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/concurrentG1Refine.hpp"
  33 #include "gc/g1/concurrentG1RefineThread.hpp"
  34 #include "gc/g1/concurrentMarkThread.inline.hpp"
  35 #include "gc/g1/g1Allocator.inline.hpp"
  36 #include "gc/g1/g1CollectedHeap.inline.hpp"
  37 #include "gc/g1/g1CollectionSet.hpp"
  38 #include "gc/g1/g1CollectorPolicy.hpp"
  39 #include "gc/g1/g1CollectorState.hpp"
  40 #include "gc/g1/g1EvacStats.inline.hpp"
  41 #include "gc/g1/g1FullGCScope.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.inline.hpp"
  52 #include "gc/g1/g1RootClosures.hpp"
  53 #include "gc/g1/g1RootProcessor.hpp"
  54 #include "gc/g1/g1SerialFullCollector.hpp"
  55 #include "gc/g1/g1StringDedup.hpp"
  56 #include "gc/g1/g1YCTypes.hpp"
  57 #include "gc/g1/heapRegion.inline.hpp"
  58 #include "gc/g1/heapRegionRemSet.hpp"
  59 #include "gc/g1/heapRegionSet.inline.hpp"
  60 #include "gc/g1/suspendibleThreadSet.hpp"
  61 #include "gc/g1/vm_operations_g1.hpp"
  62 #include "gc/shared/gcHeapSummary.hpp"
  63 #include "gc/shared/gcId.hpp"
  64 #include "gc/shared/gcLocker.inline.hpp"
  65 #include "gc/shared/gcTimer.hpp"
  66 #include "gc/shared/gcTrace.hpp"
  67 #include "gc/shared/gcTraceTime.inline.hpp"
  68 #include "gc/shared/generationSpec.hpp"
  69 #include "gc/shared/isGCActiveMark.hpp"
  70 #include "gc/shared/preservedMarks.inline.hpp"
  71 #include "gc/shared/referenceProcessor.inline.hpp"
  72 #include "gc/shared/taskqueue.inline.hpp"
  73 #include "logging/log.hpp"
  74 #include "memory/allocation.hpp"
  75 #include "memory/iterator.hpp"
  76 #include "memory/resourceArea.hpp"
  77 #include "oops/oop.inline.hpp"
  78 #include "prims/resolvedMethodTable.hpp"
  79 #include "runtime/atomic.hpp"
  80 #include "runtime/init.hpp"
  81 #include "runtime/orderAccess.inline.hpp"
  82 #include "runtime/vmThread.hpp"
  83 #include "utilities/globalDefinitions.hpp"
  84 #include "utilities/stack.inline.hpp"
  85 
  86 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  87 
  88 // INVARIANTS/NOTES
  89 //
  90 // All allocation activity covered by the G1CollectedHeap interface is
  91 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  92 // and allocate_new_tlab, which are the "entry" points to the
  93 // allocation code from the rest of the JVM.  (Note that this does not
  94 // apply to TLAB allocation, which is not part of this interface: it
  95 // is done by clients of this interface.)
  96 
  97 // Local to this file.
  98 
  99 class RefineCardTableEntryClosure: public CardTableEntryClosure {
 100   bool _concurrent;
 101 public:
 102   RefineCardTableEntryClosure() : _concurrent(true) { }
 103 
 104   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 105     G1CollectedHeap::heap()->g1_rem_set()->refine_card_concurrently(card_ptr, worker_i);
 106 
 107     if (_concurrent && SuspendibleThreadSet::should_yield()) {
 108       // Caller will actually yield.
 109       return false;
 110     }
 111     // Otherwise, we finished successfully; return true.
 112     return true;
 113   }
 114 
 115   void set_concurrent(bool b) { _concurrent = b; }
 116 };
 117 
 118 
 119 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 120  private:
 121   size_t _num_dirtied;
 122   G1CollectedHeap* _g1h;
 123   G1SATBCardTableLoggingModRefBS* _g1_bs;
 124 
 125   HeapRegion* region_for_card(jbyte* card_ptr) const {
 126     return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
 127   }
 128 
 129   bool will_become_free(HeapRegion* hr) const {
 130     // A region will be freed by free_collection_set if the region is in the
 131     // collection set and has not had an evacuation failure.
 132     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 133   }
 134 
 135  public:
 136   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
 137     _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
 138 
 139   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 140     HeapRegion* hr = region_for_card(card_ptr);
 141 
 142     // Should only dirty cards in regions that won't be freed.
 143     if (!will_become_free(hr)) {
 144       *card_ptr = CardTableModRefBS::dirty_card_val();
 145       _num_dirtied++;
 146     }
 147 
 148     return true;
 149   }
 150 
 151   size_t num_dirtied()   const { return _num_dirtied; }
 152 };
 153 
 154 
 155 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 156   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 157 }
 158 
 159 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 160   // The from card cache is not the memory that is actually committed. So we cannot
 161   // take advantage of the zero_filled parameter.
 162   reset_from_card_cache(start_idx, num_regions);
 163 }
 164 
 165 // Returns true if the reference points to an object that
 166 // can move in an incremental collection.
 167 bool G1CollectedHeap::is_scavengable(const void* p) {
 168   HeapRegion* hr = heap_region_containing(p);
 169   return !hr->is_pinned();
 170 }
 171 
 172 // Private methods.
 173 
 174 HeapRegion*
 175 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 176   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 177   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 178     if (!_secondary_free_list.is_empty()) {
 179       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 180                                       "secondary_free_list has %u entries",
 181                                       _secondary_free_list.length());
 182       // It looks as if there are free regions available on the
 183       // secondary_free_list. Let's move them to the free_list and try
 184       // again to allocate from it.
 185       append_secondary_free_list();
 186 
 187       assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
 188              "empty we should have moved at least one entry to the free_list");
 189       HeapRegion* res = _hrm.allocate_free_region(is_old);
 190       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 191                                       "allocated " HR_FORMAT " from secondary_free_list",
 192                                       HR_FORMAT_PARAMS(res));
 193       return res;
 194     }
 195 
 196     // Wait here until we get notified either when (a) there are no
 197     // more free regions coming or (b) some regions have been moved on
 198     // the secondary_free_list.
 199     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 200   }
 201 
 202   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 203                                   "could not allocate from secondary_free_list");
 204   return NULL;
 205 }
 206 
 207 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 208   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 209          "the only time we use this to allocate a humongous region is "
 210          "when we are allocating a single humongous region");
 211 
 212   HeapRegion* res;
 213   if (G1StressConcRegionFreeing) {
 214     if (!_secondary_free_list.is_empty()) {
 215       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 216                                       "forced to look at the secondary_free_list");
 217       res = new_region_try_secondary_free_list(is_old);
 218       if (res != NULL) {
 219         return res;
 220       }
 221     }
 222   }
 223 
 224   res = _hrm.allocate_free_region(is_old);
 225 
 226   if (res == NULL) {
 227     log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 228                                     "res == NULL, trying the secondary_free_list");
 229     res = new_region_try_secondary_free_list(is_old);
 230   }
 231   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 232     // Currently, only attempts to allocate GC alloc regions set
 233     // do_expand to true. So, we should only reach here during a
 234     // safepoint. If this assumption changes we might have to
 235     // reconsider the use of _expand_heap_after_alloc_failure.
