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