1 /*
   2  * Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/metadataOnStackMark.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "classfile/symbolTable.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc/g1/bufferingOopClosure.hpp"
  32 #include "gc/g1/concurrentMarkThread.inline.hpp"
  33 #include "gc/g1/g1Allocator.inline.hpp"
  34 #include "gc/g1/g1CollectedHeap.inline.hpp"
  35 #include "gc/g1/g1CollectionSet.hpp"
  36 #include "gc/g1/g1CollectorPolicy.hpp"
  37 #include "gc/g1/g1CollectorState.hpp"
  38 #include "gc/g1/g1ConcurrentRefine.hpp"
  39 #include "gc/g1/g1ConcurrentRefineThread.hpp"
  40 #include "gc/g1/g1EvacStats.inline.hpp"
  41 #include "gc/g1/g1FullCollector.hpp"
  42 #include "gc/g1/g1FullGCScope.hpp"
  43 #include "gc/g1/g1GCPhaseTimes.hpp"
  44 #include "gc/g1/g1HeapSizingPolicy.hpp"
  45 #include "gc/g1/g1HeapTransition.hpp"
  46 #include "gc/g1/g1HeapVerifier.hpp"
  47 #include "gc/g1/g1HotCardCache.hpp"
  48 #include "gc/g1/g1OopClosures.inline.hpp"
  49 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  50 #include "gc/g1/g1Policy.hpp"
  51 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  52 #include "gc/g1/g1RemSet.hpp"
  53 #include "gc/g1/g1RootClosures.hpp"
  54 #include "gc/g1/g1RootProcessor.hpp"
  55 #include "gc/g1/g1StringDedup.hpp"
  56 #include "gc/g1/g1YCTypes.hpp"
  57 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
  58 #include "gc/g1/heapRegion.inline.hpp"
  59 #include "gc/g1/heapRegionRemSet.hpp"
  60 #include "gc/g1/heapRegionSet.inline.hpp"
  61 #include "gc/g1/vm_operations_g1.hpp"
  62 #include "gc/shared/gcHeapSummary.hpp"
  63 #include "gc/shared/gcId.hpp"
  64 #include "gc/shared/gcLocker.inline.hpp"
  65 #include "gc/shared/gcTimer.hpp"
  66 #include "gc/shared/gcTrace.hpp"
  67 #include "gc/shared/gcTraceTime.inline.hpp"
  68 #include "gc/shared/generationSpec.hpp"
  69 #include "gc/shared/isGCActiveMark.hpp"
  70 #include "gc/shared/preservedMarks.inline.hpp"
  71 #include "gc/shared/suspendibleThreadSet.hpp"
  72 #include "gc/shared/referenceProcessor.inline.hpp"
  73 #include "gc/shared/taskqueue.inline.hpp"
  74 #include "gc/shared/weakProcessor.hpp"
  75 #include "logging/log.hpp"
  76 #include "memory/allocation.hpp"
  77 #include "memory/iterator.hpp"
  78 #include "memory/resourceArea.hpp"
  79 #include "oops/oop.inline.hpp"
  80 #include "prims/resolvedMethodTable.hpp"
  81 #include "runtime/atomic.hpp"
  82 #include "runtime/init.hpp"
  83 #include "runtime/orderAccess.inline.hpp"
  84 #include "runtime/vmThread.hpp"
  85 #include "utilities/align.hpp"
  86 #include "utilities/globalDefinitions.hpp"
  87 #include "utilities/stack.inline.hpp"
  88 
  89 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  90 
  91 // INVARIANTS/NOTES
  92 //
  93 // All allocation activity covered by the G1CollectedHeap interface is
  94 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  95 // and allocate_new_tlab, which are the "entry" points to the
  96 // allocation code from the rest of the JVM.  (Note that this does not
  97 // apply to TLAB allocation, which is not part of this interface: it
  98 // is done by clients of this interface.)
  99 
 100 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 101  private:
 102   size_t _num_dirtied;
 103   G1CollectedHeap* _g1h;
 104   G1SATBCardTableLoggingModRefBS* _g1_bs;
 105 
 106   HeapRegion* region_for_card(jbyte* card_ptr) const {
 107     return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
 108   }
 109 
 110   bool will_become_free(HeapRegion* hr) const {
 111     // A region will be freed by free_collection_set if the region is in the
 112     // collection set and has not had an evacuation failure.
 113     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 114   }
 115 
 116  public:
 117   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
 118     _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
 119 
 120   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 121     HeapRegion* hr = region_for_card(card_ptr);
 122 
 123     // Should only dirty cards in regions that won't be freed.
 124     if (!will_become_free(hr)) {
 125       *card_ptr = CardTableModRefBS::dirty_card_val();
 126       _num_dirtied++;
 127     }
 128 
 129     return true;
 130   }
 131 
 132   size_t num_dirtied()   const { return _num_dirtied; }
 133 };
 134 
 135 
 136 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 137   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 138 }
 139 
 140 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 141   // The from card cache is not the memory that is actually committed. So we cannot
 142   // take advantage of the zero_filled parameter.
 143   reset_from_card_cache(start_idx, num_regions);
 144 }
 145 
 146 
 147 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
 148                                              MemRegion mr) {
 149   return new HeapRegion(hrs_index, bot(), mr);
 150 }
 151 
 152 // Private methods.
 153 
 154 HeapRegion*
 155 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 156   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 157   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 158     if (!_secondary_free_list.is_empty()) {
 159       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 160                                       "secondary_free_list has %u entries",
 161                                       _secondary_free_list.length());
 162       // It looks as if there are free regions available on the
 163       // secondary_free_list. Let's move them to the free_list and try
 164       // again to allocate from it.
 165       append_secondary_free_list();
 166 
 167       assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
 168              "empty we should have moved at least one entry to the free_list");
 169       HeapRegion* res = _hrm.allocate_free_region(is_old);
 170       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 171                                       "allocated " HR_FORMAT " from secondary_free_list",
 172                                       HR_FORMAT_PARAMS(res));
 173       return res;
 174     }
 175 
 176     // Wait here until we get notified either when (a) there are no
 177     // more free regions coming or (b) some regions have been moved on
 178     // the secondary_free_list.
 179     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 180   }
 181 
 182   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 183                                   "could not allocate from secondary_free_list");
 184   return NULL;
 185 }
 186 
 187 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 188   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 189          "the only time we use this to allocate a humongous region is "
 190          "when we are allocating a single humongous region");
 191 
 192   HeapRegion* res;
 193   if (G1StressConcRegionFreeing) {
 194     if (!_secondary_free_list.is_empty()) {
 195       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 196                                       "forced to look at the secondary_free_list");
 197       res = new_region_try_secondary_free_list(is_old);
 198       if (res != NULL) {
 199         return res;
 200       }
 201     }
 202   }
 203 
 204   res = _hrm.allocate_free_region(is_old);
 205 
 206   if (res == NULL) {
 207     log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 208                                     "res == NULL, trying the secondary_free_list");
 209     res = new_region_try_secondary_free_list(is_old);
 210   }
 211   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 212     // Currently, only attempts to allocate GC alloc regions set
 213     // do_expand to true. So, we should only reach here during a
 214     // safepoint. If this assumption changes we might have to
 215     // reconsider the use of _expand_heap_after_alloc_failure.
 216     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 217 
 218     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 219                               word_size * HeapWordSize);
 220 
 221     if (expand(word_size * HeapWordSize)) {
 222       // Given that expand() succeeded in expanding the heap, and we
 223       // always expand the heap by an amount aligned to the heap
 224       // region size, the free list should in theory not be empty.
 225       // In either case allocate_free_region() will check for NULL.
 226       res = _hrm.allocate_free_region(is_old);
 227     } else {
 228       _expand_heap_after_alloc_failure = false;
 229     }
 230   }
 231   return res;
 232 }
 233 
 234 HeapWord*
 235 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 236                                                            uint num_regions,
 237                                                            size_t word_size,
 238                                                            AllocationContext_t context) {
 239   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 240   assert(is_humongous(word_size), "word_size should be humongous");
 241   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 242 
 243   // Index of last region in the series.
 244   uint last = first + num_regions - 1;
 245 
 246   // We need to initialize the region(s) we just discovered. This is
 247   // a bit tricky given that it can happen concurrently with
 248   // refinement threads refining cards on these regions and
 249   // potentially wanting to refine the BOT as they are scanning
 250   // those cards (this can happen shortly after a cleanup; see CR
 251   // 6991377). So we have to set up the region(s) carefully and in
 252   // a specific order.
 253 
 254   // The word size sum of all the regions we will allocate.
 255   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 256   assert(word_size <= word_size_sum, "sanity");
 257 
 258   // This will be the "starts humongous" region.
 259   HeapRegion* first_hr = region_at(first);
 260   // The header of the new object will be placed at the bottom of
 261   // the first region.
 262   HeapWord* new_obj = first_hr->bottom();
 263   // This will be the new top of the new object.
 264   HeapWord* obj_top = new_obj + word_size;
 265 
 266   // First, we need to zero the header of the space that we will be
 267   // allocating. When we update top further down, some refinement
 268   // threads might try to scan the region. By zeroing the header we
 269   // ensure that any thread that will try to scan the region will
 270   // come across the zero klass word and bail out.
 271   //
 272   // NOTE: It would not have been correct to have used
 273   // CollectedHeap::fill_with_object() and make the space look like
 274   // an int array. The thread that is doing the allocation will
 275   // later update the object header to a potentially different array
 276   // type and, for a very short period of time, the klass and length
 277   // fields will be inconsistent. This could cause a refinement
 278   // thread to calculate the object size incorrectly.
 279   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 280 
 281   // Next, pad out the unused tail of the last region with filler
 282   // objects, for improved usage accounting.
 283   // How many words we use for filler objects.
 284   size_t word_fill_size = word_size_sum - word_size;
 285 
 286   // How many words memory we "waste" which cannot hold a filler object.
 287   size_t words_not_fillable = 0;
 288 
 289   if (word_fill_size >= min_fill_size()) {
 290     fill_with_objects(obj_top, word_fill_size);
 291   } else if (word_fill_size > 0) {
 292     // We have space to fill, but we cannot fit an object there.
 293     words_not_fillable = word_fill_size;
 294     word_fill_size = 0;
 295   }
 296 
 297   // We will set up the first region as "starts humongous". This
 298   // will also update the BOT covering all the regions to reflect
 299   // that there is a single object that starts at the bottom of the
 300   // first region.
 301   first_hr->set_starts_humongous(obj_top, word_fill_size);
 302   first_hr->set_allocation_context(context);
 303   // Then, if there are any, we will set up the "continues
 304   // humongous" regions.
 305   HeapRegion* hr = NULL;
 306   for (uint i = first + 1; i <= last; ++i) {
 307     hr = region_at(i);
 308     hr->set_continues_humongous(first_hr);
 309     hr->set_allocation_context(context);
 310   }
 311 
 312   // Up to this point no concurrent thread would have been able to
 313   // do any scanning on any region in this series. All the top
 314   // fields still point to bottom, so the intersection between
 315   // [bottom,top] and [card_start,card_end] will be empty. Before we
 316   // update the top fields, we'll do a storestore to make sure that
 317   // no thread sees the update to top before the zeroing of the
 318   // object header and the BOT initialization.
 319   OrderAccess::storestore();
 320 
 321   // Now, we will update the top fields of the "continues humongous"
 322   // regions except the last one.
 323   for (uint i = first; i < last; ++i) {
 324     hr = region_at(i);
 325     hr->set_top(hr->end());
 326   }
 327 
 328   hr = region_at(last);
 329   // If we cannot fit a filler object, we must set top to the end
 330   // of the humongous object, otherwise we cannot iterate the heap
 331   // and the BOT will not be complete.
 332   hr->set_top(hr->end() - words_not_fillable);
 333 
 334   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 335          "obj_top should be in last region");
 336 
 337   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 338 
 339   assert(words_not_fillable == 0 ||
 340          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 341          "Miscalculation in humongous allocation");
 342 
 343   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 344 
 345   for (uint i = first; i <= last; ++i) {
 346     hr = region_at(i);
 347     _humongous_set.add(hr);
 348     _hr_printer.alloc(hr);
 349   }
 350 
 351   return new_obj;
 352 }
 353 
 354 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 355   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 356   return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 357 }
 358 
 359 // If could fit into free regions w/o expansion, try.
 360 // Otherwise, if can expand, do so.
 361 // Otherwise, if using ex regions might help, try with ex given back.
 362 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
 363   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 364 
 365   _verifier->verify_region_sets_optional();
 366 
 367   uint first = G1_NO_HRM_INDEX;
 368   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 369 
 370   if (obj_regions == 1) {
 371     // Only one region to allocate, try to use a fast path by directly allocating
 372     // from the free lists. Do not try to expand here, we will potentially do that
 373     // later.
 374     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 375     if (hr != NULL) {
 376       first = hr->hrm_index();
 377     }
 378   } else {
 379     // We can't allocate humongous regions spanning more than one region while
 380     // cleanupComplete() is running, since some of the regions we find to be
 381     // empty might not yet be added to the free list. It is not straightforward
 382     // to know in which list they are on so that we can remove them. We only
 383     // need to do this if we need to allocate more than one region to satisfy the
 384     // current humongous allocation request. If we are only allocating one region
 385     // we use the one-region region allocation code (see above), that already
 386     // potentially waits for regions from the secondary free list.
 387     wait_while_free_regions_coming();
 388     append_secondary_free_list_if_not_empty_with_lock();
 389 
 390     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 391     // are lucky enough to find some.
 392     first = _hrm.find_contiguous_only_empty(obj_regions);
 393     if (first != G1_NO_HRM_INDEX) {
 394       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 395     }
 396   }
 397 
 398   if (first == G1_NO_HRM_INDEX) {
 399     // Policy: We could not find enough regions for the humongous object in the
 400     // free list. Look through the heap to find a mix of free and uncommitted regions.
 401     // If so, try expansion.
 402     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 403     if (first != G1_NO_HRM_INDEX) {
 404       // We found something. Make sure these regions are committed, i.e. expand
 405       // the heap. Alternatively we could do a defragmentation GC.
 406       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 407                                     word_size * HeapWordSize);
 408 
 409       _hrm.expand_at(first, obj_regions, workers());
 410       g1_policy()->record_new_heap_size(num_regions());
 411 
 412 #ifdef ASSERT
 413       for (uint i = first; i < first + obj_regions; ++i) {
 414         HeapRegion* hr = region_at(i);
 415         assert(hr->is_free(), "sanity");
 416         assert(hr->is_empty(), "sanity");
 417         assert(is_on_master_free_list(hr), "sanity");
 418       }
 419 #endif
 420       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 421     } else {
 422       // Policy: Potentially trigger a defragmentation GC.
 423     }
 424   }
 425 
 426   HeapWord* result = NULL;
 427   if (first != G1_NO_HRM_INDEX) {
 428     result = humongous_obj_allocate_initialize_regions(first, obj_regions,
 429                                                        word_size, context);
 430     assert(result != NULL, "it should always return a valid result");
 431 
 432     // A successful humongous object allocation changes the used space
 433     // information of the old generation so we need to recalculate the
 434     // sizes and update the jstat counters here.
 435     g1mm()->update_sizes();
 436   }
 437 
 438   _verifier->verify_region_sets_optional();
 439 
 440   return result;
 441 }
 442 
 443 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 444   assert_heap_not_locked_and_not_at_safepoint();
 445   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 446 
 447   uint dummy_gc_count_before;
 448   uint dummy_gclocker_retry_count = 0;
 449   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 450 }
 451 
 452 HeapWord*
 453 G1CollectedHeap::mem_allocate(size_t word_size,
 454                               bool*  gc_overhead_limit_was_exceeded) {
 455   assert_heap_not_locked_and_not_at_safepoint();
 456 
 457   // Loop until the allocation is satisfied, or unsatisfied after GC.
 458   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 459     uint gc_count_before;
 460 
 461     HeapWord* result = NULL;
 462     if (!is_humongous(word_size)) {
 463       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 464     } else {
 465       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 466     }
 467     if (result != NULL) {
 468       return result;
 469     }
 470 
 471     // Create the garbage collection operation...
 472     VM_G1CollectForAllocation op(gc_count_before, word_size);
 473     op.set_allocation_context(AllocationContext::current());
 474 
 475     // ...and get the VM thread to execute it.
 476     VMThread::execute(&op);
 477 
 478     if (op.prologue_succeeded() && op.pause_succeeded()) {
 479       // If the operation was successful we'll return the result even
 480       // if it is NULL. If the allocation attempt failed immediately
 481       // after a Full GC, it's unlikely we'll be able to allocate now.
 482       HeapWord* result = op.result();
 483       if (result != NULL && !is_humongous(word_size)) {
 484         // Allocations that take place on VM operations do not do any
 485         // card dirtying and we have to do it here. We only have to do
 486         // this for non-humongous allocations, though.
 487         dirty_young_block(result, word_size);
 488       }
 489       return result;
 490     } else {
 491       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 492         return NULL;
 493       }
 494       assert(op.result() == NULL,
 495              "the result should be NULL if the VM op did not succeed");
 496     }
 497 
 498     // Give a warning if we seem to be looping forever.
 499     if ((QueuedAllocationWarningCount > 0) &&
 500         (try_count % QueuedAllocationWarningCount == 0)) {
 501       log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
 502     }
 503   }
 504 
 505   ShouldNotReachHere();
 506   return NULL;
 507 }
 508 
 509 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 510                                                    AllocationContext_t context,
 511                                                    uint* gc_count_before_ret,
 512                                                    uint* gclocker_retry_count_ret) {
 513   // Make sure you read the note in attempt_allocation_humongous().
 514 
 515   assert_heap_not_locked_and_not_at_safepoint();
 516   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 517          "be called for humongous allocation requests");
 518 
 519   // We should only get here after the first-level allocation attempt
 520   // (attempt_allocation()) failed to allocate.
 521 
 522   // We will loop until a) we manage to successfully perform the
 523   // allocation or b) we successfully schedule a collection which
 524   // fails to perform the allocation. b) is the only case when we'll
 525   // return NULL.
 526   HeapWord* result = NULL;
 527   for (int try_count = 1; /* we'll return */; try_count += 1) {
 528     bool should_try_gc;
 529     uint gc_count_before;
 530 
 531     {
 532       MutexLockerEx x(Heap_lock);
 533       result = _allocator->attempt_allocation_locked(word_size, context);
 534       if (result != NULL) {
 535         return result;
 536       }
 537 
 538       if (GCLocker::is_active_and_needs_gc()) {
 539         if (g1_policy()->can_expand_young_list()) {
 540           // No need for an ergo verbose message here,
 541           // can_expand_young_list() does this when it returns true.
 542           result = _allocator->attempt_allocation_force(word_size, context);
 543           if (result != NULL) {
 544             return result;
 545           }
 546         }
 547         should_try_gc = false;
 548       } else {
 549         // The GCLocker may not be active but the GCLocker initiated
 550         // GC may not yet have been performed (GCLocker::needs_gc()
 551         // returns true). In this case we do not try this GC and
 552         // wait until the GCLocker initiated GC is performed, and
 553         // then retry the allocation.
 554         if (GCLocker::needs_gc()) {
 555           should_try_gc = false;
 556         } else {
 557           // Read the GC count while still holding the Heap_lock.
 558           gc_count_before = total_collections();
 559           should_try_gc = true;
 560         }
 561       }
 562     }
 563 
 564     if (should_try_gc) {
 565       bool succeeded;
 566       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 567                                    GCCause::_g1_inc_collection_pause);
 568       if (result != NULL) {
 569         assert(succeeded, "only way to get back a non-NULL result");
 570         return result;
 571       }
 572 
 573       if (succeeded) {
 574         // If we get here we successfully scheduled a collection which
 575         // failed to allocate. No point in trying to allocate
 576         // further. We'll just return NULL.
 577         MutexLockerEx x(Heap_lock);
 578         *gc_count_before_ret = total_collections();
 579         return NULL;
 580       }
 581     } else {
 582       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 583         MutexLockerEx x(Heap_lock);
 584         *gc_count_before_ret = total_collections();
 585         return NULL;
 586       }
 587       // The GCLocker is either active or the GCLocker initiated
 588       // GC has not yet been performed. Stall until it is and
 589       // then retry the allocation.
 590       GCLocker::stall_until_clear();
 591       (*gclocker_retry_count_ret) += 1;
 592     }
 593 
 594     // We can reach here if we were unsuccessful in scheduling a
 595     // collection (because another thread beat us to it) or if we were
 596     // stalled due to the GC locker. In either can we should retry the
 597     // allocation attempt in case another thread successfully
 598     // performed a collection and reclaimed enough space. We do the
 599     // first attempt (without holding the Heap_lock) here and the
 600     // follow-on attempt will be at the start of the next loop
 601     // iteration (after taking the Heap_lock).
 602     result = _allocator->attempt_allocation(word_size, context);
 603     if (result != NULL) {
 604       return result;
 605     }
 606 
 607     // Give a warning if we seem to be looping forever.
 608     if ((QueuedAllocationWarningCount > 0) &&
 609         (try_count % QueuedAllocationWarningCount == 0)) {
 610       log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
 611                       "retries %d times", try_count);
 612     }
 613   }
 614 
 615   ShouldNotReachHere();
 616   return NULL;
 617 }
 618 
 619 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
 620   assert_at_safepoint(true /* should_be_vm_thread */);
 621   if (_archive_allocator == NULL) {
 622     _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
 623   }
 624 }
 625 
 626 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 627   // Allocations in archive regions cannot be of a size that would be considered
 628   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 629   // may be different at archive-restore time.