 236     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 237 
 238     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 239                               word_size * HeapWordSize);
 240 
 241     if (expand(word_size * HeapWordSize)) {
 242       // Given that expand() succeeded in expanding the heap, and we
 243       // always expand the heap by an amount aligned to the heap
 244       // region size, the free list should in theory not be empty.
 245       // In either case allocate_free_region() will check for NULL.
 246       res = _hrm.allocate_free_region(is_old);
 247     } else {
 248       _expand_heap_after_alloc_failure = false;
 249     }
 250   }
 251   return res;
 252 }
 253 
 254 HeapWord*
 255 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 256                                                            uint num_regions,
 257                                                            size_t word_size,
 258                                                            AllocationContext_t context) {
 259   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 260   assert(is_humongous(word_size), "word_size should be humongous");
 261   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 262 
 263   // Index of last region in the series.
 264   uint last = first + num_regions - 1;
 265 
 266   // We need to initialize the region(s) we just discovered. This is
 267   // a bit tricky given that it can happen concurrently with
 268   // refinement threads refining cards on these regions and
 269   // potentially wanting to refine the BOT as they are scanning
 270   // those cards (this can happen shortly after a cleanup; see CR
 271   // 6991377). So we have to set up the region(s) carefully and in
 272   // a specific order.
 273 
 274   // The word size sum of all the regions we will allocate.
 275   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 276   assert(word_size <= word_size_sum, "sanity");
 277 
 278   // This will be the "starts humongous" region.
 279   HeapRegion* first_hr = region_at(first);
 280   // The header of the new object will be placed at the bottom of
 281   // the first region.
 282   HeapWord* new_obj = first_hr->bottom();
 283   // This will be the new top of the new object.
 284   HeapWord* obj_top = new_obj + word_size;
 285 
 286   // First, we need to zero the header of the space that we will be
 287   // allocating. When we update top further down, some refinement
 288   // threads might try to scan the region. By zeroing the header we
 289   // ensure that any thread that will try to scan the region will
 290   // come across the zero klass word and bail out.
 291   //
 292   // NOTE: It would not have been correct to have used
 293   // CollectedHeap::fill_with_object() and make the space look like
 294   // an int array. The thread that is doing the allocation will
 295   // later update the object header to a potentially different array
 296   // type and, for a very short period of time, the klass and length
 297   // fields will be inconsistent. This could cause a refinement
 298   // thread to calculate the object size incorrectly.
 299   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 300 
 301   // Next, pad out the unused tail of the last region with filler
 302   // objects, for improved usage accounting.
 303   // How many words we use for filler objects.
 304   size_t word_fill_size = word_size_sum - word_size;
 305 
 306   // How many words memory we "waste" which cannot hold a filler object.
 307   size_t words_not_fillable = 0;
 308 
 309   if (word_fill_size >= min_fill_size()) {
 310     fill_with_objects(obj_top, word_fill_size);
 311   } else if (word_fill_size > 0) {
 312     // We have space to fill, but we cannot fit an object there.
 313     words_not_fillable = word_fill_size;
 314     word_fill_size = 0;
 315   }
 316 
 317   // We will set up the first region as "starts humongous". This
 318   // will also update the BOT covering all the regions to reflect
 319   // that there is a single object that starts at the bottom of the
 320   // first region.
 321   first_hr->set_starts_humongous(obj_top, word_fill_size);
 322   first_hr->set_allocation_context(context);
 323   // Then, if there are any, we will set up the "continues
 324   // humongous" regions.
 325   HeapRegion* hr = NULL;
 326   for (uint i = first + 1; i <= last; ++i) {
 327     hr = region_at(i);
 328     hr->set_continues_humongous(first_hr);
 329     hr->set_allocation_context(context);
 330   }
 331 
 332   // Up to this point no concurrent thread would have been able to
 333   // do any scanning on any region in this series. All the top
 334   // fields still point to bottom, so the intersection between
 335   // [bottom,top] and [card_start,card_end] will be empty. Before we
 336   // update the top fields, we'll do a storestore to make sure that
 337   // no thread sees the update to top before the zeroing of the
 338   // object header and the BOT initialization.
 339   OrderAccess::storestore();
 340 
 341   // Now, we will update the top fields of the "continues humongous"
 342   // regions except the last one.
 343   for (uint i = first; i < last; ++i) {
 344     hr = region_at(i);
 345     hr->set_top(hr->end());
 346   }
 347 
 348   hr = region_at(last);
 349   // If we cannot fit a filler object, we must set top to the end
 350   // of the humongous object, otherwise we cannot iterate the heap
 351   // and the BOT will not be complete.
 352   hr->set_top(hr->end() - words_not_fillable);
 353 
 354   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 355          "obj_top should be in last region");
 356 
 357   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 358 
 359   assert(words_not_fillable == 0 ||
 360          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 361          "Miscalculation in humongous allocation");
 362 
 363   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 364 
 365   for (uint i = first; i <= last; ++i) {
 366     hr = region_at(i);
 367     _humongous_set.add(hr);
 368     _hr_printer.alloc(hr);
 369   }
 370 
 371   return new_obj;
 372 }
 373 
 374 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 375   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 376   return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 377 }
 378 
 379 // If could fit into free regions w/o expansion, try.
 380 // Otherwise, if can expand, do so.
 381 // Otherwise, if using ex regions might help, try with ex given back.
 382 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
 383   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 384 
 385   _verifier->verify_region_sets_optional();
 386 
 387   uint first = G1_NO_HRM_INDEX;
 388   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 389 
 390   if (obj_regions == 1) {
 391     // Only one region to allocate, try to use a fast path by directly allocating
 392     // from the free lists. Do not try to expand here, we will potentially do that
 393     // later.
 394     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 395     if (hr != NULL) {
 396       first = hr->hrm_index();
 397     }
 398   } else {
 399     // We can't allocate humongous regions spanning more than one region while
 400     // cleanupComplete() is running, since some of the regions we find to be
 401     // empty might not yet be added to the free list. It is not straightforward
 402     // to know in which list they are on so that we can remove them. We only
 403     // need to do this if we need to allocate more than one region to satisfy the
 404     // current humongous allocation request. If we are only allocating one region
 405     // we use the one-region region allocation code (see above), that already
 406     // potentially waits for regions from the secondary free list.
 407     wait_while_free_regions_coming();
 408     append_secondary_free_list_if_not_empty_with_lock();
 409 
 410     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 411     // are lucky enough to find some.
