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   // Next, pad out the unused tail of the last region with filler
 304   // objects, for improved usage accounting.
 305   // How many words we use for filler objects.
 306   size_t word_fill_size = word_size_sum - word_size;
 307 
 308   // How many words memory we "waste" which cannot hold a filler object.
 309   size_t words_not_fillable = 0;
 310 
 311   if (word_fill_size >= min_fill_size()) {
 312     fill_with_objects(obj_top, word_fill_size);
 313   } else if (word_fill_size > 0) {
 314     // We have space to fill, but we cannot fit an object there.
 315     words_not_fillable = word_fill_size;
 316     word_fill_size = 0;
 317   }
 318 
 319   // We will set up the first region as "starts humongous". This
 320   // will also update the BOT covering all the regions to reflect
 321   // that there is a single object that starts at the bottom of the
 322   // first region.
 323   first_hr->set_starts_humongous(obj_top, word_fill_size);
 324   first_hr->set_allocation_context(context);
 325   // Then, if there are any, we will set up the "continues
 326   // humongous" regions.
 327   HeapRegion* hr = NULL;
 328   for (uint i = first + 1; i <= last; ++i) {
 329     hr = region_at(i);
 330     hr->set_continues_humongous(first_hr);
 331     hr->set_allocation_context(context);
 332   }
 333 
 334   // Up to this point no concurrent thread would have been able to
 335   // do any scanning on any region in this series. All the top
 336   // fields still point to bottom, so the intersection between
 337   // [bottom,top] and [card_start,card_end] will be empty. Before we
 338   // update the top fields, we'll do a storestore to make sure that
 339   // no thread sees the update to top before the zeroing of the
 340   // object header and the BOT initialization.
 341   OrderAccess::storestore();
 342 
 343   // Now, we will update the top fields of the "continues humongous"
 344   // regions except the last one.
 345   for (uint i = first; i < last; ++i) {
 346     hr = region_at(i);
 347     hr->set_top(hr->end());
 348   }
 349 
 350   hr = region_at(last);
 351   // If we cannot fit a filler object, we must set top to the end
 352   // of the humongous object, otherwise we cannot iterate the heap
 353   // and the BOT will not be complete.
 354   hr->set_top(hr->end() - words_not_fillable);
 355 
 356   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 357          "obj_top should be in last region");
 358 
 359   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 360 
 361   assert(words_not_fillable == 0 ||
 362          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 363          "Miscalculation in humongous allocation");
 364 
 365   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 366 
 367   for (uint i = first; i <= last; ++i) {
 368     hr = region_at(i);
 369     _humongous_set.add(hr);
 370     _hr_printer.alloc(hr);
 371   }
 372 
 373   return new_obj;
 374 }
 375 
 376 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 377   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 378   return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 379 }
 380 
 381 // If could fit into free regions w/o expansion, try.
 382 // Otherwise, if can expand, do so.
 383 // Otherwise, if using ex regions might help, try with ex given back.
 384 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
 385   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 386 
 387   _verifier->verify_region_sets_optional();
 388 
 389   uint first = G1_NO_HRM_INDEX;
 390   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 391 
 392   if (obj_regions == 1) {
 393     // Only one region to allocate, try to use a fast path by directly allocating
 394     // from the free lists. Do not try to expand here, we will potentially do that
 395     // later.
 396     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 397     if (hr != NULL) {
 398       first = hr->hrm_index();
 399     }
 400   } else {
 401     // We can't allocate humongous regions spanning more than one region while
 402     // cleanupComplete() is running, since some of the regions we find to be
 403     // empty might not yet be added to the free list. It is not straightforward
 404     // to know in which list they are on so that we can remove them. We only
 405     // need to do this if we need to allocate more than one region to satisfy the
 406     // current humongous allocation request. If we are only allocating one region
 407     // we use the one-region region allocation code (see above), that already
 408     // potentially waits for regions from the secondary free list.
 409     wait_while_free_regions_coming();
 410     append_secondary_free_list_if_not_empty_with_lock();
 411 
 412     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 413     // are lucky enough to find some.
 414     first = _hrm.find_contiguous_only_empty(obj_regions);
 415     if (first != G1_NO_HRM_INDEX) {
 416       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 417     }
 418   }
 419 
 420   if (first == G1_NO_HRM_INDEX) {
 421     // Policy: We could not find enough regions for the humongous object in the
 422     // free list. Look through the heap to find a mix of free and uncommitted regions.
 423     // If so, try expansion.
 424     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 425     if (first != G1_NO_HRM_INDEX) {
 426       // We found something. Make sure these regions are committed, i.e. expand
 427       // the heap. Alternatively we could do a defragmentation GC.
 428       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 429                                     word_size * HeapWordSize);
 430 
 431       _hrm.expand_at(first, obj_regions, workers());
 432       g1_policy()->record_new_heap_size(num_regions());
 433 
 434 #ifdef ASSERT
 435       for (uint i = first; i < first + obj_regions; ++i) {
 436         HeapRegion* hr = region_at(i);
 437         assert(hr->is_free(), "sanity");
 438         assert(hr->is_empty(), "sanity");
 439         assert(is_on_master_free_list(hr), "sanity");
 440       }
 441 #endif
 442       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 443     } else {
 444       // Policy: Potentially trigger a defragmentation GC.
 445     }
 446   }
 447 
 448   HeapWord* result = NULL;
 449   if (first != G1_NO_HRM_INDEX) {
 450     result = humongous_obj_allocate_initialize_regions(first, obj_regions,
 451                                                        word_size, context);
 452     assert(result != NULL, "it should always return a valid result");
 453 
 454     // A successful humongous object allocation changes the used space
 455     // information of the old generation so we need to recalculate the
 456     // sizes and update the jstat counters here.
 457     g1mm()->update_sizes();
 458   }
 459 
 460   _verifier->verify_region_sets_optional();
 461 
 462   return result;
 463 }
 464 
 465 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 466   assert_heap_not_locked_and_not_at_safepoint();
 467   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 468 
 469   uint dummy_gc_count_before;
 470   uint dummy_gclocker_retry_count = 0;
 471   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 472 }
 473 
 474 HeapWord*
 475 G1CollectedHeap::mem_allocate(size_t word_size,
 476                               bool*  gc_overhead_limit_was_exceeded) {
 477   assert_heap_not_locked_and_not_at_safepoint();
 478 
 479   // Loop until the allocation is satisfied, or unsatisfied after GC.
 480   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 481     uint gc_count_before;
 482 
 483     HeapWord* result = NULL;
 484     if (!is_humongous(word_size)) {
 485       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 486     } else {
 487       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 488     }
 489     if (result != NULL) {
 490       return result;
 491     }
 492 
 493     // Create the garbage collection operation...
 494     VM_G1CollectForAllocation op(gc_count_before, word_size);
 495     op.set_allocation_context(AllocationContext::current());
 496 
 497     // ...and get the VM thread to execute it.
 498     VMThread::execute(&op);
 499 
 500     if (op.prologue_succeeded() && op.pause_succeeded()) {
 501       // If the operation was successful we'll return the result even
 502       // if it is NULL. If the allocation attempt failed immediately
 503       // after a Full GC, it's unlikely we'll be able to allocate now.
 504       HeapWord* result = op.result();
 505       if (result != NULL && !is_humongous(word_size)) {
 506         // Allocations that take place on VM operations do not do any
 507         // card dirtying and we have to do it here. We only have to do
 508         // this for non-humongous allocations, though.
 509         dirty_young_block(result, word_size);
 510       }
 511       return result;
 512     } else {
 513       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 514         return NULL;
 515       }
 516       assert(op.result() == NULL,
 517              "the result should be NULL if the VM op did not succeed");
 518     }
 519 
 520     // Give a warning if we seem to be looping forever.
 521     if ((QueuedAllocationWarningCount > 0) &&
 522         (try_count % QueuedAllocationWarningCount == 0)) {
 523       log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
 524     }
 525   }
 526 
 527   ShouldNotReachHere();
 528   return NULL;
 529 }
 530 
 531 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 532                                                    AllocationContext_t context,
 533                                                    uint* gc_count_before_ret,
 534                                                    uint* gclocker_retry_count_ret) {
 535   // Make sure you read the note in attempt_allocation_humongous().
 536 
 537   assert_heap_not_locked_and_not_at_safepoint();
 538   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 539          "be called for humongous allocation requests");
 540 
 541   // We should only get here after the first-level allocation attempt
 542   // (attempt_allocation()) failed to allocate.
 543 
 544   // We will loop until a) we manage to successfully perform the
 545   // allocation or b) we successfully schedule a collection which
 546   // fails to perform the allocation. b) is the only case when we'll
 547   // return NULL.
 548   HeapWord* result = NULL;
 549   for (int try_count = 1; /* we'll return */; try_count += 1) {
 550     bool should_try_gc;
 551     uint gc_count_before;
 552 
 553     {
 554       MutexLockerEx x(Heap_lock);
 555       result = _allocator->attempt_allocation_locked(word_size, context);
 556       if (result != NULL) {
 557         return result;
 558       }
 559 
 560       if (GCLocker::is_active_and_needs_gc()) {
 561         if (g1_policy()->can_expand_young_list()) {
 562           // No need for an ergo verbose message here,
 563           // can_expand_young_list() does this when it returns true.
 564           result = _allocator->attempt_allocation_force(word_size, context);
 565           if (result != NULL) {
 566             return result;
 567           }
 568         }
 569         should_try_gc = false;
 570       } else {
 571         // The GCLocker may not be active but the GCLocker initiated
 572         // GC may not yet have been performed (GCLocker::needs_gc()
 573         // returns true). In this case we do not try this GC and
 574         // wait until the GCLocker initiated GC is performed, and
 575         // then retry the allocation.
 576         if (GCLocker::needs_gc()) {
 577           should_try_gc = false;
 578         } else {
 579           // Read the GC count while still holding the Heap_lock.
 580           gc_count_before = total_collections();
 581           should_try_gc = true;
 582         }
 583       }
 584     }
 585 
 586     if (should_try_gc) {
 587       bool succeeded;
 588       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 589                                    GCCause::_g1_inc_collection_pause);
 590       if (result != NULL) {
 591         assert(succeeded, "only way to get back a non-NULL result");
 592         return result;
 593       }
 594 
 595       if (succeeded) {
 596         // If we get here we successfully scheduled a collection which
 597         // failed to allocate. No point in trying to allocate
 598         // further. We'll just return NULL.
 599         MutexLockerEx x(Heap_lock);
 600         *gc_count_before_ret = total_collections();
 601         return NULL;
 602       }
 603     } else {
 604       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 605         MutexLockerEx x(Heap_lock);
 606         *gc_count_before_ret = total_collections();
 607         return NULL;
 608       }
 609       // The GCLocker is either active or the GCLocker initiated
 610       // GC has not yet been performed. Stall until it is and
 611       // then retry the allocation.
 612       GCLocker::stall_until_clear();
 613       (*gclocker_retry_count_ret) += 1;
 614     }
 615 
 616     // We can reach here if we were unsuccessful in scheduling a
 617     // collection (because another thread beat us to it) or if we were
 618     // stalled due to the GC locker. In either can we should retry the
 619     // allocation attempt in case another thread successfully
 620     // performed a collection and reclaimed enough space. We do the
 621     // first attempt (without holding the Heap_lock) here and the
 622     // follow-on attempt will be at the start of the next loop
 623     // iteration (after taking the Heap_lock).
 624     result = _allocator->attempt_allocation(word_size, context);
 625     if (result != NULL) {
 626       return result;
 627     }
 628 
 629     // Give a warning if we seem to be looping forever.
 630     if ((QueuedAllocationWarningCount > 0) &&
 631         (try_count % QueuedAllocationWarningCount == 0)) {
 632       log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
 633                       "retries %d times", try_count);
 634     }
 635   }
 636 
 637   ShouldNotReachHere();
 638   return NULL;
 639 }
 640 
 641 void G1CollectedHeap::begin_archive_alloc_range() {
 642   assert_at_safepoint(true /* should_be_vm_thread */);
 643   if (_archive_allocator == NULL) {
 644     _archive_allocator = G1ArchiveAllocator::create_allocator(this);
 645   }
 646 }
 647 
 648 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 649   // Allocations in archive regions cannot be of a size that would be considered
 650   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 651   // may be different at archive-restore time.
 652   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 653 }
 654 
 655 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 656   assert_at_safepoint(true /* should_be_vm_thread */);
 657   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 658   if (is_archive_alloc_too_large(word_size)) {
 659     return NULL;
 660   }
 661   return _archive_allocator->archive_mem_allocate(word_size);
 662 }
 663 
 664 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 665                                               size_t end_alignment_in_bytes) {
 666   assert_at_safepoint(true /* should_be_vm_thread */);
 667   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 668 
 669   // Call complete_archive to do the real work, filling in the MemRegion
 670   // array with the archive regions.
 671   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 672   delete _archive_allocator;
 673   _archive_allocator = NULL;
 674 }
 675 
 676 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 677   assert(ranges != NULL, "MemRegion array NULL");
 678   assert(count != 0, "No MemRegions provided");
 679   MemRegion reserved = _hrm.reserved();
 680   for (size_t i = 0; i < count; i++) {
 681     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 682       return false;
 683     }
 684   }
 685   return true;
 686 }
 687 
 688 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) {
 689   assert(!is_init_completed(), "Expect to be called at JVM init time");
 690   assert(ranges != NULL, "MemRegion array NULL");
 691   assert(count != 0, "No MemRegions provided");
 692   MutexLockerEx x(Heap_lock);
 693 
 694   MemRegion reserved = _hrm.reserved();
 695   HeapWord* prev_last_addr = NULL;
 696   HeapRegion* prev_last_region = NULL;
 697 
 698   // Temporarily disable pretouching of heap pages. This interface is used
 699   // when mmap'ing archived heap data in, so pre-touching is wasted.
 700   FlagSetting fs(AlwaysPreTouch, false);
 701 
 702   // Enable archive object checking in G1MarkSweep. We have to let it know
 703   // about each archive range, so that objects in those ranges aren't marked.
 704   G1MarkSweep::enable_archive_object_check();
 705 
 706   // For each specified MemRegion range, allocate the corresponding G1
 707   // regions and mark them as archive regions. We expect the ranges in
 708   // ascending starting address order, without overlap.
 709   for (size_t i = 0; i < count; i++) {
 710     MemRegion curr_range = ranges[i];
 711     HeapWord* start_address = curr_range.start();
 712     size_t word_size = curr_range.word_size();
 713     HeapWord* last_address = curr_range.last();
 714     size_t commits = 0;
 715 
 716     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 717               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 718               p2i(start_address), p2i(last_address));
 719     guarantee(start_address > prev_last_addr,
 720               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 721               p2i(start_address), p2i(prev_last_addr));
 722     prev_last_addr = last_address;
 723 
 724     // Check for ranges that start in the same G1 region in which the previous
 725     // range ended, and adjust the start address so we don't try to allocate
 726     // the same region again. If the current range is entirely within that
 727     // region, skip it, just adjusting the recorded top.
 728     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 729     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 730       start_address = start_region->end();
 731       if (start_address > last_address) {
 732         increase_used(word_size * HeapWordSize);
 733         start_region->set_top(last_address + 1);
 734         continue;
 735       }
 736       start_region->set_top(start_address);
 737       curr_range = MemRegion(start_address, last_address + 1);
 738       start_region = _hrm.addr_to_region(start_address);
 739     }
 740 
 741     // Perform the actual region allocation, exiting if it fails.
 742     // Then note how much new space we have allocated.
 743     if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
 744       return false;
 745     }
 746     increase_used(word_size * HeapWordSize);
 747     if (commits != 0) {
 748       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 749                                 HeapRegion::GrainWords * HeapWordSize * commits);
 750 
 751     }
 752 
 753     // Mark each G1 region touched by the range as archive, add it to the old set,
 754     // and set the allocation context and top.
 755     HeapRegion* curr_region = _hrm.addr_to_region(start_address);
 756     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 757     prev_last_region = last_region;
 758 
 759     while (curr_region != NULL) {
 760       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 761              "Region already in use (index %u)", curr_region->hrm_index());
 762       curr_region->set_allocation_context(AllocationContext::system());
 763       curr_region->set_archive();
 764       _hr_printer.alloc(curr_region);
 765       _old_set.add(curr_region);
 766       if (curr_region != last_region) {
 767         curr_region->set_top(curr_region->end());
 768         curr_region = _hrm.next_region_in_heap(curr_region);
 769       } else {
 770         curr_region->set_top(last_address + 1);
 771         curr_region = NULL;
 772       }
 773     }
 774 
 775     // Notify mark-sweep of the archive range.
 776     G1MarkSweep::set_range_archive(curr_range, true);
 777   }
 778   return true;
 779 }
 780 
 781 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 782   assert(!is_init_completed(), "Expect to be called at JVM init time");
 783   assert(ranges != NULL, "MemRegion array NULL");
 784   assert(count != 0, "No MemRegions provided");
 785   MemRegion reserved = _hrm.reserved();
 786   HeapWord *prev_last_addr = NULL;
 787   HeapRegion* prev_last_region = NULL;
 788 
 789   // For each MemRegion, create filler objects, if needed, in the G1 regions
 790   // that contain the address range. The address range actually within the
 791   // MemRegion will not be modified. That is assumed to have been initialized
 792   // elsewhere, probably via an mmap of archived heap data.
 793   MutexLockerEx x(Heap_lock);
 794   for (size_t i = 0; i < count; i++) {
 795     HeapWord* start_address = ranges[i].start();
 796     HeapWord* last_address = ranges[i].last();
 797 
 798     assert(reserved.contains(start_address) && reserved.contains(last_address),
 799            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 800            p2i(start_address), p2i(last_address));
 801     assert(start_address > prev_last_addr,
 802            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 803            p2i(start_address), p2i(prev_last_addr));
 804 
 805     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 806     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 807     HeapWord* bottom_address = start_region->bottom();
 808 
 809     // Check for a range beginning in the same region in which the
 810     // previous one ended.
 811     if (start_region == prev_last_region) {
 812       bottom_address = prev_last_addr + 1;
 813     }
 814 
 815     // Verify that the regions were all marked as archive regions by
 816     // alloc_archive_regions.
 817     HeapRegion* curr_region = start_region;
 818     while (curr_region != NULL) {
 819       guarantee(curr_region->is_archive(),
 820                 "Expected archive region at index %u", curr_region->hrm_index());
 821       if (curr_region != last_region) {
 822         curr_region = _hrm.next_region_in_heap(curr_region);
 823       } else {
 824         curr_region = NULL;
 825       }
 826     }
 827 
 828     prev_last_addr = last_address;
 829     prev_last_region = last_region;
 830 
 831     // Fill the memory below the allocated range with dummy object(s),
 832     // if the region bottom does not match the range start, or if the previous
 833     // range ended within the same G1 region, and there is a gap.
 834     if (start_address != bottom_address) {
 835       size_t fill_size = pointer_delta(start_address, bottom_address);
 836       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 837       increase_used(fill_size * HeapWordSize);
 838     }
 839   }
 840 }
 841 
 842 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
 843                                                      uint* gc_count_before_ret,
 844                                                      uint* gclocker_retry_count_ret) {
 845   assert_heap_not_locked_and_not_at_safepoint();
 846   assert(!is_humongous(word_size), "attempt_allocation() should not "
 847          "be called for humongous allocation requests");
 848 
 849   AllocationContext_t context = AllocationContext::current();
 850   HeapWord* result = _allocator->attempt_allocation(word_size, context);
 851 
 852   if (result == NULL) {
 853     result = attempt_allocation_slow(word_size,
 854                                      context,
 855                                      gc_count_before_ret,
 856                                      gclocker_retry_count_ret);
 857   }
 858   assert_heap_not_locked();
 859   if (result != NULL) {
 860     dirty_young_block(result, word_size);
 861   }
 862   return result;
 863 }
 864 
 865 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
 866   assert(!is_init_completed(), "Expect to be called at JVM init time");
 867   assert(ranges != NULL, "MemRegion array NULL");
 868   assert(count != 0, "No MemRegions provided");
 869   MemRegion reserved = _hrm.reserved();
 870   HeapWord* prev_last_addr = NULL;
 871   HeapRegion* prev_last_region = NULL;
 872   size_t size_used = 0;
 873   size_t uncommitted_regions = 0;
 874 
 875   // For each Memregion, free the G1 regions that constitute it, and
 876   // notify mark-sweep that the range is no longer to be considered 'archive.'
 877   MutexLockerEx x(Heap_lock);
 878   for (size_t i = 0; i < count; i++) {
 879     HeapWord* start_address = ranges[i].start();
 880     HeapWord* last_address = ranges[i].last();
 881 
 882     assert(reserved.contains(start_address) && reserved.contains(last_address),
 883            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 884            p2i(start_address), p2i(last_address));
 885     assert(start_address > prev_last_addr,
 886            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 887            p2i(start_address), p2i(prev_last_addr));
 888     size_used += ranges[i].byte_size();
 889     prev_last_addr = last_address;
 890 
 891     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 892     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 893 
 894     // Check for ranges that start in the same G1 region in which the previous
 895     // range ended, and adjust the start address so we don't try to free
 896     // the same region again. If the current range is entirely within that
 897     // region, skip it.
