reference object as a regular oop.
4271   // As a result the copy closure would not have been applied to the
4272   // referent object.
4273   //
4274   // We need to explicitly copy these referent objects - the references
4275   // will be processed at the end of remarking.
4276   //
4277   // We also need to do this copying before we process the reference
4278   // objects discovered by the STW ref processor in case one of these
4279   // referents points to another object which is also referenced by an
4280   // object discovered by the STW ref processor.
4281   double preserve_cm_referents_time = 0.0;
4282 
4283   // To avoid spawning task when there is no work to do, check that
4284   // a concurrent cycle is active and that some references have been
4285   // discovered.
4286   if (concurrent_mark()->cmThread()->during_cycle() &&
4287       ref_processor_cm()->has_discovered_references()) {
4288     double preserve_cm_referents_start = os::elapsedTime();
4289     uint no_of_gc_workers = workers()->active_workers();
4290     G1ParPreserveCMReferentsTask keep_cm_referents(this,
4291                                                    per_thread_states,
4292                                                    no_of_gc_workers,
4293                                                    _task_queues);
4294     workers()->run_task(&keep_cm_referents);
4295     preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4296   }
4297 
4298   g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4299 }
4300 
4301 // Weak Reference processing during an evacuation pause (part 1).
4302 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4303   double ref_proc_start = os::elapsedTime();
4304 
4305   ReferenceProcessor* rp = _ref_processor_stw;
4306   assert(rp->discovery_enabled(), "should have been enabled");
4307 
4308   // Closure to test whether a referent is alive.
4309   G1STWIsAliveClosure is_alive(this);
4310 
4311   // Even when parallel reference processing is enabled, the processing
4312   // of JNI refs is serial and performed serially by the current thread
4313   // rather than by a worker. The following PSS will be used for processing
4314   // JNI refs.
4315 
4316   // Use only a single queue for this PSS.
4317   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
4318   pss->set_ref_processor(NULL);
4319   assert(pss->queue_is_empty(), "pre-condition");
4320 
4321   // Keep alive closure.
4322   G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4323 
4324   // Serial Complete GC closure
4325   G1STWDrainQueueClosure drain_queue(this, pss);
4326 
4327   // Setup the soft refs policy...
4328   rp->setup_policy(false);
4329 
4330   ReferenceProcessorStats stats;
4331   if (!rp->processing_is_mt()) {
4332     // Serial reference processing...
4333     stats = rp->process_discovered_references(&is_alive,
4334                                               &keep_alive,
4335                                               &drain_queue,
4336                                               NULL,
4337                                               _gc_timer_stw);
4338   } else {
4339     uint no_of_gc_workers = workers()->active_workers();
4340 
4341     // Parallel reference processing
4342     assert(no_of_gc_workers <= rp->max_num_q(),
4343            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4344            no_of_gc_workers,  rp->max_num_q());
4345 
4346     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4347     stats = rp->process_discovered_references(&is_alive,
4348                                               &keep_alive,
4349                                               &drain_queue,
4350                                               &par_task_executor,
4351                                               _gc_timer_stw);
4352   }
4353 
4354   _gc_tracer_stw->report_gc_reference_stats(stats);
4355 
4356   // We have completed copying any necessary live referent objects.
4357   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4358 
4359   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4360   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4361 }
4362 
4363 // Weak Reference processing during an evacuation pause (part 2).
4364 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4365   double ref_enq_start = os::elapsedTime();
4366 
4367   ReferenceProcessor* rp = _ref_processor_stw;
4368   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4369 
4370   // Now enqueue any remaining on the discovered lists on to
4371   // the pending list.
4372   if (!rp->processing_is_mt()) {
4373     // Serial reference processing...
4374     rp->enqueue_discovered_references();
4375   } else {
4376     // Parallel reference enqueueing
4377 
4378     uint n_workers = workers()->active_workers();
4379 
4380     assert(n_workers <= rp->max_num_q(),
4381            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4382            n_workers,  rp->max_num_q());
4383 
4384     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4385     rp->enqueue_discovered_references(&par_task_executor);
4386   }
4387 
4388   rp->verify_no_references_recorded();
4389   assert(!rp->discovery_enabled(), "should have been disabled");
4390 
4391   // FIXME
4392   // CM's reference processing also cleans up the string and symbol tables.
4393   // Should we do that here also? We could, but it is a serial operation
4394   // and could significantly increase the pause time.
4395 
4396   double ref_enq_time = os::elapsedTime() - ref_enq_start;
4397   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4398 }
4399 
4400 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4401   double merge_pss_time_start = os::elapsedTime();
4402   per_thread_states->flush();
4403   g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4404 }
4405 
4406 void G1CollectedHeap::pre_evacuate_collection_set() {
4407   _expand_heap_after_alloc_failure = true;
4408   _evacuation_failed = false;
4409 
4410   // Disable the hot card cache.