 412     first = _hrm.find_contiguous_only_empty(obj_regions);
 413     if (first != G1_NO_HRM_INDEX) {
 414       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 415     }
 416   }
 417 
 418   if (first == G1_NO_HRM_INDEX) {
 419     // Policy: We could not find enough regions for the humongous object in the
 420     // free list. Look through the heap to find a mix of free and uncommitted regions.
 421     // If so, try expansion.
 422     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 423     if (first != G1_NO_HRM_INDEX) {
 424       // We found something. Make sure these regions are committed, i.e. expand
 425       // the heap. Alternatively we could do a defragmentation GC.
 426       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 427                                     word_size * HeapWordSize);
 428 
 429       _hrm.expand_at(first, obj_regions, workers());
 430       g1_policy()->record_new_heap_size(num_regions());
 431 
 432 #ifdef ASSERT
 433       for (uint i = first; i < first + obj_regions; ++i) {
 434         HeapRegion* hr = region_at(i);
 435         assert(hr->is_free(), "sanity");
 436         assert(hr->is_empty(), "sanity");
 437         assert(is_on_master_free_list(hr), "sanity");
 438       }
 439 #endif
 440       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 441     } else {
 442       // Policy: Potentially trigger a defragmentation GC.
 443     }
 444   }
 445 
 446   HeapWord* result = NULL;
 447   if (first != G1_NO_HRM_INDEX) {
 448     result = humongous_obj_allocate_initialize_regions(first, obj_regions,
 449                                                        word_size, context);
 450     assert(result != NULL, "it should always return a valid result");
 451 
 452     // A successful humongous object allocation changes the used space
 453     // information of the old generation so we need to recalculate the
 454     // sizes and update the jstat counters here.
 455     g1mm()->update_sizes();
 456   }
 457 
 458   _verifier->verify_region_sets_optional();
 459 
 460   return result;
 461 }
 462 
 463 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 464   assert_heap_not_locked_and_not_at_safepoint();
 465   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 466 
 467   uint dummy_gc_count_before;
 468   uint dummy_gclocker_retry_count = 0;
 469   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 470 }
 471 
 472 HeapWord*
 473 G1CollectedHeap::mem_allocate(size_t word_size,
 474                               bool*  gc_overhead_limit_was_exceeded) {
 475   assert_heap_not_locked_and_not_at_safepoint();
 476 
 477   // Loop until the allocation is satisfied, or unsatisfied after GC.
 478   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 479     uint gc_count_before;
 480 
 481     HeapWord* result = NULL;
 482     if (!is_humongous(word_size)) {
 483       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 484     } else {
 485       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 486     }
 487     if (result != NULL) {
 488       return result;
 489     }
 490 
 491     // Create the garbage collection operation...
 492     VM_G1CollectForAllocation op(gc_count_before, word_size);
 493     op.set_allocation_context(AllocationContext::current());
 494 
 495     // ...and get the VM thread to execute it.
 496     VMThread::execute(&op);
 497 
 498     if (op.prologue_succeeded() && op.pause_succeeded()) {
 499       // If the operation was successful we'll return the result even
 500       // if it is NULL. If the allocation attempt failed immediately
 501       // after a Full GC, it's unlikely we'll be able to allocate now.
 502       HeapWord* result = op.result();
 503       if (result != NULL && !is_humongous(word_size)) {
 504         // Allocations that take place on VM operations do not do any
 505         // card dirtying and we have to do it here. We only have to do
 506         // this for non-humongous allocations, though.
 507         dirty_young_block(result, word_size);
 508       }
 509       return result;
 510     } else {
 511       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 512         return NULL;
 513       }
 514       assert(op.result() == NULL,
 515              "the result should be NULL if the VM op did not succeed");
 516     }
 517 
 518     // Give a warning if we seem to be looping forever.
 519     if ((QueuedAllocationWarningCount > 0) &&
 520         (try_count % QueuedAllocationWarningCount == 0)) {
 521       log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
 522     }
 523   }
 524 
 525   ShouldNotReachHere();
 526   return NULL;
 527 }
 528 
 529 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 530                                                    AllocationContext_t context,
 531                                                    uint* gc_count_before_ret,
 532                                                    uint* gclocker_retry_count_ret) {
 533   // Make sure you read the note in attempt_allocation_humongous().
 534 
 535   assert_heap_not_locked_and_not_at_safepoint();
 536   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 537          "be called for humongous allocation requests");
 538 
 539   // We should only get here after the first-level allocation attempt
 540   // (attempt_allocation()) failed to allocate.
 541 
 542   // We will loop until a) we manage to successfully perform the
 543   // allocation or b) we successfully schedule a collection which
 544   // fails to perform the allocation. b) is the only case when we'll
 545   // return NULL.
 546   HeapWord* result = NULL;
 547   for (int try_count = 1; /* we'll return */; try_count += 1) {
 548     bool should_try_gc;
 549     uint gc_count_before;
 550 
 551     {
 552       MutexLockerEx x(Heap_lock);
 553       result = _allocator->attempt_allocation_locked(word_size, context);
 554       if (result != NULL) {
 555         return result;
 556       }
 557 
 558       if (GCLocker::is_active_and_needs_gc()) {
 559         if (g1_policy()->can_expand_young_list()) {
 560           // No need for an ergo verbose message here,
 561           // can_expand_young_list() does this when it returns true.
 562           result = _allocator->attempt_allocation_force(word_size, context);
 563           if (result != NULL) {
 564             return result;
 565           }
 566         }
 567         should_try_gc = false;
 568       } else {
 569         // The GCLocker may not be active but the GCLocker initiated
 570         // GC may not yet have been performed (GCLocker::needs_gc()
 571         // returns true). In this case we do not try this GC and
 572         // wait until the GCLocker initiated GC is performed, and
 573         // then retry the allocation.
 574         if (GCLocker::needs_gc()) {
 575           should_try_gc = false;
 576         } else {
 577           // Read the GC count while still holding the Heap_lock.
 578           gc_count_before = total_collections();
 579           should_try_gc = true;
 580         }
 581       }
 582     }
 583 
 584     if (should_try_gc) {
 585       bool succeeded;
 586       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 587                                    GCCause::_g1_inc_collection_pause);
 588       if (result != NULL) {
 589         assert(succeeded, "only way to get back a non-NULL result");
 590         return result;
 591       }
 592 
 593       if (succeeded) {
 594         // If we get here we successfully scheduled a collection which
 595         // failed to allocate. No point in trying to allocate
 596         // further. We'll just return NULL.
 597         MutexLockerEx x(Heap_lock);
 598         *gc_count_before_ret = total_collections();
 599         return NULL;
 600       }
 601     } else {
 602       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 603         MutexLockerEx x(Heap_lock);
 604         *gc_count_before_ret = total_collections();
 605         return NULL;
 606       }
 607       // The GCLocker is either active or the GCLocker initiated
 608       // GC has not yet been performed. Stall until it is and
 609       // then retry the allocation.