 630   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 631 }
 632 
 633 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 634   assert_at_safepoint(true /* should_be_vm_thread */);
 635   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 636   if (is_archive_alloc_too_large(word_size)) {
 637     return NULL;
 638   }
 639   return _archive_allocator->archive_mem_allocate(word_size);
 640 }
 641 
 642 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 643                                               size_t end_alignment_in_bytes) {
 644   assert_at_safepoint(true /* should_be_vm_thread */);
 645   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 646 
 647   // Call complete_archive to do the real work, filling in the MemRegion
 648   // array with the archive regions.
 649   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 650   delete _archive_allocator;
 651   _archive_allocator = NULL;
 652 }
 653 
 654 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 655   assert(ranges != NULL, "MemRegion array NULL");
 656   assert(count != 0, "No MemRegions provided");
 657   MemRegion reserved = _hrm.reserved();
 658   for (size_t i = 0; i < count; i++) {
 659     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 660       return false;
 661     }
 662   }
 663   return true;
 664 }
 665 
 666 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
 667                                             size_t count,
 668                                             bool open) {
 669   assert(!is_init_completed(), "Expect to be called at JVM init time");
 670   assert(ranges != NULL, "MemRegion array NULL");
 671   assert(count != 0, "No MemRegions provided");
 672   MutexLockerEx x(Heap_lock);
 673 
 674   MemRegion reserved = _hrm.reserved();
 675   HeapWord* prev_last_addr = NULL;
 676   HeapRegion* prev_last_region = NULL;
 677 
 678   // Temporarily disable pretouching of heap pages. This interface is used
 679   // when mmap'ing archived heap data in, so pre-touching is wasted.
 680   FlagSetting fs(AlwaysPreTouch, false);
 681 
 682   // Enable archive object checking used by G1MarkSweep. We have to let it know
 683   // about each archive range, so that objects in those ranges aren't marked.
 684   G1ArchiveAllocator::enable_archive_object_check();
 685 
 686   // For each specified MemRegion range, allocate the corresponding G1
 687   // regions and mark them as archive regions. We expect the ranges
 688   // in ascending starting address order, without overlap.
 689   for (size_t i = 0; i < count; i++) {
 690     MemRegion curr_range = ranges[i];
 691     HeapWord* start_address = curr_range.start();
 692     size_t word_size = curr_range.word_size();
 693     HeapWord* last_address = curr_range.last();
 694     size_t commits = 0;
 695 
 696     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 697               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 698               p2i(start_address), p2i(last_address));
 699     guarantee(start_address > prev_last_addr,
 700               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 701               p2i(start_address), p2i(prev_last_addr));
 702     prev_last_addr = last_address;
 703 
 704     // Check for ranges that start in the same G1 region in which the previous
 705     // range ended, and adjust the start address so we don't try to allocate
 706     // the same region again. If the current range is entirely within that
 707     // region, skip it, just adjusting the recorded top.
 708     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 709     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 710       start_address = start_region->end();
 711       if (start_address > last_address) {
 712         increase_used(word_size * HeapWordSize);
 713         start_region->set_top(last_address + 1);
 714         continue;
 715       }
 716       start_region->set_top(start_address);
 717       curr_range = MemRegion(start_address, last_address + 1);
 718       start_region = _hrm.addr_to_region(start_address);
 719     }
 720 
 721     // Perform the actual region allocation, exiting if it fails.
 722     // Then note how much new space we have allocated.
 723     if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
 724       return false;
 725     }
 726     increase_used(word_size * HeapWordSize);
 727     if (commits != 0) {
 728       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 729                                 HeapRegion::GrainWords * HeapWordSize * commits);
 730 
 731     }
 732 
 733     // Mark each G1 region touched by the range as archive, add it to
 734     // the old set, and set the allocation context and top.
 735     HeapRegion* curr_region = _hrm.addr_to_region(start_address);
 736     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 737     prev_last_region = last_region;
 738 
 739     while (curr_region != NULL) {
 740       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 741              "Region already in use (index %u)", curr_region->hrm_index());
 742       curr_region->set_allocation_context(AllocationContext::system());
 743       if (open) {
 744         curr_region->set_open_archive();
 745       } else {
 746         curr_region->set_closed_archive();
 747       }
 748       _hr_printer.alloc(curr_region);
 749       _old_set.add(curr_region);
 750       HeapWord* top;
 751       HeapRegion* next_region;
 752       if (curr_region != last_region) {
 753         top = curr_region->end();
 754         next_region = _hrm.next_region_in_heap(curr_region);
 755       } else {
 756         top = last_address + 1;
 757         next_region = NULL;
 758       }
 759       curr_region->set_top(top);
 760       curr_region->set_first_dead(top);
 761       curr_region->set_end_of_live(top);
 762       curr_region = next_region;
 763     }
 764 
 765     // Notify mark-sweep of the archive
 766     G1ArchiveAllocator::set_range_archive(curr_range, open);
 767   }
 768   return true;
 769 }
 770 
 771 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 772   assert(!is_init_completed(), "Expect to be called at JVM init time");
 773   assert(ranges != NULL, "MemRegion array NULL");
 774   assert(count != 0, "No MemRegions provided");
 775   MemRegion reserved = _hrm.reserved();
 776   HeapWord *prev_last_addr = NULL;
 777   HeapRegion* prev_last_region = NULL;
 778 
 779   // For each MemRegion, create filler objects, if needed, in the G1 regions
 780   // that contain the address range. The address range actually within the
 781   // MemRegion will not be modified. That is assumed to have been initialized
 782   // elsewhere, probably via an mmap of archived heap data.
 783   MutexLockerEx x(Heap_lock);
 784   for (size_t i = 0; i < count; i++) {
 785     HeapWord* start_address = ranges[i].start();
 786     HeapWord* last_address = ranges[i].last();
 787 
 788     assert(reserved.contains(start_address) && reserved.contains(last_address),
 789            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 790            p2i(start_address), p2i(last_address));
 791     assert(start_address > prev_last_addr,
 792            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 793            p2i(start_address), p2i(prev_last_addr));
 794 
 795     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 796     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 797     HeapWord* bottom_address = start_region->bottom();
 798 
 799     // Check for a range beginning in the same region in which the
 800     // previous one ended.
 801     if (start_region == prev_last_region) {
 802       bottom_address = prev_last_addr + 1;
 803     }
 804 
 805     // Verify that the regions were all marked as archive regions by
 806     // alloc_archive_regions.
 807     HeapRegion* curr_region = start_region;
 808     while (curr_region != NULL) {
 809       guarantee(curr_region->is_archive(),
 810                 "Expected archive region at index %u", curr_region->hrm_index());
 811       if (curr_region != last_region) {
 812         curr_region = _hrm.next_region_in_heap(curr_region);
 813       } else {
 814         curr_region = NULL;
 815       }
 816     }
 817 
 818     prev_last_addr = last_address;
 819     prev_last_region = last_region;
 820 
 821     // Fill the memory below the allocated range with dummy object(s),
 822     // if the region bottom does not match the range start, or if the previous
 823     // range ended within the same G1 region, and there is a gap.
 824     if (start_address != bottom_address) {
 825       size_t fill_size = pointer_delta(start_address, bottom_address);
 826       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 827       increase_used(fill_size * HeapWordSize);
 828     }
 829   }
 830 }
 831 
 832 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
 833                                                      uint* gc_count_before_ret,
 834                                                      uint* gclocker_retry_count_ret) {
 835   assert_heap_not_locked_and_not_at_safepoint();
 836   assert(!is_humongous(word_size), "attempt_allocation() should not "
 837          "be called for humongous allocation requests");
 838 
 839   AllocationContext_t context = AllocationContext::current();
 840   HeapWord* result = _allocator->attempt_allocation(word_size, context);
 841 
 842   if (result == NULL) {
 843     result = attempt_allocation_slow(word_size,
 844                                      context,
 845                                      gc_count_before_ret,
 846                                      gclocker_retry_count_ret);
 847   }
 848   assert_heap_not_locked();
 849   if (result != NULL) {
 850     dirty_young_block(result, word_size);
 851   }
 852   return result;
 853 }
 854 
 855 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
 856   assert(!is_init_completed(), "Expect to be called at JVM init time");
 857   assert(ranges != NULL, "MemRegion array NULL");
 858   assert(count != 0, "No MemRegions provided");
 859   MemRegion reserved = _hrm.reserved();
 860   HeapWord* prev_last_addr = NULL;
 861   HeapRegion* prev_last_region = NULL;
 862   size_t size_used = 0;
 863   size_t uncommitted_regions = 0;
 864 
 865   // For each Memregion, free the G1 regions that constitute it, and
 866   // notify mark-sweep that the range is no longer to be considered 'archive.'
 867   MutexLockerEx x(Heap_lock);
 868   for (size_t i = 0; i < count; i++) {
 869     HeapWord* start_address = ranges[i].start();
 870     HeapWord* last_address = ranges[i].last();
 871 
 872     assert(reserved.contains(start_address) && reserved.contains(last_address),
 873            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 874            p2i(start_address), p2i(last_address));
 875     assert(start_address > prev_last_addr,
 876            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 877            p2i(start_address), p2i(prev_last_addr));
 878     size_used += ranges[i].byte_size();
 879     prev_last_addr = last_address;
 880 
 881     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 882     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 883 
 884     // Check for ranges that start in the same G1 region in which the previous
 885     // range ended, and adjust the start address so we don't try to free
 886     // the same region again. If the current range is entirely within that
 887     // region, skip it.
 888     if (start_region == prev_last_region) {
 889       start_address = start_region->end();
 890       if (start_address > last_address) {
 891         continue;
 892       }
 893       start_region = _hrm.addr_to_region(start_address);
 894     }
 895     prev_last_region = last_region;
 896 
 897     // After verifying that each region was marked as an archive region by
 898     // alloc_archive_regions, set it free and empty and uncommit it.
 899     HeapRegion* curr_region = start_region;
 900     while (curr_region != NULL) {
 901       guarantee(curr_region->is_archive(),
 902                 "Expected archive region at index %u", curr_region->hrm_index());
 903       uint curr_index = curr_region->hrm_index();
 904       _old_set.remove(curr_region);
 905       curr_region->set_free();
 906       curr_region->set_top(curr_region->bottom());
 907       if (curr_region != last_region) {
 908         curr_region = _hrm.next_region_in_heap(curr_region);
 909       } else {
 910         curr_region = NULL;
 911       }
 912       _hrm.shrink_at(curr_index, 1);
 913       uncommitted_regions++;
 914     }
 915 
 916     // Notify mark-sweep that this is no longer an archive range.
 917     G1ArchiveAllocator::set_range_archive(ranges[i], false);
 918   }
 919 
 920   if (uncommitted_regions != 0) {
 921     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 922                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 923   }
 924   decrease_used(size_used);
 925 }
 926 
 927 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
 928                                                         uint* gc_count_before_ret,
 929                                                         uint* gclocker_retry_count_ret) {
 930   // The structure of this method has a lot of similarities to
 931   // attempt_allocation_slow(). The reason these two were not merged
 932   // into a single one is that such a method would require several "if
 933   // allocation is not humongous do this, otherwise do that"
 934   // conditional paths which would obscure its flow. In fact, an early
 935   // version of this code did use a unified method which was harder to
 936   // follow and, as a result, it had subtle bugs that were hard to
 937   // track down. So keeping these two methods separate allows each to
 938   // be more readable. It will be good to keep these two in sync as
 939   // much as possible.
 940 
 941   assert_heap_not_locked_and_not_at_safepoint();
 942   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 943          "should only be called for humongous allocations");
 944 
 945   // Humongous objects can exhaust the heap quickly, so we should check if we
 946   // need to start a marking cycle at each humongous object allocation. We do
 947   // the check before we do the actual allocation. The reason for doing it
 948   // before the allocation is that we avoid having to keep track of the newly
 949   // allocated memory while we do a GC.
 950   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
 951                                            word_size)) {
 952     collect(GCCause::_g1_humongous_allocation);
 953   }
 954 
 955   // We will loop until a) we manage to successfully perform the
 956   // allocation or b) we successfully schedule a collection which
 957   // fails to perform the allocation. b) is the only case when we'll
 958   // return NULL.
 959   HeapWord* result = NULL;
 960   for (int try_count = 1; /* we'll return */; try_count += 1) {
 961     bool should_try_gc;
 962     uint gc_count_before;
 963 
 964     {
 965       MutexLockerEx x(Heap_lock);
 966 
 967       // Given that humongous objects are not allocated in young
 968       // regions, we'll first try to do the allocation without doing a
 969       // collection hoping that there's enough space in the heap.
 970       result = humongous_obj_allocate(word_size, AllocationContext::current());
 971       if (result != NULL) {
 972         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 973         g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 974         return result;
 975       }
 976 
 977       if (GCLocker::is_active_and_needs_gc()) {
 978         should_try_gc = false;
 979       } else {
 980          // The GCLocker may not be active but the GCLocker initiated
 981         // GC may not yet have been performed (GCLocker::needs_gc()
 982         // returns true). In this case we do not try this GC and
 983         // wait until the GCLocker initiated GC is performed, and
 984         // then retry the allocation.
 985         if (GCLocker::needs_gc()) {
 986           should_try_gc = false;
 987         } else {
 988           // Read the GC count while still holding the Heap_lock.
 989           gc_count_before = total_collections();
 990           should_try_gc = true;
 991         }
 992       }
 993     }
 994 
 995     if (should_try_gc) {
 996       // If we failed to allocate the humongous object, we should try to
 997       // do a collection pause (if we're allowed) in case it reclaims
 998       // enough space for the allocation to succeed after the pause.
 999 
1000       bool succeeded;
1001       result = do_collection_pause(word_size, gc_count_before, &succeeded,
1002                                    GCCause::_g1_humongous_allocation);
1003       if (result != NULL) {
1004         assert(succeeded, "only way to get back a non-NULL result");
1005         return result;
1006       }
1007 
1008       if (succeeded) {
1009         // If we get here we successfully scheduled a collection which
1010         // failed to allocate. No point in trying to allocate
1011         // further. We'll just return NULL.
1012         MutexLockerEx x(Heap_lock);
1013         *gc_count_before_ret = total_collections();
1014         return NULL;
1015       }
1016     } else {
1017       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1018         MutexLockerEx x(Heap_lock);
1019         *gc_count_before_ret = total_collections();
1020         return NULL;
1021       }
1022       // The GCLocker is either active or the GCLocker initiated
1023       // GC has not yet been performed. Stall until it is and
1024       // then retry the allocation.
1025       GCLocker::stall_until_clear();
1026       (*gclocker_retry_count_ret) += 1;
1027     }
1028 
1029     // We can reach here if we were unsuccessful in scheduling a
1030     // collection (because another thread beat us to it) or if we were
1031     // stalled due to the GC locker. In either can we should retry the
1032     // allocation attempt in case another thread successfully
1033     // performed a collection and reclaimed enough space.  Give a
1034     // warning if we seem to be looping forever.
1035 
1036     if ((QueuedAllocationWarningCount > 0) &&
1037         (try_count % QueuedAllocationWarningCount == 0)) {
1038       log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
1039                       "retries %d times", try_count);
1040     }
1041   }
1042 
1043   ShouldNotReachHere();
1044   return NULL;
1045 }
1046 
1047 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1048                                                            AllocationContext_t context,
1049                                                            bool expect_null_mutator_alloc_region) {
1050   assert_at_safepoint(true /* should_be_vm_thread */);
1051   assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1052          "the current alloc region was unexpectedly found to be non-NULL");
1053 
1054   if (!is_humongous(word_size)) {
1055     return _allocator->attempt_allocation_locked(word_size, context);
1056   } else {
1057     HeapWord* result = humongous_obj_allocate(word_size, context);
1058     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1059       collector_state()->set_initiate_conc_mark_if_possible(true);
1060     }
1061     return result;
1062   }
1063 
1064   ShouldNotReachHere();
1065 }
1066 
1067 class PostCompactionPrinterClosure: public HeapRegionClosure {
1068 private:
1069   G1HRPrinter* _hr_printer;
1070 public:
1071   bool doHeapRegion(HeapRegion* hr) {
1072     assert(!hr->is_young(), "not expecting to find young regions");
1073     _hr_printer->post_compaction(hr);
1074     return false;
1075   }
1076 
1077   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1078     : _hr_printer(hr_printer) { }
1079 };
1080 
1081 void G1CollectedHeap::print_hrm_post_compaction() {
1082   if (_hr_printer.is_active()) {
1083     PostCompactionPrinterClosure cl(hr_printer());
1084     heap_region_iterate(&cl);
1085   }
1086 
1087 }
1088 
1089 void G1CollectedHeap::abort_concurrent_cycle() {
1090   // Note: When we have a more flexible GC logging framework that
1091   // allows us to add optional attributes to a GC log record we
1092   // could consider timing and reporting how long we wait in the
1093   // following two methods.
1094   wait_while_free_regions_coming();
1095   // If we start the compaction before the CM threads finish
1096   // scanning the root regions we might trip them over as we'll
1097   // be moving objects / updating references. So let's wait until
1098   // they are done. By telling them to abort, they should complete
1099   // early.
1100   _cm->root_regions()->abort();
1101   _cm->root_regions()->wait_until_scan_finished();
1102   append_secondary_free_list_if_not_empty_with_lock();
1103 
1104   // Disable discovery and empty the discovered lists
1105   // for the CM ref processor.
1106   ref_processor_cm()->disable_discovery();
1107   ref_processor_cm()->abandon_partial_discovery();
1108   ref_processor_cm()->verify_no_references_recorded();
1109 
1110   // Abandon current iterations of concurrent marking and concurrent
1111   // refinement, if any are in progress.
1112   concurrent_mark()->abort();
1113 }
1114 
1115 void G1CollectedHeap::prepare_heap_for_full_collection() {
1116   // Make sure we'll choose a new allocation region afterwards.
1117   _allocator->release_mutator_alloc_region();
1118   _allocator->abandon_gc_alloc_regions();
1119   g1_rem_set()->cleanupHRRS();
1120 
1121   // We may have added regions to the current incremental collection
1122   // set between the last GC or pause and now. We need to clear the
1123   // incremental collection set and then start rebuilding it afresh
1124   // after this full GC.
1125   abandon_collection_set(collection_set());
1126 
1127   tear_down_region_sets(false /* free_list_only */);
1128   collector_state()->set_gcs_are_young(true);
1129 }
1130 
1131 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1132   assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1133   assert(used() == recalculate_used(), "Should be equal");
1134   _verifier->verify_region_sets_optional();
1135   _verifier->verify_before_gc();
1136   _verifier->check_bitmaps("Full GC Start");
1137 }
1138 
1139 void G1CollectedHeap::prepare_heap_for_mutators() {
1140   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1141   ClassLoaderDataGraph::purge();
1142   MetaspaceAux::verify_metrics();
1143 
1144   // Prepare heap for normal collections.
1145   assert(num_free_regions() == 0, "we should not have added any free regions");
1146   rebuild_region_sets(false /* free_list_only */);
1147   abort_refinement();
1148   resize_if_necessary_after_full_collection();
1149 
1150   // Rebuild the strong code root lists for each region
1151   rebuild_strong_code_roots();
1152 
1153   // Start a new incremental collection set for the next pause
1154   start_new_collection_set();
1155 
1156   _allocator->init_mutator_alloc_region();
1157 
1158   // Post collection state updates.
1159   MetaspaceGC::compute_new_size();
1160 }
1161 
1162 void G1CollectedHeap::abort_refinement() {
1163   if (_hot_card_cache->use_cache()) {
1164     _hot_card_cache->reset_hot_cache();
1165   }
1166 
1167   // Discard all remembered set updates.
1168   JavaThread::dirty_card_queue_set().abandon_logs();
1169   assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1170 }
1171 
1172 void G1CollectedHeap::verify_after_full_collection() {
1173   check_gc_time_stamps();
1174   _hrm.verify_optional();
1175   _verifier->verify_region_sets_optional();
1176   _verifier->verify_after_gc();
1177   // Clear the previous marking bitmap, if needed for bitmap verification.
1178   // Note we cannot do this when we clear the next marking bitmap in
1179   // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1180   // objects marked during a full GC against the previous bitmap.
1181   // But we need to clear it before calling check_bitmaps below since
1182   // the full GC has compacted objects and updated TAMS but not updated
1183   // the prev bitmap.
1184   if (G1VerifyBitmaps) {
1185     GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1186     _cm->clear_prev_bitmap(workers());
1187   }
1188   _verifier->check_bitmaps("Full GC End");
1189 
1190   // At this point there should be no regions in the
1191   // entire heap tagged as young.
1192   assert(check_young_list_empty(), "young list should be empty at this point");
1193 
1194   // Note: since we've just done a full GC, concurrent
1195   // marking is no longer active. Therefore we need not
1196   // re-enable reference discovery for the CM ref processor.
1197   // That will be done at the start of the next marking cycle.
1198   // We also know that the STW processor should no longer
1199   // discover any new references.
1200   assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1201   assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1202   ref_processor_stw()->verify_no_references_recorded();
1203   ref_processor_cm()->verify_no_references_recorded();
1204 }
1205 
1206 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1207   // Post collection logging.
1208   // We should do this after we potentially resize the heap so
1209   // that all the COMMIT / UNCOMMIT events are generated before
1210   // the compaction events.
1211   print_hrm_post_compaction();
1212   heap_transition->print();
1213   print_heap_after_gc();
1214   print_heap_regions();
1215 #ifdef TRACESPINNING
1216   ParallelTaskTerminator::print_termination_counts();
1217 #endif
1218 }
1219 
1220 void G1CollectedHeap::do_full_collection_inner(G1FullGCScope* scope) {
1221   GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1222   g1_policy()->record_full_collection_start();
1223 
1224   print_heap_before_gc();
1225   print_heap_regions();
1226 
1227   abort_concurrent_cycle();
1228   verify_before_full_collection(scope->is_explicit_gc());
1229 
1230   gc_prologue(true);
1231   prepare_heap_for_full_collection();
1232 
1233   G1FullCollector collector(scope, ref_processor_stw(), concurrent_mark()->next_mark_bitmap(), workers()->active_workers());
1234   collector.prepare_collection();
1235   collector.collect();
1236   collector.complete_collection();
1237 
1238   prepare_heap_for_mutators();
1239 
1240   g1_policy()->record_full_collection_end();
1241   gc_epilogue(true);
1242 
1243   verify_after_full_collection();
1244 
1245   print_heap_after_full_collection(scope->heap_transition());
1246 }
1247 
1248 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1249                                          bool clear_all_soft_refs) {
1250   assert_at_safepoint(true /* should_be_vm_thread */);
1251 
1252   if (GCLocker::check_active_before_gc()) {
1253     // Full GC was not completed.