4411   _hot_card_cache->reset_hot_cache_claimed_index();
4412   _hot_card_cache->set_use_cache(false);
4413 
4414   g1_rem_set()->prepare_for_oops_into_collection_set_do();
4415   _preserved_marks_set.assert_empty();
4416 }
4417 
4418 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4419   // Should G1EvacuationFailureALot be in effect for this GC?
4420   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4421 
4422   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4423   double start_par_time_sec = os::elapsedTime();
4424   double end_par_time_sec;
4425 
4426   {
4427     const uint n_workers = workers()->active_workers();
4428     G1RootProcessor root_processor(this, n_workers);
4429     G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4430     // InitialMark needs claim bits to keep track of the marked-through CLDs.
4431     if (collector_state()->during_initial_mark_pause()) {
4432       ClassLoaderDataGraph::clear_claimed_marks();
4433     }
4434 
4435     print_termination_stats_hdr();
4436 
4437     workers()->run_task(&g1_par_task);
4438     end_par_time_sec = os::elapsedTime();
4439 
4440     // Closing the inner scope will execute the destructor
4441     // for the G1RootProcessor object. We record the current
4442     // elapsed time before closing the scope so that time
4443     // taken for the destructor is NOT included in the
4444     // reported parallel time.
4445   }
4446 
4447   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4448 
4449   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4450   phase_times->record_par_time(par_time_ms);
4451 
4452   double code_root_fixup_time_ms =
4453         (os::elapsedTime() - end_par_time_sec) * 1000.0;
4454   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4455 }
4456 
4457 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4458   // Process any discovered reference objects - we have
4459   // to do this _before_ we retire the GC alloc regions
4460   // as we may have to copy some 'reachable' referent
4461   // objects (and their reachable sub-graphs) that were
4462   // not copied during the pause.
4463   if (g1_policy()->should_process_references()) {
4464     preserve_cm_referents(per_thread_states);
4465     process_discovered_references(per_thread_states);
4466   } else {
4467     ref_processor_stw()->verify_no_references_recorded();
4468     process_weak_jni_handles();
4469   }
4470 
4471   if (G1StringDedup::is_enabled()) {
4472     double fixup_start = os::elapsedTime();
4473 
4474     G1STWIsAliveClosure is_alive(this);
4475     G1KeepAliveClosure keep_alive(this);
4476     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4477 
4478     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4479     g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4480   }
4481 
4482   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4483 
4484   if (evacuation_failed()) {
4485     restore_after_evac_failure();
4486 
4487     // Reset the G1EvacuationFailureALot counters and flags
4488     // Note: the values are reset only when an actual
4489     // evacuation failure occurs.
4490     NOT_PRODUCT(reset_evacuation_should_fail();)
4491   }
4492 
4493   _preserved_marks_set.assert_empty();
4494 
4495   // Enqueue any remaining references remaining on the STW
4496   // reference processor's discovered lists. We need to do
4497   // this after the card table is cleaned (and verified) as
4498   // the act of enqueueing entries on to the pending list
4499   // will log these updates (and dirty their associated
4500   // cards). We need these updates logged to update any
4501   // RSets.
4502   if (g1_policy()->should_process_references()) {
4503     enqueue_discovered_references(per_thread_states);
4504   } else {
4505     g1_policy()->phase_times()->record_ref_enq_time(0);
4506   }
4507 
4508   _allocator->release_gc_alloc_regions(evacuation_info);
4509 
4510   merge_per_thread_state_info(per_thread_states);
4511 
4512   // Reset and re-enable the hot card cache.
4513   // Note the counts for the cards in the regions in the
4514   // collection set are reset when the collection set is freed.
4515   _hot_card_cache->reset_hot_cache();
4516   _hot_card_cache->set_use_cache(true);
4517 
4518   purge_code_root_memory();
4519 
4520   redirty_logged_cards();
4521 #if defined(COMPILER2) || INCLUDE_JVMCI
4522   DerivedPointerTable::update_pointers();
4523 #endif
4524 }
4525 
4526 void G1CollectedHeap::record_obj_copy_mem_stats() {
4527   g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4528 
4529   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4530                                                create_g1_evac_summary(&_old_evac_stats));
4531 }
4532 
4533 void G1CollectedHeap::free_region(HeapRegion* hr,
4534                                   FreeRegionList* free_list,
4535                                   bool skip_remset,
4536                                   bool skip_hot_card_cache,
4537                                   bool locked) {
4538   assert(!hr->is_free(), "the region should not be free");
4539   assert(!hr->is_empty(), "the region should not be empty");
4540   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4541   assert(free_list != NULL, "pre-condition");
4542 
4543   if (G1VerifyBitmaps) {
4544     MemRegion mr(hr->bottom(), hr->end());
4545     concurrent_mark()->clearRangePrevBitmap(mr);
4546   }
4547 
4548   // Clear the card counts for this region.