 610       GCLocker::stall_until_clear();
 611       (*gclocker_retry_count_ret) += 1;
 612     }
 613 
 614     // We can reach here if we were unsuccessful in scheduling a
 615     // collection (because another thread beat us to it) or if we were
 616     // stalled due to the GC locker. In either can we should retry the
 617     // allocation attempt in case another thread successfully
 618     // performed a collection and reclaimed enough space. We do the
 619     // first attempt (without holding the Heap_lock) here and the
 620     // follow-on attempt will be at the start of the next loop
 621     // iteration (after taking the Heap_lock).
 622     result = _allocator->attempt_allocation(word_size, context);
 623     if (result != NULL) {
 624       return result;
 625     }
 626 
 627     // Give a warning if we seem to be looping forever.
 628     if ((QueuedAllocationWarningCount > 0) &&
 629         (try_count % QueuedAllocationWarningCount == 0)) {
 630       log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
 631                       "retries %d times", try_count);
 632     }
 633   }
 634 
 635   ShouldNotReachHere();
 636   return NULL;
 637 }
 638 
 639 void G1CollectedHeap::begin_archive_alloc_range() {
 640   assert_at_safepoint(true /* should_be_vm_thread */);
 641   if (_archive_allocator == NULL) {
 642     _archive_allocator = G1ArchiveAllocator::create_allocator(this);
 643   }
 644 }
 645 
 646 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 647   // Allocations in archive regions cannot be of a size that would be considered
 648   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 649   // may be different at archive-restore time.
 650   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 651 }
 652 
 653 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 654   assert_at_safepoint(true /* should_be_vm_thread */);
 655   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 656   if (is_archive_alloc_too_large(word_size)) {
 657     return NULL;
 658   }
 659   return _archive_allocator->archive_mem_allocate(word_size);
 660 }
 661 
 662 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 663                                               size_t end_alignment_in_bytes) {
 664   assert_at_safepoint(true /* should_be_vm_thread */);
 665   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 666 
 667   // Call complete_archive to do the real work, filling in the MemRegion
 668   // array with the archive regions.
 669   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 670   delete _archive_allocator;
 671   _archive_allocator = NULL;
 672 }
 673 
 674 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 675   assert(ranges != NULL, "MemRegion array NULL");
 676   assert(count != 0, "No MemRegions provided");
 677   MemRegion reserved = _hrm.reserved();
 678   for (size_t i = 0; i < count; i++) {
 679     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 680       return false;
 681     }
 682   }
 683   return true;
 684 }
 685 
 686 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) {
 687   assert(!is_init_completed(), "Expect to be called at JVM init time");
 688   assert(ranges != NULL, "MemRegion array NULL");
 689   assert(count != 0, "No MemRegions provided");
 690   MutexLockerEx x(Heap_lock);
 691 
 692   MemRegion reserved = _hrm.reserved();
 693   HeapWord* prev_last_addr = NULL;
 694   HeapRegion* prev_last_region = NULL;
 695 
 696   // Temporarily disable pretouching of heap pages. This interface is used
 697   // when mmap'ing archived heap data in, so pre-touching is wasted.
 698   FlagSetting fs(AlwaysPreTouch, false);
 699 
 700   // Enable archive object checking used by G1MarkSweep. We have to let it know
 701   // about each archive range, so that objects in those ranges aren't marked.
 702   G1ArchiveAllocator::enable_archive_object_check();
 703 
 704   // For each specified MemRegion range, allocate the corresponding G1
 705   // regions and mark them as archive regions. We expect the ranges in
 706   // ascending starting address order, without overlap.
 707   for (size_t i = 0; i < count; i++) {
 708     MemRegion curr_range = ranges[i];
 709     HeapWord* start_address = curr_range.start();
 710     size_t word_size = curr_range.word_size();
 711     HeapWord* last_address = curr_range.last();
 712     size_t commits = 0;
 713 
 714     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 715               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 716               p2i(start_address), p2i(last_address));
 717     guarantee(start_address > prev_last_addr,
 718               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 719               p2i(start_address), p2i(prev_last_addr));
 720     prev_last_addr = last_address;
 721 
 722     // Check for ranges that start in the same G1 region in which the previous
 723     // range ended, and adjust the start address so we don't try to allocate
 724     // the same region again. If the current range is entirely within that
 725     // region, skip it, just adjusting the recorded top.
 726     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 727     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 728       start_address = start_region->end();
 729       if (start_address > last_address) {
 730         increase_used(word_size * HeapWordSize);
 731         start_region->set_top(last_address + 1);
 732         continue;
 733       }
 734       start_region->set_top(start_address);
 735       curr_range = MemRegion(start_address, last_address + 1);
 736       start_region = _hrm.addr_to_region(start_address);
 737     }
 738 
 739     // Perform the actual region allocation, exiting if it fails.
 740     // Then note how much new space we have allocated.
 741     if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
 742       return false;
 743     }
 744     increase_used(word_size * HeapWordSize);
 745     if (commits != 0) {
 746       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 747                                 HeapRegion::GrainWords * HeapWordSize * commits);
 748 
 749     }
 750 
 751     // Mark each G1 region touched by the range as archive, add it to the old set,
 752     // and set the allocation context and top.
 753     HeapRegion* curr_region = _hrm.addr_to_region(start_address);
 754     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 755     prev_last_region = last_region;
 756 
 757     while (curr_region != NULL) {
 758       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 759              "Region already in use (index %u)", curr_region->hrm_index());
 760       curr_region->set_allocation_context(AllocationContext::system());
 761       curr_region->set_archive();
 762       _hr_printer.alloc(curr_region);
 763       _old_set.add(curr_region);
 764       if (curr_region != last_region) {
 765         curr_region->set_top(curr_region->end());
 766         curr_region = _hrm.next_region_in_heap(curr_region);
 767       } else {
 768         curr_region->set_top(last_address + 1);
 769         curr_region = NULL;
 770       }
 771     }
 772 
 773     // Notify mark-sweep of the archive range.
 774     G1ArchiveAllocator::set_range_archive(curr_range, true);
 775   }
 776   return true;
 777 }
 778 
 779 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 780   assert(!is_init_completed(), "Expect to be called at JVM init time");
 781   assert(ranges != NULL, "MemRegion array NULL");
 782   assert(count != 0, "No MemRegions provided");
 783   MemRegion reserved = _hrm.reserved();
 784   HeapWord *prev_last_addr = NULL;
 785   HeapRegion* prev_last_region = NULL;
 786 
 787   // For each MemRegion, create filler objects, if needed, in the G1 regions
 788   // that contain the address range. The address range actually within the
 789   // MemRegion will not be modified. That is assumed to have been initialized
 790   // elsewhere, probably via an mmap of archived heap data.