1254     return false;
1255   }
1256 
1257   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1258       collector_policy()->should_clear_all_soft_refs();
1259 
1260   G1FullGCScope scope(explicit_gc, do_clear_all_soft_refs);
1261   do_full_collection_inner(&scope);
1262 
1263   // Full collection was successfully completed.
1264   return true;
1265 }
1266 
1267 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1268   // Currently, there is no facility in the do_full_collection(bool) API to notify
1269   // the caller that the collection did not succeed (e.g., because it was locked
1270   // out by the GC locker). So, right now, we'll ignore the return value.
1271   bool dummy = do_full_collection(true,                /* explicit_gc */
1272                                   clear_all_soft_refs);
1273 }
1274 
1275 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1276   // Capacity, free and used after the GC counted as full regions to
1277   // include the waste in the following calculations.
1278   const size_t capacity_after_gc = capacity();
1279   const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1280 
1281   // This is enforced in arguments.cpp.
1282   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1283          "otherwise the code below doesn't make sense");
1284 
1285   // We don't have floating point command-line arguments
1286   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1287   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1288   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1289   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1290 
1291   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1292   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1293 
1294   // We have to be careful here as these two calculations can overflow
1295   // 32-bit size_t's.
1296   double used_after_gc_d = (double) used_after_gc;
1297   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1298   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1299 
1300   // Let's make sure that they are both under the max heap size, which
1301   // by default will make them fit into a size_t.
1302   double desired_capacity_upper_bound = (double) max_heap_size;
1303   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1304                                     desired_capacity_upper_bound);
1305   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1306                                     desired_capacity_upper_bound);
1307 
1308   // We can now safely turn them into size_t's.
1309   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1310   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1311 
1312   // This assert only makes sense here, before we adjust them
1313   // with respect to the min and max heap size.
1314   assert(minimum_desired_capacity <= maximum_desired_capacity,
1315          "minimum_desired_capacity = " SIZE_FORMAT ", "
1316          "maximum_desired_capacity = " SIZE_FORMAT,
1317          minimum_desired_capacity, maximum_desired_capacity);
1318 
1319   // Should not be greater than the heap max size. No need to adjust
1320   // it with respect to the heap min size as it's a lower bound (i.e.,
1321   // we'll try to make the capacity larger than it, not smaller).
1322   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1323   // Should not be less than the heap min size. No need to adjust it
1324   // with respect to the heap max size as it's an upper bound (i.e.,
1325   // we'll try to make the capacity smaller than it, not greater).
1326   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1327 
1328   if (capacity_after_gc < minimum_desired_capacity) {
1329     // Don't expand unless it's significant
1330     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1331 
1332     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1333                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1334                               "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1335                               capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1336 
1337     expand(expand_bytes, _workers);
1338 
1339     // No expansion, now see if we want to shrink
1340   } else if (capacity_after_gc > maximum_desired_capacity) {
1341     // Capacity too large, compute shrinking size
1342     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1343 
1344     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1345                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1346                               "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1347                               capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1348 
1349     shrink(shrink_bytes);
1350   }
1351 }
1352 
1353 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1354                                                             AllocationContext_t context,
1355                                                             bool do_gc,
1356                                                             bool clear_all_soft_refs,
1357                                                             bool expect_null_mutator_alloc_region,
1358                                                             bool* gc_succeeded) {
1359   *gc_succeeded = true;
1360   // Let's attempt the allocation first.
1361   HeapWord* result =
1362     attempt_allocation_at_safepoint(word_size,
1363                                     context,
1364                                     expect_null_mutator_alloc_region);
1365   if (result != NULL) {
1366     assert(*gc_succeeded, "sanity");
1367     return result;
1368   }
1369 
1370   // In a G1 heap, we're supposed to keep allocation from failing by
1371   // incremental pauses.  Therefore, at least for now, we'll favor
1372   // expansion over collection.  (This might change in the future if we can
1373   // do something smarter than full collection to satisfy a failed alloc.)
1374   result = expand_and_allocate(word_size, context);
1375   if (result != NULL) {
1376     assert(*gc_succeeded, "sanity");
1377     return result;
1378   }
1379 
1380   if (do_gc) {
1381     // Expansion didn't work, we'll try to do a Full GC.
1382     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1383                                        clear_all_soft_refs);
1384   }
1385 
1386   return NULL;
1387 }
1388 
1389 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1390                                                      AllocationContext_t context,
1391                                                      bool* succeeded) {
1392   assert_at_safepoint(true /* should_be_vm_thread */);
1393 
1394   // Attempts to allocate followed by Full GC.
1395   HeapWord* result =
1396     satisfy_failed_allocation_helper(word_size,
1397                                      context,
1398                                      true,  /* do_gc */
1399                                      false, /* clear_all_soft_refs */
1400                                      false, /* expect_null_mutator_alloc_region */
1401                                      succeeded);
1402 
1403   if (result != NULL || !*succeeded) {
1404     return result;
1405   }
1406 
1407   // Attempts to allocate followed by Full GC that will collect all soft references.
1408   result = satisfy_failed_allocation_helper(word_size,
1409                                             context,
1410                                             true, /* do_gc */
1411                                             true, /* clear_all_soft_refs */
1412                                             true, /* expect_null_mutator_alloc_region */
1413                                             succeeded);
1414 
1415   if (result != NULL || !*succeeded) {
1416     return result;
1417   }
1418 
1419   // Attempts to allocate, no GC
1420   result = satisfy_failed_allocation_helper(word_size,
1421                                             context,
1422                                             false, /* do_gc */
1423                                             false, /* clear_all_soft_refs */
1424                                             true,  /* expect_null_mutator_alloc_region */
1425                                             succeeded);
1426 
1427   if (result != NULL) {
1428     assert(*succeeded, "sanity");
1429     return result;
1430   }
1431 
1432   assert(!collector_policy()->should_clear_all_soft_refs(),
1433          "Flag should have been handled and cleared prior to this point");
1434 
1435   // What else?  We might try synchronous finalization later.  If the total
1436   // space available is large enough for the allocation, then a more
1437   // complete compaction phase than we've tried so far might be
1438   // appropriate.
1439   assert(*succeeded, "sanity");
1440   return NULL;
1441 }
1442 
1443 // Attempting to expand the heap sufficiently
1444 // to support an allocation of the given "word_size".  If
1445 // successful, perform the allocation and return the address of the
1446 // allocated block, or else "NULL".
1447 
1448 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1449   assert_at_safepoint(true /* should_be_vm_thread */);
1450 
1451   _verifier->verify_region_sets_optional();
1452 
1453   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1454   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1455                             word_size * HeapWordSize);
1456 
1457 
1458   if (expand(expand_bytes, _workers)) {
1459     _hrm.verify_optional();
1460     _verifier->verify_region_sets_optional();
1461     return attempt_allocation_at_safepoint(word_size,
1462                                            context,
1463                                            false /* expect_null_mutator_alloc_region */);
1464   }
1465   return NULL;
1466 }
1467 
1468 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1469   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1470   aligned_expand_bytes = align_up(aligned_expand_bytes,
1471                                        HeapRegion::GrainBytes);
1472 
1473   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1474                             expand_bytes, aligned_expand_bytes);
1475 
1476   if (is_maximal_no_gc()) {
1477     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1478     return false;
1479   }
1480 
1481   double expand_heap_start_time_sec = os::elapsedTime();
1482   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1483   assert(regions_to_expand > 0, "Must expand by at least one region");
1484 
1485   uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1486   if (expand_time_ms != NULL) {
1487     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1488   }
1489 
1490   if (expanded_by > 0) {
1491     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1492     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1493     g1_policy()->record_new_heap_size(num_regions());
1494   } else {
1495     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1496 
1497     // The expansion of the virtual storage space was unsuccessful.
1498     // Let's see if it was because we ran out of swap.
1499     if (G1ExitOnExpansionFailure &&
1500         _hrm.available() >= regions_to_expand) {
1501       // We had head room...
1502       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1503     }
1504   }
1505   return regions_to_expand > 0;
1506 }
1507 
1508 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1509   size_t aligned_shrink_bytes =
1510     ReservedSpace::page_align_size_down(shrink_bytes);
1511   aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1512                                          HeapRegion::GrainBytes);
1513   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1514 
1515   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1516   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1517 
1518 
1519   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",
1520                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1521   if (num_regions_removed > 0) {
1522     g1_policy()->record_new_heap_size(num_regions());
1523   } else {
1524     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1525   }
1526 }
1527 
1528 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1529   _verifier->verify_region_sets_optional();
1530 
1531   // We should only reach here at the end of a Full GC which means we
1532   // should not not be holding to any GC alloc regions. The method
1533   // below will make sure of that and do any remaining clean up.
1534   _allocator->abandon_gc_alloc_regions();
1535 
1536   // Instead of tearing down / rebuilding the free lists here, we
1537   // could instead use the remove_all_pending() method on free_list to
1538   // remove only the ones that we need to remove.
1539   tear_down_region_sets(true /* free_list_only */);
1540   shrink_helper(shrink_bytes);
1541   rebuild_region_sets(true /* free_list_only */);
1542 
1543   _hrm.verify_optional();
1544   _verifier->verify_region_sets_optional();
1545 }
1546 
1547 // Public methods.
1548 
1549 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1550   CollectedHeap(),
1551   _young_gen_sampling_thread(NULL),
1552   _collector_policy(collector_policy),
1553   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1554   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1555   _g1_policy(create_g1_policy(_gc_timer_stw)),
1556   _collection_set(this, _g1_policy),
1557   _dirty_card_queue_set(false),
1558   _is_alive_closure_cm(this),
1559   _is_alive_closure_stw(this),
1560   _ref_processor_cm(NULL),
1561   _ref_processor_stw(NULL),
1562   _bot(NULL),
1563   _hot_card_cache(NULL),
1564   _g1_rem_set(NULL),
1565   _cr(NULL),
1566   _g1mm(NULL),
1567   _preserved_marks_set(true /* in_c_heap */),
1568   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1569   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1570   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1571   _humongous_reclaim_candidates(),
1572   _has_humongous_reclaim_candidates(false),
1573   _archive_allocator(NULL),
1574   _free_regions_coming(false),
1575   _gc_time_stamp(0),
1576   _summary_bytes_used(0),
1577   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1578   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1579   _expand_heap_after_alloc_failure(true),
1580   _old_marking_cycles_started(0),
1581   _old_marking_cycles_completed(0),
1582   _in_cset_fast_test() {
1583 
1584   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1585                           /* are_GC_task_threads */true,
1586                           /* are_ConcurrentGC_threads */false);
1587   _workers->initialize_workers();
1588   _verifier = new G1HeapVerifier(this);
1589 
1590   _allocator = G1Allocator::create_allocator(this);
1591 
1592   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1593 
1594   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1595 
1596   // Override the default _filler_array_max_size so that no humongous filler
1597   // objects are created.
1598   _filler_array_max_size = _humongous_object_threshold_in_words;
1599 
1600   uint n_queues = ParallelGCThreads;
1601   _task_queues = new RefToScanQueueSet(n_queues);
1602 
1603   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1604 
1605   for (uint i = 0; i < n_queues; i++) {
1606     RefToScanQueue* q = new RefToScanQueue();
1607     q->initialize();
1608     _task_queues->register_queue(i, q);
1609     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1610   }
1611 
1612   // Initialize the G1EvacuationFailureALot counters and flags.
1613   NOT_PRODUCT(reset_evacuation_should_fail();)
1614 
1615   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1616 }
1617 
1618 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1619                                                                  size_t size,
1620                                                                  size_t translation_factor) {
1621   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1622   // Allocate a new reserved space, preferring to use large pages.
1623   ReservedSpace rs(size, preferred_page_size);
1624   G1RegionToSpaceMapper* result  =
1625     G1RegionToSpaceMapper::create_mapper(rs,
1626                                          size,
1627                                          rs.alignment(),
1628                                          HeapRegion::GrainBytes,
1629                                          translation_factor,
1630                                          mtGC);
1631 
1632   os::trace_page_sizes_for_requested_size(description,
1633                                           size,
1634                                           preferred_page_size,
1635                                           rs.alignment(),
1636                                           rs.base(),
1637                                           rs.size());
1638 
1639   return result;
1640 }
1641 
1642 jint G1CollectedHeap::initialize_concurrent_refinement() {
1643   jint ecode = JNI_OK;
1644   _cr = G1ConcurrentRefine::create(&ecode);
1645   return ecode;
1646 }
1647 
1648 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1649   _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1650   if (_young_gen_sampling_thread->osthread() == NULL) {
1651     vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1652     return JNI_ENOMEM;
1653   }
1654   return JNI_OK;
1655 }
1656 
1657 jint G1CollectedHeap::initialize() {
1658   CollectedHeap::pre_initialize();
1659   os::enable_vtime();
1660 
1661   // Necessary to satisfy locking discipline assertions.
1662 
1663   MutexLocker x(Heap_lock);
1664 
1665   // While there are no constraints in the GC code that HeapWordSize
1666   // be any particular value, there are multiple other areas in the
1667   // system which believe this to be true (e.g. oop->object_size in some
1668   // cases incorrectly returns the size in wordSize units rather than
1669   // HeapWordSize).
1670   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1671 
1672   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1673   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1674   size_t heap_alignment = collector_policy()->heap_alignment();
1675 
1676   // Ensure that the sizes are properly aligned.
1677   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1678   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1679   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1680 
1681   // Reserve the maximum.
1682 
1683   // When compressed oops are enabled, the preferred heap base
1684   // is calculated by subtracting the requested size from the
1685   // 32Gb boundary and using the result as the base address for
1686   // heap reservation. If the requested size is not aligned to
1687   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1688   // into the ReservedHeapSpace constructor) then the actual
1689   // base of the reserved heap may end up differing from the
1690   // address that was requested (i.e. the preferred heap base).
1691   // If this happens then we could end up using a non-optimal
1692   // compressed oops mode.
1693 
1694   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1695                                                  heap_alignment);
1696 
1697   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1698 
1699   // Create the barrier set for the entire reserved region.
1700   G1SATBCardTableLoggingModRefBS* bs
1701     = new G1SATBCardTableLoggingModRefBS(reserved_region());
1702   bs->initialize();
1703   assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1704   set_barrier_set(bs);
1705 
1706   // Create the hot card cache.
1707   _hot_card_cache = new G1HotCardCache(this);
1708 
1709   // Carve out the G1 part of the heap.
1710   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1711   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1712   G1RegionToSpaceMapper* heap_storage =
1713     G1RegionToSpaceMapper::create_mapper(g1_rs,
1714                                          g1_rs.size(),
1715                                          page_size,
1716                                          HeapRegion::GrainBytes,
1717                                          1,
1718                                          mtJavaHeap);
1719   os::trace_page_sizes("Heap",
1720                        collector_policy()->min_heap_byte_size(),
1721                        max_byte_size,
1722                        page_size,
1723                        heap_rs.base(),
1724                        heap_rs.size());
1725   heap_storage->set_mapping_changed_listener(&_listener);
1726 
1727   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1728   G1RegionToSpaceMapper* bot_storage =
1729     create_aux_memory_mapper("Block Offset Table",
1730                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1731                              G1BlockOffsetTable::heap_map_factor());
1732 
1733   G1RegionToSpaceMapper* cardtable_storage =
1734     create_aux_memory_mapper("Card Table",
1735                              G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1736                              G1SATBCardTableLoggingModRefBS::heap_map_factor());
1737 
1738   G1RegionToSpaceMapper* card_counts_storage =
1739     create_aux_memory_mapper("Card Counts Table",
1740                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1741                              G1CardCounts::heap_map_factor());
1742 
1743   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1744   G1RegionToSpaceMapper* prev_bitmap_storage =
1745     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1746   G1RegionToSpaceMapper* next_bitmap_storage =
1747     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1748 
1749   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1750   g1_barrier_set()->initialize(cardtable_storage);
1751   // Do later initialization work for concurrent refinement.
1752   _hot_card_cache->initialize(card_counts_storage);
1753 
1754   // 6843694 - ensure that the maximum region index can fit
1755   // in the remembered set structures.
1756   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1757   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1758 
1759   // Also create a G1 rem set.
1760   _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache);
1761   _g1_rem_set->initialize(max_capacity(), max_regions());
1762 
1763   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1764   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1765   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1766             "too many cards per region");
1767 
1768   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1769 
1770   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1771 
1772   {
1773     HeapWord* start = _hrm.reserved().start();
1774     HeapWord* end = _hrm.reserved().end();
1775     size_t granularity = HeapRegion::GrainBytes;
1776 
1777     _in_cset_fast_test.initialize(start, end, granularity);
1778     _humongous_reclaim_candidates.initialize(start, end, granularity);
1779   }
1780 
1781   // Create the G1ConcurrentMark data structure and thread.
1782   // (Must do this late, so that "max_regions" is defined.)
1783   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1784   if (_cm == NULL || !_cm->completed_initialization()) {
1785     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1786     return JNI_ENOMEM;
1787   }
1788   _cmThread = _cm->cm_thread();
1789 
1790   // Now expand into the initial heap size.
1791   if (!expand(init_byte_size, _workers)) {
1792     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1793     return JNI_ENOMEM;
1794   }
1795 
1796   // Perform any initialization actions delegated to the policy.
1797   g1_policy()->init(this, &_collection_set);
1798 
1799   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1800                                                SATB_Q_FL_lock,
1801                                                G1SATBProcessCompletedThreshold,
1802                                                Shared_SATB_Q_lock);
1803 
1804   jint ecode = initialize_concurrent_refinement();
1805   if (ecode != JNI_OK) {
1806     return ecode;
1807   }
1808 
1809   ecode = initialize_young_gen_sampling_thread();
1810   if (ecode != JNI_OK) {
1811     return ecode;
1812   }
1813 
1814   JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1815                                                 DirtyCardQ_FL_lock,
1816                                                 (int)concurrent_refine()->yellow_zone(),
1817                                                 (int)concurrent_refine()->red_zone(),
1818                                                 Shared_DirtyCardQ_lock,
1819                                                 NULL,  // fl_owner
1820                                                 true); // init_free_ids
1821 
1822   dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1823                                     DirtyCardQ_FL_lock,
1824                                     -1, // never trigger processing
1825                                     -1, // no limit on length
1826                                     Shared_DirtyCardQ_lock,
1827                                     &JavaThread::dirty_card_queue_set());
1828 
1829   // Here we allocate the dummy HeapRegion that is required by the
1830   // G1AllocRegion class.
1831   HeapRegion* dummy_region = _hrm.get_dummy_region();
1832 
1833   // We'll re-use the same region whether the alloc region will
1834   // require BOT updates or not and, if it doesn't, then a non-young
1835   // region will complain that it cannot support allocations without
1836   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1837   dummy_region->set_eden();
1838   // Make sure it's full.
1839   dummy_region->set_top(dummy_region->end());
1840   G1AllocRegion::setup(this, dummy_region);
1841 
1842   _allocator->init_mutator_alloc_region();
1843 
1844   // Do create of the monitoring and management support so that
1845   // values in the heap have been properly initialized.
1846   _g1mm = new G1MonitoringSupport(this);
1847 
1848   G1StringDedup::initialize();
1849 
1850   _preserved_marks_set.init(ParallelGCThreads);
1851 
1852   _collection_set.initialize(max_regions());
1853 
1854   return JNI_OK;
1855 }
1856 
1857 void G1CollectedHeap::stop() {
1858   // Stop all concurrent threads. We do this to make sure these threads
1859   // do not continue to execute and access resources (e.g. logging)
1860   // that are destroyed during shutdown.
1861   _cr->stop();
1862   _young_gen_sampling_thread->stop();
1863   _cmThread->stop();
1864   if (G1StringDedup::is_enabled()) {
1865     G1StringDedup::stop();
1866   }
1867 }
1868 
1869 void G1CollectedHeap::safepoint_synchronize_begin() {
1870   SuspendibleThreadSet::synchronize();
1871 }
1872 
1873 void G1CollectedHeap::safepoint_synchronize_end() {
1874   SuspendibleThreadSet::desynchronize();
1875 }
1876 
1877 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1878   return HeapRegion::max_region_size();
1879 }
1880 
1881 void G1CollectedHeap::post_initialize() {
1882   ref_processing_init();
1883 }
1884 
1885 void G1CollectedHeap::ref_processing_init() {
1886   // Reference processing in G1 currently works as follows:
1887   //
1888   // * There are two reference processor instances. One is
1889   //   used to record and process discovered references
1890   //   during concurrent marking; the other is used to
1891   //   record and process references during STW pauses
1892   //   (both full and incremental).
1893   // * Both ref processors need to 'span' the entire heap as
1894   //   the regions in the collection set may be dotted around.
1895   //
1896   // * For the concurrent marking ref processor:
1897   //   * Reference discovery is enabled at initial marking.
1898   //   * Reference discovery is disabled and the discovered
1899   //     references processed etc during remarking.
1900   //   * Reference discovery is MT (see below).
1901   //   * Reference discovery requires a barrier (see below).
1902   //   * Reference processing may or may not be MT
1903   //     (depending on the value of ParallelRefProcEnabled
1904   //     and ParallelGCThreads).