4549   // Note: we only need to do this if the region is not young
4550   // (since we don't refine cards in young regions).
4551   if (!skip_hot_card_cache && !hr->is_young()) {
4552     _hot_card_cache->reset_card_counts(hr);
4553   }
4554   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4555   free_list->add_ordered(hr);
4556 }
4557 
4558 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4559                                             FreeRegionList* free_list,
4560                                             bool skip_remset) {
4561   assert(hr->is_humongous(), "this is only for humongous regions");
4562   assert(free_list != NULL, "pre-condition");
4563   hr->clear_humongous();
4564   free_region(hr, free_list, skip_remset);
4565 }
4566 
4567 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4568                                            const uint humongous_regions_removed) {
4569   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4570     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4571     _old_set.bulk_remove(old_regions_removed);
4572     _humongous_set.bulk_remove(humongous_regions_removed);
4573   }
4574 
4575 }
4576 
4577 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4578   assert(list != NULL, "list can't be null");
4579   if (!list->is_empty()) {
4580     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4581     _hrm.insert_list_into_free_list(list);
4582   }
4583 }
4584 
4585 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4586   decrease_used(bytes);
4587 }
4588 
4589 class G1ParScrubRemSetTask: public AbstractGangTask {
4590 protected:
4591   G1RemSet* _g1rs;
4592   HeapRegionClaimer _hrclaimer;
4593 
4594 public:
4595   G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
4596     AbstractGangTask("G1 ScrubRS"),
4597     _g1rs(g1_rs),
4598     _hrclaimer(num_workers) {
4599   }
4600 
4601   void work(uint worker_id) {
4602     _g1rs->scrub(worker_id, &_hrclaimer);
4603   }
4604 };
4605 
4606 void G1CollectedHeap::scrub_rem_set() {
4607   uint num_workers = workers()->active_workers();
4608   G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
4609   workers()->run_task(&g1_par_scrub_rs_task);
4610 }
4611 
4612 class G1FreeCollectionSetTask : public AbstractGangTask {
4613 private:
4614 
4615   // Closure applied to all regions in the collection set to do work that needs to
4616   // be done serially in a single thread.
4617   class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4618   private:
4619     EvacuationInfo* _evacuation_info;
4620     const size_t* _surviving_young_words;
4621 
4622     // Bytes used in successfully evacuated regions before the evacuation.
4623     size_t _before_used_bytes;
4624     // Bytes used in unsucessfully evacuated regions before the evacuation
4625     size_t _after_used_bytes;
4626 
4627     size_t _bytes_allocated_in_old_since_last_gc;
4628 
4629     size_t _failure_used_words;
4630     size_t _failure_waste_words;
4631 
4632     FreeRegionList _local_free_list;
4633   public:
4634     G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4635       HeapRegionClosure(),
4636       _evacuation_info(evacuation_info),
4637       _surviving_young_words(surviving_young_words),
4638       _before_used_bytes(0),
4639       _after_used_bytes(0),
4640       _bytes_allocated_in_old_since_last_gc(0),
4641       _failure_used_words(0),
4642       _failure_waste_words(0),
4643       _local_free_list("Local Region List for CSet Freeing") {
4644     }
4645 
4646     virtual bool doHeapRegion(HeapRegion* r) {
4647       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4648 
4649       assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4650       g1h->clear_in_cset(r);
4651 
4652       if (r->is_young()) {
4653         assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4654                "Young index %d is wrong for region %u of type %s with %u young regions",
4655                r->young_index_in_cset(),
4656                r->hrm_index(),
4657                r->get_type_str(),
4658                g1h->collection_set()->young_region_length());
4659         size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4660         r->record_surv_words_in_group(words_survived);
4661       }
4662 
4663       if (!r->evacuation_failed()) {
4664         assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4665         _before_used_bytes += r->used();
4666         g1h->free_region(r,
4667                          &_local_free_list,
4668                          true, /* skip_remset */
4669                          true, /* skip_hot_card_cache */
4670                          true  /* locked */);
4671       } else {
4672         r->uninstall_surv_rate_group();
4673         r->set_young_index_in_cset(-1);
4674         r->set_evacuation_failed(false);
4675         // When moving a young gen region to old gen, we "allocate" that whole region
4676         // there. This is in addition to any already evacuated objects. Notify the
4677         // policy about that.
4678         // Old gen regions do not cause an additional allocation: both the objects
4679         // still in the region and the ones already moved are accounted for elsewhere.
4680         if (r->is_young()) {
4681           _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4682         }
4683         // The region is now considered to be old.
4684         r->set_old();
4685         // Do some allocation statistics accounting. Regions that failed evacuation
4686         // are always made old, so there is no need to update anything in the young
4687         // gen statistics, but we need to update old gen statistics.