 791   MutexLockerEx x(Heap_lock);
 792   for (size_t i = 0; i < count; i++) {
 793     HeapWord* start_address = ranges[i].start();
 794     HeapWord* last_address = ranges[i].last();
 795 
 796     assert(reserved.contains(start_address) && reserved.contains(last_address),
 797            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 798            p2i(start_address), p2i(last_address));
 799     assert(start_address > prev_last_addr,
 800            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 801            p2i(start_address), p2i(prev_last_addr));
 802 
 803     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 804     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 805     HeapWord* bottom_address = start_region->bottom();
 806 
 807     // Check for a range beginning in the same region in which the
 808     // previous one ended.
 809     if (start_region == prev_last_region) {
 810       bottom_address = prev_last_addr + 1;
 811     }
 812 
 813     // Verify that the regions were all marked as archive regions by
 814     // alloc_archive_regions.
 815     HeapRegion* curr_region = start_region;
 816     while (curr_region != NULL) {
 817       guarantee(curr_region->is_archive(),
 818                 "Expected archive region at index %u", curr_region->hrm_index());
 819       if (curr_region != last_region) {
 820         curr_region = _hrm.next_region_in_heap(curr_region);
 821       } else {
 822         curr_region = NULL;
 823       }
 824     }
 825 
 826     prev_last_addr = last_address;
 827     prev_last_region = last_region;
 828 
 829     // Fill the memory below the allocated range with dummy object(s),
 830     // if the region bottom does not match the range start, or if the previous
 831     // range ended within the same G1 region, and there is a gap.
 832     if (start_address != bottom_address) {
 833       size_t fill_size = pointer_delta(start_address, bottom_address);
 834       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 835       increase_used(fill_size * HeapWordSize);
 836     }
 837   }
 838 }
 839 
 840 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
 841                                                      uint* gc_count_before_ret,
 842                                                      uint* gclocker_retry_count_ret) {
 843   assert_heap_not_locked_and_not_at_safepoint();
 844   assert(!is_humongous(word_size), "attempt_allocation() should not "
 845          "be called for humongous allocation requests");
 846 
 847   AllocationContext_t context = AllocationContext::current();
 848   HeapWord* result = _allocator->attempt_allocation(word_size, context);
 849 
 850   if (result == NULL) {
 851     result = attempt_allocation_slow(word_size,
 852                                      context,
 853                                      gc_count_before_ret,
 854                                      gclocker_retry_count_ret);
 855   }
 856   assert_heap_not_locked();
 857   if (result != NULL) {
 858     dirty_young_block(result, word_size);
 859   }
 860   return result;
 861 }
 862 
 863 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
 864   assert(!is_init_completed(), "Expect to be called at JVM init time");
 865   assert(ranges != NULL, "MemRegion array NULL");
 866   assert(count != 0, "No MemRegions provided");
 867   MemRegion reserved = _hrm.reserved();
 868   HeapWord* prev_last_addr = NULL;
 869   HeapRegion* prev_last_region = NULL;
 870   size_t size_used = 0;
 871   size_t uncommitted_regions = 0;
 872 
 873   // For each Memregion, free the G1 regions that constitute it, and
 874   // notify mark-sweep that the range is no longer to be considered 'archive.'
 875   MutexLockerEx x(Heap_lock);
 876   for (size_t i = 0; i < count; i++) {
 877     HeapWord* start_address = ranges[i].start();
 878     HeapWord* last_address = ranges[i].last();
 879 
 880     assert(reserved.contains(start_address) && reserved.contains(last_address),
 881            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 882            p2i(start_address), p2i(last_address));
 883     assert(start_address > prev_last_addr,
 884            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 885            p2i(start_address), p2i(prev_last_addr));
 886     size_used += ranges[i].byte_size();
 887     prev_last_addr = last_address;
 888 
 889     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 890     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 891 
 892     // Check for ranges that start in the same G1 region in which the previous
 893     // range ended, and adjust the start address so we don't try to free
 894     // the same region again. If the current range is entirely within that
 895     // region, skip it.
 896     if (start_region == prev_last_region) {
 897       start_address = start_region->end();
 898       if (start_address > last_address) {
 899         continue;
 900       }
 901       start_region = _hrm.addr_to_region(start_address);
 902     }
 903     prev_last_region = last_region;
 904 
 905     // After verifying that each region was marked as an archive region by
 906     // alloc_archive_regions, set it free and empty and uncommit it.
 907     HeapRegion* curr_region = start_region;
 908     while (curr_region != NULL) {
 909       guarantee(curr_region->is_archive(),
 910                 "Expected archive region at index %u", curr_region->hrm_index());
 911       uint curr_index = curr_region->hrm_index();
 912       _old_set.remove(curr_region);
 913       curr_region->set_free();
 914       curr_region->set_top(curr_region->bottom());
 915       if (curr_region != last_region) {
 916         curr_region = _hrm.next_region_in_heap(curr_region);
 917       } else {
 918         curr_region = NULL;
 919       }
 920       _hrm.shrink_at(curr_index, 1);
 921       uncommitted_regions++;
 922     }
 923 
 924     // Notify mark-sweep that this is no longer an archive range.
 925     G1ArchiveAllocator::set_range_archive(ranges[i], false);
 926   }
 927 
 928   if (uncommitted_regions != 0) {
 929     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 930                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 931   }
 932   decrease_used(size_used);
 933 }
 934 
 935 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
 936                                                         uint* gc_count_before_ret,
 937                                                         uint* gclocker_retry_count_ret) {
 938   // The structure of this method has a lot of similarities to
 939   // attempt_allocation_slow(). The reason these two were not merged
 940   // into a single one is that such a method would require several "if
 941   // allocation is not humongous do this, otherwise do that"
 942   // conditional paths which would obscure its flow. In fact, an early
 943   // version of this code did use a unified method which was harder to
 944   // follow and, as a result, it had subtle bugs that were hard to
 945   // track down. So keeping these two methods separate allows each to
 946   // be more readable. It will be good to keep these two in sync as
 947   // much as possible.
 948 
 949   assert_heap_not_locked_and_not_at_safepoint();
 950   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 951          "should only be called for humongous allocations");
 952 
 953   // Humongous objects can exhaust the heap quickly, so we should check if we
 954   // need to start a marking cycle at each humongous object allocation. We do
 955   // the check before we do the actual allocation. The reason for doing it
 956   // before the allocation is that we avoid having to keep track of the newly
 957   // allocated memory while we do a GC.
 958   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
 959                                            word_size)) {
 960     collect(GCCause::_g1_humongous_allocation);
 961   }
 962 
 963   // We will loop until a) we manage to successfully perform the
 964   // allocation or b) we successfully schedule a collection which
 965   // fails to perform the allocation. b) is the only case when we'll
 966   // return NULL.