 898     if (start_region == prev_last_region) {
 899       start_address = start_region->end();
 900       if (start_address > last_address) {
 901         continue;
 902       }
 903       start_region = _hrm.addr_to_region(start_address);
 904     }
 905     prev_last_region = last_region;
 906 
 907     // After verifying that each region was marked as an archive region by
 908     // alloc_archive_regions, set it free and empty and uncommit it.
 909     HeapRegion* curr_region = start_region;
 910     while (curr_region != NULL) {
 911       guarantee(curr_region->is_archive(),
 912                 "Expected archive region at index %u", curr_region->hrm_index());
 913       uint curr_index = curr_region->hrm_index();
 914       _old_set.remove(curr_region);
 915       curr_region->set_free();
 916       curr_region->set_top(curr_region->bottom());
 917       if (curr_region != last_region) {
 918         curr_region = _hrm.next_region_in_heap(curr_region);
 919       } else {
 920         curr_region = NULL;
 921       }
 922       _hrm.shrink_at(curr_index, 1);
 923       uncommitted_regions++;
 924     }
 925 
 926     // Notify mark-sweep that this is no longer an archive range.
 927     G1MarkSweep::set_range_archive(ranges[i], false);
 928   }
 929 
 930   if (uncommitted_regions != 0) {
 931     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 932                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 933   }
 934   decrease_used(size_used);
 935 }
 936 
 937 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
 938                                                         uint* gc_count_before_ret,
 939                                                         uint* gclocker_retry_count_ret) {
 940   // The structure of this method has a lot of similarities to
 941   // attempt_allocation_slow(). The reason these two were not merged
 942   // into a single one is that such a method would require several "if
 943   // allocation is not humongous do this, otherwise do that"
 944   // conditional paths which would obscure its flow. In fact, an early
 945   // version of this code did use a unified method which was harder to
 946   // follow and, as a result, it had subtle bugs that were hard to
 947   // track down. So keeping these two methods separate allows each to
 948   // be more readable. It will be good to keep these two in sync as
 949   // much as possible.
 950 
 951   assert_heap_not_locked_and_not_at_safepoint();
 952   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 953          "should only be called for humongous allocations");
 954 
 955   // Humongous objects can exhaust the heap quickly, so we should check if we
 956   // need to start a marking cycle at each humongous object allocation. We do
 957   // the check before we do the actual allocation. The reason for doing it
 958   // before the allocation is that we avoid having to keep track of the newly
 959   // allocated memory while we do a GC.
 960   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
 961                                            word_size)) {
 962     collect(GCCause::_g1_humongous_allocation);
 963   }
 964 
 965   // We will loop until a) we manage to successfully perform the
 966   // allocation or b) we successfully schedule a collection which
 967   // fails to perform the allocation. b) is the only case when we'll
 968   // return NULL.
 969   HeapWord* result = NULL;
 970   for (int try_count = 1; /* we'll return */; try_count += 1) {
 971     bool should_try_gc;
 972     uint gc_count_before;
 973 
 974     {
 975       MutexLockerEx x(Heap_lock);
 976 
 977       // Given that humongous objects are not allocated in young
 978       // regions, we'll first try to do the allocation without doing a
 979       // collection hoping that there's enough space in the heap.
 980       result = humongous_obj_allocate(word_size, AllocationContext::current());
 981       if (result != NULL) {
 982         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 983         g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 984         return result;
 985       }
 986 
 987       if (GCLocker::is_active_and_needs_gc()) {
 988         should_try_gc = false;
 989       } else {
 990          // The GCLocker may not be active but the GCLocker initiated
 991         // GC may not yet have been performed (GCLocker::needs_gc()
 992         // returns true). In this case we do not try this GC and
 993         // wait until the GCLocker initiated GC is performed, and
 994         // then retry the allocation.
 995         if (GCLocker::needs_gc()) {
 996           should_try_gc = false;
 997         } else {
 998           // Read the GC count while still holding the Heap_lock.
 999           gc_count_before = total_collections();
1000           should_try_gc = true;
1001         }
1002       }
1003     }
1004 
1005     if (should_try_gc) {
1006       // If we failed to allocate the humongous object, we should try to
1007       // do a collection pause (if we're allowed) in case it reclaims
1008       // enough space for the allocation to succeed after the pause.
1009 
1010       bool succeeded;
1011       result = do_collection_pause(word_size, gc_count_before, &succeeded,
1012                                    GCCause::_g1_humongous_allocation);
1013       if (result != NULL) {
1014         assert(succeeded, "only way to get back a non-NULL result");
1015         return result;
1016       }
1017 
1018       if (succeeded) {
1019         // If we get here we successfully scheduled a collection which
1020         // failed to allocate. No point in trying to allocate
1021         // further. We'll just return NULL.
1022         MutexLockerEx x(Heap_lock);
1023         *gc_count_before_ret = total_collections();
1024         return NULL;
1025       }
1026     } else {
1027       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1028         MutexLockerEx x(Heap_lock);
1029         *gc_count_before_ret = total_collections();
1030         return NULL;
1031       }
1032       // The GCLocker is either active or the GCLocker initiated
1033       // GC has not yet been performed. Stall until it is and
1034       // then retry the allocation.
1035       GCLocker::stall_until_clear();
1036       (*gclocker_retry_count_ret) += 1;
1037     }
1038 
1039     // We can reach here if we were unsuccessful in scheduling a
1040     // collection (because another thread beat us to it) or if we were
1041     // stalled due to the GC locker. In either can we should retry the
1042     // allocation attempt in case another thread successfully
1043     // performed a collection and reclaimed enough space.  Give a
1044     // warning if we seem to be looping forever.
1045 
1046     if ((QueuedAllocationWarningCount > 0) &&
1047         (try_count % QueuedAllocationWarningCount == 0)) {
1048       log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
1049                       "retries %d times", try_count);
1050     }
1051   }
1052 
1053   ShouldNotReachHere();
1054   return NULL;
1055 }
1056 
1057 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1058                                                            AllocationContext_t context,
1059                                                            bool expect_null_mutator_alloc_region) {
1060   assert_at_safepoint(true /* should_be_vm_thread */);
1061   assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1062          "the current alloc region was unexpectedly found to be non-NULL");
1063 
1064   if (!is_humongous(word_size)) {
1065     return _allocator->attempt_allocation_locked(word_size, context);
1066   } else {
1067     HeapWord* result = humongous_obj_allocate(word_size, context);
1068     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1069       collector_state()->set_initiate_conc_mark_if_possible(true);
1070     }
1071     return result;
1072   }
1073 
1074   ShouldNotReachHere();
1075 }
1076 
1077 class PostMCRemSetClearClosure: public HeapRegionClosure {
1078   G1CollectedHeap* _g1h;
1079   ModRefBarrierSet* _mr_bs;
1080 public:
1081   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1082     _g1h(g1h), _mr_bs(mr_bs) {}
1083 
1084   bool doHeapRegion(HeapRegion* r) {
1085     HeapRegionRemSet* hrrs = r->rem_set();
1086 
1087     _g1h->reset_gc_time_stamps(r);
1088 
1089     if (r->is_continues_humongous()) {
1090       // We'll assert that the strong code root list and RSet is empty
1091       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1092       assert(hrrs->occupied() == 0, "RSet should be empty");
1093     } else {
1094       hrrs->clear();
1095     }
1096     // You might think here that we could clear just the cards
1097     // corresponding to the used region.  But no: if we leave a dirty card
1098     // in a region we might allocate into, then it would prevent that card
1099     // from being enqueued, and cause it to be missed.
1100     // Re: the performance cost: we shouldn't be doing full GC anyway!
1101     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1102 
1103     return false;
1104   }
1105 };
1106 
1107 void G1CollectedHeap::clear_rsets_post_compaction() {
1108   PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1109   heap_region_iterate(&rs_clear);
1110 }
1111 
1112 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1113   G1CollectedHeap*   _g1h;
1114   UpdateRSOopClosure _cl;
1115 public:
1116   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) :
1117     _cl(g1->g1_rem_set(), worker_i),
1118     _g1h(g1)
1119   { }
1120 
1121   bool doHeapRegion(HeapRegion* r) {
1122     if (!r->is_continues_humongous()) {
1123       _cl.set_from(r);
1124       r->oop_iterate(&_cl);
1125     }
1126     return false;
1127   }
1128 };
1129 
1130 class ParRebuildRSTask: public AbstractGangTask {
1131   G1CollectedHeap* _g1;
1132   HeapRegionClaimer _hrclaimer;
1133 
1134 public:
1135   ParRebuildRSTask(G1CollectedHeap* g1) :
1136       AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {}
1137 
1138   void work(uint worker_id) {
1139     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1140     _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer);
1141   }
1142 };
1143 
1144 class PostCompactionPrinterClosure: public HeapRegionClosure {
1145 private:
1146   G1HRPrinter* _hr_printer;
1147 public:
1148   bool doHeapRegion(HeapRegion* hr) {
1149     assert(!hr->is_young(), "not expecting to find young regions");
1150     _hr_printer->post_compaction(hr);
1151     return false;
1152   }
1153 
1154   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1155     : _hr_printer(hr_printer) { }
1156 };
1157 
1158 void G1CollectedHeap::print_hrm_post_compaction() {
1159   if (_hr_printer.is_active()) {
1160     PostCompactionPrinterClosure cl(hr_printer());
1161     heap_region_iterate(&cl);
1162   }
1163 
1164 }
1165 
1166 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1167                                          bool clear_all_soft_refs) {
1168   assert_at_safepoint(true /* should_be_vm_thread */);
1169 
1170   if (GCLocker::check_active_before_gc()) {
1171     return false;
1172   }
1173 
1174   STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1175   gc_timer->register_gc_start();
1176 
1177   SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1178   GCIdMark gc_id_mark;
1179   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1180 
1181   SvcGCMarker sgcm(SvcGCMarker::FULL);
1182   ResourceMark rm;
1183 
1184   print_heap_before_gc();
1185   print_heap_regions();
1186   trace_heap_before_gc(gc_tracer);
1187 
1188   size_t metadata_prev_used = MetaspaceAux::used_bytes();
1189 
1190   _verifier->verify_region_sets_optional();
1191 
1192   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1193                            collector_policy()->should_clear_all_soft_refs();
1194 
1195   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1196 
1197   {
1198     IsGCActiveMark x;
1199 
1200     // Timing
1201     assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1202     GCTraceCPUTime tcpu;
1203 
1204     {
1205       GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1206       TraceCollectorStats tcs(g1mm()->full_collection_counters());
1207       TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1208 
1209       G1HeapTransition heap_transition(this);
1210       g1_policy()->record_full_collection_start();
1211 
1212       // Note: When we have a more flexible GC logging framework that
1213       // allows us to add optional attributes to a GC log record we
1214       // could consider timing and reporting how long we wait in the
1215       // following two methods.
1216       wait_while_free_regions_coming();
1217       // If we start the compaction before the CM threads finish
1218       // scanning the root regions we might trip them over as we'll
1219       // be moving objects / updating references. So let's wait until
1220       // they are done. By telling them to abort, they should complete
1221       // early.
1222       _cm->root_regions()->abort();
1223       _cm->root_regions()->wait_until_scan_finished();
1224       append_secondary_free_list_if_not_empty_with_lock();
1225 
1226       gc_prologue(true);
1227       increment_total_collections(true /* full gc */);
1228       increment_old_marking_cycles_started();
1229 
1230       assert(used() == recalculate_used(), "Should be equal");
1231 
1232       _verifier->verify_before_gc();
1233 
1234       _verifier->check_bitmaps("Full GC Start");
1235       pre_full_gc_dump(gc_timer);
1236 
1237 #if defined(COMPILER2) || INCLUDE_JVMCI
1238       DerivedPointerTable::clear();
1239 #endif
1240 
1241       // Disable discovery and empty the discovered lists
1242       // for the CM ref processor.
1243       ref_processor_cm()->disable_discovery();
1244       ref_processor_cm()->abandon_partial_discovery();
1245       ref_processor_cm()->verify_no_references_recorded();
1246 
1247       // Abandon current iterations of concurrent marking and concurrent
1248       // refinement, if any are in progress.
1249       concurrent_mark()->abort();
1250 
1251       // Make sure we'll choose a new allocation region afterwards.
1252       _allocator->release_mutator_alloc_region();
1253       _allocator->abandon_gc_alloc_regions();
1254       g1_rem_set()->cleanupHRRS();
1255 
1256       // We may have added regions to the current incremental collection
1257       // set between the last GC or pause and now. We need to clear the
1258       // incremental collection set and then start rebuilding it afresh
1259       // after this full GC.
1260       abandon_collection_set(collection_set());
1261 
1262       tear_down_region_sets(false /* free_list_only */);
1263       collector_state()->set_gcs_are_young(true);
1264 
1265       // See the comments in g1CollectedHeap.hpp and
1266       // G1CollectedHeap::ref_processing_init() about
1267       // how reference processing currently works in G1.
1268 
1269       // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1270       ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1271 
1272       // Temporarily clear the STW ref processor's _is_alive_non_header field.
1273       ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1274 
1275       ref_processor_stw()->enable_discovery();
1276       ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1277 
1278       // Do collection work
1279       {
1280         HandleMark hm;  // Discard invalid handles created during gc
1281         G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1282       }
1283 
1284       assert(num_free_regions() == 0, "we should not have added any free regions");
1285       rebuild_region_sets(false /* free_list_only */);
1286 
1287       // Enqueue any discovered reference objects that have
1288       // not been removed from the discovered lists.
1289       ref_processor_stw()->enqueue_discovered_references();
1290 
1291 #if defined(COMPILER2) || INCLUDE_JVMCI
1292       DerivedPointerTable::update_pointers();
1293 #endif
1294 
1295       MemoryService::track_memory_usage();
1296 
1297       assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1298       ref_processor_stw()->verify_no_references_recorded();
1299 
1300       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1301       ClassLoaderDataGraph::purge();
1302       MetaspaceAux::verify_metrics();
1303 
1304       // Note: since we've just done a full GC, concurrent
1305       // marking is no longer active. Therefore we need not
1306       // re-enable reference discovery for the CM ref processor.
1307       // That will be done at the start of the next marking cycle.
1308       assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1309       ref_processor_cm()->verify_no_references_recorded();
1310 
1311       reset_gc_time_stamp();
1312       // Since everything potentially moved, we will clear all remembered
1313       // sets, and clear all cards.  Later we will rebuild remembered
1314       // sets. We will also reset the GC time stamps of the regions.
1315       clear_rsets_post_compaction();
1316       check_gc_time_stamps();
1317 
1318       resize_if_necessary_after_full_collection();
1319 
1320       // We should do this after we potentially resize the heap so
1321       // that all the COMMIT / UNCOMMIT events are generated before
1322       // the compaction events.
1323       print_hrm_post_compaction();
1324 
1325       if (_hot_card_cache->use_cache()) {
1326         _hot_card_cache->reset_card_counts();
1327         _hot_card_cache->reset_hot_cache();
1328       }
1329 
1330       // Rebuild remembered sets of all regions.
1331       uint n_workers =
1332         AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1333                                                 workers()->active_workers(),
1334                                                 Threads::number_of_non_daemon_threads());
1335       workers()->update_active_workers(n_workers);
1336       log_info(gc,task)("Using %u workers of %u to rebuild remembered set", n_workers, workers()->total_workers());
1337 
1338       ParRebuildRSTask rebuild_rs_task(this);
1339       workers()->run_task(&rebuild_rs_task);
1340 
1341       // Rebuild the strong code root lists for each region
1342       rebuild_strong_code_roots();
1343 
1344       if (true) { // FIXME
1345         MetaspaceGC::compute_new_size();
1346       }
1347 
1348 #ifdef TRACESPINNING
1349       ParallelTaskTerminator::print_termination_counts();
1350 #endif
1351 
1352       // Discard all rset updates
1353       JavaThread::dirty_card_queue_set().abandon_logs();
1354       assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1355 
1356       // At this point there should be no regions in the
1357       // entire heap tagged as young.
1358       assert(check_young_list_empty(), "young list should be empty at this point");
1359 
1360       // Update the number of full collections that have been completed.
1361       increment_old_marking_cycles_completed(false /* concurrent */);
1362 
1363       _hrm.verify_optional();
1364       _verifier->verify_region_sets_optional();
1365 
1366       _verifier->verify_after_gc();
1367 
1368       // Clear the previous marking bitmap, if needed for bitmap verification.
1369       // Note we cannot do this when we clear the next marking bitmap in
1370       // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1371       // objects marked during a full GC against the previous bitmap.
1372       // But we need to clear it before calling check_bitmaps below since
1373       // the full GC has compacted objects and updated TAMS but not updated
1374       // the prev bitmap.
1375       if (G1VerifyBitmaps) {
1376         GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1377         _cm->clear_prev_bitmap(workers());
1378       }
1379       _verifier->check_bitmaps("Full GC End");
1380 
1381       // Start a new incremental collection set for the next pause
1382       collection_set()->start_incremental_building();
1383 
1384       clear_cset_fast_test();
1385 
1386       _allocator->init_mutator_alloc_region();
1387 
1388       g1_policy()->record_full_collection_end();
1389 
1390       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1391       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1392       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1393       // before any GC notifications are raised.
1394       g1mm()->update_sizes();
1395 
1396       gc_epilogue(true);
1397 
1398       heap_transition.print();
1399 
1400       print_heap_after_gc();
1401       print_heap_regions();
1402       trace_heap_after_gc(gc_tracer);
1403 
1404       post_full_gc_dump(gc_timer);
1405     }
1406 
1407     gc_timer->register_gc_end();
1408     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1409   }
1410 
1411   return true;
1412 }
1413 
1414 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1415   // Currently, there is no facility in the do_full_collection(bool) API to notify
1416   // the caller that the collection did not succeed (e.g., because it was locked
1417   // out by the GC locker). So, right now, we'll ignore the return value.
1418   bool dummy = do_full_collection(true,                /* explicit_gc */
1419                                   clear_all_soft_refs);
1420 }
1421 
1422 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1423   // Include bytes that will be pre-allocated to support collections, as "used".
1424   const size_t used_after_gc = used();
1425   const size_t capacity_after_gc = capacity();
1426   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1427 
1428   // This is enforced in arguments.cpp.
1429   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1430          "otherwise the code below doesn't make sense");
1431 
1432   // We don't have floating point command-line arguments
1433   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1434   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1435   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1436   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1437 
1438   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1439   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1440 
1441   // We have to be careful here as these two calculations can overflow
1442   // 32-bit size_t's.
1443   double used_after_gc_d = (double) used_after_gc;
1444   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1445   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1446 
1447   // Let's make sure that they are both under the max heap size, which
1448   // by default will make them fit into a size_t.
1449   double desired_capacity_upper_bound = (double) max_heap_size;
1450   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1451                                     desired_capacity_upper_bound);
1452   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1453                                     desired_capacity_upper_bound);
1454 
1455   // We can now safely turn them into size_t's.
1456   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1457   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1458 
1459   // This assert only makes sense here, before we adjust them
1460   // with respect to the min and max heap size.
1461   assert(minimum_desired_capacity <= maximum_desired_capacity,
1462          "minimum_desired_capacity = " SIZE_FORMAT ", "
1463          "maximum_desired_capacity = " SIZE_FORMAT,
1464          minimum_desired_capacity, maximum_desired_capacity);
1465 
1466   // Should not be greater than the heap max size. No need to adjust
1467   // it with respect to the heap min size as it's a lower bound (i.e.,
1468   // we'll try to make the capacity larger than it, not smaller).
1469   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1470   // Should not be less than the heap min size. No need to adjust it
1471   // with respect to the heap max size as it's an upper bound (i.e.,
1472   // we'll try to make the capacity smaller than it, not greater).
1473   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1474 
1475   if (capacity_after_gc < minimum_desired_capacity) {
1476     // Don't expand unless it's significant
1477     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1478 
1479     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1480                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1481                               capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1482 
1483     expand(expand_bytes, _workers);
1484 
1485     // No expansion, now see if we want to shrink
1486   } else if (capacity_after_gc > maximum_desired_capacity) {
1487     // Capacity too large, compute shrinking size
1488     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1489 
1490     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1491                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1492                               capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1493 
1494     shrink(shrink_bytes);
1495   }
1496 }
1497 
1498 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1499                                                             AllocationContext_t context,
1500                                                             bool do_gc,
1501                                                             bool clear_all_soft_refs,
1502                                                             bool expect_null_mutator_alloc_region,
1503                                                             bool* gc_succeeded) {
1504   *gc_succeeded = true;
1505   // Let's attempt the allocation first.