4688         size_t used_words = r->marked_bytes() / HeapWordSize;
4689 
4690         _failure_used_words += used_words;
4691         _failure_waste_words += HeapRegion::GrainWords - used_words;
4692 
4693         g1h->old_set_add(r);
4694         _after_used_bytes += r->used();
4695       }
4696       return false;
4697     }
4698 
4699     void complete_work() {
4700       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4701 
4702       _evacuation_info->set_regions_freed(_local_free_list.length());
4703       _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4704 
4705       g1h->prepend_to_freelist(&_local_free_list);
4706       g1h->decrement_summary_bytes(_before_used_bytes);
4707 
4708       G1Policy* policy = g1h->g1_policy();
4709       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4710 
4711       g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4712     }
4713   };
4714 
4715   G1CollectionSet* _collection_set;
4716   G1SerialFreeCollectionSetClosure _cl;
4717   const size_t* _surviving_young_words;
4718 
4719   size_t _rs_lengths;
4720 
4721   volatile jint _serial_work_claim;
4722 
4723   struct WorkItem {
4724     uint region_idx;
4725     bool is_young;
4726     bool evacuation_failed;
4727 
4728     WorkItem(HeapRegion* r) {
4729       region_idx = r->hrm_index();
4730       is_young = r->is_young();
4731       evacuation_failed = r->evacuation_failed();
4732     }
4733   };
4734 
4735   volatile size_t _parallel_work_claim;
4736   size_t _num_work_items;
4737   WorkItem* _work_items;
4738 
4739   void do_serial_work() {
4740     // Need to grab the lock to be allowed to modify the old region list.
4741     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4742     _collection_set->iterate(&_cl);
4743   }
4744 
4745   void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4746     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4747 
4748     HeapRegion* r = g1h->region_at(region_idx);
4749     assert(!g1h->is_on_master_free_list(r), "sanity");
4750 
4751     Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4752 
4753     if (!is_young) {
4754       g1h->_hot_card_cache->reset_card_counts(r);
4755     }
4756 
4757     if (!evacuation_failed) {
4758       r->rem_set()->clear_locked();
4759     }
4760   }
4761 
4762   class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4763   private:
4764     size_t _cur_idx;
4765     WorkItem* _work_items;
4766   public:
4767     G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4768 
4769     virtual bool doHeapRegion(HeapRegion* r) {
4770       _work_items[_cur_idx++] = WorkItem(r);
4771       return false;
4772     }
4773   };
4774 
4775   void prepare_work() {
4776     G1PrepareFreeCollectionSetClosure cl(_work_items);
4777     _collection_set->iterate(&cl);
4778   }
4779 
4780   void complete_work() {
4781     _cl.complete_work();
4782 
4783     G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4784     policy->record_max_rs_lengths(_rs_lengths);
4785     policy->cset_regions_freed();
4786   }
4787 public:
4788   G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4789     AbstractGangTask("G1 Free Collection Set"),
4790     _cl(evacuation_info, surviving_young_words),
4791     _collection_set(collection_set),
4792     _surviving_young_words(surviving_young_words),
4793     _serial_work_claim(0),
4794     _rs_lengths(0),
4795     _parallel_work_claim(0),
4796     _num_work_items(collection_set->region_length()),
4797     _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4798     prepare_work();
4799   }
4800 
4801   ~G1FreeCollectionSetTask() {
4802     complete_work();
4803     FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4804   }
4805 
4806   // Chunk size for work distribution. The chosen value has been determined experimentally
4807   // to be a good tradeoff between overhead and achievable parallelism.
4808   static uint chunk_size() { return 32; }
4809 
4810   virtual void work(uint worker_id) {
4811     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4812 
4813     // Claim serial work.
4814     if (_serial_work_claim == 0) {
4815       jint value = Atomic::add(1, &_serial_work_claim) - 1;
4816       if (value == 0) {
4817         double serial_time = os::elapsedTime();
4818         do_serial_work();
4819         timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4820       }
4821     }
4822 
4823     // Start parallel work.