 967   HeapWord* result = NULL;
 968   for (int try_count = 1; /* we'll return */; try_count += 1) {
 969     bool should_try_gc;
 970     uint gc_count_before;
 971 
 972     {
 973       MutexLockerEx x(Heap_lock);
 974 
 975       // Given that humongous objects are not allocated in young
 976       // regions, we'll first try to do the allocation without doing a
 977       // collection hoping that there's enough space in the heap.
 978       result = humongous_obj_allocate(word_size, AllocationContext::current());
 979       if (result != NULL) {
 980         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 981         g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 982         return result;
 983       }
 984 
 985       if (GCLocker::is_active_and_needs_gc()) {
 986         should_try_gc = false;
 987       } else {
 988          // The GCLocker may not be active but the GCLocker initiated
 989         // GC may not yet have been performed (GCLocker::needs_gc()
 990         // returns true). In this case we do not try this GC and
 991         // wait until the GCLocker initiated GC is performed, and
 992         // then retry the allocation.
 993         if (GCLocker::needs_gc()) {
 994           should_try_gc = false;
 995         } else {
 996           // Read the GC count while still holding the Heap_lock.
 997           gc_count_before = total_collections();
 998           should_try_gc = true;
 999         }
1000       }
1001     }
1002 
1003     if (should_try_gc) {
1004       // If we failed to allocate the humongous object, we should try to
1005       // do a collection pause (if we're allowed) in case it reclaims
1006       // enough space for the allocation to succeed after the pause.
1007 
1008       bool succeeded;
1009       result = do_collection_pause(word_size, gc_count_before, &succeeded,
1010                                    GCCause::_g1_humongous_allocation);
1011       if (result != NULL) {
1012         assert(succeeded, "only way to get back a non-NULL result");
1013         return result;
1014       }
1015 
1016       if (succeeded) {
1017         // If we get here we successfully scheduled a collection which
1018         // failed to allocate. No point in trying to allocate
1019         // further. We'll just return NULL.
1020         MutexLockerEx x(Heap_lock);
1021         *gc_count_before_ret = total_collections();
1022         return NULL;
1023       }
1024     } else {
1025       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1026         MutexLockerEx x(Heap_lock);
1027         *gc_count_before_ret = total_collections();
1028         return NULL;
1029       }
1030       // The GCLocker is either active or the GCLocker initiated
1031       // GC has not yet been performed. Stall until it is and
1032       // then retry the allocation.
1033       GCLocker::stall_until_clear();
1034       (*gclocker_retry_count_ret) += 1;
1035     }
1036 
1037     // We can reach here if we were unsuccessful in scheduling a
1038     // collection (because another thread beat us to it) or if we were
1039     // stalled due to the GC locker. In either can we should retry the
1040     // allocation attempt in case another thread successfully
1041     // performed a collection and reclaimed enough space.  Give a
1042     // warning if we seem to be looping forever.
1043 
1044     if ((QueuedAllocationWarningCount > 0) &&
1045         (try_count % QueuedAllocationWarningCount == 0)) {
1046       log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
1047                       "retries %d times", try_count);
1048     }
1049   }
1050 
1051   ShouldNotReachHere();
1052   return NULL;
1053 }
1054 
1055 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1056                                                            AllocationContext_t context,
1057                                                            bool expect_null_mutator_alloc_region) {
1058   assert_at_safepoint(true /* should_be_vm_thread */);
1059   assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1060          "the current alloc region was unexpectedly found to be non-NULL");
1061 
1062   if (!is_humongous(word_size)) {
1063     return _allocator->attempt_allocation_locked(word_size, context);
1064   } else {
1065     HeapWord* result = humongous_obj_allocate(word_size, context);
1066     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1067       collector_state()->set_initiate_conc_mark_if_possible(true);
1068     }
1069     return result;
1070   }
1071 
1072   ShouldNotReachHere();
1073 }
1074 
1075 class PostCompactionPrinterClosure: public HeapRegionClosure {
1076 private:
1077   G1HRPrinter* _hr_printer;
1078 public:
1079   bool doHeapRegion(HeapRegion* hr) {
1080     assert(!hr->is_young(), "not expecting to find young regions");
1081     _hr_printer->post_compaction(hr);
1082     return false;
1083   }
1084 
1085   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1086     : _hr_printer(hr_printer) { }
1087 };
1088 
1089 void G1CollectedHeap::print_hrm_post_compaction() {
1090   if (_hr_printer.is_active()) {
1091     PostCompactionPrinterClosure cl(hr_printer());
1092     heap_region_iterate(&cl);
1093   }
1094 
1095 }
1096 
1097 void G1CollectedHeap::abort_concurrent_cycle() {
1098   // Note: When we have a more flexible GC logging framework that
1099   // allows us to add optional attributes to a GC log record we
1100   // could consider timing and reporting how long we wait in the
1101   // following two methods.
1102   wait_while_free_regions_coming();
1103   // If we start the compaction before the CM threads finish
1104   // scanning the root regions we might trip them over as we'll
1105   // be moving objects / updating references. So let's wait until
1106   // they are done. By telling them to abort, they should complete
1107   // early.
1108   _cm->root_regions()->abort();
1109   _cm->root_regions()->wait_until_scan_finished();
1110   append_secondary_free_list_if_not_empty_with_lock();
1111 
1112   // Disable discovery and empty the discovered lists
1113   // for the CM ref processor.
1114   ref_processor_cm()->disable_discovery();
1115   ref_processor_cm()->abandon_partial_discovery();
1116   ref_processor_cm()->verify_no_references_recorded();
1117 
1118   // Abandon current iterations of concurrent marking and concurrent
1119   // refinement, if any are in progress.
1120   concurrent_mark()->abort();
1121 }
1122 
1123 void G1CollectedHeap::prepare_heap_for_full_collection() {
1124   // Make sure we'll choose a new allocation region afterwards.
1125   _allocator->release_mutator_alloc_region();
1126   _allocator->abandon_gc_alloc_regions();
1127   g1_rem_set()->cleanupHRRS();
1128 
1129   // We may have added regions to the current incremental collection
1130   // set between the last GC or pause and now. We need to clear the
1131   // incremental collection set and then start rebuilding it afresh
1132   // after this full GC.
1133   abandon_collection_set(collection_set());
1134 
1135   tear_down_region_sets(false /* free_list_only */);
1136   collector_state()->set_gcs_are_young(true);
1137 }
1138 
1139 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1140   assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1141   assert(used() == recalculate_used(), "Should be equal");
1142   _verifier->verify_region_sets_optional();
1143   _verifier->verify_before_gc();
1144   _verifier->check_bitmaps("Full GC Start");
1145 }
1146 
1147 void G1CollectedHeap::prepare_heap_for_mutators() {
1148   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1149   ClassLoaderDataGraph::purge();
1150   MetaspaceAux::verify_metrics();
1151 
1152   // Prepare heap for normal collections.