1905   //   * A full GC disables reference discovery by the CM
1906   //     ref processor and abandons any entries on it's
1907   //     discovered lists.
1908   //
1909   // * For the STW processor:
1910   //   * Non MT discovery is enabled at the start of a full GC.
1911   //   * Processing and enqueueing during a full GC is non-MT.
1912   //   * During a full GC, references are processed after marking.
1913   //
1914   //   * Discovery (may or may not be MT) is enabled at the start
1915   //     of an incremental evacuation pause.
1916   //   * References are processed near the end of a STW evacuation pause.
1917   //   * For both types of GC:
1918   //     * Discovery is atomic - i.e. not concurrent.
1919   //     * Reference discovery will not need a barrier.
1920 
1921   MemRegion mr = reserved_region();
1922 
1923   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1924 
1925   // Concurrent Mark ref processor
1926   _ref_processor_cm =
1927     new ReferenceProcessor(mr,    // span
1928                            mt_processing,
1929                                 // mt processing
1930                            ParallelGCThreads,
1931                                 // degree of mt processing
1932                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
1933                                 // mt discovery
1934                            MAX2(ParallelGCThreads, ConcGCThreads),
1935                                 // degree of mt discovery
1936                            false,
1937                                 // Reference discovery is not atomic
1938                            &_is_alive_closure_cm);
1939                                 // is alive closure
1940                                 // (for efficiency/performance)
1941 
1942   // STW ref processor
1943   _ref_processor_stw =
1944     new ReferenceProcessor(mr,    // span
1945                            mt_processing,
1946                                 // mt processing
1947                            ParallelGCThreads,
1948                                 // degree of mt processing
1949                            (ParallelGCThreads > 1),
1950                                 // mt discovery
1951                            ParallelGCThreads,
1952                                 // degree of mt discovery
1953                            true,
1954                                 // Reference discovery is atomic
1955                            &_is_alive_closure_stw);
1956                                 // is alive closure
1957                                 // (for efficiency/performance)
1958 }
1959 
1960 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1961   return _collector_policy;
1962 }
1963 
1964 size_t G1CollectedHeap::capacity() const {
1965   return _hrm.length() * HeapRegion::GrainBytes;
1966 }
1967 
1968 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1969   return _hrm.total_free_bytes();
1970 }
1971 
1972 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
1973   hr->reset_gc_time_stamp();
1974 }
1975 
1976 #ifndef PRODUCT
1977 
1978 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
1979 private:
1980   unsigned _gc_time_stamp;
1981   bool _failures;
1982 
1983 public:
1984   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
1985     _gc_time_stamp(gc_time_stamp), _failures(false) { }
1986 
1987   virtual bool doHeapRegion(HeapRegion* hr) {
1988     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
1989     if (_gc_time_stamp != region_gc_time_stamp) {
1990       log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
1991                             region_gc_time_stamp, _gc_time_stamp);
1992       _failures = true;
1993     }
1994     return false;
1995   }
1996 
1997   bool failures() { return _failures; }
1998 };
1999 
2000 void G1CollectedHeap::check_gc_time_stamps() {
2001   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2002   heap_region_iterate(&cl);
2003   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2004 }
2005 #endif // PRODUCT
2006 
2007 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
2008   _hot_card_cache->drain(cl, worker_i);
2009 }
2010 
2011 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
2012   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2013   size_t n_completed_buffers = 0;
2014   while (dcqs.apply_closure_during_gc(cl, worker_i)) {
2015     n_completed_buffers++;
2016   }
2017   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2018   dcqs.clear_n_completed_buffers();
2019   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2020 }
2021 
2022 // Computes the sum of the storage used by the various regions.
2023 size_t G1CollectedHeap::used() const {
2024   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
2025   if (_archive_allocator != NULL) {
2026     result += _archive_allocator->used();
2027   }
2028   return result;
2029 }
2030 
2031 size_t G1CollectedHeap::used_unlocked() const {
2032   return _summary_bytes_used;
2033 }
2034 
2035 class SumUsedClosure: public HeapRegionClosure {
2036   size_t _used;
2037 public:
2038   SumUsedClosure() : _used(0) {}
2039   bool doHeapRegion(HeapRegion* r) {
2040     _used += r->used();
2041     return false;
2042   }
2043   size_t result() { return _used; }
2044 };
2045 
2046 size_t G1CollectedHeap::recalculate_used() const {
2047   double recalculate_used_start = os::elapsedTime();
2048 
2049   SumUsedClosure blk;
2050   heap_region_iterate(&blk);
2051 
2052   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2053   return blk.result();
2054 }
2055 
2056 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2057   switch (cause) {
2058     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
2059     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
2060     case GCCause::_update_allocation_context_stats_inc: return true;
2061     case GCCause::_wb_conc_mark:                        return true;
2062     default :                                           return false;
2063   }
2064 }
2065 
2066 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2067   switch (cause) {
2068     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2069     case GCCause::_g1_humongous_allocation: return true;
2070     default:                                return is_user_requested_concurrent_full_gc(cause);
2071   }
2072 }
2073 
2074 #ifndef PRODUCT
2075 void G1CollectedHeap::allocate_dummy_regions() {
2076   // Let's fill up most of the region
2077   size_t word_size = HeapRegion::GrainWords - 1024;
2078   // And as a result the region we'll allocate will be humongous.
2079   guarantee(is_humongous(word_size), "sanity");
2080 
2081   // _filler_array_max_size is set to humongous object threshold
2082   // but temporarily change it to use CollectedHeap::fill_with_object().
2083   SizeTFlagSetting fs(_filler_array_max_size, word_size);
2084 
2085   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2086     // Let's use the existing mechanism for the allocation
2087     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2088                                                  AllocationContext::system());
2089     if (dummy_obj != NULL) {
2090       MemRegion mr(dummy_obj, word_size);
2091       CollectedHeap::fill_with_object(mr);
2092     } else {
2093       // If we can't allocate once, we probably cannot allocate
2094       // again. Let's get out of the loop.
2095       break;
2096     }
2097   }
2098 }
2099 #endif // !PRODUCT
2100 
2101 void G1CollectedHeap::increment_old_marking_cycles_started() {
2102   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2103          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2104          "Wrong marking cycle count (started: %d, completed: %d)",
2105          _old_marking_cycles_started, _old_marking_cycles_completed);
2106 
2107   _old_marking_cycles_started++;
2108 }
2109 
2110 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2111   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2112 
2113   // We assume that if concurrent == true, then the caller is a
2114   // concurrent thread that was joined the Suspendible Thread
2115   // Set. If there's ever a cheap way to check this, we should add an
2116   // assert here.
2117 
2118   // Given that this method is called at the end of a Full GC or of a
2119   // concurrent cycle, and those can be nested (i.e., a Full GC can
2120   // interrupt a concurrent cycle), the number of full collections
2121   // completed should be either one (in the case where there was no
2122   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2123   // behind the number of full collections started.
2124 
2125   // This is the case for the inner caller, i.e. a Full GC.
2126   assert(concurrent ||
2127          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2128          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2129          "for inner caller (Full GC): _old_marking_cycles_started = %u "
2130          "is inconsistent with _old_marking_cycles_completed = %u",
2131          _old_marking_cycles_started, _old_marking_cycles_completed);
2132 
2133   // This is the case for the outer caller, i.e. the concurrent cycle.
2134   assert(!concurrent ||
2135          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2136          "for outer caller (concurrent cycle): "
2137          "_old_marking_cycles_started = %u "
2138          "is inconsistent with _old_marking_cycles_completed = %u",
2139          _old_marking_cycles_started, _old_marking_cycles_completed);
2140 
2141   _old_marking_cycles_completed += 1;
2142 
2143   // We need to clear the "in_progress" flag in the CM thread before
2144   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2145   // is set) so that if a waiter requests another System.gc() it doesn't
2146   // incorrectly see that a marking cycle is still in progress.
2147   if (concurrent) {
2148     _cmThread->set_idle();
2149   }
2150 
2151   // This notify_all() will ensure that a thread that called
2152   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2153   // and it's waiting for a full GC to finish will be woken up. It is
2154   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2155   FullGCCount_lock->notify_all();
2156 }
2157 
2158 void G1CollectedHeap::collect(GCCause::Cause cause) {
2159   assert_heap_not_locked();
2160 
2161   uint gc_count_before;
2162   uint old_marking_count_before;
2163   uint full_gc_count_before;
2164   bool retry_gc;
2165 
2166   do {
2167     retry_gc = false;
2168 
2169     {
2170       MutexLocker ml(Heap_lock);
2171 
2172       // Read the GC count while holding the Heap_lock
2173       gc_count_before = total_collections();
2174       full_gc_count_before = total_full_collections();
2175       old_marking_count_before = _old_marking_cycles_started;
2176     }
2177 
2178     if (should_do_concurrent_full_gc(cause)) {
2179       // Schedule an initial-mark evacuation pause that will start a
2180       // concurrent cycle. We're setting word_size to 0 which means that
2181       // we are not requesting a post-GC allocation.
2182       VM_G1IncCollectionPause op(gc_count_before,
2183                                  0,     /* word_size */
2184                                  true,  /* should_initiate_conc_mark */
2185                                  g1_policy()->max_pause_time_ms(),
2186                                  cause);
2187       op.set_allocation_context(AllocationContext::current());
2188 
2189       VMThread::execute(&op);
2190       if (!op.pause_succeeded()) {
2191         if (old_marking_count_before == _old_marking_cycles_started) {
2192           retry_gc = op.should_retry_gc();
2193         } else {
2194           // A Full GC happened while we were trying to schedule the
2195           // initial-mark GC. No point in starting a new cycle given
2196           // that the whole heap was collected anyway.
2197         }
2198 
2199         if (retry_gc) {
2200           if (GCLocker::is_active_and_needs_gc()) {
2201             GCLocker::stall_until_clear();
2202           }
2203         }
2204       }
2205     } else {
2206       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2207           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2208 
2209         // Schedule a standard evacuation pause. We're setting word_size
2210         // to 0 which means that we are not requesting a post-GC allocation.
2211         VM_G1IncCollectionPause op(gc_count_before,
2212                                    0,     /* word_size */
2213                                    false, /* should_initiate_conc_mark */
2214                                    g1_policy()->max_pause_time_ms(),
2215                                    cause);
2216         VMThread::execute(&op);
2217       } else {
2218         // Schedule a Full GC.
2219         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2220         VMThread::execute(&op);
2221       }
2222     }
2223   } while (retry_gc);
2224 }
2225 
2226 bool G1CollectedHeap::is_in(const void* p) const {
2227   if (_hrm.reserved().contains(p)) {
2228     // Given that we know that p is in the reserved space,
2229     // heap_region_containing() should successfully
2230     // return the containing region.
2231     HeapRegion* hr = heap_region_containing(p);
2232     return hr->is_in(p);
2233   } else {
2234     return false;
2235   }
2236 }
2237 
2238 #ifdef ASSERT
2239 bool G1CollectedHeap::is_in_exact(const void* p) const {
2240   bool contains = reserved_region().contains(p);
2241   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2242   if (contains && available) {
2243     return true;
2244   } else {
2245     return false;
2246   }
2247 }
2248 #endif
2249 
2250 // Iteration functions.
2251 
2252 // Iterates an ObjectClosure over all objects within a HeapRegion.
2253 
2254 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2255   ObjectClosure* _cl;
2256 public:
2257   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2258   bool doHeapRegion(HeapRegion* r) {
2259     if (!r->is_continues_humongous()) {
2260       r->object_iterate(_cl);
2261     }
2262     return false;
2263   }
2264 };
2265 
2266 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2267   IterateObjectClosureRegionClosure blk(cl);
2268   heap_region_iterate(&blk);
2269 }
2270 
2271 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2272   _hrm.iterate(cl);
2273 }
2274 
2275 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2276                                                                  HeapRegionClaimer *hrclaimer,
2277                                                                  uint worker_id) const {
2278   _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2279 }
2280 
2281 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2282                                                          HeapRegionClaimer *hrclaimer) const {
2283   _hrm.par_iterate(cl, hrclaimer, 0);
2284 }
2285 
2286 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2287   _collection_set.iterate(cl);
2288 }
2289 
2290 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2291   _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2292 }
2293 
2294 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2295   HeapRegion* hr = heap_region_containing(addr);
2296   return hr->block_start(addr);
2297 }
2298 
2299 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2300   HeapRegion* hr = heap_region_containing(addr);
2301   return hr->block_size(addr);
2302 }
2303 
2304 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2305   HeapRegion* hr = heap_region_containing(addr);
2306   return hr->block_is_obj(addr);
2307 }
2308 
2309 bool G1CollectedHeap::supports_tlab_allocation() const {
2310   return true;
2311 }
2312 
2313 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2314   return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2315 }
2316 
2317 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2318   return _eden.length() * HeapRegion::GrainBytes;
2319 }
2320 
2321 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2322 // must be equal to the humongous object limit.
2323 size_t G1CollectedHeap::max_tlab_size() const {
2324   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2325 }
2326 
2327 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2328   AllocationContext_t context = AllocationContext::current();
2329   return _allocator->unsafe_max_tlab_alloc(context);
2330 }
2331 
2332 size_t G1CollectedHeap::max_capacity() const {
2333   return _hrm.reserved().byte_size();
2334 }
2335 
2336 jlong G1CollectedHeap::millis_since_last_gc() {
2337   // See the notes in GenCollectedHeap::millis_since_last_gc()
2338   // for more information about the implementation.
2339   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2340     _g1_policy->collection_pause_end_millis();
2341   if (ret_val < 0) {
2342     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2343       ". returning zero instead.", ret_val);
2344     return 0;
2345   }
2346   return ret_val;
2347 }
2348 
2349 void G1CollectedHeap::prepare_for_verify() {
2350   _verifier->prepare_for_verify();
2351 }
2352 
2353 void G1CollectedHeap::verify(VerifyOption vo) {
2354   _verifier->verify(vo);
2355 }
2356 
2357 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2358   return true;
2359 }
2360 
2361 const char* const* G1CollectedHeap::concurrent_phases() const {
2362   return _cmThread->concurrent_phases();
2363 }
2364 
2365 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2366   return _cmThread->request_concurrent_phase(phase);
2367 }
2368 
2369 class PrintRegionClosure: public HeapRegionClosure {
2370   outputStream* _st;
2371 public:
2372   PrintRegionClosure(outputStream* st) : _st(st) {}
2373   bool doHeapRegion(HeapRegion* r) {
2374     r->print_on(_st);
2375     return false;
2376   }
2377 };
2378 
2379 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2380                                        const HeapRegion* hr,
2381                                        const VerifyOption vo) const {
2382   switch (vo) {
2383   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2384   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2385   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2386   default:                            ShouldNotReachHere();
2387   }
2388   return false; // keep some compilers happy
2389 }
2390 
2391 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2392                                        const VerifyOption vo) const {
2393   switch (vo) {
2394   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2395   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2396   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2397   default:                            ShouldNotReachHere();
2398   }
2399   return false; // keep some compilers happy
2400 }
2401 
2402 void G1CollectedHeap::print_heap_regions() const {
2403   LogTarget(Trace, gc, heap, region) lt;
2404   if (lt.is_enabled()) {
2405     LogStream ls(lt);
2406     print_regions_on(&ls);
2407   }
2408 }
2409 
2410 void G1CollectedHeap::print_on(outputStream* st) const {
2411   st->print(" %-20s", "garbage-first heap");
2412   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2413             capacity()/K, used_unlocked()/K);
2414   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2415             p2i(_hrm.reserved().start()),
2416             p2i(_hrm.reserved().end()));
2417   st->cr();
2418   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2419   uint young_regions = young_regions_count();
2420   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2421             (size_t) young_regions * HeapRegion::GrainBytes / K);
2422   uint survivor_regions = survivor_regions_count();
2423   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2424             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2425   st->cr();
2426   MetaspaceAux::print_on(st);
2427 }
2428 
2429 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2430   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2431                "HS=humongous(starts), HC=humongous(continues), "
2432                "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2433                "AC=allocation context, "
2434                "TAMS=top-at-mark-start (previous, next)");
2435   PrintRegionClosure blk(st);
2436   heap_region_iterate(&blk);
2437 }
2438 
2439 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2440   print_on(st);
2441 
2442   // Print the per-region information.
2443   print_regions_on(st);
2444 }
2445 
2446 void G1CollectedHeap::print_on_error(outputStream* st) const {
2447   this->CollectedHeap::print_on_error(st);
2448 
2449   if (_cm != NULL) {
2450     st->cr();
2451     _cm->print_on_error(st);
2452   }
2453 }
2454 
2455 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2456   workers()->print_worker_threads_on(st);
2457   _cmThread->print_on(st);
2458   st->cr();
2459   _cm->print_worker_threads_on(st);
2460   _cr->print_threads_on(st);
2461   _young_gen_sampling_thread->print_on(st);
2462   if (G1StringDedup::is_enabled()) {
2463     G1StringDedup::print_worker_threads_on(st);
2464   }
2465 }
2466 
2467 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2468   workers()->threads_do(tc);
2469   tc->do_thread(_cmThread);
2470   _cm->threads_do(tc);
2471   _cr->threads_do(tc);
2472   tc->do_thread(_young_gen_sampling_thread);
2473   if (G1StringDedup::is_enabled()) {
2474     G1StringDedup::threads_do(tc);
2475   }
2476 }
2477 
2478 void G1CollectedHeap::print_tracing_info() const {
2479   g1_rem_set()->print_summary_info();
2480   concurrent_mark()->print_summary_info();
2481 }
2482 
2483 #ifndef PRODUCT
2484 // Helpful for debugging RSet issues.
2485 
2486 class PrintRSetsClosure : public HeapRegionClosure {
2487 private:
2488   const char* _msg;
2489   size_t _occupied_sum;
2490 
2491 public:
2492   bool doHeapRegion(HeapRegion* r) {
2493     HeapRegionRemSet* hrrs = r->rem_set();
2494     size_t occupied = hrrs->occupied();
2495     _occupied_sum += occupied;
2496 
2497     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2498     if (occupied == 0) {
2499       tty->print_cr("  RSet is empty");
2500     } else {
2501       hrrs->print();
2502     }
2503     tty->print_cr("----------");
2504     return false;
2505   }
2506 
2507   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2508     tty->cr();
2509     tty->print_cr("========================================");
2510     tty->print_cr("%s", msg);
2511     tty->cr();
2512   }
2513 
2514   ~PrintRSetsClosure() {
2515     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2516     tty->print_cr("========================================");
2517     tty->cr();
2518   }
2519 };
2520 
2521 void G1CollectedHeap::print_cset_rsets() {
2522   PrintRSetsClosure cl("Printing CSet RSets");
2523   collection_set_iterate(&cl);
2524 }
2525 
2526 void G1CollectedHeap::print_all_rsets() {
2527   PrintRSetsClosure cl("Printing All RSets");;
2528   heap_region_iterate(&cl);
2529 }
2530 #endif // PRODUCT
2531 
2532 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2533 
2534   size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2535   size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2536   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2537 
2538   size_t eden_capacity_bytes =
2539     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2540 
2541   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2542   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2543                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2544 }
2545 
2546 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2547   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2548                        stats->unused(), stats->used(), stats->region_end_waste(),
2549                        stats->regions_filled(), stats->direct_allocated(),
2550                        stats->failure_used(), stats->failure_waste());
2551 }
2552 
2553 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2554   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2555   gc_tracer->report_gc_heap_summary(when, heap_summary);
2556 
2557   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2558   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2559 }
2560 
2561 G1CollectedHeap* G1CollectedHeap::heap() {
2562   CollectedHeap* heap = Universe::heap();
2563   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2564   assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2565   return (G1CollectedHeap*)heap;
2566 }
2567 
2568 void G1CollectedHeap::gc_prologue(bool full) {
2569   // always_do_update_barrier = false;
2570   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2571 
2572   // This summary needs to be printed before incrementing total collections.
2573   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2574 
2575   // Update common counters.
2576   increment_total_collections(full /* full gc */);
2577   if (full) {
2578     increment_old_marking_cycles_started();
2579     reset_gc_time_stamp();
2580   } else {
2581     increment_gc_time_stamp();
2582   }
2583 
2584   // Fill TLAB's and such
2585   double start = os::elapsedTime();
2586   accumulate_statistics_all_tlabs();
2587   ensure_parsability(true);
2588   g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2589 }
2590 
2591 void G1CollectedHeap::gc_epilogue(bool full) {
2592   // Update common counters.
2593   if (full) {
2594     // Update the number of full collections that have been completed.
2595     increment_old_marking_cycles_completed(false /* concurrent */);
2596   }
2597 
2598   // We are at the end of the GC. Total collections has already been increased.
2599   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2600 
2601   // FIXME: what is this about?
2602   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2603   // is set.