4824     double young_time = 0.0;
4825     bool has_young_time = false;
4826     double non_young_time = 0.0;
4827     bool has_non_young_time = false;
4828 
4829     while (true) {
4830       size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4831       size_t cur = end - chunk_size();
4832 
4833       if (cur >= _num_work_items) {
4834         break;
4835       }
4836 
4837       double start_time = os::elapsedTime();
4838 
4839       end = MIN2(end, _num_work_items);
4840 
4841       for (; cur < end; cur++) {
4842         bool is_young = _work_items[cur].is_young;
4843 
4844         do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4845 
4846         double end_time = os::elapsedTime();
4847         double time_taken = end_time - start_time;
4848         if (is_young) {
4849           young_time += time_taken;
4850           has_young_time = true;
4851         } else {
4852           non_young_time += time_taken;
4853           has_non_young_time = true;
4854         }
4855         start_time = end_time;
4856       }
4857     }
4858 
4859     if (has_young_time) {
4860       timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4861     }
4862     if (has_non_young_time) {
4863       timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time);
4864     }
4865   }
4866 };
4867 
4868 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4869   _eden.clear();
4870 
4871   double free_cset_start_time = os::elapsedTime();
4872 
4873   {
4874     uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4875     uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4876 
4877     G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4878 
4879     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4880                         cl.name(),
4881                         num_workers,
4882                         _collection_set.region_length());
4883     workers()->run_task(&cl, num_workers);
4884   }
4885   g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4886 
4887   collection_set->clear();
4888 }
4889 
4890 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4891  private:
4892   FreeRegionList* _free_region_list;
4893   HeapRegionSet* _proxy_set;
4894   uint _humongous_regions_removed;
4895   size_t _freed_bytes;
4896  public:
4897 
4898   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4899     _free_region_list(free_region_list), _humongous_regions_removed(0), _freed_bytes(0) {
4900   }
4901 
4902   virtual bool doHeapRegion(HeapRegion* r) {
4903     if (!r->is_starts_humongous()) {
4904       return false;
4905     }
4906 
4907     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4908 
4909     oop obj = (oop)r->bottom();
4910     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
4911 
4912     // The following checks whether the humongous object is live are sufficient.
4913     // The main additional check (in addition to having a reference from the roots
4914     // or the young gen) is whether the humongous object has a remembered set entry.
4915     //
4916     // A humongous object cannot be live if there is no remembered set for it
4917     // because:
4918     // - there can be no references from within humongous starts regions referencing
4919     // the object because we never allocate other objects into them.
4920     // (I.e. there are no intra-region references that may be missed by the
4921     // remembered set)
4922     // - as soon there is a remembered set entry to the humongous starts region
4923     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4924     // until the end of a concurrent mark.
4925     //
4926     // It is not required to check whether the object has been found dead by marking
4927     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4928     // all objects allocated during that time are considered live.
4929     // SATB marking is even more conservative than the remembered set.
4930     // So if at this point in the collection there is no remembered set entry,
4931     // nobody has a reference to it.
4932     // At the start of collection we flush all refinement logs, and remembered sets
4933     // are completely up-to-date wrt to references to the humongous object.
4934     //
4935     // Other implementation considerations:
4936     // - never consider object arrays at this time because they would pose
4937     // considerable effort for cleaning up the the remembered sets. This is
4938     // required because stale remembered sets might reference locations that
4939     // are currently allocated into.
4940     uint region_idx = r->hrm_index();
4941     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4942         !r->rem_set()->is_empty()) {
4943       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",
4944                                region_idx,
4945                                (size_t)obj->size() * HeapWordSize,
4946                                p2i(r->bottom()),
4947                                r->rem_set()->occupied(),
4948                                r->rem_set()->strong_code_roots_list_length(),
4949                                next_bitmap->isMarked(r->bottom()),
4950                                g1h->is_humongous_reclaim_candidate(region_idx),
4951                                obj->is_typeArray()
4952                               );
4953       return false;
4954     }
4955 
4956     guarantee(obj->is_typeArray(),
4957               "Only eagerly reclaiming type arrays is supported, but the object "
4958               PTR_FORMAT " is not.", p2i(r->bottom()));
4959 
4960     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",
4961                              region_idx,
4962                              (size_t)obj->size() * HeapWordSize,
4963                              p2i(r->bottom()),
4964                              r->rem_set()->occupied(),
4965                              r->rem_set()->strong_code_roots_list_length(),
4966                              next_bitmap->isMarked(r->bottom()),
4967                              g1h->is_humongous_reclaim_candidate(region_idx),
4968                              obj->is_typeArray()
4969                             );
4970 
4971     // Need to clear mark bit of the humongous object if already set.