1506   HeapWord* result =
1507     attempt_allocation_at_safepoint(word_size,
1508                                     context,
1509                                     expect_null_mutator_alloc_region);
1510   if (result != NULL) {
1511     assert(*gc_succeeded, "sanity");
1512     return result;
1513   }
1514 
1515   // In a G1 heap, we're supposed to keep allocation from failing by
1516   // incremental pauses.  Therefore, at least for now, we'll favor
1517   // expansion over collection.  (This might change in the future if we can
1518   // do something smarter than full collection to satisfy a failed alloc.)
1519   result = expand_and_allocate(word_size, context);
1520   if (result != NULL) {
1521     assert(*gc_succeeded, "sanity");
1522     return result;
1523   }
1524 
1525   if (do_gc) {
1526     // Expansion didn't work, we'll try to do a Full GC.
1527     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1528                                        clear_all_soft_refs);
1529   }
1530 
1531   return NULL;
1532 }
1533 
1534 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1535                                                      AllocationContext_t context,
1536                                                      bool* succeeded) {
1537   assert_at_safepoint(true /* should_be_vm_thread */);
1538 
1539   // Attempts to allocate followed by Full GC.
1540   HeapWord* result =
1541     satisfy_failed_allocation_helper(word_size,
1542                                      context,
1543                                      true,  /* do_gc */
1544                                      false, /* clear_all_soft_refs */
1545                                      false, /* expect_null_mutator_alloc_region */
1546                                      succeeded);
1547 
1548   if (result != NULL || !*succeeded) {
1549     return result;
1550   }
1551 
1552   // Attempts to allocate followed by Full GC that will collect all soft references.
1553   result = satisfy_failed_allocation_helper(word_size,
1554                                             context,
1555                                             true, /* do_gc */
1556                                             true, /* clear_all_soft_refs */
1557                                             true, /* expect_null_mutator_alloc_region */
1558                                             succeeded);
1559 
1560   if (result != NULL || !*succeeded) {
1561     return result;
1562   }
1563 
1564   // Attempts to allocate, no GC
1565   result = satisfy_failed_allocation_helper(word_size,
1566                                             context,
1567                                             false, /* do_gc */
1568                                             false, /* clear_all_soft_refs */
1569                                             true,  /* expect_null_mutator_alloc_region */
1570                                             succeeded);
1571 
1572   if (result != NULL) {
1573     assert(*succeeded, "sanity");
1574     return result;
1575   }
1576 
1577   assert(!collector_policy()->should_clear_all_soft_refs(),
1578          "Flag should have been handled and cleared prior to this point");
1579 
1580   // What else?  We might try synchronous finalization later.  If the total
1581   // space available is large enough for the allocation, then a more
1582   // complete compaction phase than we've tried so far might be
1583   // appropriate.
1584   assert(*succeeded, "sanity");
1585   return NULL;
1586 }
1587 
1588 // Attempting to expand the heap sufficiently
1589 // to support an allocation of the given "word_size".  If
1590 // successful, perform the allocation and return the address of the
1591 // allocated block, or else "NULL".
1592 
1593 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1594   assert_at_safepoint(true /* should_be_vm_thread */);
1595 
1596   _verifier->verify_region_sets_optional();
1597 
1598   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1599   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1600                             word_size * HeapWordSize);
1601 
1602 
1603   if (expand(expand_bytes, _workers)) {
1604     _hrm.verify_optional();
1605     _verifier->verify_region_sets_optional();
1606     return attempt_allocation_at_safepoint(word_size,
1607                                            context,
1608                                            false /* expect_null_mutator_alloc_region */);
1609   }
1610   return NULL;
1611 }
1612 
1613 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1614   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1615   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1616                                        HeapRegion::GrainBytes);
1617 
1618   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount:" SIZE_FORMAT "B expansion amount:" SIZE_FORMAT "B",
1619                             expand_bytes, aligned_expand_bytes);
1620 
1621   if (is_maximal_no_gc()) {
1622     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1623     return false;
1624   }
1625 
1626   double expand_heap_start_time_sec = os::elapsedTime();
1627   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1628   assert(regions_to_expand > 0, "Must expand by at least one region");
1629 
1630   uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1631   if (expand_time_ms != NULL) {
1632     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1633   }
1634 
1635   if (expanded_by > 0) {
1636     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1637     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1638     g1_policy()->record_new_heap_size(num_regions());
1639   } else {
1640     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1641 
1642     // The expansion of the virtual storage space was unsuccessful.
1643     // Let's see if it was because we ran out of swap.
1644     if (G1ExitOnExpansionFailure &&
1645         _hrm.available() >= regions_to_expand) {
1646       // We had head room...
1647       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1648     }
1649   }
1650   return regions_to_expand > 0;
1651 }
1652 
1653 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1654   size_t aligned_shrink_bytes =
1655     ReservedSpace::page_align_size_down(shrink_bytes);
1656   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1657                                          HeapRegion::GrainBytes);
1658   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1659 
1660   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1661   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1662 
1663 
1664   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",
1665                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1666   if (num_regions_removed > 0) {
1667     g1_policy()->record_new_heap_size(num_regions());
1668   } else {
1669     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1670   }
1671 }
1672 
1673 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1674   _verifier->verify_region_sets_optional();
1675 
1676   // We should only reach here at the end of a Full GC which means we
1677   // should not not be holding to any GC alloc regions. The method
1678   // below will make sure of that and do any remaining clean up.
1679   _allocator->abandon_gc_alloc_regions();
1680 
1681   // Instead of tearing down / rebuilding the free lists here, we
1682   // could instead use the remove_all_pending() method on free_list to
1683   // remove only the ones that we need to remove.
1684   tear_down_region_sets(true /* free_list_only */);
1685   shrink_helper(shrink_bytes);
1686   rebuild_region_sets(true /* free_list_only */);
1687 
1688   _hrm.verify_optional();
1689   _verifier->verify_region_sets_optional();
1690 }
1691 
1692 // Public methods.
1693 
1694 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1695   CollectedHeap(),
1696   _collector_policy(collector_policy),
1697   _g1_policy(create_g1_policy()),
1698   _collection_set(this, _g1_policy),
1699   _dirty_card_queue_set(false),
1700   _is_alive_closure_cm(this),
1701   _is_alive_closure_stw(this),
1702   _ref_processor_cm(NULL),
1703   _ref_processor_stw(NULL),
1704   _bot(NULL),
1705   _hot_card_cache(NULL),
1706   _g1_rem_set(NULL),
1707   _cg1r(NULL),
1708   _g1mm(NULL),
1709   _refine_cte_cl(NULL),
1710   _preserved_marks_set(true /* in_c_heap */),
1711   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1712   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1713   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1714   _humongous_reclaim_candidates(),
1715   _has_humongous_reclaim_candidates(false),
1716   _archive_allocator(NULL),
1717   _free_regions_coming(false),
1718   _gc_time_stamp(0),
1719   _summary_bytes_used(0),
1720   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1721   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1722   _expand_heap_after_alloc_failure(true),
1723   _old_marking_cycles_started(0),
1724   _old_marking_cycles_completed(0),
1725   _in_cset_fast_test(),
1726   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1727   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()) {
1728 
1729   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1730                           /* are_GC_task_threads */true,
1731                           /* are_ConcurrentGC_threads */false);
1732   _workers->initialize_workers();
1733   _verifier = new G1HeapVerifier(this);
1734 
1735   _allocator = G1Allocator::create_allocator(this);
1736 
1737   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1738 
1739   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1740 
1741   // Override the default _filler_array_max_size so that no humongous filler
1742   // objects are created.
1743   _filler_array_max_size = _humongous_object_threshold_in_words;
1744 
1745   uint n_queues = ParallelGCThreads;
1746   _task_queues = new RefToScanQueueSet(n_queues);
1747 
1748   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1749 
1750   for (uint i = 0; i < n_queues; i++) {
1751     RefToScanQueue* q = new RefToScanQueue();
1752     q->initialize();
1753     _task_queues->register_queue(i, q);
1754     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1755   }
1756 
1757   // Initialize the G1EvacuationFailureALot counters and flags.
1758   NOT_PRODUCT(reset_evacuation_should_fail();)
1759 
1760   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1761 }
1762 
1763 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1764                                                                  size_t size,
1765                                                                  size_t translation_factor) {
1766   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1767   // Allocate a new reserved space, preferring to use large pages.
1768   ReservedSpace rs(size, preferred_page_size);
1769   G1RegionToSpaceMapper* result  =
1770     G1RegionToSpaceMapper::create_mapper(rs,
1771                                          size,
1772                                          rs.alignment(),
1773                                          HeapRegion::GrainBytes,
1774                                          translation_factor,
1775                                          mtGC);
1776 
1777   os::trace_page_sizes_for_requested_size(description,
1778                                           size,
1779                                           preferred_page_size,
1780                                           rs.alignment(),
1781                                           rs.base(),
1782                                           rs.size());
1783 
1784   return result;
1785 }
1786 
1787 jint G1CollectedHeap::initialize() {
1788   CollectedHeap::pre_initialize();
1789   os::enable_vtime();
1790 
1791   // Necessary to satisfy locking discipline assertions.
1792 
1793   MutexLocker x(Heap_lock);
1794 
1795   // While there are no constraints in the GC code that HeapWordSize
1796   // be any particular value, there are multiple other areas in the
1797   // system which believe this to be true (e.g. oop->object_size in some
1798   // cases incorrectly returns the size in wordSize units rather than
1799   // HeapWordSize).
1800   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1801 
1802   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1803   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1804   size_t heap_alignment = collector_policy()->heap_alignment();
1805 
1806   // Ensure that the sizes are properly aligned.
1807   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1808   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1809   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1810 
1811   _refine_cte_cl = new RefineCardTableEntryClosure();
1812 
1813   jint ecode = JNI_OK;
1814   _cg1r = ConcurrentG1Refine::create(_refine_cte_cl, &ecode);
1815   if (_cg1r == NULL) {
1816     return ecode;
1817   }
1818 
1819   // Reserve the maximum.
1820 
1821   // When compressed oops are enabled, the preferred heap base
1822   // is calculated by subtracting the requested size from the
1823   // 32Gb boundary and using the result as the base address for
1824   // heap reservation. If the requested size is not aligned to
1825   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1826   // into the ReservedHeapSpace constructor) then the actual
1827   // base of the reserved heap may end up differing from the
1828   // address that was requested (i.e. the preferred heap base).
1829   // If this happens then we could end up using a non-optimal
1830   // compressed oops mode.
1831 
1832   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1833                                                  heap_alignment);
1834 
1835   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1836 
1837   // Create the barrier set for the entire reserved region.
1838   G1SATBCardTableLoggingModRefBS* bs
1839     = new G1SATBCardTableLoggingModRefBS(reserved_region());
1840   bs->initialize();
1841   assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1842   set_barrier_set(bs);
1843 
1844   // Create the hot card cache.
1845   _hot_card_cache = new G1HotCardCache(this);
1846 
1847   // Also create a G1 rem set.
1848   _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache);
1849 
1850   // Carve out the G1 part of the heap.
1851   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1852   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1853   G1RegionToSpaceMapper* heap_storage =
1854     G1RegionToSpaceMapper::create_mapper(g1_rs,
1855                                          g1_rs.size(),
1856                                          page_size,
1857                                          HeapRegion::GrainBytes,
1858                                          1,
1859                                          mtJavaHeap);
1860   os::trace_page_sizes("Heap",
1861                        collector_policy()->min_heap_byte_size(),
1862                        max_byte_size,
1863                        page_size,
1864                        heap_rs.base(),
1865                        heap_rs.size());
1866   heap_storage->set_mapping_changed_listener(&_listener);
1867 
1868   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1869   G1RegionToSpaceMapper* bot_storage =
1870     create_aux_memory_mapper("Block Offset Table",
1871                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1872                              G1BlockOffsetTable::heap_map_factor());
1873 
1874   ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1875   G1RegionToSpaceMapper* cardtable_storage =
1876     create_aux_memory_mapper("Card Table",
1877                              G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1878                              G1SATBCardTableLoggingModRefBS::heap_map_factor());
1879 
1880   G1RegionToSpaceMapper* card_counts_storage =
1881     create_aux_memory_mapper("Card Counts Table",
1882                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1883                              G1CardCounts::heap_map_factor());
1884 
1885   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1886   G1RegionToSpaceMapper* prev_bitmap_storage =
1887     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1888   G1RegionToSpaceMapper* next_bitmap_storage =
1889     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1890 
1891   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1892   g1_barrier_set()->initialize(cardtable_storage);
1893   // Do later initialization work for concurrent refinement.
1894   _hot_card_cache->initialize(card_counts_storage);
1895 
1896   // 6843694 - ensure that the maximum region index can fit
1897   // in the remembered set structures.
1898   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1899   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1900 
1901   g1_rem_set()->initialize(max_capacity(), max_regions());
1902 
1903   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1904   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1905   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1906             "too many cards per region");
1907 
1908   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1909 
1910   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1911 
1912   {
1913     HeapWord* start = _hrm.reserved().start();
1914     HeapWord* end = _hrm.reserved().end();
1915     size_t granularity = HeapRegion::GrainBytes;
1916 
1917     _in_cset_fast_test.initialize(start, end, granularity);
1918     _humongous_reclaim_candidates.initialize(start, end, granularity);
1919   }
1920 
1921   // Create the G1ConcurrentMark data structure and thread.
1922   // (Must do this late, so that "max_regions" is defined.)
1923   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1924   if (_cm == NULL || !_cm->completed_initialization()) {
1925     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1926     return JNI_ENOMEM;
1927   }
1928   _cmThread = _cm->cmThread();
1929 
1930   // Now expand into the initial heap size.
1931   if (!expand(init_byte_size, _workers)) {
1932     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1933     return JNI_ENOMEM;
1934   }
1935 
1936   // Perform any initialization actions delegated to the policy.
1937   g1_policy()->init(this, &_collection_set);
1938 
1939   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1940                                                SATB_Q_FL_lock,
1941                                                G1SATBProcessCompletedThreshold,
1942                                                Shared_SATB_Q_lock);
1943 
1944   JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
1945                                                 DirtyCardQ_CBL_mon,
1946                                                 DirtyCardQ_FL_lock,
1947                                                 (int)concurrent_g1_refine()->yellow_zone(),
1948                                                 (int)concurrent_g1_refine()->red_zone(),
1949                                                 Shared_DirtyCardQ_lock,
1950                                                 NULL,  // fl_owner
1951                                                 true); // init_free_ids
1952 
1953   dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
1954                                     DirtyCardQ_CBL_mon,
1955                                     DirtyCardQ_FL_lock,
1956                                     -1, // never trigger processing
1957                                     -1, // no limit on length
1958                                     Shared_DirtyCardQ_lock,
1959                                     &JavaThread::dirty_card_queue_set());
1960 
1961   // Here we allocate the dummy HeapRegion that is required by the
1962   // G1AllocRegion class.
1963   HeapRegion* dummy_region = _hrm.get_dummy_region();
1964 
1965   // We'll re-use the same region whether the alloc region will
1966   // require BOT updates or not and, if it doesn't, then a non-young
1967   // region will complain that it cannot support allocations without
1968   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1969   dummy_region->set_eden();
1970   // Make sure it's full.
1971   dummy_region->set_top(dummy_region->end());
1972   G1AllocRegion::setup(this, dummy_region);
1973 
1974   _allocator->init_mutator_alloc_region();
1975 
1976   // Do create of the monitoring and management support so that
1977   // values in the heap have been properly initialized.
1978   _g1mm = new G1MonitoringSupport(this);
1979 
1980   G1StringDedup::initialize();
1981 
1982   _preserved_marks_set.init(ParallelGCThreads);
1983 
1984   _collection_set.initialize(max_regions());
1985 
1986   return JNI_OK;
1987 }
1988 
1989 void G1CollectedHeap::stop() {
1990   // Stop all concurrent threads. We do this to make sure these threads
1991   // do not continue to execute and access resources (e.g. logging)
1992   // that are destroyed during shutdown.
1993   _cg1r->stop();
1994   _cmThread->stop();
1995   if (G1StringDedup::is_enabled()) {
1996     G1StringDedup::stop();
1997   }
1998 }
1999 
2000 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2001   return HeapRegion::max_region_size();
2002 }
2003 
2004 void G1CollectedHeap::post_initialize() {
2005   ref_processing_init();
2006 }
2007 
2008 void G1CollectedHeap::ref_processing_init() {
2009   // Reference processing in G1 currently works as follows:
2010   //
2011   // * There are two reference processor instances. One is
2012   //   used to record and process discovered references
2013   //   during concurrent marking; the other is used to
2014   //   record and process references during STW pauses
2015   //   (both full and incremental).
2016   // * Both ref processors need to 'span' the entire heap as
2017   //   the regions in the collection set may be dotted around.
2018   //
2019   // * For the concurrent marking ref processor:
2020   //   * Reference discovery is enabled at initial marking.
2021   //   * Reference discovery is disabled and the discovered
2022   //     references processed etc during remarking.
2023   //   * Reference discovery is MT (see below).
2024   //   * Reference discovery requires a barrier (see below).
2025   //   * Reference processing may or may not be MT
2026   //     (depending on the value of ParallelRefProcEnabled
2027   //     and ParallelGCThreads).
2028   //   * A full GC disables reference discovery by the CM
2029   //     ref processor and abandons any entries on it's
2030   //     discovered lists.
2031   //
2032   // * For the STW processor:
2033   //   * Non MT discovery is enabled at the start of a full GC.
2034   //   * Processing and enqueueing during a full GC is non-MT.
2035   //   * During a full GC, references are processed after marking.
2036   //
2037   //   * Discovery (may or may not be MT) is enabled at the start
2038   //     of an incremental evacuation pause.
2039   //   * References are processed near the end of a STW evacuation pause.
2040   //   * For both types of GC:
2041   //     * Discovery is atomic - i.e. not concurrent.
2042   //     * Reference discovery will not need a barrier.
2043 
2044   MemRegion mr = reserved_region();
2045 
2046   // Concurrent Mark ref processor
2047   _ref_processor_cm =
2048     new ReferenceProcessor(mr,    // span
2049                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2050                                 // mt processing
2051                            ParallelGCThreads,
2052                                 // degree of mt processing
2053                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2054                                 // mt discovery
2055                            MAX2(ParallelGCThreads, ConcGCThreads),
2056                                 // degree of mt discovery
2057                            false,
2058                                 // Reference discovery is not atomic
2059                            &_is_alive_closure_cm);
2060                                 // is alive closure
2061                                 // (for efficiency/performance)
2062 
2063   // STW ref processor
2064   _ref_processor_stw =
2065     new ReferenceProcessor(mr,    // span
2066                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2067                                 // mt processing
2068                            ParallelGCThreads,
2069                                 // degree of mt processing
2070                            (ParallelGCThreads > 1),
2071                                 // mt discovery
2072                            ParallelGCThreads,
2073                                 // degree of mt discovery
2074                            true,
2075                                 // Reference discovery is atomic
2076                            &_is_alive_closure_stw);
2077                                 // is alive closure
2078                                 // (for efficiency/performance)
2079 }
2080 
2081 CollectorPolicy* G1CollectedHeap::collector_policy() const {
2082   return _collector_policy;
2083 }
2084 
2085 size_t G1CollectedHeap::capacity() const {
2086   return _hrm.length() * HeapRegion::GrainBytes;
2087 }
2088 
2089 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2090   hr->reset_gc_time_stamp();
2091 }
2092 
2093 #ifndef PRODUCT
2094 
2095 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2096 private:
2097   unsigned _gc_time_stamp;
2098   bool _failures;
2099 
2100 public:
2101   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2102     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2103 
2104   virtual bool doHeapRegion(HeapRegion* hr) {
2105     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2106     if (_gc_time_stamp != region_gc_time_stamp) {
2107       log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
2108                             region_gc_time_stamp, _gc_time_stamp);
2109       _failures = true;
2110     }
2111     return false;
2112   }
2113 
2114   bool failures() { return _failures; }
2115 };
2116 
2117 void G1CollectedHeap::check_gc_time_stamps() {
2118   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2119   heap_region_iterate(&cl);
2120   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2121 }
2122 #endif // PRODUCT
2123 
2124 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
2125   _hot_card_cache->drain(cl, worker_i);
2126 }
2127 
2128 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
2129   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2130   size_t n_completed_buffers = 0;
2131   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2132     n_completed_buffers++;
2133   }
2134   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2135   dcqs.clear_n_completed_buffers();
2136   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2137 }
2138 
2139 // Computes the sum of the storage used by the various regions.