2604 #if COMPILER2_OR_JVMCI
2605   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2606 #endif
2607   // always_do_update_barrier = true;
2608 
2609   double start = os::elapsedTime();
2610   resize_all_tlabs();
2611   g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2612 
2613   allocation_context_stats().update(full);
2614 
2615   MemoryService::track_memory_usage();
2616   // We have just completed a GC. Update the soft reference
2617   // policy with the new heap occupancy
2618   Universe::update_heap_info_at_gc();
2619 }
2620 
2621 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2622                                                uint gc_count_before,
2623                                                bool* succeeded,
2624                                                GCCause::Cause gc_cause) {
2625   assert_heap_not_locked_and_not_at_safepoint();
2626   VM_G1IncCollectionPause op(gc_count_before,
2627                              word_size,
2628                              false, /* should_initiate_conc_mark */
2629                              g1_policy()->max_pause_time_ms(),
2630                              gc_cause);
2631 
2632   op.set_allocation_context(AllocationContext::current());
2633   VMThread::execute(&op);
2634 
2635   HeapWord* result = op.result();
2636   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2637   assert(result == NULL || ret_succeeded,
2638          "the result should be NULL if the VM did not succeed");
2639   *succeeded = ret_succeeded;
2640 
2641   assert_heap_not_locked();
2642   return result;
2643 }
2644 
2645 void
2646 G1CollectedHeap::doConcurrentMark() {
2647   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2648   if (!_cmThread->in_progress()) {
2649     _cmThread->set_started();
2650     CGC_lock->notify();
2651   }
2652 }
2653 
2654 size_t G1CollectedHeap::pending_card_num() {
2655   size_t extra_cards = 0;
2656   JavaThread *curr = Threads::first();
2657   while (curr != NULL) {
2658     DirtyCardQueue& dcq = curr->dirty_card_queue();
2659     extra_cards += dcq.size();
2660     curr = curr->next();
2661   }
2662   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2663   size_t buffer_size = dcqs.buffer_size();
2664   size_t buffer_num = dcqs.completed_buffers_num();
2665 
2666   return buffer_size * buffer_num + extra_cards;
2667 }
2668 
2669 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2670  private:
2671   size_t _total_humongous;
2672   size_t _candidate_humongous;
2673 
2674   DirtyCardQueue _dcq;
2675 
2676   // We don't nominate objects with many remembered set entries, on
2677   // the assumption that such objects are likely still live.
2678   bool is_remset_small(HeapRegion* region) const {
2679     HeapRegionRemSet* const rset = region->rem_set();
2680     return G1EagerReclaimHumongousObjectsWithStaleRefs
2681       ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2682       : rset->is_empty();
2683   }
2684 
2685   bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2686     assert(region->is_starts_humongous(), "Must start a humongous object");
2687 
2688     oop obj = oop(region->bottom());
2689 
2690     // Dead objects cannot be eager reclaim candidates. Due to class
2691     // unloading it is unsafe to query their classes so we return early.
2692     if (heap->is_obj_dead(obj, region)) {
2693       return false;
2694     }
2695 
2696     // Candidate selection must satisfy the following constraints
2697     // while concurrent marking is in progress:
2698     //
2699     // * In order to maintain SATB invariants, an object must not be
2700     // reclaimed if it was allocated before the start of marking and
2701     // has not had its references scanned.  Such an object must have
2702     // its references (including type metadata) scanned to ensure no
2703     // live objects are missed by the marking process.  Objects
2704     // allocated after the start of concurrent marking don't need to
2705     // be scanned.
2706     //
2707     // * An object must not be reclaimed if it is on the concurrent
2708     // mark stack.  Objects allocated after the start of concurrent
2709     // marking are never pushed on the mark stack.
2710     //
2711     // Nominating only objects allocated after the start of concurrent
2712     // marking is sufficient to meet both constraints.  This may miss
2713     // some objects that satisfy the constraints, but the marking data
2714     // structures don't support efficiently performing the needed
2715     // additional tests or scrubbing of the mark stack.
2716     //
2717     // However, we presently only nominate is_typeArray() objects.
2718     // A humongous object containing references induces remembered
2719     // set entries on other regions.  In order to reclaim such an
2720     // object, those remembered sets would need to be cleaned up.
2721     //
2722     // We also treat is_typeArray() objects specially, allowing them
2723     // to be reclaimed even if allocated before the start of
2724     // concurrent mark.  For this we rely on mark stack insertion to
2725     // exclude is_typeArray() objects, preventing reclaiming an object
2726     // that is in the mark stack.  We also rely on the metadata for
2727     // such objects to be built-in and so ensured to be kept live.
2728     // Frequent allocation and drop of large binary blobs is an
2729     // important use case for eager reclaim, and this special handling
2730     // may reduce needed headroom.
2731 
2732     return obj->is_typeArray() && is_remset_small(region);
2733   }
2734 
2735  public:
2736   RegisterHumongousWithInCSetFastTestClosure()
2737   : _total_humongous(0),
2738     _candidate_humongous(0),
2739     _dcq(&JavaThread::dirty_card_queue_set()) {
2740   }
2741 
2742   virtual bool doHeapRegion(HeapRegion* r) {
2743     if (!r->is_starts_humongous()) {
2744       return false;
2745     }
2746     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2747 
2748     bool is_candidate = humongous_region_is_candidate(g1h, r);
2749     uint rindex = r->hrm_index();
2750     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2751     if (is_candidate) {
2752       _candidate_humongous++;
2753       g1h->register_humongous_region_with_cset(rindex);
2754       // Is_candidate already filters out humongous object with large remembered sets.
2755       // If we have a humongous object with a few remembered sets, we simply flush these
2756       // remembered set entries into the DCQS. That will result in automatic
2757       // re-evaluation of their remembered set entries during the following evacuation
2758       // phase.
2759       if (!r->rem_set()->is_empty()) {
2760         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2761                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2762         G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
2763         HeapRegionRemSetIterator hrrs(r->rem_set());
2764         size_t card_index;
2765         while (hrrs.has_next(card_index)) {
2766           jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
2767           // The remembered set might contain references to already freed
2768           // regions. Filter out such entries to avoid failing card table
2769           // verification.
2770           if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
2771             if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
2772               *card_ptr = CardTableModRefBS::dirty_card_val();
2773               _dcq.enqueue(card_ptr);
2774             }
2775           }
2776         }
2777         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2778                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2779                hrrs.n_yielded(), r->rem_set()->occupied());
2780         r->rem_set()->clear_locked();
2781       }
2782       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2783     }
2784     _total_humongous++;
2785 
2786     return false;
2787   }
2788 
2789   size_t total_humongous() const { return _total_humongous; }
2790   size_t candidate_humongous() const { return _candidate_humongous; }
2791 
2792   void flush_rem_set_entries() { _dcq.flush(); }
2793 };
2794 
2795 void G1CollectedHeap::register_humongous_regions_with_cset() {
2796   if (!G1EagerReclaimHumongousObjects) {
2797     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2798     return;
2799   }
2800   double time = os::elapsed_counter();
2801 
2802   // Collect reclaim candidate information and register candidates with cset.
2803   RegisterHumongousWithInCSetFastTestClosure cl;
2804   heap_region_iterate(&cl);
2805 
2806   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2807   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2808                                                                   cl.total_humongous(),
2809                                                                   cl.candidate_humongous());
2810   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2811 
2812   // Finally flush all remembered set entries to re-check into the global DCQS.
2813   cl.flush_rem_set_entries();
2814 }
2815 
2816 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2817   public:
2818     bool doHeapRegion(HeapRegion* hr) {
2819       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2820         hr->verify_rem_set();
2821       }
2822       return false;
2823     }
2824 };
2825 
2826 uint G1CollectedHeap::num_task_queues() const {
2827   return _task_queues->size();
2828 }
2829 
2830 #if TASKQUEUE_STATS
2831 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2832   st->print_raw_cr("GC Task Stats");
2833   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2834   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2835 }
2836 
2837 void G1CollectedHeap::print_taskqueue_stats() const {
2838   if (!log_is_enabled(Trace, gc, task, stats)) {
2839     return;
2840   }
2841   Log(gc, task, stats) log;
2842   ResourceMark rm;
2843   LogStream ls(log.trace());
2844   outputStream* st = &ls;
2845 
2846   print_taskqueue_stats_hdr(st);
2847 
2848   TaskQueueStats totals;
2849   const uint n = num_task_queues();
2850   for (uint i = 0; i < n; ++i) {
2851     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2852     totals += task_queue(i)->stats;
2853   }
2854   st->print_raw("tot "); totals.print(st); st->cr();
2855 
2856   DEBUG_ONLY(totals.verify());
2857 }
2858 
2859 void G1CollectedHeap::reset_taskqueue_stats() {
2860   const uint n = num_task_queues();
2861   for (uint i = 0; i < n; ++i) {
2862     task_queue(i)->stats.reset();
2863   }
2864 }
2865 #endif // TASKQUEUE_STATS
2866 
2867 void G1CollectedHeap::wait_for_root_region_scanning() {
2868   double scan_wait_start = os::elapsedTime();
2869   // We have to wait until the CM threads finish scanning the
2870   // root regions as it's the only way to ensure that all the
2871   // objects on them have been correctly scanned before we start
2872   // moving them during the GC.
2873   bool waited = _cm->root_regions()->wait_until_scan_finished();
2874   double wait_time_ms = 0.0;
2875   if (waited) {
2876     double scan_wait_end = os::elapsedTime();
2877     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2878   }
2879   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2880 }
2881 
2882 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2883 private:
2884   G1HRPrinter* _hr_printer;
2885 public:
2886   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2887 
2888   virtual bool doHeapRegion(HeapRegion* r) {
2889     _hr_printer->cset(r);
2890     return false;
2891   }
2892 };
2893 
2894 void G1CollectedHeap::start_new_collection_set() {
2895   collection_set()->start_incremental_building();
2896 
2897   clear_cset_fast_test();
2898 
2899   guarantee(_eden.length() == 0, "eden should have been cleared");
2900   g1_policy()->transfer_survivors_to_cset(survivor());
2901 }
2902 
2903 bool
2904 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2905   assert_at_safepoint(true /* should_be_vm_thread */);
2906   guarantee(!is_gc_active(), "collection is not reentrant");
2907 
2908   if (GCLocker::check_active_before_gc()) {
2909     return false;
2910   }
2911 
2912   _gc_timer_stw->register_gc_start();
2913 
2914   GCIdMark gc_id_mark;
2915   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2916 
2917   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2918   ResourceMark rm;
2919 
2920   g1_policy()->note_gc_start();
2921 
2922   wait_for_root_region_scanning();
2923 
2924   print_heap_before_gc();
2925   print_heap_regions();
2926   trace_heap_before_gc(_gc_tracer_stw);
2927 
2928   _verifier->verify_region_sets_optional();
2929   _verifier->verify_dirty_young_regions();
2930 
2931   // We should not be doing initial mark unless the conc mark thread is running
2932   if (!_cmThread->should_terminate()) {
2933     // This call will decide whether this pause is an initial-mark
2934     // pause. If it is, during_initial_mark_pause() will return true
2935     // for the duration of this pause.
2936     g1_policy()->decide_on_conc_mark_initiation();
2937   }
2938 
2939   // We do not allow initial-mark to be piggy-backed on a mixed GC.
2940   assert(!collector_state()->during_initial_mark_pause() ||
2941           collector_state()->gcs_are_young(), "sanity");
2942 
2943   // We also do not allow mixed GCs during marking.
2944   assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
2945 
2946   // Record whether this pause is an initial mark. When the current
2947   // thread has completed its logging output and it's safe to signal
2948   // the CM thread, the flag's value in the policy has been reset.
2949   bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
2950 
2951   // Inner scope for scope based logging, timers, and stats collection
2952   {
2953     EvacuationInfo evacuation_info;
2954 
2955     if (collector_state()->during_initial_mark_pause()) {
2956       // We are about to start a marking cycle, so we increment the
2957       // full collection counter.
2958       increment_old_marking_cycles_started();
2959       _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2960     }
2961 
2962     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2963 
2964     GCTraceCPUTime tcpu;
2965 
2966     FormatBuffer<> gc_string("Pause ");
2967     if (collector_state()->during_initial_mark_pause()) {
2968       gc_string.append("Initial Mark");
2969     } else if (collector_state()->gcs_are_young()) {
2970       gc_string.append("Young");
2971     } else {
2972       gc_string.append("Mixed");
2973     }
2974     GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2975 
2976     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2977                                                                   workers()->active_workers(),
2978                                                                   Threads::number_of_non_daemon_threads());
2979     workers()->update_active_workers(active_workers);
2980     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2981 
2982     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2983     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
2984 
2985     // If the secondary_free_list is not empty, append it to the
2986     // free_list. No need to wait for the cleanup operation to finish;
2987     // the region allocation code will check the secondary_free_list
2988     // and wait if necessary. If the G1StressConcRegionFreeing flag is
2989     // set, skip this step so that the region allocation code has to
2990     // get entries from the secondary_free_list.
2991     if (!G1StressConcRegionFreeing) {
2992       append_secondary_free_list_if_not_empty_with_lock();
2993     }
2994 
2995     G1HeapTransition heap_transition(this);
2996     size_t heap_used_bytes_before_gc = used();
2997 
2998     // Don't dynamically change the number of GC threads this early.  A value of
2999     // 0 is used to indicate serial work.  When parallel work is done,
3000     // it will be set.
3001 
3002     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3003       IsGCActiveMark x;
3004 
3005       gc_prologue(false);
3006 
3007       if (VerifyRememberedSets) {
3008         log_info(gc, verify)("[Verifying RemSets before GC]");
3009         VerifyRegionRemSetClosure v_cl;
3010         heap_region_iterate(&v_cl);
3011       }
3012 
3013       _verifier->verify_before_gc();
3014 
3015       _verifier->check_bitmaps("GC Start");
3016 
3017 #if COMPILER2_OR_JVMCI
3018       DerivedPointerTable::clear();
3019 #endif
3020 
3021       // Please see comment in g1CollectedHeap.hpp and
3022       // G1CollectedHeap::ref_processing_init() to see how
3023       // reference processing currently works in G1.
3024 
3025       // Enable discovery in the STW reference processor
3026       if (g1_policy()->should_process_references()) {
3027         ref_processor_stw()->enable_discovery();
3028       } else {
3029         ref_processor_stw()->disable_discovery();
3030       }
3031 
3032       {
3033         // We want to temporarily turn off discovery by the
3034         // CM ref processor, if necessary, and turn it back on
3035         // on again later if we do. Using a scoped
3036         // NoRefDiscovery object will do this.
3037         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3038 
3039         // Forget the current alloc region (we might even choose it to be part
3040         // of the collection set!).
3041         _allocator->release_mutator_alloc_region();
3042 
3043         // This timing is only used by the ergonomics to handle our pause target.
3044         // It is unclear why this should not include the full pause. We will
3045         // investigate this in CR 7178365.
3046         //
3047         // Preserving the old comment here if that helps the investigation:
3048         //
3049         // The elapsed time induced by the start time below deliberately elides
3050         // the possible verification above.
3051         double sample_start_time_sec = os::elapsedTime();
3052 
3053         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3054 
3055         if (collector_state()->during_initial_mark_pause()) {
3056           concurrent_mark()->checkpoint_roots_initial_pre();
3057         }
3058 
3059         g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
3060 
3061         evacuation_info.set_collectionset_regions(collection_set()->region_length());
3062 
3063         // Make sure the remembered sets are up to date. This needs to be
3064         // done before register_humongous_regions_with_cset(), because the
3065         // remembered sets are used there to choose eager reclaim candidates.
3066         // If the remembered sets are not up to date we might miss some
3067         // entries that need to be handled.
3068         g1_rem_set()->cleanupHRRS();
3069 
3070         register_humongous_regions_with_cset();
3071 
3072         assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3073 
3074         // We call this after finalize_cset() to
3075         // ensure that the CSet has been finalized.
3076         _cm->verify_no_cset_oops();
3077 
3078         if (_hr_printer.is_active()) {
3079           G1PrintCollectionSetClosure cl(&_hr_printer);
3080           _collection_set.iterate(&cl);
3081         }
3082 
3083         // Initialize the GC alloc regions.
3084         _allocator->init_gc_alloc_regions(evacuation_info);
3085 
3086         G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3087         pre_evacuate_collection_set();
3088 
3089         // Actually do the work...
3090         evacuate_collection_set(evacuation_info, &per_thread_states);
3091 
3092         post_evacuate_collection_set(evacuation_info, &per_thread_states);
3093 
3094         const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3095         free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
3096 
3097         eagerly_reclaim_humongous_regions();
3098 
3099         record_obj_copy_mem_stats();
3100         _survivor_evac_stats.adjust_desired_plab_sz();
3101         _old_evac_stats.adjust_desired_plab_sz();
3102 
3103         double start = os::elapsedTime();
3104         start_new_collection_set();
3105         g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
3106 
3107         if (evacuation_failed()) {
3108           set_used(recalculate_used());
3109           if (_archive_allocator != NULL) {
3110             _archive_allocator->clear_used();
3111           }
3112           for (uint i = 0; i < ParallelGCThreads; i++) {
3113             if (_evacuation_failed_info_array[i].has_failed()) {
3114               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3115             }
3116           }
3117         } else {
3118           // The "used" of the the collection set have already been subtracted
3119           // when they were freed.  Add in the bytes evacuated.
3120           increase_used(g1_policy()->bytes_copied_during_gc());
3121         }
3122 
3123         if (collector_state()->during_initial_mark_pause()) {
3124           // We have to do this before we notify the CM threads that
3125           // they can start working to make sure that all the
3126           // appropriate initialization is done on the CM object.
3127           concurrent_mark()->checkpoint_roots_initial_post();
3128           collector_state()->set_mark_in_progress(true);
3129           // Note that we don't actually trigger the CM thread at
3130           // this point. We do that later when we're sure that
3131           // the current thread has completed its logging output.
3132         }
3133 
3134         allocate_dummy_regions();
3135 
3136         _allocator->init_mutator_alloc_region();
3137 
3138         {
3139           size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3140           if (expand_bytes > 0) {
3141             size_t bytes_before = capacity();
3142             // No need for an ergo logging here,
3143             // expansion_amount() does this when it returns a value > 0.
3144             double expand_ms;
3145             if (!expand(expand_bytes, _workers, &expand_ms)) {
3146               // We failed to expand the heap. Cannot do anything about it.
3147             }
3148             g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3149           }
3150         }
3151 
3152         // We redo the verification but now wrt to the new CSet which
3153         // has just got initialized after the previous CSet was freed.
3154         _cm->verify_no_cset_oops();
3155 
3156         // This timing is only used by the ergonomics to handle our pause target.
3157         // It is unclear why this should not include the full pause. We will
3158         // investigate this in CR 7178365.
3159         double sample_end_time_sec = os::elapsedTime();
3160         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3161         size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
3162         g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3163 
3164         evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3165         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3166 
3167         if (VerifyRememberedSets) {
3168           log_info(gc, verify)("[Verifying RemSets after GC]");
3169           VerifyRegionRemSetClosure v_cl;
3170           heap_region_iterate(&v_cl);
3171         }
3172 
3173         _verifier->verify_after_gc();
3174         _verifier->check_bitmaps("GC End");
3175 
3176         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3177         ref_processor_stw()->verify_no_references_recorded();
3178 
3179         // CM reference discovery will be re-enabled if necessary.
3180       }
3181 
3182 #ifdef TRACESPINNING
3183       ParallelTaskTerminator::print_termination_counts();
3184 #endif
3185 
3186       gc_epilogue(false);
3187     }
3188 
3189     // Print the remainder of the GC log output.
3190     if (evacuation_failed()) {
3191       log_info(gc)("To-space exhausted");
3192     }
3193 
3194     g1_policy()->print_phases();
3195     heap_transition.print();
3196 
3197     // It is not yet to safe to tell the concurrent mark to
3198     // start as we have some optional output below. We don't want the
3199     // output from the concurrent mark thread interfering with this
3200     // logging output either.
3201 
3202     _hrm.verify_optional();
3203     _verifier->verify_region_sets_optional();
3204 
3205     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3206     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3207 
3208     print_heap_after_gc();
3209     print_heap_regions();
3210     trace_heap_after_gc(_gc_tracer_stw);
3211 
3212     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3213     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3214     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3215     // before any GC notifications are raised.
3216     g1mm()->update_sizes();
3217 
3218     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3219     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3220     _gc_timer_stw->register_gc_end();
3221     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3222   }
3223   // It should now be safe to tell the concurrent mark thread to start
3224   // without its logging output interfering with the logging output
3225   // that came from the pause.
3226 
3227   if (should_start_conc_mark) {
3228     // CAUTION: after the doConcurrentMark() call below,
3229     // the concurrent marking thread(s) could be running
3230     // concurrently with us. Make sure that anything after
3231     // this point does not assume that we are the only GC thread
3232     // running. Note: of course, the actual marking work will
3233     // not start until the safepoint itself is released in
3234     // SuspendibleThreadSet::desynchronize().
3235     doConcurrentMark();
3236   }
3237 
3238   return true;
3239 }
3240 
3241 void G1CollectedHeap::remove_self_forwarding_pointers() {
3242   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3243   workers()->run_task(&rsfp_task);
3244 }
3245 
3246 void G1CollectedHeap::restore_after_evac_failure() {
3247   double remove_self_forwards_start = os::elapsedTime();
3248 
3249   remove_self_forwarding_pointers();
3250   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3251   _preserved_marks_set.restore(&task_executor);
3252 
3253   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3254 }
3255 
3256 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3257   if (!_evacuation_failed) {
3258     _evacuation_failed = true;
3259   }
3260 
3261   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3262   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3263 }
3264 
3265 bool G1ParEvacuateFollowersClosure::offer_termination() {
3266   G1ParScanThreadState* const pss = par_scan_state();
3267   start_term_time();
3268   const bool res = terminator()->offer_termination();
3269   end_term_time();
3270   return res;
3271 }
3272 
3273 void G1ParEvacuateFollowersClosure::do_void() {
3274   G1ParScanThreadState* const pss = par_scan_state();
3275   pss->trim_queue();
3276   do {
3277     pss->steal_and_trim_queue(queues());
3278   } while (!offer_termination());
3279 }
3280 
3281 class G1ParTask : public AbstractGangTask {
3282 protected:
3283   G1CollectedHeap*         _g1h;
3284   G1ParScanThreadStateSet* _pss;
3285   RefToScanQueueSet*       _queues;
3286   G1RootProcessor*         _root_processor;
3287   ParallelTaskTerminator   _terminator;
3288   uint                     _n_workers;
3289 
3290 public:
3291   G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3292     : AbstractGangTask("G1 collection"),
3293       _g1h(g1h),
3294       _pss(per_thread_states),
3295       _queues(task_queues),
3296       _root_processor(root_processor),
3297       _terminator(n_workers, _queues),
3298       _n_workers(n_workers)
3299   {}
3300 
3301   void work(uint worker_id) {
3302     if (worker_id >= _n_workers) return;  // no work needed this round
3303 
3304     double start_sec = os::elapsedTime();
3305     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3306 
3307     {
3308       ResourceMark rm;
3309       HandleMark   hm;
3310 
3311       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
3312 
3313       G1ParScanThreadState*           pss = _pss->state_for_worker(worker_id);
3314       pss->set_ref_processor(rp);
3315 
3316       double start_strong_roots_sec = os::elapsedTime();
3317 
3318       _root_processor->evacuate_roots(pss->closures(), worker_id);
3319 
3320       // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3321       // treating the nmethods visited to act as roots for concurrent marking.