1153   assert(num_free_regions() == 0, "we should not have added any free regions");
1154   rebuild_region_sets(false /* free_list_only */);
1155   abort_refinement();
1156   resize_if_necessary_after_full_collection();
1157 
1158   // Rebuild the strong code root lists for each region
1159   rebuild_strong_code_roots();
1160 
1161   // Start a new incremental collection set for the next pause
1162   start_new_collection_set();
1163 
1164   _allocator->init_mutator_alloc_region();
1165 
1166   // Post collection state updates.
1167   MetaspaceGC::compute_new_size();
1168 }
1169 
1170 void G1CollectedHeap::abort_refinement() {
1171   if (_hot_card_cache->use_cache()) {
1172     _hot_card_cache->reset_card_counts();
1173     _hot_card_cache->reset_hot_cache();
1174   }
1175 
1176   // Discard all remembered set updates.
1177   JavaThread::dirty_card_queue_set().abandon_logs();
1178   assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1179 }
1180 
1181 void G1CollectedHeap::verify_after_full_collection() {
1182   check_gc_time_stamps();
1183   _hrm.verify_optional();
1184   _verifier->verify_region_sets_optional();
1185   _verifier->verify_after_gc();
1186   // Clear the previous marking bitmap, if needed for bitmap verification.
1187   // Note we cannot do this when we clear the next marking bitmap in
1188   // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1189   // objects marked during a full GC against the previous bitmap.
1190   // But we need to clear it before calling check_bitmaps below since
1191   // the full GC has compacted objects and updated TAMS but not updated
1192   // the prev bitmap.
1193   if (G1VerifyBitmaps) {
1194     GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1195     _cm->clear_prev_bitmap(workers());
1196   }
1197   _verifier->check_bitmaps("Full GC End");
1198 
1199   // At this point there should be no regions in the
1200   // entire heap tagged as young.
1201   assert(check_young_list_empty(), "young list should be empty at this point");
1202 
1203   // Note: since we've just done a full GC, concurrent
1204   // marking is no longer active. Therefore we need not
1205   // re-enable reference discovery for the CM ref processor.
1206   // That will be done at the start of the next marking cycle.
1207   // We also know that the STW processor should no longer
1208   // discover any new references.
1209   assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1210   assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1211   ref_processor_stw()->verify_no_references_recorded();
1212   ref_processor_cm()->verify_no_references_recorded();
1213 }
1214 
1215 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1216   print_hrm_post_compaction();
1217   heap_transition->print();
1218   print_heap_after_gc();
1219   print_heap_regions();
1220 #ifdef TRACESPINNING
1221   ParallelTaskTerminator::print_termination_counts();
1222 #endif
1223 }
1224 
1225 void G1CollectedHeap::do_full_collection_inner(G1FullGCScope* scope) {
1226   GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1227   g1_policy()->record_full_collection_start();
1228 
1229   print_heap_before_gc();
1230   print_heap_regions();
1231 
1232   abort_concurrent_cycle();
1233   verify_before_full_collection(scope->is_explicit_gc());
1234 
1235   gc_prologue(true);
1236   prepare_heap_for_full_collection();
1237 
1238   G1SerialFullCollector serial(scope, ref_processor_stw());
1239   serial.prepare_collection();
1240   serial.collect();
1241   serial.complete_collection();
1242 
1243   prepare_heap_for_mutators();
1244 
1245   g1_policy()->record_full_collection_end();
1246   gc_epilogue(true);
1247 
1248   // Post collection verification.
1249   verify_after_full_collection();
1250 
1251   // Post collection logging.
1252   // We should do this after we potentially resize the heap so
1253   // that all the COMMIT / UNCOMMIT events are generated before
1254   // the compaction events.
1255   print_heap_after_full_collection(scope->heap_transition());
1256 }
1257 
1258 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1259                                          bool clear_all_soft_refs) {
1260   assert_at_safepoint(true /* should_be_vm_thread */);
1261 
1262   if (GCLocker::check_active_before_gc()) {
1263     // Full GC was not completed.
1264     return false;
1265   }
1266 
1267   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1268       collector_policy()->should_clear_all_soft_refs();
1269 
1270   G1FullGCScope scope(explicit_gc, do_clear_all_soft_refs);
1271   do_full_collection_inner(&scope);
1272 
1273   // Full collection was successfully completed.
1274   return true;
1275 }
1276 
1277 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1278   // Currently, there is no facility in the do_full_collection(bool) API to notify
1279   // the caller that the collection did not succeed (e.g., because it was locked
1280   // out by the GC locker). So, right now, we'll ignore the return value.
1281   bool dummy = do_full_collection(true,                /* explicit_gc */
1282                                   clear_all_soft_refs);
1283 }
1284 
1285 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1286   // Include bytes that will be pre-allocated to support collections, as "used".
1287   const size_t used_after_gc = used();
1288   const size_t capacity_after_gc = capacity();
1289   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1290 
1291   // This is enforced in arguments.cpp.
1292   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1293          "otherwise the code below doesn't make sense");
1294 
1295   // We don't have floating point command-line arguments
1296   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1297   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1298   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1299   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1300 
1301   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1302   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1303 
1304   // We have to be careful here as these two calculations can overflow
1305   // 32-bit size_t's.
1306   double used_after_gc_d = (double) used_after_gc;
1307   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1308   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1309 
1310   // Let's make sure that they are both under the max heap size, which
1311   // by default will make them fit into a size_t.
1312   double desired_capacity_upper_bound = (double) max_heap_size;
1313   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1314                                     desired_capacity_upper_bound);
1315   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1316                                     desired_capacity_upper_bound);
1317 
1318   // We can now safely turn them into size_t's.
1319   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1320   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1321 
1322   // This assert only makes sense here, before we adjust them
1323   // with respect to the min and max heap size.
1324   assert(minimum_desired_capacity <= maximum_desired_capacity,
1325          "minimum_desired_capacity = " SIZE_FORMAT ", "
1326          "maximum_desired_capacity = " SIZE_FORMAT,
1327          minimum_desired_capacity, maximum_desired_capacity);
1328 
1329   // Should not be greater than the heap max size. No need to adjust
1330   // it with respect to the heap min size as it's a lower bound (i.e.,
1331   // we'll try to make the capacity larger than it, not smaller).
1332   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1333   // Should not be less than the heap min size. No need to adjust it
1334   // with respect to the heap max size as it's an upper bound (i.e.,
1335   // we'll try to make the capacity smaller than it, not greater).