2140 size_t G1CollectedHeap::used() const {
2141   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
2142   if (_archive_allocator != NULL) {
2143     result += _archive_allocator->used();
2144   }
2145   return result;
2146 }
2147 
2148 size_t G1CollectedHeap::used_unlocked() const {
2149   return _summary_bytes_used;
2150 }
2151 
2152 class SumUsedClosure: public HeapRegionClosure {
2153   size_t _used;
2154 public:
2155   SumUsedClosure() : _used(0) {}
2156   bool doHeapRegion(HeapRegion* r) {
2157     _used += r->used();
2158     return false;
2159   }
2160   size_t result() { return _used; }
2161 };
2162 
2163 size_t G1CollectedHeap::recalculate_used() const {
2164   double recalculate_used_start = os::elapsedTime();
2165 
2166   SumUsedClosure blk;
2167   heap_region_iterate(&blk);
2168 
2169   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2170   return blk.result();
2171 }
2172 
2173 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2174   switch (cause) {
2175     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
2176     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
2177     case GCCause::_update_allocation_context_stats_inc: return true;
2178     case GCCause::_wb_conc_mark:                        return true;
2179     default :                                           return false;
2180   }
2181 }
2182 
2183 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2184   switch (cause) {
2185     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2186     case GCCause::_g1_humongous_allocation: return true;
2187     default:                                return is_user_requested_concurrent_full_gc(cause);
2188   }
2189 }
2190 
2191 #ifndef PRODUCT
2192 void G1CollectedHeap::allocate_dummy_regions() {
2193   // Let's fill up most of the region
2194   size_t word_size = HeapRegion::GrainWords - 1024;
2195   // And as a result the region we'll allocate will be humongous.
2196   guarantee(is_humongous(word_size), "sanity");
2197 
2198   // _filler_array_max_size is set to humongous object threshold
2199   // but temporarily change it to use CollectedHeap::fill_with_object().
2200   SizeTFlagSetting fs(_filler_array_max_size, word_size);
2201 
2202   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2203     // Let's use the existing mechanism for the allocation
2204     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2205                                                  AllocationContext::system());
2206     if (dummy_obj != NULL) {
2207       MemRegion mr(dummy_obj, word_size);
2208       CollectedHeap::fill_with_object(mr);
2209     } else {
2210       // If we can't allocate once, we probably cannot allocate
2211       // again. Let's get out of the loop.
2212       break;
2213     }
2214   }
2215 }
2216 #endif // !PRODUCT
2217 
2218 void G1CollectedHeap::increment_old_marking_cycles_started() {
2219   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2220          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2221          "Wrong marking cycle count (started: %d, completed: %d)",
2222          _old_marking_cycles_started, _old_marking_cycles_completed);
2223 
2224   _old_marking_cycles_started++;
2225 }
2226 
2227 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2228   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2229 
2230   // We assume that if concurrent == true, then the caller is a
2231   // concurrent thread that was joined the Suspendible Thread
2232   // Set. If there's ever a cheap way to check this, we should add an
2233   // assert here.
2234 
2235   // Given that this method is called at the end of a Full GC or of a
2236   // concurrent cycle, and those can be nested (i.e., a Full GC can
2237   // interrupt a concurrent cycle), the number of full collections
2238   // completed should be either one (in the case where there was no
2239   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2240   // behind the number of full collections started.
2241 
2242   // This is the case for the inner caller, i.e. a Full GC.
2243   assert(concurrent ||
2244          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2245          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2246          "for inner caller (Full GC): _old_marking_cycles_started = %u "
2247          "is inconsistent with _old_marking_cycles_completed = %u",
2248          _old_marking_cycles_started, _old_marking_cycles_completed);
2249 
2250   // This is the case for the outer caller, i.e. the concurrent cycle.
2251   assert(!concurrent ||
2252          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2253          "for outer caller (concurrent cycle): "
2254          "_old_marking_cycles_started = %u "
2255          "is inconsistent with _old_marking_cycles_completed = %u",
2256          _old_marking_cycles_started, _old_marking_cycles_completed);
2257 
2258   _old_marking_cycles_completed += 1;
2259 
2260   // We need to clear the "in_progress" flag in the CM thread before
2261   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2262   // is set) so that if a waiter requests another System.gc() it doesn't
2263   // incorrectly see that a marking cycle is still in progress.
2264   if (concurrent) {
2265     _cmThread->set_idle();
2266   }
2267 
2268   // This notify_all() will ensure that a thread that called
2269   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2270   // and it's waiting for a full GC to finish will be woken up. It is
2271   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2272   FullGCCount_lock->notify_all();
2273 }
2274 
2275 void G1CollectedHeap::collect(GCCause::Cause cause) {
2276   assert_heap_not_locked();
2277 
2278   uint gc_count_before;
2279   uint old_marking_count_before;
2280   uint full_gc_count_before;
2281   bool retry_gc;
2282 
2283   do {
2284     retry_gc = false;
2285 
2286     {
2287       MutexLocker ml(Heap_lock);
2288 
2289       // Read the GC count while holding the Heap_lock
2290       gc_count_before = total_collections();
2291       full_gc_count_before = total_full_collections();
2292       old_marking_count_before = _old_marking_cycles_started;
2293     }
2294 
2295     if (should_do_concurrent_full_gc(cause)) {
2296       // Schedule an initial-mark evacuation pause that will start a
2297       // concurrent cycle. We're setting word_size to 0 which means that
2298       // we are not requesting a post-GC allocation.
2299       VM_G1IncCollectionPause op(gc_count_before,
2300                                  0,     /* word_size */
2301                                  true,  /* should_initiate_conc_mark */
2302                                  g1_policy()->max_pause_time_ms(),
2303                                  cause);
2304       op.set_allocation_context(AllocationContext::current());
2305 
2306       VMThread::execute(&op);
2307       if (!op.pause_succeeded()) {
2308         if (old_marking_count_before == _old_marking_cycles_started) {
2309           retry_gc = op.should_retry_gc();
2310         } else {
2311           // A Full GC happened while we were trying to schedule the
2312           // initial-mark GC. No point in starting a new cycle given
2313           // that the whole heap was collected anyway.
2314         }
2315 
2316         if (retry_gc) {
2317           if (GCLocker::is_active_and_needs_gc()) {
2318             GCLocker::stall_until_clear();
2319           }
2320         }
2321       }
2322     } else {
2323       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2324           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2325 
2326         // Schedule a standard evacuation pause. We're setting word_size
2327         // to 0 which means that we are not requesting a post-GC allocation.
2328         VM_G1IncCollectionPause op(gc_count_before,
2329                                    0,     /* word_size */
2330                                    false, /* should_initiate_conc_mark */
2331                                    g1_policy()->max_pause_time_ms(),
2332                                    cause);
2333         VMThread::execute(&op);
2334       } else {
2335         // Schedule a Full GC.
2336         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2337         VMThread::execute(&op);
2338       }
2339     }
2340   } while (retry_gc);
2341 }
2342 
2343 bool G1CollectedHeap::is_in(const void* p) const {
2344   if (_hrm.reserved().contains(p)) {
2345     // Given that we know that p is in the reserved space,
2346     // heap_region_containing() should successfully
2347     // return the containing region.
2348     HeapRegion* hr = heap_region_containing(p);
2349     return hr->is_in(p);
2350   } else {
2351     return false;
2352   }
2353 }
2354 
2355 #ifdef ASSERT
2356 bool G1CollectedHeap::is_in_exact(const void* p) const {
2357   bool contains = reserved_region().contains(p);
2358   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2359   if (contains && available) {
2360     return true;
2361   } else {
2362     return false;
2363   }
2364 }
2365 #endif
2366 
2367 bool G1CollectedHeap::obj_in_cs(oop obj) {
2368   HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj);
2369   return r != NULL && r->in_collection_set();
2370 }
2371 
2372 // Iteration functions.
2373 
2374 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2375 
2376 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2377   ExtendedOopClosure* _cl;
2378 public:
2379   IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2380   bool doHeapRegion(HeapRegion* r) {
2381     if (!r->is_continues_humongous()) {
2382       r->oop_iterate(_cl);
2383     }
2384     return false;
2385   }
2386 };
2387 
2388 // Iterates an ObjectClosure over all objects within a HeapRegion.
2389 
2390 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2391   ObjectClosure* _cl;
2392 public:
2393   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2394   bool doHeapRegion(HeapRegion* r) {
2395     if (!r->is_continues_humongous()) {
2396       r->object_iterate(_cl);
2397     }
2398     return false;
2399   }
2400 };
2401 
2402 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2403   IterateObjectClosureRegionClosure blk(cl);
2404   heap_region_iterate(&blk);
2405 }
2406 
2407 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2408   _hrm.iterate(cl);
2409 }
2410 
2411 void
2412 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2413                                          uint worker_id,
2414                                          HeapRegionClaimer *hrclaimer,
2415                                          bool concurrent) const {
2416   _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent);
2417 }
2418 
2419 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2420   _collection_set.iterate(cl);
2421 }
2422 
2423 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2424   _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2425 }
2426 
2427 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2428   HeapRegion* result = _hrm.next_region_in_heap(from);
2429   while (result != NULL && result->is_pinned()) {
2430     result = _hrm.next_region_in_heap(result);
2431   }
2432   return result;
2433 }
2434 
2435 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2436   HeapRegion* hr = heap_region_containing(addr);
2437   return hr->block_start(addr);
2438 }
2439 
2440 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2441   HeapRegion* hr = heap_region_containing(addr);
2442   return hr->block_size(addr);
2443 }
2444 
2445 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2446   HeapRegion* hr = heap_region_containing(addr);
2447   return hr->block_is_obj(addr);
2448 }
2449 
2450 bool G1CollectedHeap::supports_tlab_allocation() const {
2451   return true;
2452 }
2453 
2454 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2455   return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2456 }
2457 
2458 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2459   return _eden.length() * HeapRegion::GrainBytes;
2460 }
2461 
2462 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2463 // must be equal to the humongous object limit.
2464 size_t G1CollectedHeap::max_tlab_size() const {
2465   return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment);
2466 }
2467 
2468 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2469   AllocationContext_t context = AllocationContext::current();
2470   return _allocator->unsafe_max_tlab_alloc(context);
2471 }
2472 
2473 size_t G1CollectedHeap::max_capacity() const {
2474   return _hrm.reserved().byte_size();
2475 }
2476 
2477 jlong G1CollectedHeap::millis_since_last_gc() {
2478   // See the notes in GenCollectedHeap::millis_since_last_gc()
2479   // for more information about the implementation.
2480   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2481     _g1_policy->collection_pause_end_millis();
2482   if (ret_val < 0) {
2483     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2484       ". returning zero instead.", ret_val);
2485     return 0;
2486   }
2487   return ret_val;
2488 }
2489 
2490 void G1CollectedHeap::prepare_for_verify() {
2491   _verifier->prepare_for_verify();
2492 }
2493 
2494 void G1CollectedHeap::verify(VerifyOption vo) {
2495   _verifier->verify(vo);
2496 }
2497 
2498 class PrintRegionClosure: public HeapRegionClosure {
2499   outputStream* _st;
2500 public:
2501   PrintRegionClosure(outputStream* st) : _st(st) {}
2502   bool doHeapRegion(HeapRegion* r) {
2503     r->print_on(_st);
2504     return false;
2505   }
2506 };
2507 
2508 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2509                                        const HeapRegion* hr,
2510                                        const VerifyOption vo) const {
2511   switch (vo) {
2512   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2513   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2514   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked() && !hr->is_archive();
2515   default:                            ShouldNotReachHere();
2516   }
2517   return false; // keep some compilers happy
2518 }
2519 
2520 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2521                                        const VerifyOption vo) const {
2522   switch (vo) {
2523   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2524   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2525   case VerifyOption_G1UseMarkWord: {
2526     HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj);
2527     return !obj->is_gc_marked() && !hr->is_archive();
2528   }
2529   default:                            ShouldNotReachHere();
2530   }
2531   return false; // keep some compilers happy
2532 }
2533 
2534 void G1CollectedHeap::print_heap_regions() const {
2535   Log(gc, heap, region) log;
2536   if (log.is_trace()) {
2537     ResourceMark rm;
2538     print_regions_on(log.trace_stream());
2539   }
2540 }
2541 
2542 void G1CollectedHeap::print_on(outputStream* st) const {
2543   st->print(" %-20s", "garbage-first heap");
2544   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2545             capacity()/K, used_unlocked()/K);
2546   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
2547             p2i(_hrm.reserved().start()),
2548             p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords),
2549             p2i(_hrm.reserved().end()));
2550   st->cr();
2551   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2552   uint young_regions = young_regions_count();
2553   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2554             (size_t) young_regions * HeapRegion::GrainBytes / K);
2555   uint survivor_regions = survivor_regions_count();
2556   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2557             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2558   st->cr();
2559   MetaspaceAux::print_on(st);
2560 }
2561 
2562 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2563   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2564                "HS=humongous(starts), HC=humongous(continues), "
2565                "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2566                "AC=allocation context, "
2567                "TAMS=top-at-mark-start (previous, next)");
2568   PrintRegionClosure blk(st);
2569   heap_region_iterate(&blk);
2570 }
2571 
2572 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2573   print_on(st);
2574 
2575   // Print the per-region information.
2576   print_regions_on(st);
2577 }
2578 
2579 void G1CollectedHeap::print_on_error(outputStream* st) const {
2580   this->CollectedHeap::print_on_error(st);
2581 
2582   if (_cm != NULL) {
2583     st->cr();
2584     _cm->print_on_error(st);
2585   }
2586 }
2587 
2588 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2589   workers()->print_worker_threads_on(st);
2590   _cmThread->print_on(st);
2591   st->cr();
2592   _cm->print_worker_threads_on(st);
2593   _cg1r->print_worker_threads_on(st); // also prints the sample thread
2594   if (G1StringDedup::is_enabled()) {
2595     G1StringDedup::print_worker_threads_on(st);
2596   }
2597 }
2598 
2599 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2600   workers()->threads_do(tc);
2601   tc->do_thread(_cmThread);
2602   _cm->threads_do(tc);
2603   _cg1r->threads_do(tc); // also iterates over the sample thread
2604   if (G1StringDedup::is_enabled()) {
2605     G1StringDedup::threads_do(tc);
2606   }
2607 }
2608 
2609 void G1CollectedHeap::print_tracing_info() const {
2610   g1_rem_set()->print_summary_info();
2611   concurrent_mark()->print_summary_info();
2612 }
2613 
2614 #ifndef PRODUCT
2615 // Helpful for debugging RSet issues.
2616 
2617 class PrintRSetsClosure : public HeapRegionClosure {
2618 private:
2619   const char* _msg;
2620   size_t _occupied_sum;
2621 
2622 public:
2623   bool doHeapRegion(HeapRegion* r) {
2624     HeapRegionRemSet* hrrs = r->rem_set();
2625     size_t occupied = hrrs->occupied();
2626     _occupied_sum += occupied;
2627 
2628     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2629     if (occupied == 0) {
2630       tty->print_cr("  RSet is empty");
2631     } else {
2632       hrrs->print();
2633     }
2634     tty->print_cr("----------");
2635     return false;
2636   }
2637 
2638   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2639     tty->cr();
2640     tty->print_cr("========================================");
2641     tty->print_cr("%s", msg);
2642     tty->cr();
2643   }
2644 
2645   ~PrintRSetsClosure() {
2646     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2647     tty->print_cr("========================================");
2648     tty->cr();
2649   }
2650 };
2651 
2652 void G1CollectedHeap::print_cset_rsets() {
2653   PrintRSetsClosure cl("Printing CSet RSets");
2654   collection_set_iterate(&cl);
2655 }
2656 
2657 void G1CollectedHeap::print_all_rsets() {
2658   PrintRSetsClosure cl("Printing All RSets");;
2659   heap_region_iterate(&cl);
2660 }
2661 #endif // PRODUCT
2662 
2663 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2664 
2665   size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2666   size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2667   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2668 
2669   size_t eden_capacity_bytes =
2670     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2671 
2672   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2673   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2674                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2675 }
2676 
2677 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2678   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2679                        stats->unused(), stats->used(), stats->region_end_waste(),
2680                        stats->regions_filled(), stats->direct_allocated(),
2681                        stats->failure_used(), stats->failure_waste());
2682 }
2683 
2684 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2685   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2686   gc_tracer->report_gc_heap_summary(when, heap_summary);
2687 
2688   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2689   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2690 }
2691 
2692 G1CollectedHeap* G1CollectedHeap::heap() {
2693   CollectedHeap* heap = Universe::heap();
2694   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2695   assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2696   return (G1CollectedHeap*)heap;
2697 }
2698 
2699 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
2700   // always_do_update_barrier = false;
2701   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2702   // Fill TLAB's and such
2703   accumulate_statistics_all_tlabs();
2704   ensure_parsability(true);
2705 
2706   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2707 }
2708 
2709 void G1CollectedHeap::gc_epilogue(bool full) {
2710   // we are at the end of the GC. Total collections has already been increased.
2711   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2712 
2713   // FIXME: what is this about?
2714   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2715   // is set.
2716 #if defined(COMPILER2) || INCLUDE_JVMCI
2717   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2718 #endif
2719   // always_do_update_barrier = true;
2720 
2721   resize_all_tlabs();
2722   allocation_context_stats().update(full);
2723 
2724   // We have just completed a GC. Update the soft reference
2725   // policy with the new heap occupancy
2726   Universe::update_heap_info_at_gc();
2727 }
2728 
2729 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2730                                                uint gc_count_before,
2731                                                bool* succeeded,
2732                                                GCCause::Cause gc_cause) {
2733   assert_heap_not_locked_and_not_at_safepoint();
2734   VM_G1IncCollectionPause op(gc_count_before,
2735                              word_size,
2736                              false, /* should_initiate_conc_mark */
2737                              g1_policy()->max_pause_time_ms(),
2738                              gc_cause);
2739 
2740   op.set_allocation_context(AllocationContext::current());
2741   VMThread::execute(&op);
2742 
2743   HeapWord* result = op.result();
2744   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2745   assert(result == NULL || ret_succeeded,
2746          "the result should be NULL if the VM did not succeed");
2747   *succeeded = ret_succeeded;
2748 
2749   assert_heap_not_locked();
2750   return result;
2751 }
2752 
2753 void
2754 G1CollectedHeap::doConcurrentMark() {
2755   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2756   if (!_cmThread->in_progress()) {
2757     _cmThread->set_started();
2758     CGC_lock->notify();
2759   }
2760 }
2761 
2762 size_t G1CollectedHeap::pending_card_num() {
2763   size_t extra_cards = 0;
2764   JavaThread *curr = Threads::first();
2765   while (curr != NULL) {
2766     DirtyCardQueue& dcq = curr->dirty_card_queue();
2767     extra_cards += dcq.size();
2768     curr = curr->next();
2769   }
2770   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2771   size_t buffer_size = dcqs.buffer_size();
2772   size_t buffer_num = dcqs.completed_buffers_num();
2773 
2774   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
2775   // in bytes - not the number of 'entries'. We need to convert
2776   // into a number of cards.
2777   return (buffer_size * buffer_num + extra_cards) / oopSize;
2778 }
2779 
2780 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2781  private:
2782   size_t _total_humongous;
2783   size_t _candidate_humongous;
2784 
2785   DirtyCardQueue _dcq;
2786 
2787   // We don't nominate objects with many remembered set entries, on
2788   // the assumption that such objects are likely still live.
2789   bool is_remset_small(HeapRegion* region) const {
2790     HeapRegionRemSet* const rset = region->rem_set();
2791     return G1EagerReclaimHumongousObjectsWithStaleRefs
2792       ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2793       : rset->is_empty();
2794   }
2795 
2796   bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2797     assert(region->is_starts_humongous(), "Must start a humongous object");
2798 
2799     oop obj = oop(region->bottom());
2800 
2801     // Dead objects cannot be eager reclaim candidates. Due to class
2802     // unloading it is unsafe to query their classes so we return early.
2803     if (heap->is_obj_dead(obj, region)) {
2804       return false;
2805     }
2806 
2807     // Candidate selection must satisfy the following constraints
2808     // while concurrent marking is in progress:
2809     //
2810     // * In order to maintain SATB invariants, an object must not be
2811     // reclaimed if it was allocated before the start of marking and
2812     // has not had its references scanned.  Such an object must have
2813     // its references (including type metadata) scanned to ensure no
2814     // live objects are missed by the marking process.  Objects
2815     // allocated after the start of concurrent marking don't need to
2816     // be scanned.
2817     //
2818     // * An object must not be reclaimed if it is on the concurrent
2819     // mark stack.  Objects allocated after the start of concurrent
2820     // marking are never pushed on the mark stack.
2821     //
2822     // Nominating only objects allocated after the start of concurrent
2823     // marking is sufficient to meet both constraints.  This may miss
2824     // some objects that satisfy the constraints, but the marking data
2825     // structures don't support efficiently performing the needed
2826     // additional tests or scrubbing of the mark stack.
2827     //
2828     // However, we presently only nominate is_typeArray() objects.
2829     // A humongous object containing references induces remembered
2830     // set entries on other regions.  In order to reclaim such an
2831     // object, those remembered sets would need to be cleaned up.
2832     //
2833     // We also treat is_typeArray() objects specially, allowing them
2834     // to be reclaimed even if allocated before the start of
2835     // concurrent mark.  For this we rely on mark stack insertion to
2836     // exclude is_typeArray() objects, preventing reclaiming an object
2837     // that is in the mark stack.  We also rely on the metadata for
2838     // such objects to be built-in and so ensured to be kept live.