3322       // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3323       // objects copied by the current evacuation.
3324       _g1h->g1_rem_set()->oops_into_collection_set_do(pss,
3325                                                       pss->closures()->weak_codeblobs(),
3326                                                       worker_id);
3327 
3328       double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3329 
3330       double term_sec = 0.0;
3331       size_t evac_term_attempts = 0;
3332       {
3333         double start = os::elapsedTime();
3334         G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3335         evac.do_void();
3336 
3337         evac_term_attempts = evac.term_attempts();
3338         term_sec = evac.term_time();
3339         double elapsed_sec = os::elapsedTime() - start;
3340         _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3341         _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3342         _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3343       }
3344 
3345       assert(pss->queue_is_empty(), "should be empty");
3346 
3347       if (log_is_enabled(Debug, gc, task, stats)) {
3348         MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3349         size_t lab_waste;
3350         size_t lab_undo_waste;
3351         pss->waste(lab_waste, lab_undo_waste);
3352         _g1h->print_termination_stats(worker_id,
3353                                       (os::elapsedTime() - start_sec) * 1000.0,   /* elapsed time */
3354                                       strong_roots_sec * 1000.0,                  /* strong roots time */
3355                                       term_sec * 1000.0,                          /* evac term time */
3356                                       evac_term_attempts,                         /* evac term attempts */
3357                                       lab_waste,                                  /* alloc buffer waste */
3358                                       lab_undo_waste                              /* undo waste */
3359                                       );
3360       }
3361 
3362       // Close the inner scope so that the ResourceMark and HandleMark
3363       // destructors are executed here and are included as part of the
3364       // "GC Worker Time".
3365     }
3366     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3367   }
3368 };
3369 
3370 void G1CollectedHeap::print_termination_stats_hdr() {
3371   log_debug(gc, task, stats)("GC Termination Stats");
3372   log_debug(gc, task, stats)("     elapsed  --strong roots-- -------termination------- ------waste (KiB)------");
3373   log_debug(gc, task, stats)("thr     ms        ms      %%        ms      %%    attempts  total   alloc    undo");
3374   log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3375 }
3376 
3377 void G1CollectedHeap::print_termination_stats(uint worker_id,
3378                                               double elapsed_ms,
3379                                               double strong_roots_ms,
3380                                               double term_ms,
3381                                               size_t term_attempts,
3382                                               size_t alloc_buffer_waste,
3383                                               size_t undo_waste) const {
3384   log_debug(gc, task, stats)
3385               ("%3d %9.2f %9.2f %6.2f "
3386                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3387                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3388                worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3389                term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3390                (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3391                alloc_buffer_waste * HeapWordSize / K,
3392                undo_waste * HeapWordSize / K);
3393 }
3394 
3395 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3396 private:
3397   BoolObjectClosure* _is_alive;
3398   G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3399 
3400   int _initial_string_table_size;
3401   int _initial_symbol_table_size;
3402 
3403   bool  _process_strings;
3404   int _strings_processed;
3405   int _strings_removed;
3406 
3407   bool  _process_symbols;
3408   int _symbols_processed;
3409   int _symbols_removed;
3410 
3411   bool _process_string_dedup;
3412 
3413 public:
3414   G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3415     AbstractGangTask("String/Symbol Unlinking"),
3416     _is_alive(is_alive),
3417     _dedup_closure(is_alive, NULL, false),
3418     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3419     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3420     _process_string_dedup(process_string_dedup) {
3421 
3422     _initial_string_table_size = StringTable::the_table()->table_size();
3423     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3424     if (process_strings) {
3425       StringTable::clear_parallel_claimed_index();
3426     }
3427     if (process_symbols) {
3428       SymbolTable::clear_parallel_claimed_index();
3429     }
3430   }
3431 
3432   ~G1StringAndSymbolCleaningTask() {
3433     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3434               "claim value %d after unlink less than initial string table size %d",
3435               StringTable::parallel_claimed_index(), _initial_string_table_size);
3436     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3437               "claim value %d after unlink less than initial symbol table size %d",
3438               SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3439 
3440     log_info(gc, stringtable)(
3441         "Cleaned string and symbol table, "
3442         "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3443         "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3444         strings_processed(), strings_removed(),
3445         symbols_processed(), symbols_removed());
3446   }
3447 
3448   void work(uint worker_id) {
3449     int strings_processed = 0;
3450     int strings_removed = 0;
3451     int symbols_processed = 0;
3452     int symbols_removed = 0;
3453     if (_process_strings) {
3454       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3455       Atomic::add(strings_processed, &_strings_processed);
3456       Atomic::add(strings_removed, &_strings_removed);
3457     }
3458     if (_process_symbols) {
3459       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3460       Atomic::add(symbols_processed, &_symbols_processed);
3461       Atomic::add(symbols_removed, &_symbols_removed);
3462     }
3463     if (_process_string_dedup) {
3464       G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3465     }
3466   }
3467 
3468   size_t strings_processed() const { return (size_t)_strings_processed; }
3469   size_t strings_removed()   const { return (size_t)_strings_removed; }
3470 
3471   size_t symbols_processed() const { return (size_t)_symbols_processed; }
3472   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
3473 };
3474 
3475 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3476 private:
3477   static Monitor* _lock;
3478 
3479   BoolObjectClosure* const _is_alive;
3480   const bool               _unloading_occurred;
3481   const uint               _num_workers;
3482 
3483   // Variables used to claim nmethods.
3484   CompiledMethod* _first_nmethod;
3485   CompiledMethod* volatile _claimed_nmethod;
3486 
3487   // The list of nmethods that need to be processed by the second pass.
3488   CompiledMethod* volatile _postponed_list;
3489   volatile uint            _num_entered_barrier;
3490 
3491  public:
3492   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3493       _is_alive(is_alive),
3494       _unloading_occurred(unloading_occurred),
3495       _num_workers(num_workers),
3496       _first_nmethod(NULL),
3497       _claimed_nmethod(NULL),
3498       _postponed_list(NULL),
3499       _num_entered_barrier(0)
3500   {
3501     CompiledMethod::increase_unloading_clock();
3502     // Get first alive nmethod
3503     CompiledMethodIterator iter = CompiledMethodIterator();
3504     if(iter.next_alive()) {
3505       _first_nmethod = iter.method();
3506     }
3507     _claimed_nmethod = _first_nmethod;
3508   }
3509 
3510   ~G1CodeCacheUnloadingTask() {
3511     CodeCache::verify_clean_inline_caches();
3512 
3513     CodeCache::set_needs_cache_clean(false);
3514     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3515 
3516     CodeCache::verify_icholder_relocations();
3517   }
3518 
3519  private:
3520   void add_to_postponed_list(CompiledMethod* nm) {
3521       CompiledMethod* old;
3522       do {
3523         old = _postponed_list;
3524         nm->set_unloading_next(old);
3525       } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
3526   }
3527 
3528   void clean_nmethod(CompiledMethod* nm) {
3529     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3530 
3531     if (postponed) {
3532       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3533       add_to_postponed_list(nm);
3534     }
3535 
3536     // Mark that this thread has been cleaned/unloaded.
3537     // After this call, it will be safe to ask if this nmethod was unloaded or not.
3538     nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3539   }
3540 
3541   void clean_nmethod_postponed(CompiledMethod* nm) {
3542     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3543   }
3544 
3545   static const int MaxClaimNmethods = 16;
3546 
3547   void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3548     CompiledMethod* first;
3549     CompiledMethodIterator last;
3550 
3551     do {
3552       *num_claimed_nmethods = 0;
3553 
3554       first = _claimed_nmethod;
3555       last = CompiledMethodIterator(first);
3556 
3557       if (first != NULL) {
3558 
3559         for (int i = 0; i < MaxClaimNmethods; i++) {
3560           if (!last.next_alive()) {
3561             break;
3562           }
3563           claimed_nmethods[i] = last.method();
3564           (*num_claimed_nmethods)++;
3565         }
3566       }
3567 
3568     } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
3569   }
3570 
3571   CompiledMethod* claim_postponed_nmethod() {
3572     CompiledMethod* claim;
3573     CompiledMethod* next;
3574 
3575     do {
3576       claim = _postponed_list;
3577       if (claim == NULL) {
3578         return NULL;
3579       }
3580 
3581       next = claim->unloading_next();
3582 
3583     } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
3584 
3585     return claim;
3586   }
3587 
3588  public:
3589   // Mark that we're done with the first pass of nmethod cleaning.
3590   void barrier_mark(uint worker_id) {
3591     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3592     _num_entered_barrier++;
3593     if (_num_entered_barrier == _num_workers) {
3594       ml.notify_all();
3595     }
3596   }
3597 
3598   // See if we have to wait for the other workers to
3599   // finish their first-pass nmethod cleaning work.
3600   void barrier_wait(uint worker_id) {
3601     if (_num_entered_barrier < _num_workers) {
3602       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3603       while (_num_entered_barrier < _num_workers) {
3604           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3605       }
3606     }
3607   }
3608 
3609   // Cleaning and unloading of nmethods. Some work has to be postponed
3610   // to the second pass, when we know which nmethods survive.
3611   void work_first_pass(uint worker_id) {
3612     // The first nmethods is claimed by the first worker.
3613     if (worker_id == 0 && _first_nmethod != NULL) {
3614       clean_nmethod(_first_nmethod);
3615       _first_nmethod = NULL;
3616     }
3617 
3618     int num_claimed_nmethods;
3619     CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3620 
3621     while (true) {
3622       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3623 
3624       if (num_claimed_nmethods == 0) {
3625         break;
3626       }
3627 
3628       for (int i = 0; i < num_claimed_nmethods; i++) {
3629         clean_nmethod(claimed_nmethods[i]);
3630       }
3631     }
3632   }
3633 
3634   void work_second_pass(uint worker_id) {
3635     CompiledMethod* nm;
3636     // Take care of postponed nmethods.
3637     while ((nm = claim_postponed_nmethod()) != NULL) {
3638       clean_nmethod_postponed(nm);
3639     }
3640   }
3641 };
3642 
3643 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3644 
3645 class G1KlassCleaningTask : public StackObj {
3646   BoolObjectClosure*                      _is_alive;
3647   volatile int                            _clean_klass_tree_claimed;
3648   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3649 
3650  public:
3651   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3652       _is_alive(is_alive),
3653       _clean_klass_tree_claimed(0),
3654       _klass_iterator() {
3655   }
3656 
3657  private:
3658   bool claim_clean_klass_tree_task() {
3659     if (_clean_klass_tree_claimed) {
3660       return false;
3661     }
3662 
3663     return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0;
3664   }
3665 
3666   InstanceKlass* claim_next_klass() {
3667     Klass* klass;
3668     do {
3669       klass =_klass_iterator.next_klass();
3670     } while (klass != NULL && !klass->is_instance_klass());
3671 
3672     // this can be null so don't call InstanceKlass::cast
3673     return static_cast<InstanceKlass*>(klass);
3674   }
3675 
3676 public:
3677 
3678   void clean_klass(InstanceKlass* ik) {
3679     ik->clean_weak_instanceklass_links(_is_alive);
3680   }
3681 
3682   void work() {
3683     ResourceMark rm;
3684 
3685     // One worker will clean the subklass/sibling klass tree.
3686     if (claim_clean_klass_tree_task()) {
3687       Klass::clean_subklass_tree(_is_alive);
3688     }
3689 
3690     // All workers will help cleaning the classes,
3691     InstanceKlass* klass;
3692     while ((klass = claim_next_klass()) != NULL) {
3693       clean_klass(klass);
3694     }
3695   }
3696 };
3697 
3698 class G1ResolvedMethodCleaningTask : public StackObj {
3699   BoolObjectClosure* _is_alive;
3700   volatile int       _resolved_method_task_claimed;
3701 public:
3702   G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) :
3703       _is_alive(is_alive), _resolved_method_task_claimed(0) {}
3704 
3705   bool claim_resolved_method_task() {
3706     if (_resolved_method_task_claimed) {
3707       return false;
3708     }
3709     return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0;
3710   }
3711 
3712   // These aren't big, one thread can do it all.
3713   void work() {
3714     if (claim_resolved_method_task()) {
3715       ResolvedMethodTable::unlink(_is_alive);
3716     }
3717   }
3718 };
3719 
3720 
3721 // To minimize the remark pause times, the tasks below are done in parallel.
3722 class G1ParallelCleaningTask : public AbstractGangTask {
3723 private:
3724   G1StringAndSymbolCleaningTask _string_symbol_task;
3725   G1CodeCacheUnloadingTask      _code_cache_task;
3726   G1KlassCleaningTask           _klass_cleaning_task;
3727   G1ResolvedMethodCleaningTask  _resolved_method_cleaning_task;
3728 
3729 public:
3730   // The constructor is run in the VMThread.
3731   G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3732       AbstractGangTask("Parallel Cleaning"),
3733       _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3734       _code_cache_task(num_workers, is_alive, unloading_occurred),
3735       _klass_cleaning_task(is_alive),
3736       _resolved_method_cleaning_task(is_alive) {
3737   }
3738 
3739   // The parallel work done by all worker threads.
3740   void work(uint worker_id) {
3741     // Do first pass of code cache cleaning.
3742     _code_cache_task.work_first_pass(worker_id);
3743 
3744     // Let the threads mark that the first pass is done.
3745     _code_cache_task.barrier_mark(worker_id);
3746 
3747     // Clean the Strings and Symbols.
3748     _string_symbol_task.work(worker_id);
3749 
3750     // Clean unreferenced things in the ResolvedMethodTable
3751     _resolved_method_cleaning_task.work();
3752 
3753     // Wait for all workers to finish the first code cache cleaning pass.
3754     _code_cache_task.barrier_wait(worker_id);
3755 
3756     // Do the second code cache cleaning work, which realize on
3757     // the liveness information gathered during the first pass.
3758     _code_cache_task.work_second_pass(worker_id);
3759 
3760     // Clean all klasses that were not unloaded.
3761     _klass_cleaning_task.work();
3762   }
3763 };
3764 
3765 
3766 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3767                                         bool class_unloading_occurred) {
3768   uint n_workers = workers()->active_workers();
3769 
3770   G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3771   workers()->run_task(&g1_unlink_task);
3772 }
3773 
3774 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3775                                        bool process_strings,
3776                                        bool process_symbols,
3777                                        bool process_string_dedup) {
3778   if (!process_strings && !process_symbols && !process_string_dedup) {
3779     // Nothing to clean.
3780     return;
3781   }
3782 
3783   G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3784   workers()->run_task(&g1_unlink_task);
3785 
3786 }
3787 
3788 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3789  private:
3790   DirtyCardQueueSet* _queue;
3791   G1CollectedHeap* _g1h;
3792  public:
3793   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3794     _queue(queue), _g1h(g1h) { }
3795 
3796   virtual void work(uint worker_id) {
3797     G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3798     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3799 
3800     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3801     _queue->par_apply_closure_to_all_completed_buffers(&cl);
3802 
3803     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3804   }
3805 };
3806 
3807 void G1CollectedHeap::redirty_logged_cards() {
3808   double redirty_logged_cards_start = os::elapsedTime();
3809 
3810   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3811   dirty_card_queue_set().reset_for_par_iteration();
3812   workers()->run_task(&redirty_task);
3813 
3814   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
3815   dcq.merge_bufferlists(&dirty_card_queue_set());
3816   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3817 
3818   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3819 }
3820 
3821 // Weak Reference Processing support
3822 
3823 // An always "is_alive" closure that is used to preserve referents.
3824 // If the object is non-null then it's alive.  Used in the preservation
3825 // of referent objects that are pointed to by reference objects
3826 // discovered by the CM ref processor.
3827 class G1AlwaysAliveClosure: public BoolObjectClosure {
3828   G1CollectedHeap* _g1;
3829 public:
3830   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3831   bool do_object_b(oop p) {
3832     if (p != NULL) {
3833       return true;
3834     }
3835     return false;
3836   }
3837 };
3838 
3839 bool G1STWIsAliveClosure::do_object_b(oop p) {
3840   // An object is reachable if it is outside the collection set,
3841   // or is inside and copied.
3842   return !_g1->is_in_cset(p) || p->is_forwarded();
3843 }
3844 
3845 // Non Copying Keep Alive closure
3846 class G1KeepAliveClosure: public OopClosure {
3847   G1CollectedHeap* _g1;
3848 public:
3849   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3850   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3851   void do_oop(oop* p) {
3852     oop obj = *p;
3853     assert(obj != NULL, "the caller should have filtered out NULL values");
3854 
3855     const InCSetState cset_state = _g1->in_cset_state(obj);
3856     if (!cset_state.is_in_cset_or_humongous()) {
3857       return;
3858     }
3859     if (cset_state.is_in_cset()) {
3860       assert( obj->is_forwarded(), "invariant" );
3861       *p = obj->forwardee();
3862     } else {
3863       assert(!obj->is_forwarded(), "invariant" );
3864       assert(cset_state.is_humongous(),
3865              "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3866       _g1->set_humongous_is_live(obj);
3867     }
3868   }
3869 };
3870 
3871 // Copying Keep Alive closure - can be called from both
3872 // serial and parallel code as long as different worker
3873 // threads utilize different G1ParScanThreadState instances
3874 // and different queues.
3875 
3876 class G1CopyingKeepAliveClosure: public OopClosure {
3877   G1CollectedHeap*         _g1h;
3878   OopClosure*              _copy_non_heap_obj_cl;
3879   G1ParScanThreadState*    _par_scan_state;
3880 
3881 public:
3882   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3883                             OopClosure* non_heap_obj_cl,
3884                             G1ParScanThreadState* pss):
3885     _g1h(g1h),
3886     _copy_non_heap_obj_cl(non_heap_obj_cl),
3887     _par_scan_state(pss)
3888   {}
3889 
3890   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3891   virtual void do_oop(      oop* p) { do_oop_work(p); }
3892 
3893   template <class T> void do_oop_work(T* p) {
3894     oop obj = oopDesc::load_decode_heap_oop(p);
3895 
3896     if (_g1h->is_in_cset_or_humongous(obj)) {
3897       // If the referent object has been forwarded (either copied
3898       // to a new location or to itself in the event of an
3899       // evacuation failure) then we need to update the reference
3900       // field and, if both reference and referent are in the G1
3901       // heap, update the RSet for the referent.
3902       //
3903       // If the referent has not been forwarded then we have to keep
3904       // it alive by policy. Therefore we have copy the referent.
3905       //
3906       // If the reference field is in the G1 heap then we can push
3907       // on the PSS queue. When the queue is drained (after each
3908       // phase of reference processing) the object and it's followers
3909       // will be copied, the reference field set to point to the
3910       // new location, and the RSet updated. Otherwise we need to
3911       // use the the non-heap or metadata closures directly to copy
3912       // the referent object and update the pointer, while avoiding
3913       // updating the RSet.
3914 
3915       if (_g1h->is_in_g1_reserved(p)) {
3916         _par_scan_state->push_on_queue(p);
3917       } else {
3918         assert(!Metaspace::contains((const void*)p),
3919                "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3920         _copy_non_heap_obj_cl->do_oop(p);
3921       }
3922     }
3923   }
3924 };
3925 
3926 // Serial drain queue closure. Called as the 'complete_gc'
3927 // closure for each discovered list in some of the
3928 // reference processing phases.
3929 
3930 class G1STWDrainQueueClosure: public VoidClosure {
3931 protected:
3932   G1CollectedHeap* _g1h;
3933   G1ParScanThreadState* _par_scan_state;
3934 
3935   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3936 
3937 public:
3938   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3939     _g1h(g1h),
3940     _par_scan_state(pss)
3941   { }
3942 
3943   void do_void() {
3944     G1ParScanThreadState* const pss = par_scan_state();
3945     pss->trim_queue();
3946   }
3947 };
3948 
3949 // Parallel Reference Processing closures
3950 
3951 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3952 // processing during G1 evacuation pauses.
3953 
3954 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3955 private:
3956   G1CollectedHeap*          _g1h;
3957   G1ParScanThreadStateSet*  _pss;
3958   RefToScanQueueSet*        _queues;
3959   WorkGang*                 _workers;
3960   uint                      _active_workers;
3961 
3962 public:
3963   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3964                            G1ParScanThreadStateSet* per_thread_states,
3965                            WorkGang* workers,
3966                            RefToScanQueueSet *task_queues,
3967                            uint n_workers) :
3968     _g1h(g1h),
3969     _pss(per_thread_states),
3970     _queues(task_queues),
3971     _workers(workers),
3972     _active_workers(n_workers)
3973   {
3974     g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
3975   }
3976 
3977   // Executes the given task using concurrent marking worker threads.