4972     if (next_bitmap->isMarked(r->bottom())) {
4973       next_bitmap->clear(r->bottom());
4974     }
4975     do {
4976       HeapRegion* next = g1h->next_region_in_humongous(r);
4977       _freed_bytes += r->used();
4978       r->set_containing_set(NULL);
4979       _humongous_regions_removed++;
4980       g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ );
4981       r = next;
4982     } while (r != NULL);
4983 
4984     return false;
4985   }
4986 
4987   uint humongous_free_count() {
4988     return _humongous_regions_removed;
4989   }
4990 
4991   size_t bytes_freed() const {
4992     return _freed_bytes;
4993   }
4994 };
4995 
4996 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4997   assert_at_safepoint(true);
4998 
4999   if (!G1EagerReclaimHumongousObjects ||
5000       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
5001     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
5002     return;
5003   }
5004 
5005   double start_time = os::elapsedTime();
5006 
5007   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
5008 
5009   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
5010   heap_region_iterate(&cl);
5011 
5012   remove_from_old_sets(0, cl.humongous_free_count());
5013 
5014   G1HRPrinter* hrp = hr_printer();
5015   if (hrp->is_active()) {
5016     FreeRegionListIterator iter(&local_cleanup_list);
5017     while (iter.more_available()) {
5018       HeapRegion* hr = iter.get_next();
5019       hrp->cleanup(hr);
5020     }
5021   }
5022 
5023   prepend_to_freelist(&local_cleanup_list);
5024   decrement_summary_bytes(cl.bytes_freed());
5025 
5026   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
5027                                                                     cl.humongous_free_count());
5028 }
5029 
5030 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
5031 public:
5032   virtual bool doHeapRegion(HeapRegion* r) {
5033     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
5034     G1CollectedHeap::heap()->clear_in_cset(r);
5035     r->set_young_index_in_cset(-1);
5036     return false;
5037   }
5038 };
5039 
5040 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
5041   G1AbandonCollectionSetClosure cl;
5042   collection_set->iterate(&cl);
5043 
5044   collection_set->clear();
5045   collection_set->stop_incremental_building();
5046 }
5047 
5048 void G1CollectedHeap::set_free_regions_coming() {
5049   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
5050 
5051   assert(!free_regions_coming(), "pre-condition");
5052   _free_regions_coming = true;
5053 }
5054 
5055 void G1CollectedHeap::reset_free_regions_coming() {
5056   assert(free_regions_coming(), "pre-condition");
5057 
5058   {
5059     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5060     _free_regions_coming = false;
5061     SecondaryFreeList_lock->notify_all();
5062   }
5063 
5064   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
5065 }
5066 
5067 void G1CollectedHeap::wait_while_free_regions_coming() {
5068   // Most of the time we won't have to wait, so let's do a quick test
5069   // first before we take the lock.
5070   if (!free_regions_coming()) {
5071     return;
5072   }
5073 
5074   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
5075 
5076   {
5077     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5078     while (free_regions_coming()) {
5079       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5080     }
5081   }
5082 
5083   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
5084 }
5085 
5086 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
5087   return _allocator->is_retained_old_region(hr);
5088 }
5089 
5090 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5091   _eden.add(hr);
5092   _g1_policy->set_region_eden(hr);
5093 }
5094 
5095 #ifdef ASSERT
5096 
5097 class NoYoungRegionsClosure: public HeapRegionClosure {
5098 private:
5099   bool _success;
5100 public:
5101   NoYoungRegionsClosure() : _success(true) { }
5102   bool doHeapRegion(HeapRegion* r) {
5103     if (r->is_young()) {
5104       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5105                             p2i(r->bottom()), p2i(r->end()));
5106       _success = false;
5107     }
5108     return false;
5109   }
5110   bool success() { return _success; }
5111 };
5112 
5113 bool G1CollectedHeap::check_young_list_empty() {
5114   bool ret = (young_regions_count() == 0);
5115 
5116   NoYoungRegionsClosure closure;
5117   heap_region_iterate(&closure);
5118   ret = ret && closure.success();
5119 
5120   return ret;
5121 }
5122 
5123 #endif // ASSERT
5124 
5125 class TearDownRegionSetsClosure : public HeapRegionClosure {
5126 private:
5127   HeapRegionSet *_old_set;
5128 
5129 public:
5130   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5131 
5132   bool doHeapRegion(HeapRegion* r) {
5133     if (r->is_old()) {
5134       _old_set->remove(r);
5135     } else if(r->is_young()) {
5136       r->uninstall_surv_rate_group();
5137     } else {
5138       // We ignore free regions, we'll empty the free list afterwards.
5139       // We ignore humongous regions, we're not tearing down the
5140       // humongous regions set.
5141       assert(r->is_free() || r->is_humongous(),
5142              "it cannot be another type");
5143     }
5144     return false;
5145   }
5146 
5147   ~TearDownRegionSetsClosure() {
5148     assert(_old_set->is_empty(), "post-condition");
5149   }
5150 };
5151 
5152 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5153   assert_at_safepoint(true /* should_be_vm_thread */);
5154 
5155   if (!free_list_only) {
5156     TearDownRegionSetsClosure cl(&_old_set);
5157     heap_region_iterate(&cl);
5158 
5159     // Note that emptying the _young_list is postponed and instead done as
5160     // the first step when rebuilding the regions sets again. The reason for
5161     // this is that during a full GC string deduplication needs to know if
5162     // a collected region was young or old when the full GC was initiated.