2839     // Frequent allocation and drop of large binary blobs is an
2840     // important use case for eager reclaim, and this special handling
2841     // may reduce needed headroom.
2842 
2843     return obj->is_typeArray() && is_remset_small(region);
2844   }
2845 
2846  public:
2847   RegisterHumongousWithInCSetFastTestClosure()
2848   : _total_humongous(0),
2849     _candidate_humongous(0),
2850     _dcq(&JavaThread::dirty_card_queue_set()) {
2851   }
2852 
2853   virtual bool doHeapRegion(HeapRegion* r) {
2854     if (!r->is_starts_humongous()) {
2855       return false;
2856     }
2857     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2858 
2859     bool is_candidate = humongous_region_is_candidate(g1h, r);
2860     uint rindex = r->hrm_index();
2861     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2862     if (is_candidate) {
2863       _candidate_humongous++;
2864       g1h->register_humongous_region_with_cset(rindex);
2865       // Is_candidate already filters out humongous object with large remembered sets.
2866       // If we have a humongous object with a few remembered sets, we simply flush these
2867       // remembered set entries into the DCQS. That will result in automatic
2868       // re-evaluation of their remembered set entries during the following evacuation
2869       // phase.
2870       if (!r->rem_set()->is_empty()) {
2871         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2872                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2873         G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
2874         HeapRegionRemSetIterator hrrs(r->rem_set());
2875         size_t card_index;
2876         while (hrrs.has_next(card_index)) {
2877           jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
2878           // The remembered set might contain references to already freed
2879           // regions. Filter out such entries to avoid failing card table
2880           // verification.
2881           if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
2882             if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
2883               *card_ptr = CardTableModRefBS::dirty_card_val();
2884               _dcq.enqueue(card_ptr);
2885             }
2886           }
2887         }
2888         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2889                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2890                hrrs.n_yielded(), r->rem_set()->occupied());
2891         r->rem_set()->clear_locked();
2892       }
2893       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2894     }
2895     _total_humongous++;
2896 
2897     return false;
2898   }
2899 
2900   size_t total_humongous() const { return _total_humongous; }
2901   size_t candidate_humongous() const { return _candidate_humongous; }
2902 
2903   void flush_rem_set_entries() { _dcq.flush(); }
2904 };
2905 
2906 void G1CollectedHeap::register_humongous_regions_with_cset() {
2907   if (!G1EagerReclaimHumongousObjects) {
2908     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2909     return;
2910   }
2911   double time = os::elapsed_counter();
2912 
2913   // Collect reclaim candidate information and register candidates with cset.
2914   RegisterHumongousWithInCSetFastTestClosure cl;
2915   heap_region_iterate(&cl);
2916 
2917   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2918   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2919                                                                   cl.total_humongous(),
2920                                                                   cl.candidate_humongous());
2921   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2922 
2923   // Finally flush all remembered set entries to re-check into the global DCQS.
2924   cl.flush_rem_set_entries();
2925 }
2926 
2927 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2928   public:
2929     bool doHeapRegion(HeapRegion* hr) {
2930       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2931         hr->verify_rem_set();
2932       }
2933       return false;
2934     }
2935 };
2936 
2937 uint G1CollectedHeap::num_task_queues() const {
2938   return _task_queues->size();
2939 }
2940 
2941 #if TASKQUEUE_STATS
2942 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2943   st->print_raw_cr("GC Task Stats");
2944   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2945   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2946 }
2947 
2948 void G1CollectedHeap::print_taskqueue_stats() const {
2949   if (!log_is_enabled(Trace, gc, task, stats)) {
2950     return;
2951   }
2952   Log(gc, task, stats) log;
2953   ResourceMark rm;
2954   outputStream* st = log.trace_stream();
2955 
2956   print_taskqueue_stats_hdr(st);
2957 
2958   TaskQueueStats totals;
2959   const uint n = num_task_queues();
2960   for (uint i = 0; i < n; ++i) {
2961     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2962     totals += task_queue(i)->stats;
2963   }
2964   st->print_raw("tot "); totals.print(st); st->cr();
2965 
2966   DEBUG_ONLY(totals.verify());
2967 }
2968 
2969 void G1CollectedHeap::reset_taskqueue_stats() {
2970   const uint n = num_task_queues();
2971   for (uint i = 0; i < n; ++i) {
2972     task_queue(i)->stats.reset();
2973   }
2974 }
2975 #endif // TASKQUEUE_STATS
2976 
2977 void G1CollectedHeap::wait_for_root_region_scanning() {
2978   double scan_wait_start = os::elapsedTime();
2979   // We have to wait until the CM threads finish scanning the
2980   // root regions as it's the only way to ensure that all the
2981   // objects on them have been correctly scanned before we start
2982   // moving them during the GC.
2983   bool waited = _cm->root_regions()->wait_until_scan_finished();
2984   double wait_time_ms = 0.0;
2985   if (waited) {
2986     double scan_wait_end = os::elapsedTime();
2987     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2988   }
2989   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2990 }
2991 
2992 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2993 private:
2994   G1HRPrinter* _hr_printer;
2995 public:
2996   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2997 
2998   virtual bool doHeapRegion(HeapRegion* r) {
2999     _hr_printer->cset(r);
3000     return false;
3001   }
3002 };
3003 
3004 bool
3005 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3006   assert_at_safepoint(true /* should_be_vm_thread */);
3007   guarantee(!is_gc_active(), "collection is not reentrant");
3008 
3009   if (GCLocker::check_active_before_gc()) {
3010     return false;
3011   }
3012 
3013   _gc_timer_stw->register_gc_start();
3014 
3015   GCIdMark gc_id_mark;
3016   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3017 
3018   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3019   ResourceMark rm;
3020 
3021   g1_policy()->note_gc_start();
3022 
3023   wait_for_root_region_scanning();
3024 
3025   print_heap_before_gc();
3026   print_heap_regions();
3027   trace_heap_before_gc(_gc_tracer_stw);
3028 
3029   _verifier->verify_region_sets_optional();
3030   _verifier->verify_dirty_young_regions();
3031 
3032   // We should not be doing initial mark unless the conc mark thread is running
3033   if (!_cmThread->should_terminate()) {
3034     // This call will decide whether this pause is an initial-mark
3035     // pause. If it is, during_initial_mark_pause() will return true
3036     // for the duration of this pause.
3037     g1_policy()->decide_on_conc_mark_initiation();
3038   }
3039 
3040   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3041   assert(!collector_state()->during_initial_mark_pause() ||
3042           collector_state()->gcs_are_young(), "sanity");
3043 
3044   // We also do not allow mixed GCs during marking.
3045   assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
3046 
3047   // Record whether this pause is an initial mark. When the current
3048   // thread has completed its logging output and it's safe to signal
3049   // the CM thread, the flag's value in the policy has been reset.
3050   bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
3051 
3052   // Inner scope for scope based logging, timers, and stats collection
3053   {
3054     EvacuationInfo evacuation_info;
3055 
3056     if (collector_state()->during_initial_mark_pause()) {
3057       // We are about to start a marking cycle, so we increment the
3058       // full collection counter.
3059       increment_old_marking_cycles_started();
3060       _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
3061     }
3062 
3063     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
3064 
3065     GCTraceCPUTime tcpu;
3066 
3067     FormatBuffer<> gc_string("Pause ");
3068     if (collector_state()->during_initial_mark_pause()) {
3069       gc_string.append("Initial Mark");
3070     } else if (collector_state()->gcs_are_young()) {
3071       gc_string.append("Young");
3072     } else {
3073       gc_string.append("Mixed");
3074     }
3075     GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
3076 
3077     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
3078                                                                   workers()->active_workers(),
3079                                                                   Threads::number_of_non_daemon_threads());
3080     workers()->update_active_workers(active_workers);
3081     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
3082 
3083     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3084     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3085 
3086     // If the secondary_free_list is not empty, append it to the
3087     // free_list. No need to wait for the cleanup operation to finish;
3088     // the region allocation code will check the secondary_free_list
3089     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3090     // set, skip this step so that the region allocation code has to
3091     // get entries from the secondary_free_list.
3092     if (!G1StressConcRegionFreeing) {
3093       append_secondary_free_list_if_not_empty_with_lock();
3094     }
3095 
3096     G1HeapTransition heap_transition(this);
3097     size_t heap_used_bytes_before_gc = used();
3098 
3099     // Don't dynamically change the number of GC threads this early.  A value of
3100     // 0 is used to indicate serial work.  When parallel work is done,
3101     // it will be set.
3102 
3103     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3104       IsGCActiveMark x;
3105 
3106       gc_prologue(false);
3107       increment_total_collections(false /* full gc */);
3108       increment_gc_time_stamp();
3109 
3110       if (VerifyRememberedSets) {
3111         log_info(gc, verify)("[Verifying RemSets before GC]");
3112         VerifyRegionRemSetClosure v_cl;
3113         heap_region_iterate(&v_cl);
3114       }
3115 
3116       _verifier->verify_before_gc();
3117 
3118       _verifier->check_bitmaps("GC Start");
3119 
3120 #if defined(COMPILER2) || INCLUDE_JVMCI
3121       DerivedPointerTable::clear();
3122 #endif
3123 
3124       // Please see comment in g1CollectedHeap.hpp and
3125       // G1CollectedHeap::ref_processing_init() to see how
3126       // reference processing currently works in G1.
3127 
3128       // Enable discovery in the STW reference processor
3129       if (g1_policy()->should_process_references()) {
3130         ref_processor_stw()->enable_discovery();
3131       } else {
3132         ref_processor_stw()->disable_discovery();
3133       }
3134 
3135       {
3136         // We want to temporarily turn off discovery by the
3137         // CM ref processor, if necessary, and turn it back on
3138         // on again later if we do. Using a scoped
3139         // NoRefDiscovery object will do this.
3140         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3141 
3142         // Forget the current alloc region (we might even choose it to be part
3143         // of the collection set!).
3144         _allocator->release_mutator_alloc_region();
3145 
3146         // This timing is only used by the ergonomics to handle our pause target.
3147         // It is unclear why this should not include the full pause. We will
3148         // investigate this in CR 7178365.
3149         //
3150         // Preserving the old comment here if that helps the investigation:
3151         //
3152         // The elapsed time induced by the start time below deliberately elides
3153         // the possible verification above.
3154         double sample_start_time_sec = os::elapsedTime();
3155 
3156         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3157 
3158         if (collector_state()->during_initial_mark_pause()) {
3159           concurrent_mark()->checkpointRootsInitialPre();
3160         }
3161 
3162         g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
3163 
3164         evacuation_info.set_collectionset_regions(collection_set()->region_length());
3165 
3166         // Make sure the remembered sets are up to date. This needs to be
3167         // done before register_humongous_regions_with_cset(), because the
3168         // remembered sets are used there to choose eager reclaim candidates.
3169         // If the remembered sets are not up to date we might miss some
3170         // entries that need to be handled.
3171         g1_rem_set()->cleanupHRRS();
3172 
3173         register_humongous_regions_with_cset();
3174 
3175         assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3176 
3177         // We call this after finalize_cset() to
3178         // ensure that the CSet has been finalized.
3179         _cm->verify_no_cset_oops();
3180 
3181         if (_hr_printer.is_active()) {
3182           G1PrintCollectionSetClosure cl(&_hr_printer);
3183           _collection_set.iterate(&cl);
3184         }
3185 
3186         // Initialize the GC alloc regions.
3187         _allocator->init_gc_alloc_regions(evacuation_info);
3188 
3189         G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3190         pre_evacuate_collection_set();
3191 
3192         // Actually do the work...
3193         evacuate_collection_set(evacuation_info, &per_thread_states);
3194 
3195         post_evacuate_collection_set(evacuation_info, &per_thread_states);
3196 
3197         const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3198         free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
3199 
3200         eagerly_reclaim_humongous_regions();
3201 
3202         record_obj_copy_mem_stats();
3203         _survivor_evac_stats.adjust_desired_plab_sz();
3204         _old_evac_stats.adjust_desired_plab_sz();
3205 
3206         // Start a new incremental collection set for the next pause.
3207         collection_set()->start_incremental_building();
3208 
3209         clear_cset_fast_test();
3210 
3211         guarantee(_eden.length() == 0, "eden should have been cleared");
3212         g1_policy()->transfer_survivors_to_cset(survivor());
3213 
3214         if (evacuation_failed()) {
3215           set_used(recalculate_used());
3216           if (_archive_allocator != NULL) {
3217             _archive_allocator->clear_used();
3218           }
3219           for (uint i = 0; i < ParallelGCThreads; i++) {
3220             if (_evacuation_failed_info_array[i].has_failed()) {
3221               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3222             }
3223           }
3224         } else {
3225           // The "used" of the the collection set have already been subtracted
3226           // when they were freed.  Add in the bytes evacuated.
3227           increase_used(g1_policy()->bytes_copied_during_gc());
3228         }
3229 
3230         if (collector_state()->during_initial_mark_pause()) {
3231           // We have to do this before we notify the CM threads that
3232           // they can start working to make sure that all the
3233           // appropriate initialization is done on the CM object.
3234           concurrent_mark()->checkpointRootsInitialPost();
3235           collector_state()->set_mark_in_progress(true);
3236           // Note that we don't actually trigger the CM thread at
3237           // this point. We do that later when we're sure that
3238           // the current thread has completed its logging output.
3239         }
3240 
3241         allocate_dummy_regions();
3242 
3243         _allocator->init_mutator_alloc_region();
3244 
3245         {
3246           size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3247           if (expand_bytes > 0) {
3248             size_t bytes_before = capacity();
3249             // No need for an ergo logging here,
3250             // expansion_amount() does this when it returns a value > 0.
3251             double expand_ms;
3252             if (!expand(expand_bytes, _workers, &expand_ms)) {
3253               // We failed to expand the heap. Cannot do anything about it.
3254             }
3255             g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3256           }
3257         }
3258 
3259         // We redo the verification but now wrt to the new CSet which
3260         // has just got initialized after the previous CSet was freed.
3261         _cm->verify_no_cset_oops();
3262 
3263         // This timing is only used by the ergonomics to handle our pause target.
3264         // It is unclear why this should not include the full pause. We will
3265         // investigate this in CR 7178365.
3266         double sample_end_time_sec = os::elapsedTime();
3267         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3268         size_t total_cards_scanned = per_thread_states.total_cards_scanned();
3269         g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3270 
3271         evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3272         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3273 
3274         MemoryService::track_memory_usage();
3275 
3276         // In prepare_for_verify() below we'll need to scan the deferred
3277         // update buffers to bring the RSets up-to-date if
3278         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3279         // the update buffers we'll probably need to scan cards on the
3280         // regions we just allocated to (i.e., the GC alloc
3281         // regions). However, during the last GC we called
3282         // set_saved_mark() on all the GC alloc regions, so card
3283         // scanning might skip the [saved_mark_word()...top()] area of
3284         // those regions (i.e., the area we allocated objects into
3285         // during the last GC). But it shouldn't. Given that
3286         // saved_mark_word() is conditional on whether the GC time stamp
3287         // on the region is current or not, by incrementing the GC time
3288         // stamp here we invalidate all the GC time stamps on all the
3289         // regions and saved_mark_word() will simply return top() for
3290         // all the regions. This is a nicer way of ensuring this rather
3291         // than iterating over the regions and fixing them. In fact, the
3292         // GC time stamp increment here also ensures that
3293         // saved_mark_word() will return top() between pauses, i.e.,
3294         // during concurrent refinement. So we don't need the
3295         // is_gc_active() check to decided which top to use when
3296         // scanning cards (see CR 7039627).
3297         increment_gc_time_stamp();
3298 
3299         if (VerifyRememberedSets) {
3300           log_info(gc, verify)("[Verifying RemSets after GC]");
3301           VerifyRegionRemSetClosure v_cl;
3302           heap_region_iterate(&v_cl);
3303         }
3304 
3305         _verifier->verify_after_gc();
3306         _verifier->check_bitmaps("GC End");
3307 
3308         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3309         ref_processor_stw()->verify_no_references_recorded();
3310 
3311         // CM reference discovery will be re-enabled if necessary.
3312       }
3313 
3314 #ifdef TRACESPINNING
3315       ParallelTaskTerminator::print_termination_counts();
3316 #endif
3317 
3318       gc_epilogue(false);
3319     }
3320 
3321     // Print the remainder of the GC log output.
3322     if (evacuation_failed()) {
3323       log_info(gc)("To-space exhausted");
3324     }
3325 
3326     g1_policy()->print_phases();
3327     heap_transition.print();
3328 
3329     // It is not yet to safe to tell the concurrent mark to
3330     // start as we have some optional output below. We don't want the
3331     // output from the concurrent mark thread interfering with this
3332     // logging output either.
3333 
3334     _hrm.verify_optional();
3335     _verifier->verify_region_sets_optional();
3336 
3337     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3338     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3339 
3340     print_heap_after_gc();
3341     print_heap_regions();
3342     trace_heap_after_gc(_gc_tracer_stw);
3343 
3344     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3345     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3346     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3347     // before any GC notifications are raised.
3348     g1mm()->update_sizes();
3349 
3350     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3351     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3352     _gc_timer_stw->register_gc_end();
3353     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3354   }
3355   // It should now be safe to tell the concurrent mark thread to start
3356   // without its logging output interfering with the logging output
3357   // that came from the pause.
3358 
3359   if (should_start_conc_mark) {
3360     // CAUTION: after the doConcurrentMark() call below,
3361     // the concurrent marking thread(s) could be running
3362     // concurrently with us. Make sure that anything after
3363     // this point does not assume that we are the only GC thread
3364     // running. Note: of course, the actual marking work will
3365     // not start until the safepoint itself is released in
3366     // SuspendibleThreadSet::desynchronize().
3367     doConcurrentMark();
3368   }
3369 
3370   return true;
3371 }
3372 
3373 void G1CollectedHeap::remove_self_forwarding_pointers() {
3374   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3375   workers()->run_task(&rsfp_task);
3376 }
3377 
3378 void G1CollectedHeap::restore_after_evac_failure() {
3379   double remove_self_forwards_start = os::elapsedTime();
3380 
3381   remove_self_forwarding_pointers();
3382   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3383   _preserved_marks_set.restore(&task_executor);
3384 
3385   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3386 }
3387 
3388 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3389   if (!_evacuation_failed) {
3390     _evacuation_failed = true;
3391   }
3392 
3393   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3394   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3395 }
3396 
3397 bool G1ParEvacuateFollowersClosure::offer_termination() {
3398   G1ParScanThreadState* const pss = par_scan_state();
3399   start_term_time();
3400   const bool res = terminator()->offer_termination();
3401   end_term_time();
3402   return res;
3403 }
3404 
3405 void G1ParEvacuateFollowersClosure::do_void() {
3406   G1ParScanThreadState* const pss = par_scan_state();
3407   pss->trim_queue();
3408   do {
3409     pss->steal_and_trim_queue(queues());
3410   } while (!offer_termination());
3411 }
3412 
3413 class G1ParTask : public AbstractGangTask {
3414 protected:
3415   G1CollectedHeap*         _g1h;
3416   G1ParScanThreadStateSet* _pss;
3417   RefToScanQueueSet*       _queues;
3418   G1RootProcessor*         _root_processor;
3419   ParallelTaskTerminator   _terminator;
3420   uint                     _n_workers;
3421 
3422 public:
3423   G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3424     : AbstractGangTask("G1 collection"),
3425       _g1h(g1h),
3426       _pss(per_thread_states),
3427       _queues(task_queues),
3428       _root_processor(root_processor),
3429       _terminator(n_workers, _queues),
3430       _n_workers(n_workers)
3431   {}
3432 
3433   void work(uint worker_id) {
3434     if (worker_id >= _n_workers) return;  // no work needed this round
3435 
3436     double start_sec = os::elapsedTime();
3437     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3438 
3439     {
3440       ResourceMark rm;
3441       HandleMark   hm;
3442 
3443       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
3444 
3445       G1ParScanThreadState*           pss = _pss->state_for_worker(worker_id);
3446       pss->set_ref_processor(rp);
3447 
3448       double start_strong_roots_sec = os::elapsedTime();
3449 
3450       _root_processor->evacuate_roots(pss->closures(), worker_id);
3451 
3452       G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss);
3453 
3454       // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3455       // treating the nmethods visited to act as roots for concurrent marking.
3456       // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3457       // objects copied by the current evacuation.