3978   virtual void execute(ProcessTask& task);
3979   virtual void execute(EnqueueTask& task);
3980 };
3981 
3982 // Gang task for possibly parallel reference processing
3983 
3984 class G1STWRefProcTaskProxy: public AbstractGangTask {
3985   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3986   ProcessTask&     _proc_task;
3987   G1CollectedHeap* _g1h;
3988   G1ParScanThreadStateSet* _pss;
3989   RefToScanQueueSet* _task_queues;
3990   ParallelTaskTerminator* _terminator;
3991 
3992 public:
3993   G1STWRefProcTaskProxy(ProcessTask& proc_task,
3994                         G1CollectedHeap* g1h,
3995                         G1ParScanThreadStateSet* per_thread_states,
3996                         RefToScanQueueSet *task_queues,
3997                         ParallelTaskTerminator* terminator) :
3998     AbstractGangTask("Process reference objects in parallel"),
3999     _proc_task(proc_task),
4000     _g1h(g1h),
4001     _pss(per_thread_states),
4002     _task_queues(task_queues),
4003     _terminator(terminator)
4004   {}
4005 
4006   virtual void work(uint worker_id) {
4007     // The reference processing task executed by a single worker.
4008     ResourceMark rm;
4009     HandleMark   hm;
4010 
4011     G1STWIsAliveClosure is_alive(_g1h);
4012 
4013     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4014     pss->set_ref_processor(NULL);
4015 
4016     // Keep alive closure.
4017     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4018 
4019     // Complete GC closure
4020     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
4021 
4022     // Call the reference processing task's work routine.
4023     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
4024 
4025     // Note we cannot assert that the refs array is empty here as not all
4026     // of the processing tasks (specifically phase2 - pp2_work) execute
4027     // the complete_gc closure (which ordinarily would drain the queue) so
4028     // the queue may not be empty.
4029   }
4030 };
4031 
4032 // Driver routine for parallel reference processing.
4033 // Creates an instance of the ref processing gang
4034 // task and has the worker threads execute it.
4035 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4036   assert(_workers != NULL, "Need parallel worker threads.");
4037 
4038   ParallelTaskTerminator terminator(_active_workers, _queues);
4039   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4040 
4041   _workers->run_task(&proc_task_proxy);
4042 }
4043 
4044 // Gang task for parallel reference enqueueing.
4045 
4046 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4047   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4048   EnqueueTask& _enq_task;
4049 
4050 public:
4051   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4052     AbstractGangTask("Enqueue reference objects in parallel"),
4053     _enq_task(enq_task)
4054   { }
4055 
4056   virtual void work(uint worker_id) {
4057     _enq_task.work(worker_id);
4058   }
4059 };
4060 
4061 // Driver routine for parallel reference enqueueing.
4062 // Creates an instance of the ref enqueueing gang
4063 // task and has the worker threads execute it.
4064 
4065 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4066   assert(_workers != NULL, "Need parallel worker threads.");
4067 
4068   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4069 
4070   _workers->run_task(&enq_task_proxy);
4071 }
4072 
4073 // End of weak reference support closures
4074 
4075 // Abstract task used to preserve (i.e. copy) any referent objects
4076 // that are in the collection set and are pointed to by reference
4077 // objects discovered by the CM ref processor.
4078 
4079 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4080 protected:
4081   G1CollectedHeap*         _g1h;
4082   G1ParScanThreadStateSet* _pss;
4083   RefToScanQueueSet*       _queues;
4084   ParallelTaskTerminator   _terminator;
4085   uint                     _n_workers;
4086 
4087 public:
4088   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4089     AbstractGangTask("ParPreserveCMReferents"),
4090     _g1h(g1h),
4091     _pss(per_thread_states),
4092     _queues(task_queues),
4093     _terminator(workers, _queues),
4094     _n_workers(workers)
4095   {
4096     g1h->ref_processor_cm()->set_active_mt_degree(workers);
4097   }
4098 
4099   void work(uint worker_id) {
4100     G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4101 
4102     ResourceMark rm;
4103     HandleMark   hm;
4104 
4105     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4106     pss->set_ref_processor(NULL);
4107     assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4108 
4109     // Is alive closure
4110     G1AlwaysAliveClosure always_alive(_g1h);
4111 
4112     // Copying keep alive closure. Applied to referent objects that need
4113     // to be copied.
4114     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4115 
4116     ReferenceProcessor* rp = _g1h->ref_processor_cm();
4117 
4118     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4119     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4120 
4121     // limit is set using max_num_q() - which was set using ParallelGCThreads.
4122     // So this must be true - but assert just in case someone decides to
4123     // change the worker ids.
4124     assert(worker_id < limit, "sanity");
4125     assert(!rp->discovery_is_atomic(), "check this code");
4126 
4127     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4128     for (uint idx = worker_id; idx < limit; idx += stride) {
4129       DiscoveredList& ref_list = rp->discovered_refs()[idx];
4130 
4131       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4132       while (iter.has_next()) {
4133         // Since discovery is not atomic for the CM ref processor, we
4134         // can see some null referent objects.
4135         iter.load_ptrs(DEBUG_ONLY(true));
4136         oop ref = iter.obj();
4137 
4138         // This will filter nulls.
4139         if (iter.is_referent_alive()) {
4140           iter.make_referent_alive();
4141         }
4142         iter.move_to_next();
4143       }
4144     }
4145 
4146     // Drain the queue - which may cause stealing
4147     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4148     drain_queue.do_void();
4149     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4150     assert(pss->queue_is_empty(), "should be");
4151   }
4152 };
4153 
4154 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4155   // Any reference objects, in the collection set, that were 'discovered'
4156   // by the CM ref processor should have already been copied (either by
4157   // applying the external root copy closure to the discovered lists, or
4158   // by following an RSet entry).
4159   //
4160   // But some of the referents, that are in the collection set, that these
4161   // reference objects point to may not have been copied: the STW ref
4162   // processor would have seen that the reference object had already
4163   // been 'discovered' and would have skipped discovering the reference,
4164   // but would not have treated the reference object as a regular oop.
4165   // As a result the copy closure would not have been applied to the
4166   // referent object.
4167   //
4168   // We need to explicitly copy these referent objects - the references
4169   // will be processed at the end of remarking.
4170   //
4171   // We also need to do this copying before we process the reference
4172   // objects discovered by the STW ref processor in case one of these
4173   // referents points to another object which is also referenced by an
4174   // object discovered by the STW ref processor.
4175   double preserve_cm_referents_time = 0.0;
4176 
4177   // To avoid spawning task when there is no work to do, check that
4178   // a concurrent cycle is active and that some references have been
4179   // discovered.
4180   if (concurrent_mark()->cm_thread()->during_cycle() &&
4181       ref_processor_cm()->has_discovered_references()) {
4182     double preserve_cm_referents_start = os::elapsedTime();
4183     uint no_of_gc_workers = workers()->active_workers();
4184     G1ParPreserveCMReferentsTask keep_cm_referents(this,
4185                                                    per_thread_states,
4186                                                    no_of_gc_workers,
4187                                                    _task_queues);
4188     workers()->run_task(&keep_cm_referents);
4189     preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4190   }
4191 
4192   g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4193 }
4194 
4195 // Weak Reference processing during an evacuation pause (part 1).
4196 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4197   double ref_proc_start = os::elapsedTime();
4198 
4199   ReferenceProcessor* rp = _ref_processor_stw;
4200   assert(rp->discovery_enabled(), "should have been enabled");
4201 
4202   // Closure to test whether a referent is alive.
4203   G1STWIsAliveClosure is_alive(this);
4204 
4205   // Even when parallel reference processing is enabled, the processing
4206   // of JNI refs is serial and performed serially by the current thread
4207   // rather than by a worker. The following PSS will be used for processing
4208   // JNI refs.
4209 
4210   // Use only a single queue for this PSS.
4211   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
4212   pss->set_ref_processor(NULL);
4213   assert(pss->queue_is_empty(), "pre-condition");
4214 
4215   // Keep alive closure.
4216   G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4217 
4218   // Serial Complete GC closure
4219   G1STWDrainQueueClosure drain_queue(this, pss);
4220 
4221   // Setup the soft refs policy...
4222   rp->setup_policy(false);
4223 
4224   ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4225 
4226   ReferenceProcessorStats stats;
4227   if (!rp->processing_is_mt()) {
4228     // Serial reference processing...
4229     stats = rp->process_discovered_references(&is_alive,
4230                                               &keep_alive,
4231                                               &drain_queue,
4232                                               NULL,
4233                                               pt);
4234   } else {
4235     uint no_of_gc_workers = workers()->active_workers();
4236 
4237     // Parallel reference processing
4238     assert(no_of_gc_workers <= rp->max_num_q(),
4239            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4240            no_of_gc_workers,  rp->max_num_q());
4241 
4242     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4243     stats = rp->process_discovered_references(&is_alive,
4244                                               &keep_alive,
4245                                               &drain_queue,
4246                                               &par_task_executor,
4247                                               pt);
4248   }
4249 
4250   _gc_tracer_stw->report_gc_reference_stats(stats);
4251 
4252   // We have completed copying any necessary live referent objects.
4253   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4254 
4255   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4256   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4257 }
4258 
4259 // Weak Reference processing during an evacuation pause (part 2).
4260 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4261   double ref_enq_start = os::elapsedTime();
4262 
4263   ReferenceProcessor* rp = _ref_processor_stw;
4264   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4265 
4266   ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4267 
4268   // Now enqueue any remaining on the discovered lists on to
4269   // the pending list.
4270   if (!rp->processing_is_mt()) {
4271     // Serial reference processing...
4272     rp->enqueue_discovered_references(NULL, pt);
4273   } else {
4274     // Parallel reference enqueueing
4275 
4276     uint n_workers = workers()->active_workers();
4277 
4278     assert(n_workers <= rp->max_num_q(),
4279            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4280            n_workers,  rp->max_num_q());
4281 
4282     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4283     rp->enqueue_discovered_references(&par_task_executor, pt);
4284   }
4285 
4286   rp->verify_no_references_recorded();
4287   assert(!rp->discovery_enabled(), "should have been disabled");
4288 
4289   // If during an initial mark pause we install a pending list head which is not otherwise reachable
4290   // ensure that it is marked in the bitmap for concurrent marking to discover.
4291   if (collector_state()->during_initial_mark_pause()) {
4292     oop pll_head = Universe::reference_pending_list();
4293     if (pll_head != NULL) {
4294       _cm->mark_in_next_bitmap(pll_head);
4295     }
4296   }
4297 
4298   // FIXME
4299   // CM's reference processing also cleans up the string and symbol tables.
4300   // Should we do that here also? We could, but it is a serial operation
4301   // and could significantly increase the pause time.
4302 
4303   double ref_enq_time = os::elapsedTime() - ref_enq_start;
4304   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4305 }
4306 
4307 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4308   double merge_pss_time_start = os::elapsedTime();
4309   per_thread_states->flush();
4310   g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4311 }
4312 
4313 void G1CollectedHeap::pre_evacuate_collection_set() {
4314   _expand_heap_after_alloc_failure = true;
4315   _evacuation_failed = false;
4316 
4317   // Disable the hot card cache.
4318   _hot_card_cache->reset_hot_cache_claimed_index();
4319   _hot_card_cache->set_use_cache(false);
4320 
4321   g1_rem_set()->prepare_for_oops_into_collection_set_do();
4322   _preserved_marks_set.assert_empty();
4323 
4324   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4325 
4326   // InitialMark needs claim bits to keep track of the marked-through CLDs.
4327   if (collector_state()->during_initial_mark_pause()) {
4328     double start_clear_claimed_marks = os::elapsedTime();
4329 
4330     ClassLoaderDataGraph::clear_claimed_marks();
4331 
4332     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
4333     phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
4334   }
4335 }
4336 
4337 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4338   // Should G1EvacuationFailureALot be in effect for this GC?
4339   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4340 
4341   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4342 
4343   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4344 
4345   double start_par_time_sec = os::elapsedTime();
4346   double end_par_time_sec;
4347 
4348   {
4349     const uint n_workers = workers()->active_workers();
4350     G1RootProcessor root_processor(this, n_workers);
4351     G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4352 
4353     print_termination_stats_hdr();
4354 
4355     workers()->run_task(&g1_par_task);
4356     end_par_time_sec = os::elapsedTime();
4357 
4358     // Closing the inner scope will execute the destructor
4359     // for the G1RootProcessor object. We record the current
4360     // elapsed time before closing the scope so that time
4361     // taken for the destructor is NOT included in the
4362     // reported parallel time.
4363   }
4364 
4365   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4366   phase_times->record_par_time(par_time_ms);
4367 
4368   double code_root_fixup_time_ms =
4369         (os::elapsedTime() - end_par_time_sec) * 1000.0;
4370   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4371 }
4372 
4373 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4374   // Process any discovered reference objects - we have
4375   // to do this _before_ we retire the GC alloc regions
4376   // as we may have to copy some 'reachable' referent
4377   // objects (and their reachable sub-graphs) that were
4378   // not copied during the pause.
4379   if (g1_policy()->should_process_references()) {
4380     preserve_cm_referents(per_thread_states);
4381     process_discovered_references(per_thread_states);
4382   } else {
4383     ref_processor_stw()->verify_no_references_recorded();
4384   }
4385 
4386   G1STWIsAliveClosure is_alive(this);
4387   G1KeepAliveClosure keep_alive(this);
4388 
4389   {
4390     double start = os::elapsedTime();
4391 
4392     WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
4393 
4394     double time_ms = (os::elapsedTime() - start) * 1000.0;
4395     g1_policy()->phase_times()->record_ref_proc_time(time_ms);
4396   }
4397 
4398   if (G1StringDedup::is_enabled()) {
4399     double fixup_start = os::elapsedTime();
4400 
4401     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4402 
4403     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4404     g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4405   }
4406 
4407   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4408 
4409   if (evacuation_failed()) {
4410     restore_after_evac_failure();
4411 
4412     // Reset the G1EvacuationFailureALot counters and flags
4413     // Note: the values are reset only when an actual
4414     // evacuation failure occurs.
4415     NOT_PRODUCT(reset_evacuation_should_fail();)
4416   }
4417 
4418   _preserved_marks_set.assert_empty();
4419 
4420   // Enqueue any remaining references remaining on the STW
4421   // reference processor's discovered lists. We need to do
4422   // this after the card table is cleaned (and verified) as
4423   // the act of enqueueing entries on to the pending list
4424   // will log these updates (and dirty their associated
4425   // cards). We need these updates logged to update any
4426   // RSets.
4427   if (g1_policy()->should_process_references()) {
4428     enqueue_discovered_references(per_thread_states);
4429   } else {
4430     g1_policy()->phase_times()->record_ref_enq_time(0);
4431   }
4432 
4433   _allocator->release_gc_alloc_regions(evacuation_info);
4434 
4435   merge_per_thread_state_info(per_thread_states);
4436 
4437   // Reset and re-enable the hot card cache.
4438   // Note the counts for the cards in the regions in the
4439   // collection set are reset when the collection set is freed.
4440   _hot_card_cache->reset_hot_cache();
4441   _hot_card_cache->set_use_cache(true);
4442 
4443   purge_code_root_memory();
4444 
4445   redirty_logged_cards();
4446 #if COMPILER2_OR_JVMCI
4447   double start = os::elapsedTime();
4448   DerivedPointerTable::update_pointers();
4449   g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4450 #endif
4451   g1_policy()->print_age_table();
4452 }
4453 
4454 void G1CollectedHeap::record_obj_copy_mem_stats() {
4455   g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4456 
4457   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4458                                                create_g1_evac_summary(&_old_evac_stats));
4459 }
4460 
4461 void G1CollectedHeap::free_region(HeapRegion* hr,
4462                                   FreeRegionList* free_list,
4463                                   bool skip_remset,
4464                                   bool skip_hot_card_cache,
4465                                   bool locked) {
4466   assert(!hr->is_free(), "the region should not be free");
4467   assert(!hr->is_empty(), "the region should not be empty");
4468   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4469   assert(free_list != NULL, "pre-condition");
4470 
4471   if (G1VerifyBitmaps) {
4472     MemRegion mr(hr->bottom(), hr->end());
4473     concurrent_mark()->clear_range_in_prev_bitmap(mr);
4474   }
4475 
4476   // Clear the card counts for this region.
4477   // Note: we only need to do this if the region is not young
4478   // (since we don't refine cards in young regions).
4479   if (!skip_hot_card_cache && !hr->is_young()) {
4480     _hot_card_cache->reset_card_counts(hr);
4481   }
4482   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4483   free_list->add_ordered(hr);
4484 }
4485 
4486 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4487                                             FreeRegionList* free_list,
4488                                             bool skip_remset) {
4489   assert(hr->is_humongous(), "this is only for humongous regions");
4490   assert(free_list != NULL, "pre-condition");
4491   hr->clear_humongous();
4492   free_region(hr, free_list, skip_remset);
4493 }
4494 
4495 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4496                                            const uint humongous_regions_removed) {
4497   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4498     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4499     _old_set.bulk_remove(old_regions_removed);
4500     _humongous_set.bulk_remove(humongous_regions_removed);
4501   }
4502 
4503 }
4504 
4505 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4506   assert(list != NULL, "list can't be null");
4507   if (!list->is_empty()) {
4508     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4509     _hrm.insert_list_into_free_list(list);
4510   }
4511 }
4512 
4513 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4514   decrease_used(bytes);
4515 }
4516 
4517 class G1ParScrubRemSetTask: public AbstractGangTask {
4518 protected:
4519   G1RemSet* _g1rs;
4520   HeapRegionClaimer _hrclaimer;
4521 
4522 public:
4523   G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
4524     AbstractGangTask("G1 ScrubRS"),
4525     _g1rs(g1_rs),
4526     _hrclaimer(num_workers) {
4527   }
4528 
4529   void work(uint worker_id) {
4530     _g1rs->scrub(worker_id, &_hrclaimer);
4531   }
4532 };
4533 
4534 void G1CollectedHeap::scrub_rem_set() {
4535   uint num_workers = workers()->active_workers();
4536   G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
4537   workers()->run_task(&g1_par_scrub_rs_task);
4538 }
4539 
4540 class G1FreeCollectionSetTask : public AbstractGangTask {
4541 private:
4542 
4543   // Closure applied to all regions in the collection set to do work that needs to
4544   // be done serially in a single thread.
4545   class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4546   private:
4547     EvacuationInfo* _evacuation_info;
4548     const size_t* _surviving_young_words;
4549 
4550     // Bytes used in successfully evacuated regions before the evacuation.
4551     size_t _before_used_bytes;
4552     // Bytes used in unsucessfully evacuated regions before the evacuation
4553     size_t _after_used_bytes;
4554 
4555     size_t _bytes_allocated_in_old_since_last_gc;
4556 
4557     size_t _failure_used_words;
4558     size_t _failure_waste_words;
4559 
4560     FreeRegionList _local_free_list;
4561   public:
4562     G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4563       HeapRegionClosure(),
4564       _evacuation_info(evacuation_info),
4565       _surviving_young_words(surviving_young_words),
4566       _before_used_bytes(0),
4567       _after_used_bytes(0),
4568       _bytes_allocated_in_old_since_last_gc(0),
4569       _failure_used_words(0),
4570       _failure_waste_words(0),
4571       _local_free_list("Local Region List for CSet Freeing") {
4572     }
4573 
4574     virtual bool doHeapRegion(HeapRegion* r) {
4575       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4576 
4577       assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4578       g1h->clear_in_cset(r);
4579 
4580       if (r->is_young()) {
4581         assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4582                "Young index %d is wrong for region %u of type %s with %u young regions",
4583                r->young_index_in_cset(),
4584                r->hrm_index(),
4585                r->get_type_str(),
4586                g1h->collection_set()->young_region_length());
4587         size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4588         r->record_surv_words_in_group(words_survived);
4589       }
4590 
4591       if (!r->evacuation_failed()) {
4592         assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4593         _before_used_bytes += r->used();
4594         g1h->free_region(r,
4595                          &_local_free_list,
4596                          true, /* skip_remset */
4597                          true, /* skip_hot_card_cache */
4598                          true  /* locked */);
4599       } else {
4600         r->uninstall_surv_rate_group();
4601         r->set_young_index_in_cset(-1);
4602         r->set_evacuation_failed(false);
4603         // When moving a young gen region to old gen, we "allocate" that whole region
4604         // there. This is in addition to any already evacuated objects. Notify the
4605         // policy about that.
4606         // Old gen regions do not cause an additional allocation: both the objects
4607         // still in the region and the ones already moved are accounted for elsewhere.
4608         if (r->is_young()) {
4609           _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4610         }
4611         // The region is now considered to be old.
4612         r->set_old();
4613         // Do some allocation statistics accounting. Regions that failed evacuation
4614         // are always made old, so there is no need to update anything in the young
4615         // gen statistics, but we need to update old gen statistics.
4616         size_t used_words = r->marked_bytes() / HeapWordSize;
4617 
4618         _failure_used_words += used_words;
4619         _failure_waste_words += HeapRegion::GrainWords - used_words;
4620 
4621         g1h->old_set_add(r);
4622         _after_used_bytes += r->used();
4623       }
4624       return false;
4625     }
4626 
4627     void complete_work() {
4628       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4629 
4630       _evacuation_info->set_regions_freed(_local_free_list.length());
4631       _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4632 
4633       g1h->prepend_to_freelist(&_local_free_list);
4634       g1h->decrement_summary_bytes(_before_used_bytes);
4635 
4636       G1Policy* policy = g1h->g1_policy();
4637       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4638 
4639       g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4640     }
4641   };
4642 
4643   G1CollectionSet* _collection_set;
4644   G1SerialFreeCollectionSetClosure _cl;
4645   const size_t* _surviving_young_words;
4646 
4647   size_t _rs_lengths;
4648 
4649   volatile jint _serial_work_claim;
4650 
4651   struct WorkItem {
4652     uint region_idx;
4653     bool is_young;
4654     bool evacuation_failed;
4655 
4656     WorkItem(HeapRegion* r) {
4657       region_idx = r->hrm_index();
4658       is_young = r->is_young();
4659       evacuation_failed = r->evacuation_failed();
4660     }
4661   };
4662 
4663   volatile size_t _parallel_work_claim;
4664   size_t _num_work_items;
4665   WorkItem* _work_items;
4666 
4667   void do_serial_work() {
4668     // Need to grab the lock to be allowed to modify the old region list.