5163   }
5164   _hrm.remove_all_free_regions();
5165 }
5166 
5167 void G1CollectedHeap::increase_used(size_t bytes) {
5168   _summary_bytes_used += bytes;
5169 }
5170 
5171 void G1CollectedHeap::decrease_used(size_t bytes) {
5172   assert(_summary_bytes_used >= bytes,
5173          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5174          _summary_bytes_used, bytes);
5175   _summary_bytes_used -= bytes;
5176 }
5177 
5178 void G1CollectedHeap::set_used(size_t bytes) {
5179   _summary_bytes_used = bytes;
5180 }
5181 
5182 class RebuildRegionSetsClosure : public HeapRegionClosure {
5183 private:
5184   bool            _free_list_only;
5185   HeapRegionSet*   _old_set;
5186   HeapRegionManager*   _hrm;
5187   size_t          _total_used;
5188 
5189 public:
5190   RebuildRegionSetsClosure(bool free_list_only,
5191                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
5192     _free_list_only(free_list_only),
5193     _old_set(old_set), _hrm(hrm), _total_used(0) {
5194     assert(_hrm->num_free_regions() == 0, "pre-condition");
5195     if (!free_list_only) {
5196       assert(_old_set->is_empty(), "pre-condition");
5197     }
5198   }
5199 
5200   bool doHeapRegion(HeapRegion* r) {
5201     if (r->is_empty()) {
5202       // Add free regions to the free list
5203       r->set_free();
5204       r->set_allocation_context(AllocationContext::system());
5205       _hrm->insert_into_free_list(r);
5206     } else if (!_free_list_only) {
5207 
5208       if (r->is_humongous()) {
5209         // We ignore humongous regions. We left the humongous set unchanged.
5210       } else {
5211         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
5212         // We now consider all regions old, so register as such. Leave
5213         // archive regions set that way, however, while still adding
5214         // them to the old set.
5215         if (!r->is_archive()) {
5216           r->set_old();
5217         }
5218         _old_set->add(r);
5219       }
5220       _total_used += r->used();
5221     }
5222 
5223     return false;
5224   }
5225 
5226   size_t total_used() {
5227     return _total_used;
5228   }
5229 };
5230 
5231 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5232   assert_at_safepoint(true /* should_be_vm_thread */);
5233 
5234   if (!free_list_only) {
5235     _eden.clear();
5236     _survivor.clear();
5237   }
5238 
5239   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5240   heap_region_iterate(&cl);
5241 
5242   if (!free_list_only) {
5243     set_used(cl.total_used());
5244     if (_archive_allocator != NULL) {
5245       _archive_allocator->clear_used();
5246     }
5247   }
5248   assert(used_unlocked() == recalculate_used(),
5249          "inconsistent used_unlocked(), "
5250          "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5251          used_unlocked(), recalculate_used());
5252 }
5253 
5254 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
5255   _refine_cte_cl->set_concurrent(concurrent);
5256 }
5257 
5258 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5259   HeapRegion* hr = heap_region_containing(p);
5260   return hr->is_in(p);
5261 }
5262 
5263 // Methods for the mutator alloc region
5264 
5265 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5266                                                       bool force) {
5267   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5268   assert(!force || g1_policy()->can_expand_young_list(),
5269          "if force is true we should be able to expand the young list");
5270   bool should_allocate = g1_policy()->should_allocate_mutator_region();
5271   if (force || should_allocate) {
5272     HeapRegion* new_alloc_region = new_region(word_size,
5273                                               false /* is_old */,
5274                                               false /* do_expand */);
5275     if (new_alloc_region != NULL) {
5276       set_region_short_lived_locked(new_alloc_region);
5277       _hr_printer.alloc(new_alloc_region, !should_allocate);
5278       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5279       return new_alloc_region;
5280     }
5281   }
5282   return NULL;
5283 }
5284 
5285 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5286                                                   size_t allocated_bytes) {
5287   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5288   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5289 
5290   collection_set()->add_eden_region(alloc_region);
5291   increase_used(allocated_bytes);
5292   _hr_printer.retire(alloc_region);
5293   // We update the eden sizes here, when the region is retired,
5294   // instead of when it's allocated, since this is the point that its
5295   // used space has been recored in _summary_bytes_used.
5296   g1mm()->update_eden_size();
5297 }
5298 
5299 // Methods for the GC alloc regions
5300 
5301 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
5302   if (dest.is_old()) {
5303     return true;
5304   } else {
5305     return survivor_regions_count() < g1_policy()->max_survivor_regions();
5306   }
5307 }
5308 
5309 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
5310   assert(FreeList_lock->owned_by_self(), "pre-condition");
5311 
5312   if (!has_more_regions(dest)) {
5313     return NULL;
5314   }
5315 
5316   const bool is_survivor = dest.is_young();
5317 
5318   HeapRegion* new_alloc_region = new_region(word_size,
5319                                             !is_survivor,
5320                                             true /* do_expand */);
5321   if (new_alloc_region != NULL) {
5322     // We really only need to do this for old regions given that we
5323     // should never scan survivors. But it doesn't hurt to do it
5324     // for survivors too.