3458       size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl,
3459                                                                              pss->closures()->weak_codeblobs(),
3460                                                                              worker_id);
3461 
3462       _pss->add_cards_scanned(worker_id, cards_scanned);
3463 
3464       double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3465 
3466       double term_sec = 0.0;
3467       size_t evac_term_attempts = 0;
3468       {
3469         double start = os::elapsedTime();
3470         G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3471         evac.do_void();
3472 
3473         evac_term_attempts = evac.term_attempts();
3474         term_sec = evac.term_time();
3475         double elapsed_sec = os::elapsedTime() - start;
3476         _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3477         _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3478         _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3479       }
3480 
3481       assert(pss->queue_is_empty(), "should be empty");
3482 
3483       if (log_is_enabled(Debug, gc, task, stats)) {
3484         MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3485         size_t lab_waste;
3486         size_t lab_undo_waste;
3487         pss->waste(lab_waste, lab_undo_waste);
3488         _g1h->print_termination_stats(worker_id,
3489                                       (os::elapsedTime() - start_sec) * 1000.0,   /* elapsed time */
3490                                       strong_roots_sec * 1000.0,                  /* strong roots time */
3491                                       term_sec * 1000.0,                          /* evac term time */
3492                                       evac_term_attempts,                         /* evac term attempts */
3493                                       lab_waste,                                  /* alloc buffer waste */
3494                                       lab_undo_waste                              /* undo waste */
3495                                       );
3496       }
3497 
3498       // Close the inner scope so that the ResourceMark and HandleMark
3499       // destructors are executed here and are included as part of the
3500       // "GC Worker Time".
3501     }
3502     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3503   }
3504 };
3505 
3506 void G1CollectedHeap::print_termination_stats_hdr() {
3507   log_debug(gc, task, stats)("GC Termination Stats");
3508   log_debug(gc, task, stats)("     elapsed  --strong roots-- -------termination------- ------waste (KiB)------");
3509   log_debug(gc, task, stats)("thr     ms        ms      %%        ms      %%    attempts  total   alloc    undo");
3510   log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3511 }
3512 
3513 void G1CollectedHeap::print_termination_stats(uint worker_id,
3514                                               double elapsed_ms,
3515                                               double strong_roots_ms,
3516                                               double term_ms,
3517                                               size_t term_attempts,
3518                                               size_t alloc_buffer_waste,
3519                                               size_t undo_waste) const {
3520   log_debug(gc, task, stats)
3521               ("%3d %9.2f %9.2f %6.2f "
3522                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3523                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3524                worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3525                term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3526                (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3527                alloc_buffer_waste * HeapWordSize / K,
3528                undo_waste * HeapWordSize / K);
3529 }
3530 
3531 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
3532 private:
3533   BoolObjectClosure* _is_alive;
3534   int _initial_string_table_size;
3535   int _initial_symbol_table_size;
3536 
3537   bool  _process_strings;
3538   int _strings_processed;
3539   int _strings_removed;
3540 
3541   bool  _process_symbols;
3542   int _symbols_processed;
3543   int _symbols_removed;
3544 
3545 public:
3546   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
3547     AbstractGangTask("String/Symbol Unlinking"),
3548     _is_alive(is_alive),
3549     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3550     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
3551 
3552     _initial_string_table_size = StringTable::the_table()->table_size();
3553     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3554     if (process_strings) {
3555       StringTable::clear_parallel_claimed_index();
3556     }
3557     if (process_symbols) {
3558       SymbolTable::clear_parallel_claimed_index();
3559     }
3560   }
3561 
3562   ~G1StringSymbolTableUnlinkTask() {
3563     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3564               "claim value %d after unlink less than initial string table size %d",
3565               StringTable::parallel_claimed_index(), _initial_string_table_size);
3566     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3567               "claim value %d after unlink less than initial symbol table size %d",
3568               SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3569 
3570     log_info(gc, stringtable)(
3571         "Cleaned string and symbol table, "
3572         "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3573         "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3574         strings_processed(), strings_removed(),
3575         symbols_processed(), symbols_removed());
3576   }
3577 
3578   void work(uint worker_id) {
3579     int strings_processed = 0;
3580     int strings_removed = 0;
3581     int symbols_processed = 0;
3582     int symbols_removed = 0;
3583     if (_process_strings) {
3584       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3585       Atomic::add(strings_processed, &_strings_processed);
3586       Atomic::add(strings_removed, &_strings_removed);
3587     }
3588     if (_process_symbols) {
3589       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3590       Atomic::add(symbols_processed, &_symbols_processed);
3591       Atomic::add(symbols_removed, &_symbols_removed);
3592     }
3593   }
3594 
3595   size_t strings_processed() const { return (size_t)_strings_processed; }
3596   size_t strings_removed()   const { return (size_t)_strings_removed; }
3597 
3598   size_t symbols_processed() const { return (size_t)_symbols_processed; }
3599   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
3600 };
3601 
3602 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3603 private:
3604   static Monitor* _lock;
3605 
3606   BoolObjectClosure* const _is_alive;
3607   const bool               _unloading_occurred;
3608   const uint               _num_workers;
3609 
3610   // Variables used to claim nmethods.
3611   CompiledMethod* _first_nmethod;
3612   volatile CompiledMethod* _claimed_nmethod;
3613 
3614   // The list of nmethods that need to be processed by the second pass.
3615   volatile CompiledMethod* _postponed_list;
3616   volatile uint            _num_entered_barrier;
3617 
3618  public:
3619   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3620       _is_alive(is_alive),
3621       _unloading_occurred(unloading_occurred),
3622       _num_workers(num_workers),
3623       _first_nmethod(NULL),
3624       _claimed_nmethod(NULL),
3625       _postponed_list(NULL),
3626       _num_entered_barrier(0)
3627   {
3628     CompiledMethod::increase_unloading_clock();
3629     // Get first alive nmethod
3630     CompiledMethodIterator iter = CompiledMethodIterator();
3631     if(iter.next_alive()) {
3632       _first_nmethod = iter.method();
3633     }
3634     _claimed_nmethod = (volatile CompiledMethod*)_first_nmethod;
3635   }
3636 
3637   ~G1CodeCacheUnloadingTask() {
3638     CodeCache::verify_clean_inline_caches();
3639 
3640     CodeCache::set_needs_cache_clean(false);
3641     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3642 
3643     CodeCache::verify_icholder_relocations();
3644   }
3645 
3646  private:
3647   void add_to_postponed_list(CompiledMethod* nm) {
3648       CompiledMethod* old;
3649       do {
3650         old = (CompiledMethod*)_postponed_list;
3651         nm->set_unloading_next(old);
3652       } while ((CompiledMethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
3653   }
3654 
3655   void clean_nmethod(CompiledMethod* nm) {
3656     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3657 
3658     if (postponed) {
3659       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3660       add_to_postponed_list(nm);
3661     }
3662 
3663     // Mark that this thread has been cleaned/unloaded.
3664     // After this call, it will be safe to ask if this nmethod was unloaded or not.
3665     nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3666   }
3667 
3668   void clean_nmethod_postponed(CompiledMethod* nm) {
3669     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3670   }
3671 
3672   static const int MaxClaimNmethods = 16;
3673 
3674   void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3675     CompiledMethod* first;
3676     CompiledMethodIterator last;
3677 
3678     do {
3679       *num_claimed_nmethods = 0;
3680 
3681       first = (CompiledMethod*)_claimed_nmethod;
3682       last = CompiledMethodIterator(first);
3683 
3684       if (first != NULL) {
3685 
3686         for (int i = 0; i < MaxClaimNmethods; i++) {
3687           if (!last.next_alive()) {
3688             break;
3689           }
3690           claimed_nmethods[i] = last.method();
3691           (*num_claimed_nmethods)++;
3692         }
3693       }
3694 
3695     } while ((CompiledMethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
3696   }
3697 
3698   CompiledMethod* claim_postponed_nmethod() {
3699     CompiledMethod* claim;
3700     CompiledMethod* next;
3701 
3702     do {
3703       claim = (CompiledMethod*)_postponed_list;
3704       if (claim == NULL) {
3705         return NULL;
3706       }
3707 
3708       next = claim->unloading_next();
3709 
3710     } while ((CompiledMethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
3711 
3712     return claim;
3713   }
3714 
3715  public:
3716   // Mark that we're done with the first pass of nmethod cleaning.
3717   void barrier_mark(uint worker_id) {
3718     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3719     _num_entered_barrier++;
3720     if (_num_entered_barrier == _num_workers) {
3721       ml.notify_all();
3722     }
3723   }
3724 
3725   // See if we have to wait for the other workers to
3726   // finish their first-pass nmethod cleaning work.
3727   void barrier_wait(uint worker_id) {
3728     if (_num_entered_barrier < _num_workers) {
3729       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3730       while (_num_entered_barrier < _num_workers) {
3731           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3732       }
3733     }
3734   }
3735 
3736   // Cleaning and unloading of nmethods. Some work has to be postponed
3737   // to the second pass, when we know which nmethods survive.
3738   void work_first_pass(uint worker_id) {
3739     // The first nmethods is claimed by the first worker.
3740     if (worker_id == 0 && _first_nmethod != NULL) {
3741       clean_nmethod(_first_nmethod);
3742       _first_nmethod = NULL;
3743     }
3744 
3745     int num_claimed_nmethods;
3746     CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3747 
3748     while (true) {
3749       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3750 
3751       if (num_claimed_nmethods == 0) {
3752         break;
3753       }
3754 
3755       for (int i = 0; i < num_claimed_nmethods; i++) {
3756         clean_nmethod(claimed_nmethods[i]);
3757       }
3758     }
3759   }
3760 
3761   void work_second_pass(uint worker_id) {
3762     CompiledMethod* nm;
3763     // Take care of postponed nmethods.
3764     while ((nm = claim_postponed_nmethod()) != NULL) {
3765       clean_nmethod_postponed(nm);
3766     }
3767   }
3768 };
3769 
3770 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3771 
3772 class G1KlassCleaningTask : public StackObj {
3773   BoolObjectClosure*                      _is_alive;
3774   volatile jint                           _clean_klass_tree_claimed;
3775   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3776 
3777  public:
3778   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3779       _is_alive(is_alive),
3780       _clean_klass_tree_claimed(0),
3781       _klass_iterator() {
3782   }
3783 
3784  private:
3785   bool claim_clean_klass_tree_task() {
3786     if (_clean_klass_tree_claimed) {
3787       return false;
3788     }
3789 
3790     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
3791   }
3792 
3793   InstanceKlass* claim_next_klass() {
3794     Klass* klass;
3795     do {
3796       klass =_klass_iterator.next_klass();
3797     } while (klass != NULL && !klass->is_instance_klass());
3798 
3799     // this can be null so don't call InstanceKlass::cast
3800     return static_cast<InstanceKlass*>(klass);
3801   }
3802 
3803 public:
3804 
3805   void clean_klass(InstanceKlass* ik) {
3806     ik->clean_weak_instanceklass_links(_is_alive);
3807   }
3808 
3809   void work() {
3810     ResourceMark rm;
3811 
3812     // One worker will clean the subklass/sibling klass tree.
3813     if (claim_clean_klass_tree_task()) {
3814       Klass::clean_subklass_tree(_is_alive);
3815     }
3816 
3817     // All workers will help cleaning the classes,
3818     InstanceKlass* klass;
3819     while ((klass = claim_next_klass()) != NULL) {
3820       clean_klass(klass);
3821     }
3822   }
3823 };
3824 
3825 // To minimize the remark pause times, the tasks below are done in parallel.
3826 class G1ParallelCleaningTask : public AbstractGangTask {
3827 private:
3828   G1StringSymbolTableUnlinkTask _string_symbol_task;
3829   G1CodeCacheUnloadingTask      _code_cache_task;
3830   G1KlassCleaningTask           _klass_cleaning_task;
3831 
3832 public:
3833   // The constructor is run in the VMThread.
3834   G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
3835       AbstractGangTask("Parallel Cleaning"),
3836       _string_symbol_task(is_alive, process_strings, process_symbols),
3837       _code_cache_task(num_workers, is_alive, unloading_occurred),
3838       _klass_cleaning_task(is_alive) {
3839   }
3840 
3841   // The parallel work done by all worker threads.
3842   void work(uint worker_id) {
3843     // Do first pass of code cache cleaning.
3844     _code_cache_task.work_first_pass(worker_id);
3845 
3846     // Let the threads mark that the first pass is done.
3847     _code_cache_task.barrier_mark(worker_id);
3848 
3849     // Clean the Strings and Symbols.
3850     _string_symbol_task.work(worker_id);
3851 
3852     // Wait for all workers to finish the first code cache cleaning pass.
3853     _code_cache_task.barrier_wait(worker_id);
3854 
3855     // Do the second code cache cleaning work, which realize on
3856     // the liveness information gathered during the first pass.
3857     _code_cache_task.work_second_pass(worker_id);
3858 
3859     // Clean all klasses that were not unloaded.
3860     _klass_cleaning_task.work();
3861   }
3862 };
3863 
3864 
3865 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
3866                                         bool process_strings,
3867                                         bool process_symbols,
3868                                         bool class_unloading_occurred) {
3869   uint n_workers = workers()->active_workers();
3870 
3871   G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
3872                                         n_workers, class_unloading_occurred);
3873   workers()->run_task(&g1_unlink_task);
3874 }
3875 
3876 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
3877                                                      bool process_strings, bool process_symbols) {
3878   { // Timing scope
3879     G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
3880     workers()->run_task(&g1_unlink_task);
3881   }
3882 }
3883 
3884 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3885  private:
3886   DirtyCardQueueSet* _queue;
3887   G1CollectedHeap* _g1h;
3888  public:
3889   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3890     _queue(queue), _g1h(g1h) { }
3891 
3892   virtual void work(uint worker_id) {
3893     G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3894     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3895 
3896     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3897     _queue->par_apply_closure_to_all_completed_buffers(&cl);
3898 
3899     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3900   }
3901 };
3902 
3903 void G1CollectedHeap::redirty_logged_cards() {
3904   double redirty_logged_cards_start = os::elapsedTime();
3905 
3906   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3907   dirty_card_queue_set().reset_for_par_iteration();
3908   workers()->run_task(&redirty_task);
3909 
3910   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
3911   dcq.merge_bufferlists(&dirty_card_queue_set());
3912   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3913 
3914   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3915 }
3916 
3917 // Weak Reference Processing support
3918 
3919 // An always "is_alive" closure that is used to preserve referents.
3920 // If the object is non-null then it's alive.  Used in the preservation
3921 // of referent objects that are pointed to by reference objects
3922 // discovered by the CM ref processor.
3923 class G1AlwaysAliveClosure: public BoolObjectClosure {
3924   G1CollectedHeap* _g1;
3925 public:
3926   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3927   bool do_object_b(oop p) {
3928     if (p != NULL) {
3929       return true;
3930     }
3931     return false;
3932   }
3933 };
3934 
3935 bool G1STWIsAliveClosure::do_object_b(oop p) {
3936   // An object is reachable if it is outside the collection set,
3937   // or is inside and copied.
3938   return !_g1->is_in_cset(p) || p->is_forwarded();
3939 }
3940 
3941 // Non Copying Keep Alive closure
3942 class G1KeepAliveClosure: public OopClosure {
3943   G1CollectedHeap* _g1;
3944 public:
3945   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3946   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3947   void do_oop(oop* p) {
3948     oop obj = *p;
3949     assert(obj != NULL, "the caller should have filtered out NULL values");
3950 
3951     const InCSetState cset_state = _g1->in_cset_state(obj);
3952     if (!cset_state.is_in_cset_or_humongous()) {
3953       return;
3954     }
3955     if (cset_state.is_in_cset()) {
3956       assert( obj->is_forwarded(), "invariant" );
3957       *p = obj->forwardee();
3958     } else {
3959       assert(!obj->is_forwarded(), "invariant" );
3960       assert(cset_state.is_humongous(),
3961              "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3962       _g1->set_humongous_is_live(obj);
3963     }
3964   }
3965 };
3966 
3967 // Copying Keep Alive closure - can be called from both
3968 // serial and parallel code as long as different worker
3969 // threads utilize different G1ParScanThreadState instances
3970 // and different queues.
3971 
3972 class G1CopyingKeepAliveClosure: public OopClosure {
3973   G1CollectedHeap*         _g1h;
3974   OopClosure*              _copy_non_heap_obj_cl;
3975   G1ParScanThreadState*    _par_scan_state;
3976 
3977 public:
3978   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3979                             OopClosure* non_heap_obj_cl,
3980                             G1ParScanThreadState* pss):
3981     _g1h(g1h),
3982     _copy_non_heap_obj_cl(non_heap_obj_cl),
3983     _par_scan_state(pss)
3984   {}
3985 
3986   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3987   virtual void do_oop(      oop* p) { do_oop_work(p); }
3988 
3989   template <class T> void do_oop_work(T* p) {
3990     oop obj = oopDesc::load_decode_heap_oop(p);
3991 
3992     if (_g1h->is_in_cset_or_humongous(obj)) {
3993       // If the referent object has been forwarded (either copied
3994       // to a new location or to itself in the event of an
3995       // evacuation failure) then we need to update the reference
3996       // field and, if both reference and referent are in the G1
3997       // heap, update the RSet for the referent.
3998       //
3999       // If the referent has not been forwarded then we have to keep
4000       // it alive by policy. Therefore we have copy the referent.
4001       //
4002       // If the reference field is in the G1 heap then we can push
4003       // on the PSS queue. When the queue is drained (after each
4004       // phase of reference processing) the object and it's followers
4005       // will be copied, the reference field set to point to the
4006       // new location, and the RSet updated. Otherwise we need to
4007       // use the the non-heap or metadata closures directly to copy
4008       // the referent object and update the pointer, while avoiding
4009       // updating the RSet.
4010 
4011       if (_g1h->is_in_g1_reserved(p)) {
4012         _par_scan_state->push_on_queue(p);
4013       } else {
4014         assert(!Metaspace::contains((const void*)p),
4015                "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
4016         _copy_non_heap_obj_cl->do_oop(p);
4017       }
4018     }
4019   }
4020 };
4021 
4022 // Serial drain queue closure. Called as the 'complete_gc'
4023 // closure for each discovered list in some of the
4024 // reference processing phases.
4025 
4026 class G1STWDrainQueueClosure: public VoidClosure {
4027 protected:
4028   G1CollectedHeap* _g1h;
4029   G1ParScanThreadState* _par_scan_state;
4030 
4031   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4032 
4033 public:
4034   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
4035     _g1h(g1h),
4036     _par_scan_state(pss)
4037   { }
4038 
4039   void do_void() {
4040     G1ParScanThreadState* const pss = par_scan_state();
4041     pss->trim_queue();
4042   }
4043 };
4044 
4045 // Parallel Reference Processing closures
4046 
4047 // Implementation of AbstractRefProcTaskExecutor for parallel reference
4048 // processing during G1 evacuation pauses.
4049 
4050 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
4051 private:
4052   G1CollectedHeap*          _g1h;
4053   G1ParScanThreadStateSet*  _pss;
4054   RefToScanQueueSet*        _queues;
4055   WorkGang*                 _workers;
4056   uint                      _active_workers;
4057 
4058 public:
4059   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
4060                            G1ParScanThreadStateSet* per_thread_states,
4061                            WorkGang* workers,
4062                            RefToScanQueueSet *task_queues,
4063                            uint n_workers) :
4064     _g1h(g1h),
4065     _pss(per_thread_states),
4066     _queues(task_queues),
4067     _workers(workers),
4068     _active_workers(n_workers)
4069   {
4070     g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
4071   }
4072 
4073   // Executes the given task using concurrent marking worker threads.
4074   virtual void execute(ProcessTask& task);
4075   virtual void execute(EnqueueTask& task);
4076 };
4077 
4078 // Gang task for possibly parallel reference processing
4079 
4080 class G1STWRefProcTaskProxy: public AbstractGangTask {
4081   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
4082   ProcessTask&     _proc_task;
4083   G1CollectedHeap* _g1h;
4084   G1ParScanThreadStateSet* _pss;
4085   RefToScanQueueSet* _task_queues;
4086   ParallelTaskTerminator* _terminator;
4087 
4088 public:
4089   G1STWRefProcTaskProxy(ProcessTask& proc_task,
4090                         G1CollectedHeap* g1h,
4091                         G1ParScanThreadStateSet* per_thread_states,
4092                         RefToScanQueueSet *task_queues,
4093                         ParallelTaskTerminator* terminator) :
4094     AbstractGangTask("Process reference objects in parallel"),
4095     _proc_task(proc_task),
4096     _g1h(g1h),
4097     _pss(per_thread_states),
4098     _task_queues(task_queues),
4099     _terminator(terminator)
4100   {}
4101 
4102   virtual void work(uint worker_id) {
4103     // The reference processing task executed by a single worker.
4104     ResourceMark rm;
4105     HandleMark   hm;
4106 
4107     G1STWIsAliveClosure is_alive(_g1h);
4108 
4109     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4110     pss->set_ref_processor(NULL);
4111 
4112     // Keep alive closure.
4113     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4114 
4115     // Complete GC closure
4116     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
4117 
4118     // Call the reference processing task's work routine.
4119     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
4120 
4121     // Note we cannot assert that the refs array is empty here as not all
4122     // of the processing tasks (specifically phase2 - pp2_work) execute
4123     // the complete_gc closure (which ordinarily would drain the queue) so
4124     // the queue may not be empty.
4125   }
4126 };
4127 
4128 // Driver routine for parallel reference processing.