4669     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4670     _collection_set->iterate(&_cl);
4671   }
4672 
4673   void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4674     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4675 
4676     HeapRegion* r = g1h->region_at(region_idx);
4677     assert(!g1h->is_on_master_free_list(r), "sanity");
4678 
4679     Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4680 
4681     if (!is_young) {
4682       g1h->_hot_card_cache->reset_card_counts(r);
4683     }
4684 
4685     if (!evacuation_failed) {
4686       r->rem_set()->clear_locked();
4687     }
4688   }
4689 
4690   class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4691   private:
4692     size_t _cur_idx;
4693     WorkItem* _work_items;
4694   public:
4695     G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4696 
4697     virtual bool doHeapRegion(HeapRegion* r) {
4698       _work_items[_cur_idx++] = WorkItem(r);
4699       return false;
4700     }
4701   };
4702 
4703   void prepare_work() {
4704     G1PrepareFreeCollectionSetClosure cl(_work_items);
4705     _collection_set->iterate(&cl);
4706   }
4707 
4708   void complete_work() {
4709     _cl.complete_work();
4710 
4711     G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4712     policy->record_max_rs_lengths(_rs_lengths);
4713     policy->cset_regions_freed();
4714   }
4715 public:
4716   G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4717     AbstractGangTask("G1 Free Collection Set"),
4718     _cl(evacuation_info, surviving_young_words),
4719     _collection_set(collection_set),
4720     _surviving_young_words(surviving_young_words),
4721     _serial_work_claim(0),
4722     _rs_lengths(0),
4723     _parallel_work_claim(0),
4724     _num_work_items(collection_set->region_length()),
4725     _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4726     prepare_work();
4727   }
4728 
4729   ~G1FreeCollectionSetTask() {
4730     complete_work();
4731     FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4732   }
4733 
4734   // Chunk size for work distribution. The chosen value has been determined experimentally
4735   // to be a good tradeoff between overhead and achievable parallelism.
4736   static uint chunk_size() { return 32; }
4737 
4738   virtual void work(uint worker_id) {
4739     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4740 
4741     // Claim serial work.
4742     if (_serial_work_claim == 0) {
4743       jint value = Atomic::add(1, &_serial_work_claim) - 1;
4744       if (value == 0) {
4745         double serial_time = os::elapsedTime();
4746         do_serial_work();
4747         timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4748       }
4749     }
4750 
4751     // Start parallel work.
4752     double young_time = 0.0;
4753     bool has_young_time = false;
4754     double non_young_time = 0.0;
4755     bool has_non_young_time = false;
4756 
4757     while (true) {
4758       size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4759       size_t cur = end - chunk_size();
4760 
4761       if (cur >= _num_work_items) {
4762         break;
4763       }
4764 
4765       double start_time = os::elapsedTime();
4766 
4767       end = MIN2(end, _num_work_items);
4768 
4769       for (; cur < end; cur++) {
4770         bool is_young = _work_items[cur].is_young;
4771 
4772         do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4773 
4774         double end_time = os::elapsedTime();
4775         double time_taken = end_time - start_time;
4776         if (is_young) {
4777           young_time += time_taken;
4778           has_young_time = true;
4779         } else {
4780           non_young_time += time_taken;
4781           has_non_young_time = true;
4782         }
4783         start_time = end_time;
4784       }
4785     }
4786 
4787     if (has_young_time) {
4788       timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4789     }
4790     if (has_non_young_time) {
4791       timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time);
4792     }
4793   }
4794 };
4795 
4796 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4797   _eden.clear();
4798 
4799   double free_cset_start_time = os::elapsedTime();
4800 
4801   {
4802     uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4803     uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4804 
4805     G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4806 
4807     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4808                         cl.name(),
4809                         num_workers,
4810                         _collection_set.region_length());
4811     workers()->run_task(&cl, num_workers);
4812   }
4813   g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4814 
4815   collection_set->clear();
4816 }
4817 
4818 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4819  private:
4820   FreeRegionList* _free_region_list;
4821   HeapRegionSet* _proxy_set;
4822   uint _humongous_objects_reclaimed;
4823   uint _humongous_regions_reclaimed;
4824   size_t _freed_bytes;
4825  public:
4826 
4827   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4828     _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4829   }
4830 
4831   virtual bool doHeapRegion(HeapRegion* r) {
4832     if (!r->is_starts_humongous()) {
4833       return false;
4834     }
4835 
4836     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4837 
4838     oop obj = (oop)r->bottom();
4839     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4840 
4841     // The following checks whether the humongous object is live are sufficient.
4842     // The main additional check (in addition to having a reference from the roots
4843     // or the young gen) is whether the humongous object has a remembered set entry.
4844     //
4845     // A humongous object cannot be live if there is no remembered set for it
4846     // because:
4847     // - there can be no references from within humongous starts regions referencing
4848     // the object because we never allocate other objects into them.
4849     // (I.e. there are no intra-region references that may be missed by the
4850     // remembered set)
4851     // - as soon there is a remembered set entry to the humongous starts region
4852     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4853     // until the end of a concurrent mark.
4854     //
4855     // It is not required to check whether the object has been found dead by marking
4856     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4857     // all objects allocated during that time are considered live.
4858     // SATB marking is even more conservative than the remembered set.
4859     // So if at this point in the collection there is no remembered set entry,
4860     // nobody has a reference to it.
4861     // At the start of collection we flush all refinement logs, and remembered sets
4862     // are completely up-to-date wrt to references to the humongous object.
4863     //
4864     // Other implementation considerations:
4865     // - never consider object arrays at this time because they would pose
4866     // considerable effort for cleaning up the the remembered sets. This is
4867     // required because stale remembered sets might reference locations that
4868     // are currently allocated into.
4869     uint region_idx = r->hrm_index();
4870     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4871         !r->rem_set()->is_empty()) {
4872       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",
4873                                region_idx,
4874                                (size_t)obj->size() * HeapWordSize,
4875                                p2i(r->bottom()),
4876                                r->rem_set()->occupied(),
4877                                r->rem_set()->strong_code_roots_list_length(),
4878                                next_bitmap->is_marked(r->bottom()),
4879                                g1h->is_humongous_reclaim_candidate(region_idx),
4880                                obj->is_typeArray()
4881                               );
4882       return false;
4883     }
4884 
4885     guarantee(obj->is_typeArray(),
4886               "Only eagerly reclaiming type arrays is supported, but the object "
4887               PTR_FORMAT " is not.", p2i(r->bottom()));
4888 
4889     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",
4890                              region_idx,
4891                              (size_t)obj->size() * HeapWordSize,
4892                              p2i(r->bottom()),
4893                              r->rem_set()->occupied(),
4894                              r->rem_set()->strong_code_roots_list_length(),
4895                              next_bitmap->is_marked(r->bottom()),
4896                              g1h->is_humongous_reclaim_candidate(region_idx),
4897                              obj->is_typeArray()
4898                             );
4899 
4900     // Need to clear mark bit of the humongous object if already set.
4901     if (next_bitmap->is_marked(r->bottom())) {
4902       next_bitmap->clear(r->bottom());
4903     }
4904     _humongous_objects_reclaimed++;
4905     do {
4906       HeapRegion* next = g1h->next_region_in_humongous(r);
4907       _freed_bytes += r->used();
4908       r->set_containing_set(NULL);
4909       _humongous_regions_reclaimed++;
4910       g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ );
4911       r = next;
4912     } while (r != NULL);
4913 
4914     return false;
4915   }
4916 
4917   uint humongous_objects_reclaimed() {
4918     return _humongous_objects_reclaimed;
4919   }
4920 
4921   uint humongous_regions_reclaimed() {
4922     return _humongous_regions_reclaimed;
4923   }
4924 
4925   size_t bytes_freed() const {
4926     return _freed_bytes;
4927   }
4928 };
4929 
4930 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4931   assert_at_safepoint(true);
4932 
4933   if (!G1EagerReclaimHumongousObjects ||
4934       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4935     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4936     return;
4937   }
4938 
4939   double start_time = os::elapsedTime();
4940 
4941   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4942 
4943   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4944   heap_region_iterate(&cl);
4945 
4946   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4947 
4948   G1HRPrinter* hrp = hr_printer();
4949   if (hrp->is_active()) {
4950     FreeRegionListIterator iter(&local_cleanup_list);
4951     while (iter.more_available()) {
4952       HeapRegion* hr = iter.get_next();
4953       hrp->cleanup(hr);
4954     }
4955   }
4956 
4957   prepend_to_freelist(&local_cleanup_list);
4958   decrement_summary_bytes(cl.bytes_freed());
4959 
4960   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4961                                                                     cl.humongous_objects_reclaimed());
4962 }
4963 
4964 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4965 public:
4966   virtual bool doHeapRegion(HeapRegion* r) {
4967     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4968     G1CollectedHeap::heap()->clear_in_cset(r);
4969     r->set_young_index_in_cset(-1);
4970     return false;
4971   }
4972 };
4973 
4974 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4975   G1AbandonCollectionSetClosure cl;
4976   collection_set->iterate(&cl);
4977 
4978   collection_set->clear();
4979   collection_set->stop_incremental_building();
4980 }
4981 
4982 void G1CollectedHeap::set_free_regions_coming() {
4983   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
4984 
4985   assert(!free_regions_coming(), "pre-condition");
4986   _free_regions_coming = true;
4987 }
4988 
4989 void G1CollectedHeap::reset_free_regions_coming() {
4990   assert(free_regions_coming(), "pre-condition");
4991 
4992   {
4993     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4994     _free_regions_coming = false;
4995     SecondaryFreeList_lock->notify_all();
4996   }
4997 
4998   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
4999 }
5000 
5001 void G1CollectedHeap::wait_while_free_regions_coming() {
5002   // Most of the time we won't have to wait, so let's do a quick test
5003   // first before we take the lock.
5004   if (!free_regions_coming()) {
5005     return;
5006   }
5007 
5008   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
5009 
5010   {
5011     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5012     while (free_regions_coming()) {
5013       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5014     }
5015   }
5016 
5017   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
5018 }
5019 
5020 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
5021   return _allocator->is_retained_old_region(hr);
5022 }
5023 
5024 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5025   _eden.add(hr);
5026   _g1_policy->set_region_eden(hr);
5027 }
5028 
5029 #ifdef ASSERT
5030 
5031 class NoYoungRegionsClosure: public HeapRegionClosure {
5032 private:
5033   bool _success;
5034 public:
5035   NoYoungRegionsClosure() : _success(true) { }
5036   bool doHeapRegion(HeapRegion* r) {
5037     if (r->is_young()) {
5038       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5039                             p2i(r->bottom()), p2i(r->end()));
5040       _success = false;
5041     }
5042     return false;
5043   }
5044   bool success() { return _success; }
5045 };
5046 
5047 bool G1CollectedHeap::check_young_list_empty() {
5048   bool ret = (young_regions_count() == 0);
5049 
5050   NoYoungRegionsClosure closure;
5051   heap_region_iterate(&closure);
5052   ret = ret && closure.success();
5053 
5054   return ret;
5055 }
5056 
5057 #endif // ASSERT
5058 
5059 class TearDownRegionSetsClosure : public HeapRegionClosure {
5060 private:
5061   HeapRegionSet *_old_set;
5062 
5063 public:
5064   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5065 
5066   bool doHeapRegion(HeapRegion* r) {
5067     if (r->is_old()) {
5068       _old_set->remove(r);
5069     } else if(r->is_young()) {
5070       r->uninstall_surv_rate_group();
5071     } else {
5072       // We ignore free regions, we'll empty the free list afterwards.
5073       // We ignore humongous regions, we're not tearing down the
5074       // humongous regions set.
5075       assert(r->is_free() || r->is_humongous(),
5076              "it cannot be another type");
5077     }
5078     return false;
5079   }
5080 
5081   ~TearDownRegionSetsClosure() {
5082     assert(_old_set->is_empty(), "post-condition");
5083   }
5084 };
5085 
5086 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5087   assert_at_safepoint(true /* should_be_vm_thread */);
5088 
5089   if (!free_list_only) {
5090     TearDownRegionSetsClosure cl(&_old_set);
5091     heap_region_iterate(&cl);
5092 
5093     // Note that emptying the _young_list is postponed and instead done as
5094     // the first step when rebuilding the regions sets again. The reason for
5095     // this is that during a full GC string deduplication needs to know if
5096     // a collected region was young or old when the full GC was initiated.
5097   }
5098   _hrm.remove_all_free_regions();
5099 }
5100 
5101 void G1CollectedHeap::increase_used(size_t bytes) {
5102   _summary_bytes_used += bytes;
5103 }
5104 
5105 void G1CollectedHeap::decrease_used(size_t bytes) {
5106   assert(_summary_bytes_used >= bytes,
5107          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5108          _summary_bytes_used, bytes);
5109   _summary_bytes_used -= bytes;
5110 }
5111 
5112 void G1CollectedHeap::set_used(size_t bytes) {
5113   _summary_bytes_used = bytes;
5114 }
5115 
5116 class RebuildRegionSetsClosure : public HeapRegionClosure {
5117 private:
5118   bool            _free_list_only;
5119   HeapRegionSet*   _old_set;
5120   HeapRegionManager*   _hrm;
5121   size_t          _total_used;
5122 
5123 public:
5124   RebuildRegionSetsClosure(bool free_list_only,
5125                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
5126     _free_list_only(free_list_only),
5127     _old_set(old_set), _hrm(hrm), _total_used(0) {
5128     assert(_hrm->num_free_regions() == 0, "pre-condition");
5129     if (!free_list_only) {
5130       assert(_old_set->is_empty(), "pre-condition");
5131     }
5132   }
5133 
5134   bool doHeapRegion(HeapRegion* r) {
5135     if (r->is_empty()) {
5136       // Add free regions to the free list
5137       r->set_free();
5138       r->set_allocation_context(AllocationContext::system());
5139       _hrm->insert_into_free_list(r);
5140     } else if (!_free_list_only) {
5141 
5142       if (r->is_humongous()) {
5143         // We ignore humongous regions. We left the humongous set unchanged.
5144       } else {
5145         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
5146         // We now move all (non-humongous, non-old) regions to old gen, and register them as such.
5147         r->move_to_old();
5148         _old_set->add(r);
5149       }
5150       _total_used += r->used();
5151     }
5152 
5153     return false;
5154   }
5155 
5156   size_t total_used() {
5157     return _total_used;
5158   }
5159 };
5160 
5161 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5162   assert_at_safepoint(true /* should_be_vm_thread */);
5163 
5164   if (!free_list_only) {
5165     _eden.clear();
5166     _survivor.clear();
5167   }
5168 
5169   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5170   heap_region_iterate(&cl);
5171 
5172   if (!free_list_only) {
5173     set_used(cl.total_used());
5174     if (_archive_allocator != NULL) {
5175       _archive_allocator->clear_used();
5176     }
5177   }
5178   assert(used_unlocked() == recalculate_used(),
5179          "inconsistent used_unlocked(), "
5180          "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5181          used_unlocked(), recalculate_used());
5182 }
5183 
5184 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5185   HeapRegion* hr = heap_region_containing(p);
5186   return hr->is_in(p);
5187 }
5188 
5189 // Methods for the mutator alloc region
5190 
5191 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5192                                                       bool force) {
5193   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5194   bool should_allocate = g1_policy()->should_allocate_mutator_region();
5195   if (force || should_allocate) {
5196     HeapRegion* new_alloc_region = new_region(word_size,
5197                                               false /* is_old */,
5198                                               false /* do_expand */);
5199     if (new_alloc_region != NULL) {
5200       set_region_short_lived_locked(new_alloc_region);
5201       _hr_printer.alloc(new_alloc_region, !should_allocate);
5202       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5203       return new_alloc_region;
5204     }
5205   }
5206   return NULL;
5207 }
5208 
5209 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5210                                                   size_t allocated_bytes) {
5211   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5212   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5213 
5214   collection_set()->add_eden_region(alloc_region);
5215   increase_used(allocated_bytes);
5216   _hr_printer.retire(alloc_region);
5217   // We update the eden sizes here, when the region is retired,
5218   // instead of when it's allocated, since this is the point that its
5219   // used space has been recored in _summary_bytes_used.
5220   g1mm()->update_eden_size();
5221 }
5222 
5223 // Methods for the GC alloc regions
5224 
5225 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
5226   if (dest.is_old()) {
5227     return true;
5228   } else {
5229     return survivor_regions_count() < g1_policy()->max_survivor_regions();
5230   }
5231 }
5232 
5233 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
5234   assert(FreeList_lock->owned_by_self(), "pre-condition");
5235 
5236   if (!has_more_regions(dest)) {
5237     return NULL;
5238   }
5239 
5240   const bool is_survivor = dest.is_young();
5241 
5242   HeapRegion* new_alloc_region = new_region(word_size,
5243                                             !is_survivor,
5244                                             true /* do_expand */);
5245   if (new_alloc_region != NULL) {
5246     // We really only need to do this for old regions given that we
5247     // should never scan survivors. But it doesn't hurt to do it
5248     // for survivors too.
5249     new_alloc_region->record_timestamp();
5250     if (is_survivor) {
5251       new_alloc_region->set_survivor();
5252       _survivor.add(new_alloc_region);
5253       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5254     } else {
5255       new_alloc_region->set_old();
5256       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5257     }
5258     _hr_printer.alloc(new_alloc_region);
5259     bool during_im = collector_state()->during_initial_mark_pause();
5260     new_alloc_region->note_start_of_copying(during_im);
5261     return new_alloc_region;
5262   }
5263   return NULL;
5264 }
5265 
5266 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5267                                              size_t allocated_bytes,
5268                                              InCSetState dest) {
5269   bool during_im = collector_state()->during_initial_mark_pause();
5270   alloc_region->note_end_of_copying(during_im);
5271   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5272   if (dest.is_old()) {
5273     _old_set.add(alloc_region);
5274   }
5275   _hr_printer.retire(alloc_region);
5276 }
5277 
5278 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5279   bool expanded = false;
5280   uint index = _hrm.find_highest_free(&expanded);
5281 
5282   if (index != G1_NO_HRM_INDEX) {
5283     if (expanded) {
5284       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5285                                 HeapRegion::GrainWords * HeapWordSize);
5286     }
5287     _hrm.allocate_free_regions_starting_at(index, 1);
5288     return region_at(index);
5289   }
5290   return NULL;
5291 }
5292 
5293 // Optimized nmethod scanning
5294 
5295 class RegisterNMethodOopClosure: public OopClosure {
5296   G1CollectedHeap* _g1h;
5297   nmethod* _nm;
5298 
5299   template <class T> void do_oop_work(T* p) {
5300     T heap_oop = oopDesc::load_heap_oop(p);
5301     if (!oopDesc::is_null(heap_oop)) {
5302       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5303       HeapRegion* hr = _g1h->heap_region_containing(obj);
5304       assert(!hr->is_continues_humongous(),
5305              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5306              " starting at " HR_FORMAT,
5307              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5308 
5309       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5310       hr->add_strong_code_root_locked(_nm);
5311     }
5312   }
5313 
5314 public:
5315   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5316     _g1h(g1h), _nm(nm) {}
5317 
5318   void do_oop(oop* p)       { do_oop_work(p); }
5319   void do_oop(narrowOop* p) { do_oop_work(p); }
5320 };
5321 
5322 class UnregisterNMethodOopClosure: public OopClosure {
5323   G1CollectedHeap* _g1h;
5324   nmethod* _nm;
5325 
5326   template <class T> void do_oop_work(T* p) {
5327     T heap_oop = oopDesc::load_heap_oop(p);
5328     if (!oopDesc::is_null(heap_oop)) {
5329       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5330       HeapRegion* hr = _g1h->heap_region_containing(obj);
5331       assert(!hr->is_continues_humongous(),
5332              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5333              " starting at " HR_FORMAT,
5334              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5335 
5336       hr->remove_strong_code_root(_nm);
5337     }
5338   }
5339 
5340 public:
5341   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5342     _g1h(g1h), _nm(nm) {}
5343 
5344   void do_oop(oop* p)       { do_oop_work(p); }
5345   void do_oop(narrowOop* p) { do_oop_work(p); }
5346 };
5347 
5348 // Returns true if the reference points to an object that
5349 // can move in an incremental collection.
5350 bool G1CollectedHeap::is_scavengable(oop obj) {
5351   HeapRegion* hr = heap_region_containing(obj);
5352   return !hr->is_pinned();
5353 }
5354 
5355 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5356   guarantee(nm != NULL, "sanity");
5357   RegisterNMethodOopClosure reg_cl(this, nm);
5358   nm->oops_do(&reg_cl);
5359 }
5360 
5361 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5362   guarantee(nm != NULL, "sanity");
5363   UnregisterNMethodOopClosure reg_cl(this, nm);
5364   nm->oops_do(&reg_cl, true);
5365 }
5366 
5367 void G1CollectedHeap::purge_code_root_memory() {
5368   double purge_start = os::elapsedTime();
5369   G1CodeRootSet::purge();
5370   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5371   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5372 }
5373 
5374 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5375   G1CollectedHeap* _g1h;
5376 
5377 public:
5378   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5379     _g1h(g1h) {}
5380 
5381   void do_code_blob(CodeBlob* cb) {
5382     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5383     if (nm == NULL) {
5384       return;
5385     }
5386 
5387     if (ScavengeRootsInCode) {
5388       _g1h->register_nmethod(nm);
5389     }
5390   }
5391 };
5392 
5393 void G1CollectedHeap::rebuild_strong_code_roots() {
5394   RebuildStrongCodeRootClosure blob_cl(this);
5395   CodeCache::blobs_do(&blob_cl);
5396 }