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