4129 // Creates an instance of the ref processing gang
4130 // task and has the worker threads execute it.
4131 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4132   assert(_workers != NULL, "Need parallel worker threads.");
4133 
4134   ParallelTaskTerminator terminator(_active_workers, _queues);
4135   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4136 
4137   _workers->run_task(&proc_task_proxy);
4138 }
4139 
4140 // Gang task for parallel reference enqueueing.
4141 
4142 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4143   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4144   EnqueueTask& _enq_task;
4145 
4146 public:
4147   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4148     AbstractGangTask("Enqueue reference objects in parallel"),
4149     _enq_task(enq_task)
4150   { }
4151 
4152   virtual void work(uint worker_id) {
4153     _enq_task.work(worker_id);
4154   }
4155 };
4156 
4157 // Driver routine for parallel reference enqueueing.
4158 // Creates an instance of the ref enqueueing gang
4159 // task and has the worker threads execute it.
4160 
4161 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4162   assert(_workers != NULL, "Need parallel worker threads.");
4163 
4164   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4165 
4166   _workers->run_task(&enq_task_proxy);
4167 }
4168 
4169 // End of weak reference support closures
4170 
4171 // Abstract task used to preserve (i.e. copy) any referent objects
4172 // that are in the collection set and are pointed to by reference
4173 // objects discovered by the CM ref processor.
4174 
4175 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4176 protected:
4177   G1CollectedHeap*         _g1h;
4178   G1ParScanThreadStateSet* _pss;
4179   RefToScanQueueSet*       _queues;
4180   ParallelTaskTerminator   _terminator;
4181   uint                     _n_workers;
4182 
4183 public:
4184   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4185     AbstractGangTask("ParPreserveCMReferents"),
4186     _g1h(g1h),
4187     _pss(per_thread_states),
4188     _queues(task_queues),
4189     _terminator(workers, _queues),
4190     _n_workers(workers)
4191   {
4192     g1h->ref_processor_cm()->set_active_mt_degree(workers);
4193   }
4194 
4195   void work(uint worker_id) {
4196     G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4197 
4198     ResourceMark rm;
4199     HandleMark   hm;
4200 
4201     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4202     pss->set_ref_processor(NULL);
4203     assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4204 
4205     // Is alive closure
4206     G1AlwaysAliveClosure always_alive(_g1h);
4207 
4208     // Copying keep alive closure. Applied to referent objects that need
4209     // to be copied.
4210     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4211 
4212     ReferenceProcessor* rp = _g1h->ref_processor_cm();
4213 
4214     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4215     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4216 
4217     // limit is set using max_num_q() - which was set using ParallelGCThreads.
4218     // So this must be true - but assert just in case someone decides to
4219     // change the worker ids.
4220     assert(worker_id < limit, "sanity");
4221     assert(!rp->discovery_is_atomic(), "check this code");
4222 
4223     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4224     for (uint idx = worker_id; idx < limit; idx += stride) {
4225       DiscoveredList& ref_list = rp->discovered_refs()[idx];
4226 
4227       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4228       while (iter.has_next()) {
4229         // Since discovery is not atomic for the CM ref processor, we
4230         // can see some null referent objects.
4231         iter.load_ptrs(DEBUG_ONLY(true));
4232         oop ref = iter.obj();
4233 
4234         // This will filter nulls.
4235         if (iter.is_referent_alive()) {
4236           iter.make_referent_alive();
4237         }
4238         iter.move_to_next();
4239       }
4240     }
4241 
4242     // Drain the queue - which may cause stealing
4243     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4244     drain_queue.do_void();
4245     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4246     assert(pss->queue_is_empty(), "should be");
4247   }
4248 };
4249 
4250 void G1CollectedHeap::process_weak_jni_handles() {
4251   double ref_proc_start = os::elapsedTime();
4252 
4253   G1STWIsAliveClosure is_alive(this);
4254   G1KeepAliveClosure keep_alive(this);
4255   JNIHandles::weak_oops_do(&is_alive, &keep_alive);
4256 
4257   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4258   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4259 }
4260 
4261 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4262   // Any reference objects, in the collection set, that were 'discovered'
4263   // by the CM ref processor should have already been copied (either by
4264   // applying the external root copy closure to the discovered lists, or
4265   // by following an RSet entry).
4266   //
4267   // But some of the referents, that are in the collection set, that these
4268   // reference objects point to may not have been copied: the STW ref
4269   // processor would have seen that the reference object had already
4270   // been 'discovered' and would have skipped discovering the reference,
4271   // but would not have treated the reference object as a regular oop.
4272   // As a result the copy closure would not have been applied to the
4273   // referent object.
4274   //
4275   // We need to explicitly copy these referent objects - the references
4276   // will be processed at the end of remarking.
4277   //
4278   // We also need to do this copying before we process the reference
4279   // objects discovered by the STW ref processor in case one of these
4280   // referents points to another object which is also referenced by an
4281   // object discovered by the STW ref processor.
4282   double preserve_cm_referents_time = 0.0;
4283 
4284   // To avoid spawning task when there is no work to do, check that
4285   // a concurrent cycle is active and that some references have been
4286   // discovered.
4287   if (concurrent_mark()->cmThread()->during_cycle() &&
4288       ref_processor_cm()->has_discovered_references()) {
4289     double preserve_cm_referents_start = os::elapsedTime();
4290     uint no_of_gc_workers = workers()->active_workers();
4291     G1ParPreserveCMReferentsTask keep_cm_referents(this,
4292                                                    per_thread_states,
4293                                                    no_of_gc_workers,
4294                                                    _task_queues);
4295     workers()->run_task(&keep_cm_referents);
4296     preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4297   }
4298 
4299   g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4300 }
4301 
4302 // Weak Reference processing during an evacuation pause (part 1).
4303 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4304   double ref_proc_start = os::elapsedTime();
4305 
4306   ReferenceProcessor* rp = _ref_processor_stw;
4307   assert(rp->discovery_enabled(), "should have been enabled");
4308 
4309   // Closure to test whether a referent is alive.
4310   G1STWIsAliveClosure is_alive(this);
4311 
4312   // Even when parallel reference processing is enabled, the processing
4313   // of JNI refs is serial and performed serially by the current thread
4314   // rather than by a worker. The following PSS will be used for processing
4315   // JNI refs.
4316 
4317   // Use only a single queue for this PSS.
4318   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
4319   pss->set_ref_processor(NULL);
4320   assert(pss->queue_is_empty(), "pre-condition");
4321 
4322   // Keep alive closure.
4323   G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4324 
4325   // Serial Complete GC closure
4326   G1STWDrainQueueClosure drain_queue(this, pss);
4327 
4328   // Setup the soft refs policy...
4329   rp->setup_policy(false);
4330 
4331   ReferenceProcessorStats stats;
4332   if (!rp->processing_is_mt()) {
4333     // Serial reference processing...
4334     stats = rp->process_discovered_references(&is_alive,
4335                                               &keep_alive,
4336                                               &drain_queue,
4337                                               NULL,
4338                                               _gc_timer_stw);
4339   } else {
4340     uint no_of_gc_workers = workers()->active_workers();
4341 
4342     // Parallel reference processing
4343     assert(no_of_gc_workers <= rp->max_num_q(),
4344            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4345            no_of_gc_workers,  rp->max_num_q());
4346 
4347     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4348     stats = rp->process_discovered_references(&is_alive,
4349                                               &keep_alive,
4350                                               &drain_queue,
4351                                               &par_task_executor,
4352                                               _gc_timer_stw);
4353   }
4354 
4355   _gc_tracer_stw->report_gc_reference_stats(stats);
4356 
4357   // We have completed copying any necessary live referent objects.
4358   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4359 
4360   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4361   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4362 }
4363 
4364 // Weak Reference processing during an evacuation pause (part 2).
4365 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4366   double ref_enq_start = os::elapsedTime();
4367 
4368   ReferenceProcessor* rp = _ref_processor_stw;
4369   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4370 
4371   // Now enqueue any remaining on the discovered lists on to
4372   // the pending list.
4373   if (!rp->processing_is_mt()) {
4374     // Serial reference processing...
4375     rp->enqueue_discovered_references();
4376   } else {
4377     // Parallel reference enqueueing
4378 
4379     uint n_workers = workers()->active_workers();
4380 
4381     assert(n_workers <= rp->max_num_q(),
4382            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4383            n_workers,  rp->max_num_q());
4384 
4385     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4386     rp->enqueue_discovered_references(&par_task_executor);
4387   }
4388 
4389   rp->verify_no_references_recorded();
4390   assert(!rp->discovery_enabled(), "should have been disabled");
4391 









4392   // FIXME
4393   // CM's reference processing also cleans up the string and symbol tables.
4394   // Should we do that here also? We could, but it is a serial operation
4395   // and could significantly increase the pause time.
4396 
4397   double ref_enq_time = os::elapsedTime() - ref_enq_start;
4398   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4399 }
4400 
4401 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4402   double merge_pss_time_start = os::elapsedTime();
4403   per_thread_states->flush();
4404   g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4405 }
4406 
4407 void G1CollectedHeap::pre_evacuate_collection_set() {
4408   _expand_heap_after_alloc_failure = true;
4409   _evacuation_failed = false;
4410 
4411   // Disable the hot card cache.
4412   _hot_card_cache->reset_hot_cache_claimed_index();
4413   _hot_card_cache->set_use_cache(false);
4414 
4415   g1_rem_set()->prepare_for_oops_into_collection_set_do();
4416   _preserved_marks_set.assert_empty();
4417 }
4418 
4419 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4420   // Should G1EvacuationFailureALot be in effect for this GC?
4421   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4422 
4423   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4424 
4425   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4426 
4427   // InitialMark needs claim bits to keep track of the marked-through CLDs.
4428   if (collector_state()->during_initial_mark_pause()) {
4429     double start_clear_claimed_marks = os::elapsedTime();
4430 
4431     ClassLoaderDataGraph::clear_claimed_marks();
4432 
4433     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
4434     phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
4435   }
4436 
4437   double start_par_time_sec = os::elapsedTime();
4438   double end_par_time_sec;
4439 
4440   {
4441     const uint n_workers = workers()->active_workers();
4442     G1RootProcessor root_processor(this, n_workers);
4443     G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4444 
4445     print_termination_stats_hdr();
4446 
4447     workers()->run_task(&g1_par_task);
4448     end_par_time_sec = os::elapsedTime();
4449 
4450     // Closing the inner scope will execute the destructor
4451     // for the G1RootProcessor object. We record the current
4452     // elapsed time before closing the scope so that time
4453     // taken for the destructor is NOT included in the
4454     // reported parallel time.
4455   }
4456 
4457   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4458   phase_times->record_par_time(par_time_ms);
4459 
4460   double code_root_fixup_time_ms =
4461         (os::elapsedTime() - end_par_time_sec) * 1000.0;
4462   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4463 }
4464 
4465 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4466   // Process any discovered reference objects - we have
4467   // to do this _before_ we retire the GC alloc regions
4468   // as we may have to copy some 'reachable' referent
4469   // objects (and their reachable sub-graphs) that were
4470   // not copied during the pause.
4471   if (g1_policy()->should_process_references()) {
4472     preserve_cm_referents(per_thread_states);
4473     process_discovered_references(per_thread_states);
4474   } else {
4475     ref_processor_stw()->verify_no_references_recorded();
4476     process_weak_jni_handles();
4477   }
4478 
4479   if (G1StringDedup::is_enabled()) {
4480     double fixup_start = os::elapsedTime();
4481 
4482     G1STWIsAliveClosure is_alive(this);
4483     G1KeepAliveClosure keep_alive(this);
4484     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4485 
4486     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4487     g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4488   }
4489 
4490   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4491 
4492   if (evacuation_failed()) {
4493     restore_after_evac_failure();
4494 
4495     // Reset the G1EvacuationFailureALot counters and flags
4496     // Note: the values are reset only when an actual
4497     // evacuation failure occurs.
4498     NOT_PRODUCT(reset_evacuation_should_fail();)
4499   }
4500 
4501   _preserved_marks_set.assert_empty();
4502 
4503   // Enqueue any remaining references remaining on the STW
4504   // reference processor's discovered lists. We need to do
4505   // this after the card table is cleaned (and verified) as
4506   // the act of enqueueing entries on to the pending list
4507   // will log these updates (and dirty their associated
4508   // cards). We need these updates logged to update any
4509   // RSets.
4510   if (g1_policy()->should_process_references()) {
4511     enqueue_discovered_references(per_thread_states);
4512   } else {
4513     g1_policy()->phase_times()->record_ref_enq_time(0);
4514   }
4515 
4516   _allocator->release_gc_alloc_regions(evacuation_info);
4517 
4518   merge_per_thread_state_info(per_thread_states);
4519 
4520   // Reset and re-enable the hot card cache.
4521   // Note the counts for the cards in the regions in the
4522   // collection set are reset when the collection set is freed.
4523   _hot_card_cache->reset_hot_cache();
4524   _hot_card_cache->set_use_cache(true);
4525 
4526   purge_code_root_memory();
4527 
4528   redirty_logged_cards();
4529 #if defined(COMPILER2) || INCLUDE_JVMCI
4530   DerivedPointerTable::update_pointers();
4531 #endif
4532   g1_policy()->print_age_table();
4533 }
4534 
4535 void G1CollectedHeap::record_obj_copy_mem_stats() {
4536   g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4537 
4538   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4539                                                create_g1_evac_summary(&_old_evac_stats));
4540 }
4541 
4542 void G1CollectedHeap::free_region(HeapRegion* hr,
4543                                   FreeRegionList* free_list,
4544                                   bool skip_remset,
4545                                   bool skip_hot_card_cache,
4546                                   bool locked) {
4547   assert(!hr->is_free(), "the region should not be free");
4548   assert(!hr->is_empty(), "the region should not be empty");
4549   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4550   assert(free_list != NULL, "pre-condition");
4551 
4552   if (G1VerifyBitmaps) {
4553     MemRegion mr(hr->bottom(), hr->end());
4554     concurrent_mark()->clearRangePrevBitmap(mr);
4555   }
4556 
4557   // Clear the card counts for this region.
4558   // Note: we only need to do this if the region is not young
4559   // (since we don't refine cards in young regions).
4560   if (!skip_hot_card_cache && !hr->is_young()) {
4561     _hot_card_cache->reset_card_counts(hr);
4562   }
4563   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4564   free_list->add_ordered(hr);
4565 }
4566 
4567 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4568                                             FreeRegionList* free_list,
4569                                             bool skip_remset) {
4570   assert(hr->is_humongous(), "this is only for humongous regions");
4571   assert(free_list != NULL, "pre-condition");
4572   hr->clear_humongous();
4573   free_region(hr, free_list, skip_remset);
4574 }
4575 
4576 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4577                                            const uint humongous_regions_removed) {
4578   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4579     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4580     _old_set.bulk_remove(old_regions_removed);
4581     _humongous_set.bulk_remove(humongous_regions_removed);
4582   }
4583 
4584 }
4585 
4586 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4587   assert(list != NULL, "list can't be null");
4588   if (!list->is_empty()) {
4589     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4590     _hrm.insert_list_into_free_list(list);
4591   }
4592 }
4593 
4594 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4595   decrease_used(bytes);
4596 }
4597 
4598 class G1ParScrubRemSetTask: public AbstractGangTask {
4599 protected:
4600   G1RemSet* _g1rs;
4601   HeapRegionClaimer _hrclaimer;
4602 
4603 public:
4604   G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
4605     AbstractGangTask("G1 ScrubRS"),
4606     _g1rs(g1_rs),
4607     _hrclaimer(num_workers) {
4608   }
4609 
4610   void work(uint worker_id) {
4611     _g1rs->scrub(worker_id, &_hrclaimer);
4612   }
4613 };
4614 
4615 void G1CollectedHeap::scrub_rem_set() {
4616   uint num_workers = workers()->active_workers();
4617   G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
4618   workers()->run_task(&g1_par_scrub_rs_task);
4619 }
4620 
4621 class G1FreeCollectionSetTask : public AbstractGangTask {
4622 private:
4623 
4624   // Closure applied to all regions in the collection set to do work that needs to
4625   // be done serially in a single thread.
4626   class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4627   private:
4628     EvacuationInfo* _evacuation_info;
4629     const size_t* _surviving_young_words;
4630 
4631     // Bytes used in successfully evacuated regions before the evacuation.
4632     size_t _before_used_bytes;
4633     // Bytes used in unsucessfully evacuated regions before the evacuation
4634     size_t _after_used_bytes;
4635 
4636     size_t _bytes_allocated_in_old_since_last_gc;
4637 
4638     size_t _failure_used_words;
4639     size_t _failure_waste_words;
4640 
4641     FreeRegionList _local_free_list;
4642   public:
4643     G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4644       HeapRegionClosure(),
4645       _evacuation_info(evacuation_info),
4646       _surviving_young_words(surviving_young_words),
4647       _before_used_bytes(0),
4648       _after_used_bytes(0),
4649       _bytes_allocated_in_old_since_last_gc(0),
4650       _failure_used_words(0),
4651       _failure_waste_words(0),
4652       _local_free_list("Local Region List for CSet Freeing") {
4653     }
4654 
4655     virtual bool doHeapRegion(HeapRegion* r) {
4656       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4657 
4658       assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4659       g1h->clear_in_cset(r);
4660 
4661       if (r->is_young()) {
4662         assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4663                "Young index %d is wrong for region %u of type %s with %u young regions",
4664                r->young_index_in_cset(),
4665                r->hrm_index(),
4666                r->get_type_str(),
4667                g1h->collection_set()->young_region_length());
4668         size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4669         r->record_surv_words_in_group(words_survived);
4670       }
4671 
4672       if (!r->evacuation_failed()) {
4673         assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4674         _before_used_bytes += r->used();
4675         g1h->free_region(r,
4676                          &_local_free_list,
4677                          true, /* skip_remset */
4678                          true, /* skip_hot_card_cache */
4679                          true  /* locked */);
4680       } else {
4681         r->uninstall_surv_rate_group();
4682         r->set_young_index_in_cset(-1);
4683         r->set_evacuation_failed(false);
4684         // When moving a young gen region to old gen, we "allocate" that whole region
4685         // there. This is in addition to any already evacuated objects. Notify the
4686         // policy about that.
4687         // Old gen regions do not cause an additional allocation: both the objects
4688         // still in the region and the ones already moved are accounted for elsewhere.
4689         if (r->is_young()) {
4690           _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4691         }
4692         // The region is now considered to be old.
4693         r->set_old();
4694         // Do some allocation statistics accounting. Regions that failed evacuation
4695         // are always made old, so there is no need to update anything in the young
4696         // gen statistics, but we need to update old gen statistics.
4697         size_t used_words = r->marked_bytes() / HeapWordSize;
4698 
4699         _failure_used_words += used_words;
4700         _failure_waste_words += HeapRegion::GrainWords - used_words;
4701 
4702         g1h->old_set_add(r);
4703         _after_used_bytes += r->used();
4704       }
4705       return false;
4706     }
4707 
4708     void complete_work() {
4709       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4710 
4711       _evacuation_info->set_regions_freed(_local_free_list.length());
4712       _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4713 
4714       g1h->prepend_to_freelist(&_local_free_list);
4715       g1h->decrement_summary_bytes(_before_used_bytes);
4716 
4717       G1Policy* policy = g1h->g1_policy();
4718       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4719 
4720       g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4721     }
4722   };
4723 
4724   G1CollectionSet* _collection_set;
4725   G1SerialFreeCollectionSetClosure _cl;
4726   const size_t* _surviving_young_words;
4727 
4728   size_t _rs_lengths;
4729 
4730   volatile jint _serial_work_claim;
4731 
4732   struct WorkItem {
4733     uint region_idx;
4734     bool is_young;
4735     bool evacuation_failed;
4736 
4737     WorkItem(HeapRegion* r) {
4738       region_idx = r->hrm_index();
4739       is_young = r->is_young();
4740       evacuation_failed = r->evacuation_failed();
4741     }
4742   };
4743 
4744   volatile size_t _parallel_work_claim;
4745   size_t _num_work_items;
4746   WorkItem* _work_items;
4747 
4748   void do_serial_work() {
4749     // Need to grab the lock to be allowed to modify the old region list.