5325     new_alloc_region->record_timestamp();
5326     if (is_survivor) {
5327       new_alloc_region->set_survivor();
5328       _survivor.add(new_alloc_region);
5329       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5330     } else {
5331       new_alloc_region->set_old();
5332       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5333     }
5334     _hr_printer.alloc(new_alloc_region);
5335     bool during_im = collector_state()->during_initial_mark_pause();
5336     new_alloc_region->note_start_of_copying(during_im);
5337     return new_alloc_region;
5338   }
5339   return NULL;
5340 }
5341 
5342 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5343                                              size_t allocated_bytes,
5344                                              InCSetState dest) {
5345   bool during_im = collector_state()->during_initial_mark_pause();
5346   alloc_region->note_end_of_copying(during_im);
5347   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5348   if (dest.is_old()) {
5349     _old_set.add(alloc_region);
5350   }
5351   _hr_printer.retire(alloc_region);
5352 }
5353 
5354 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5355   bool expanded = false;
5356   uint index = _hrm.find_highest_free(&expanded);
5357 
5358   if (index != G1_NO_HRM_INDEX) {
5359     if (expanded) {
5360       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5361                                 HeapRegion::GrainWords * HeapWordSize);
5362     }
5363     _hrm.allocate_free_regions_starting_at(index, 1);
5364     return region_at(index);
5365   }
5366   return NULL;
5367 }
5368 
5369 // Optimized nmethod scanning
5370 
5371 class RegisterNMethodOopClosure: public OopClosure {
5372   G1CollectedHeap* _g1h;
5373   nmethod* _nm;
5374 
5375   template <class T> void do_oop_work(T* p) {
5376     T heap_oop = oopDesc::load_heap_oop(p);
5377     if (!oopDesc::is_null(heap_oop)) {
5378       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5379       HeapRegion* hr = _g1h->heap_region_containing(obj);
5380       assert(!hr->is_continues_humongous(),
5381              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5382              " starting at " HR_FORMAT,
5383              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5384 
5385       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5386       hr->add_strong_code_root_locked(_nm);
5387     }
5388   }
5389 
5390 public:
5391   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5392     _g1h(g1h), _nm(nm) {}
5393 
5394   void do_oop(oop* p)       { do_oop_work(p); }
5395   void do_oop(narrowOop* p) { do_oop_work(p); }
5396 };
5397 
5398 class UnregisterNMethodOopClosure: public OopClosure {
5399   G1CollectedHeap* _g1h;
5400   nmethod* _nm;
5401 
5402   template <class T> void do_oop_work(T* p) {
5403     T heap_oop = oopDesc::load_heap_oop(p);
5404     if (!oopDesc::is_null(heap_oop)) {
5405       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5406       HeapRegion* hr = _g1h->heap_region_containing(obj);
5407       assert(!hr->is_continues_humongous(),
5408              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5409              " starting at " HR_FORMAT,
5410              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5411 
5412       hr->remove_strong_code_root(_nm);
5413     }
5414   }
5415 
5416 public:
5417   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5418     _g1h(g1h), _nm(nm) {}
5419 
5420   void do_oop(oop* p)       { do_oop_work(p); }
5421   void do_oop(narrowOop* p) { do_oop_work(p); }
5422 };
5423 
5424 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5425   CollectedHeap::register_nmethod(nm);
5426 
5427   guarantee(nm != NULL, "sanity");
5428   RegisterNMethodOopClosure reg_cl(this, nm);
5429   nm->oops_do(&reg_cl);
5430 }
5431 
5432 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5433   CollectedHeap::unregister_nmethod(nm);
5434 
5435   guarantee(nm != NULL, "sanity");
5436   UnregisterNMethodOopClosure reg_cl(this, nm);
5437   nm->oops_do(&reg_cl, true);
5438 }
5439 
5440 void G1CollectedHeap::purge_code_root_memory() {
5441   double purge_start = os::elapsedTime();
5442   G1CodeRootSet::purge();
5443   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5444   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5445 }
5446 
5447 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5448   G1CollectedHeap* _g1h;
5449 
5450 public:
5451   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5452     _g1h(g1h) {}
5453 
5454   void do_code_blob(CodeBlob* cb) {
5455     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5456     if (nm == NULL) {
5457       return;
5458     }
5459 
5460     if (ScavengeRootsInCode) {
5461       _g1h->register_nmethod(nm);
5462     }
5463   }
5464 };
5465 
5466 void G1CollectedHeap::rebuild_strong_code_roots() {
5467   RebuildStrongCodeRootClosure blob_cl(this);
5468   CodeCache::blobs_do(&blob_cl);
5469 }