4750     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4751     _collection_set->iterate(&_cl);
4752   }
4753 
4754   void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4755     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4756 
4757     HeapRegion* r = g1h->region_at(region_idx);
4758     assert(!g1h->is_on_master_free_list(r), "sanity");
4759 
4760     Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4761 
4762     if (!is_young) {
4763       g1h->_hot_card_cache->reset_card_counts(r);
4764     }
4765 
4766     if (!evacuation_failed) {
4767       r->rem_set()->clear_locked();
4768     }
4769   }
4770 
4771   class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4772   private:
4773     size_t _cur_idx;
4774     WorkItem* _work_items;
4775   public:
4776     G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4777 
4778     virtual bool doHeapRegion(HeapRegion* r) {
4779       _work_items[_cur_idx++] = WorkItem(r);
4780       return false;
4781     }
4782   };
4783 
4784   void prepare_work() {
4785     G1PrepareFreeCollectionSetClosure cl(_work_items);
4786     _collection_set->iterate(&cl);
4787   }
4788 
4789   void complete_work() {
4790     _cl.complete_work();
4791 
4792     G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4793     policy->record_max_rs_lengths(_rs_lengths);
4794     policy->cset_regions_freed();
4795   }
4796 public:
4797   G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4798     AbstractGangTask("G1 Free Collection Set"),
4799     _cl(evacuation_info, surviving_young_words),
4800     _collection_set(collection_set),
4801     _surviving_young_words(surviving_young_words),
4802     _serial_work_claim(0),
4803     _rs_lengths(0),
4804     _parallel_work_claim(0),
4805     _num_work_items(collection_set->region_length()),
4806     _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4807     prepare_work();
4808   }
4809 
4810   ~G1FreeCollectionSetTask() {
4811     complete_work();
4812     FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4813   }
4814 
4815   // Chunk size for work distribution. The chosen value has been determined experimentally
4816   // to be a good tradeoff between overhead and achievable parallelism.
4817   static uint chunk_size() { return 32; }
4818 
4819   virtual void work(uint worker_id) {
4820     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4821 
4822     // Claim serial work.
4823     if (_serial_work_claim == 0) {
4824       jint value = Atomic::add(1, &_serial_work_claim) - 1;
4825       if (value == 0) {
4826         double serial_time = os::elapsedTime();
4827         do_serial_work();
4828         timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4829       }
4830     }
4831 
4832     // Start parallel work.
4833     double young_time = 0.0;
4834     bool has_young_time = false;
4835     double non_young_time = 0.0;
4836     bool has_non_young_time = false;
4837 
4838     while (true) {
4839       size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4840       size_t cur = end - chunk_size();
4841 
4842       if (cur >= _num_work_items) {
4843         break;
4844       }
4845 
4846       double start_time = os::elapsedTime();
4847 
4848       end = MIN2(end, _num_work_items);
4849 
4850       for (; cur < end; cur++) {
4851         bool is_young = _work_items[cur].is_young;
4852 
4853         do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4854 
4855         double end_time = os::elapsedTime();
4856         double time_taken = end_time - start_time;
4857         if (is_young) {
4858           young_time += time_taken;
4859           has_young_time = true;
4860         } else {
4861           non_young_time += time_taken;
4862           has_non_young_time = true;
4863         }
4864         start_time = end_time;
4865       }
4866     }
4867 
4868     if (has_young_time) {
4869       timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4870     }
4871     if (has_non_young_time) {
4872       timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time);
4873     }
4874   }
4875 };
4876 
4877 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4878   _eden.clear();
4879 
4880   double free_cset_start_time = os::elapsedTime();
4881 
4882   {
4883     uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4884     uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4885 
4886     G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4887 
4888     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4889                         cl.name(),
4890                         num_workers,
4891                         _collection_set.region_length());
4892     workers()->run_task(&cl, num_workers);
4893   }
4894   g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4895 
4896   collection_set->clear();
4897 }
4898 
4899 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4900  private:
4901   FreeRegionList* _free_region_list;
4902   HeapRegionSet* _proxy_set;
4903   uint _humongous_regions_removed;
4904   size_t _freed_bytes;
4905  public:
4906 
4907   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4908     _free_region_list(free_region_list), _humongous_regions_removed(0), _freed_bytes(0) {
4909   }
4910 
4911   virtual bool doHeapRegion(HeapRegion* r) {
4912     if (!r->is_starts_humongous()) {
4913       return false;
4914     }
4915 
4916     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4917 
4918     oop obj = (oop)r->bottom();
4919     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
4920 
4921     // The following checks whether the humongous object is live are sufficient.
4922     // The main additional check (in addition to having a reference from the roots
4923     // or the young gen) is whether the humongous object has a remembered set entry.
4924     //
4925     // A humongous object cannot be live if there is no remembered set for it
4926     // because:
4927     // - there can be no references from within humongous starts regions referencing
4928     // the object because we never allocate other objects into them.
4929     // (I.e. there are no intra-region references that may be missed by the
4930     // remembered set)
4931     // - as soon there is a remembered set entry to the humongous starts region
4932     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4933     // until the end of a concurrent mark.
4934     //
4935     // It is not required to check whether the object has been found dead by marking
4936     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4937     // all objects allocated during that time are considered live.
4938     // SATB marking is even more conservative than the remembered set.
4939     // So if at this point in the collection there is no remembered set entry,
4940     // nobody has a reference to it.
4941     // At the start of collection we flush all refinement logs, and remembered sets
4942     // are completely up-to-date wrt to references to the humongous object.
4943     //
4944     // Other implementation considerations:
4945     // - never consider object arrays at this time because they would pose
4946     // considerable effort for cleaning up the the remembered sets. This is
4947     // required because stale remembered sets might reference locations that
4948     // are currently allocated into.
4949     uint region_idx = r->hrm_index();
4950     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4951         !r->rem_set()->is_empty()) {
4952       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",
4953                                region_idx,
4954                                (size_t)obj->size() * HeapWordSize,
4955                                p2i(r->bottom()),
4956                                r->rem_set()->occupied(),
4957                                r->rem_set()->strong_code_roots_list_length(),
4958                                next_bitmap->isMarked(r->bottom()),
4959                                g1h->is_humongous_reclaim_candidate(region_idx),
4960                                obj->is_typeArray()
4961                               );
4962       return false;
4963     }
4964 
4965     guarantee(obj->is_typeArray(),
4966               "Only eagerly reclaiming type arrays is supported, but the object "
4967               PTR_FORMAT " is not.", p2i(r->bottom()));
4968 
4969     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",
4970                              region_idx,
4971                              (size_t)obj->size() * HeapWordSize,
4972                              p2i(r->bottom()),
4973                              r->rem_set()->occupied(),
4974                              r->rem_set()->strong_code_roots_list_length(),
4975                              next_bitmap->isMarked(r->bottom()),
4976                              g1h->is_humongous_reclaim_candidate(region_idx),
4977                              obj->is_typeArray()
4978                             );
4979 
4980     // Need to clear mark bit of the humongous object if already set.
4981     if (next_bitmap->isMarked(r->bottom())) {
4982       next_bitmap->clear(r->bottom());
4983     }
4984     do {
4985       HeapRegion* next = g1h->next_region_in_humongous(r);
4986       _freed_bytes += r->used();
4987       r->set_containing_set(NULL);
4988       _humongous_regions_removed++;
4989       g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ );
4990       r = next;
4991     } while (r != NULL);
4992 
4993     return false;
4994   }
4995 
4996   uint humongous_free_count() {
4997     return _humongous_regions_removed;
4998   }
4999 
5000   size_t bytes_freed() const {
5001     return _freed_bytes;
5002   }
5003 };
5004 
5005 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
5006   assert_at_safepoint(true);
5007 
5008   if (!G1EagerReclaimHumongousObjects ||
5009       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
5010     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
5011     return;
5012   }
5013 
5014   double start_time = os::elapsedTime();
5015 
5016   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
5017 
5018   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
5019   heap_region_iterate(&cl);
5020 
5021   remove_from_old_sets(0, cl.humongous_free_count());
5022 
5023   G1HRPrinter* hrp = hr_printer();
5024   if (hrp->is_active()) {
5025     FreeRegionListIterator iter(&local_cleanup_list);
5026     while (iter.more_available()) {
5027       HeapRegion* hr = iter.get_next();
5028       hrp->cleanup(hr);
5029     }
5030   }
5031 
5032   prepend_to_freelist(&local_cleanup_list);
5033   decrement_summary_bytes(cl.bytes_freed());
5034 
5035   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
5036                                                                     cl.humongous_free_count());
5037 }
5038 
5039 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
5040 public:
5041   virtual bool doHeapRegion(HeapRegion* r) {
5042     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
5043     G1CollectedHeap::heap()->clear_in_cset(r);
5044     r->set_young_index_in_cset(-1);
5045     return false;
5046   }
5047 };
5048 
5049 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
5050   G1AbandonCollectionSetClosure cl;
5051   collection_set->iterate(&cl);
5052 
5053   collection_set->clear();
5054   collection_set->stop_incremental_building();
5055 }
5056 
5057 void G1CollectedHeap::set_free_regions_coming() {
5058   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
5059 
5060   assert(!free_regions_coming(), "pre-condition");
5061   _free_regions_coming = true;
5062 }
5063 
5064 void G1CollectedHeap::reset_free_regions_coming() {
5065   assert(free_regions_coming(), "pre-condition");
5066 
5067   {
5068     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5069     _free_regions_coming = false;
5070     SecondaryFreeList_lock->notify_all();
5071   }
5072 
5073   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
5074 }
5075 
5076 void G1CollectedHeap::wait_while_free_regions_coming() {
5077   // Most of the time we won't have to wait, so let's do a quick test
5078   // first before we take the lock.
5079   if (!free_regions_coming()) {
5080     return;
5081   }
5082 
5083   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
5084 
5085   {
5086     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5087     while (free_regions_coming()) {
5088       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5089     }
5090   }
5091 
5092   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
5093 }
5094 
5095 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
5096   return _allocator->is_retained_old_region(hr);
5097 }
5098 
5099 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5100   _eden.add(hr);
5101   _g1_policy->set_region_eden(hr);
5102 }
5103 
5104 #ifdef ASSERT
5105 
5106 class NoYoungRegionsClosure: public HeapRegionClosure {
5107 private:
5108   bool _success;
5109 public:
5110   NoYoungRegionsClosure() : _success(true) { }
5111   bool doHeapRegion(HeapRegion* r) {
5112     if (r->is_young()) {
5113       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5114                             p2i(r->bottom()), p2i(r->end()));
5115       _success = false;
5116     }
5117     return false;
5118   }
5119   bool success() { return _success; }
5120 };
5121 
5122 bool G1CollectedHeap::check_young_list_empty() {
5123   bool ret = (young_regions_count() == 0);
5124 
5125   NoYoungRegionsClosure closure;
5126   heap_region_iterate(&closure);
5127   ret = ret && closure.success();
5128 
5129   return ret;
5130 }
5131 
5132 #endif // ASSERT
5133 
5134 class TearDownRegionSetsClosure : public HeapRegionClosure {
5135 private:
5136   HeapRegionSet *_old_set;
5137 
5138 public:
5139   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5140 
5141   bool doHeapRegion(HeapRegion* r) {
5142     if (r->is_old()) {
5143       _old_set->remove(r);
5144     } else if(r->is_young()) {
5145       r->uninstall_surv_rate_group();
5146     } else {
5147       // We ignore free regions, we'll empty the free list afterwards.
5148       // We ignore humongous regions, we're not tearing down the
5149       // humongous regions set.
5150       assert(r->is_free() || r->is_humongous(),
5151              "it cannot be another type");
5152     }
5153     return false;
5154   }
5155 
5156   ~TearDownRegionSetsClosure() {
5157     assert(_old_set->is_empty(), "post-condition");
5158   }
5159 };
5160 
5161 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5162   assert_at_safepoint(true /* should_be_vm_thread */);
5163 
5164   if (!free_list_only) {
5165     TearDownRegionSetsClosure cl(&_old_set);
5166     heap_region_iterate(&cl);
5167 
5168     // Note that emptying the _young_list is postponed and instead done as
5169     // the first step when rebuilding the regions sets again. The reason for
5170     // this is that during a full GC string deduplication needs to know if
5171     // a collected region was young or old when the full GC was initiated.
5172   }
5173   _hrm.remove_all_free_regions();
5174 }
5175 
5176 void G1CollectedHeap::increase_used(size_t bytes) {
5177   _summary_bytes_used += bytes;
5178 }
5179 
5180 void G1CollectedHeap::decrease_used(size_t bytes) {
5181   assert(_summary_bytes_used >= bytes,
5182          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5183          _summary_bytes_used, bytes);
5184   _summary_bytes_used -= bytes;
5185 }
5186 
5187 void G1CollectedHeap::set_used(size_t bytes) {
5188   _summary_bytes_used = bytes;
5189 }
5190 
5191 class RebuildRegionSetsClosure : public HeapRegionClosure {
5192 private:
5193   bool            _free_list_only;
5194   HeapRegionSet*   _old_set;
5195   HeapRegionManager*   _hrm;
5196   size_t          _total_used;
5197 
5198 public:
5199   RebuildRegionSetsClosure(bool free_list_only,
5200                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
5201     _free_list_only(free_list_only),
5202     _old_set(old_set), _hrm(hrm), _total_used(0) {
5203     assert(_hrm->num_free_regions() == 0, "pre-condition");
5204     if (!free_list_only) {
5205       assert(_old_set->is_empty(), "pre-condition");
5206     }
5207   }
5208 
5209   bool doHeapRegion(HeapRegion* r) {
5210     if (r->is_empty()) {
5211       // Add free regions to the free list
5212       r->set_free();
5213       r->set_allocation_context(AllocationContext::system());
5214       _hrm->insert_into_free_list(r);
5215     } else if (!_free_list_only) {
5216 
5217       if (r->is_humongous()) {
5218         // We ignore humongous regions. We left the humongous set unchanged.
5219       } else {
5220         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
5221         // We now consider all regions old, so register as such. Leave
5222         // archive regions set that way, however, while still adding
5223         // them to the old set.
5224         if (!r->is_archive()) {
5225           r->set_old();
5226         }
5227         _old_set->add(r);
5228       }
5229       _total_used += r->used();
5230     }
5231 
5232     return false;
5233   }
5234 
5235   size_t total_used() {
5236     return _total_used;
5237   }
5238 };
5239 
5240 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5241   assert_at_safepoint(true /* should_be_vm_thread */);
5242 
5243   if (!free_list_only) {
5244     _eden.clear();
5245     _survivor.clear();
5246   }
5247 
5248   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5249   heap_region_iterate(&cl);
5250 
5251   if (!free_list_only) {
5252     set_used(cl.total_used());
5253     if (_archive_allocator != NULL) {
5254       _archive_allocator->clear_used();
5255     }
5256   }
5257   assert(used_unlocked() == recalculate_used(),
5258          "inconsistent used_unlocked(), "
5259          "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5260          used_unlocked(), recalculate_used());
5261 }
5262 
5263 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
5264   _refine_cte_cl->set_concurrent(concurrent);
5265 }
5266 
5267 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5268   HeapRegion* hr = heap_region_containing(p);
5269   return hr->is_in(p);
5270 }
5271 
5272 // Methods for the mutator alloc region
5273 
5274 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5275                                                       bool force) {
5276   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5277   assert(!force || g1_policy()->can_expand_young_list(),
5278          "if force is true we should be able to expand the young list");
5279   bool should_allocate = g1_policy()->should_allocate_mutator_region();
5280   if (force || should_allocate) {
5281     HeapRegion* new_alloc_region = new_region(word_size,
5282                                               false /* is_old */,
5283                                               false /* do_expand */);
5284     if (new_alloc_region != NULL) {
5285       set_region_short_lived_locked(new_alloc_region);
5286       _hr_printer.alloc(new_alloc_region, !should_allocate);
5287       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5288       return new_alloc_region;
5289     }
5290   }
5291   return NULL;
5292 }
5293 
5294 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5295                                                   size_t allocated_bytes) {
5296   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5297   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5298 
5299   collection_set()->add_eden_region(alloc_region);
5300   increase_used(allocated_bytes);
5301   _hr_printer.retire(alloc_region);
5302   // We update the eden sizes here, when the region is retired,
5303   // instead of when it's allocated, since this is the point that its
5304   // used space has been recored in _summary_bytes_used.
5305   g1mm()->update_eden_size();
5306 }
5307 
5308 // Methods for the GC alloc regions
5309 
5310 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
5311   if (dest.is_old()) {
5312     return true;
5313   } else {
5314     return survivor_regions_count() < g1_policy()->max_survivor_regions();
5315   }
5316 }
5317 
5318 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
5319   assert(FreeList_lock->owned_by_self(), "pre-condition");
5320 
5321   if (!has_more_regions(dest)) {
5322     return NULL;
5323   }
5324 
5325   const bool is_survivor = dest.is_young();
5326 
5327   HeapRegion* new_alloc_region = new_region(word_size,
5328                                             !is_survivor,
5329                                             true /* do_expand */);
5330   if (new_alloc_region != NULL) {
5331     // We really only need to do this for old regions given that we
5332     // should never scan survivors. But it doesn't hurt to do it
5333     // for survivors too.
5334     new_alloc_region->record_timestamp();
5335     if (is_survivor) {
5336       new_alloc_region->set_survivor();
5337       _survivor.add(new_alloc_region);
5338       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5339     } else {
5340       new_alloc_region->set_old();
5341       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5342     }
5343     _hr_printer.alloc(new_alloc_region);
5344     bool during_im = collector_state()->during_initial_mark_pause();
5345     new_alloc_region->note_start_of_copying(during_im);
5346     return new_alloc_region;
5347   }
5348   return NULL;
5349 }
5350 
5351 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5352                                              size_t allocated_bytes,
5353                                              InCSetState dest) {
5354   bool during_im = collector_state()->during_initial_mark_pause();
5355   alloc_region->note_end_of_copying(during_im);
5356   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5357   if (dest.is_old()) {
5358     _old_set.add(alloc_region);
5359   }
5360   _hr_printer.retire(alloc_region);
5361 }
5362 
5363 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5364   bool expanded = false;
5365   uint index = _hrm.find_highest_free(&expanded);
5366 
5367   if (index != G1_NO_HRM_INDEX) {
5368     if (expanded) {
5369       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5370                                 HeapRegion::GrainWords * HeapWordSize);
5371     }
5372     _hrm.allocate_free_regions_starting_at(index, 1);
5373     return region_at(index);
5374   }
5375   return NULL;
5376 }
5377 
5378 // Optimized nmethod scanning
5379 
5380 class RegisterNMethodOopClosure: public OopClosure {
5381   G1CollectedHeap* _g1h;
5382   nmethod* _nm;
5383 
5384   template <class T> void do_oop_work(T* p) {
5385     T heap_oop = oopDesc::load_heap_oop(p);
5386     if (!oopDesc::is_null(heap_oop)) {
5387       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5388       HeapRegion* hr = _g1h->heap_region_containing(obj);
5389       assert(!hr->is_continues_humongous(),
5390              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5391              " starting at " HR_FORMAT,
5392              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5393 
5394       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5395       hr->add_strong_code_root_locked(_nm);
5396     }
5397   }
5398 
5399 public:
5400   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5401     _g1h(g1h), _nm(nm) {}
5402 
5403   void do_oop(oop* p)       { do_oop_work(p); }
5404   void do_oop(narrowOop* p) { do_oop_work(p); }
5405 };
5406 
5407 class UnregisterNMethodOopClosure: public OopClosure {
5408   G1CollectedHeap* _g1h;
5409   nmethod* _nm;
5410 
5411   template <class T> void do_oop_work(T* p) {
5412     T heap_oop = oopDesc::load_heap_oop(p);
5413     if (!oopDesc::is_null(heap_oop)) {
5414       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5415       HeapRegion* hr = _g1h->heap_region_containing(obj);
5416       assert(!hr->is_continues_humongous(),
5417              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5418              " starting at " HR_FORMAT,
5419              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5420 
5421       hr->remove_strong_code_root(_nm);
5422     }
5423   }
5424 
5425 public:
5426   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5427     _g1h(g1h), _nm(nm) {}
5428 
5429   void do_oop(oop* p)       { do_oop_work(p); }
5430   void do_oop(narrowOop* p) { do_oop_work(p); }
5431 };
5432 
5433 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5434   CollectedHeap::register_nmethod(nm);
5435 
5436   guarantee(nm != NULL, "sanity");
5437   RegisterNMethodOopClosure reg_cl(this, nm);
5438   nm->oops_do(&reg_cl);
5439 }
5440 
5441 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5442   CollectedHeap::unregister_nmethod(nm);
5443 
5444   guarantee(nm != NULL, "sanity");
5445   UnregisterNMethodOopClosure reg_cl(this, nm);
5446   nm->oops_do(&reg_cl, true);
5447 }
5448 
5449 void G1CollectedHeap::purge_code_root_memory() {
5450   double purge_start = os::elapsedTime();
5451   G1CodeRootSet::purge();
5452   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5453   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5454 }
5455 
5456 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5457   G1CollectedHeap* _g1h;
5458 
5459 public:
5460   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5461     _g1h(g1h) {}
5462 
5463   void do_code_blob(CodeBlob* cb) {
5464     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5465     if (nm == NULL) {
5466       return;
5467     }
5468 
5469     if (ScavengeRootsInCode) {
5470       _g1h->register_nmethod(nm);
5471     }
5472   }
5473 };
5474 
5475 void G1CollectedHeap::rebuild_strong_code_roots() {
5476   RebuildStrongCodeRootClosure blob_cl(this);
5477   CodeCache::blobs_do(&blob_cl);
5478 }
--- EOF ---