1336   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1337 
1338   if (capacity_after_gc < minimum_desired_capacity) {
1339     // Don't expand unless it's significant
1340     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1341 
1342     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1343                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1344                               capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1345 
1346     expand(expand_bytes, _workers);
1347 
1348     // No expansion, now see if we want to shrink
1349   } else if (capacity_after_gc > maximum_desired_capacity) {
1350     // Capacity too large, compute shrinking size
1351     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1352 
1353     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1354                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1355                               capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1356 
1357     shrink(shrink_bytes);
1358   }
1359 }
1360 
1361 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1362                                                             AllocationContext_t context,
1363                                                             bool do_gc,
1364                                                             bool clear_all_soft_refs,
1365                                                             bool expect_null_mutator_alloc_region,
1366                                                             bool* gc_succeeded) {
1367   *gc_succeeded = true;
1368   // Let's attempt the allocation first.
1369   HeapWord* result =
1370     attempt_allocation_at_safepoint(word_size,
1371                                     context,
1372                                     expect_null_mutator_alloc_region);
1373   if (result != NULL) {
1374     assert(*gc_succeeded, "sanity");
1375     return result;
1376   }
1377 
1378   // In a G1 heap, we're supposed to keep allocation from failing by
1379   // incremental pauses.  Therefore, at least for now, we'll favor
1380   // expansion over collection.  (This might change in the future if we can
1381   // do something smarter than full collection to satisfy a failed alloc.)
1382   result = expand_and_allocate(word_size, context);
1383   if (result != NULL) {
1384     assert(*gc_succeeded, "sanity");
1385     return result;
1386   }
1387 
1388   if (do_gc) {
1389     // Expansion didn't work, we'll try to do a Full GC.
1390     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1391                                        clear_all_soft_refs);
1392   }
1393 
1394   return NULL;
1395 }
1396 
1397 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1398                                                      AllocationContext_t context,
1399                                                      bool* succeeded) {
1400   assert_at_safepoint(true /* should_be_vm_thread */);
1401 
1402   // Attempts to allocate followed by Full GC.
1403   HeapWord* result =
1404     satisfy_failed_allocation_helper(word_size,
1405                                      context,
1406                                      true,  /* do_gc */
1407                                      false, /* clear_all_soft_refs */
1408                                      false, /* expect_null_mutator_alloc_region */
1409                                      succeeded);
1410 
1411   if (result != NULL || !*succeeded) {
1412     return result;
1413   }
1414 
1415   // Attempts to allocate followed by Full GC that will collect all soft references.
1416   result = satisfy_failed_allocation_helper(word_size,
1417                                             context,
1418                                             true, /* do_gc */
1419                                             true, /* clear_all_soft_refs */
1420                                             true, /* expect_null_mutator_alloc_region */
1421                                             succeeded);
1422 
1423   if (result != NULL || !*succeeded) {
1424     return result;
1425   }
1426 
1427   // Attempts to allocate, no GC
1428   result = satisfy_failed_allocation_helper(word_size,
1429                                             context,
1430                                             false, /* do_gc */
1431                                             false, /* clear_all_soft_refs */
1432                                             true,  /* expect_null_mutator_alloc_region */
1433                                             succeeded);
1434 
1435   if (result != NULL) {
1436     assert(*succeeded, "sanity");
1437     return result;
1438   }
1439 
1440   assert(!collector_policy()->should_clear_all_soft_refs(),
1441          "Flag should have been handled and cleared prior to this point");
1442 
1443   // What else?  We might try synchronous finalization later.  If the total
1444   // space available is large enough for the allocation, then a more
1445   // complete compaction phase than we've tried so far might be
1446   // appropriate.
1447   assert(*succeeded, "sanity");
1448   return NULL;
1449 }
1450 
1451 // Attempting to expand the heap sufficiently
1452 // to support an allocation of the given "word_size".  If
1453 // successful, perform the allocation and return the address of the
1454 // allocated block, or else "NULL".
1455 
1456 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1457   assert_at_safepoint(true /* should_be_vm_thread */);
1458 
1459   _verifier->verify_region_sets_optional();
1460 
1461   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1462   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1463                             word_size * HeapWordSize);
1464 
1465 
1466   if (expand(expand_bytes, _workers)) {
1467     _hrm.verify_optional();
1468     _verifier->verify_region_sets_optional();
1469     return attempt_allocation_at_safepoint(word_size,
1470                                            context,
1471                                            false /* expect_null_mutator_alloc_region */);
1472   }
1473   return NULL;
1474 }
1475 
1476 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1477   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1478   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1479                                        HeapRegion::GrainBytes);
1480 
1481   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1482                             expand_bytes, aligned_expand_bytes);
1483 
1484   if (is_maximal_no_gc()) {
1485     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1486     return false;
1487   }
1488 
1489   double expand_heap_start_time_sec = os::elapsedTime();
1490   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1491   assert(regions_to_expand > 0, "Must expand by at least one region");
1492 
1493   uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1494   if (expand_time_ms != NULL) {
1495     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1496   }
1497 
1498   if (expanded_by > 0) {
1499     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1500     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1501     g1_policy()->record_new_heap_size(num_regions());
1502   } else {
1503     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1504 
1505     // The expansion of the virtual storage space was unsuccessful.
1506     // Let's see if it was because we ran out of swap.
1507     if (G1ExitOnExpansionFailure &&
1508         _hrm.available() >= regions_to_expand) {
1509       // We had head room...
1510       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1511     }
1512   }
1513   return regions_to_expand > 0;
1514 }
1515 
1516 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1517   size_t aligned_shrink_bytes =
1518     ReservedSpace::page_align_size_down(shrink_bytes);
1519   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1520                                          HeapRegion::GrainBytes);
1521   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1522 
1523   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1524   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1525 
1526 
1527   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",
1528                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1529   if (num_regions_removed > 0) {
1530     g1_policy()->record_new_heap_size(num_regions());
1531   } else {
1532     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1533   }
1534 }
1535 
1536 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1537   _verifier->verify_region_sets_optional();
1538 
1539   // We should only reach here at the end of a Full GC which means we
1540   // should not not be holding to any GC alloc regions. The method
1541   // below will make sure of that and do any remaining clean up.
1542   _allocator->abandon_gc_alloc_regions();
1543 
1544   // Instead of tearing down / rebuilding the free lists here, we
1545   // could instead use the remove_all_pending() method on free_list to
1546   // remove only the ones that we need to remove.
1547   tear_down_region_sets(true /* free_list_only */);
1548   shrink_helper(shrink_bytes);
1549   rebuild_region_sets(true /* free_list_only */);
1550 
1551   _hrm.verify_optional();
1552   _verifier->verify_region_sets_optional();
1553 }
1554 
1555 // Public methods.
1556 
1557 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1558   CollectedHeap(),
1559   _collector_policy(collector_policy),
1560   _g1_policy(create_g1_policy()),
1561   _collection_set(this, _g1_policy),
1562   _dirty_card_queue_set(false),
1563   _is_alive_closure_cm(this),
1564   _is_alive_closure_stw(this),
1565   _ref_processor_cm(NULL),
1566   _ref_processor_stw(NULL),
1567   _bot(NULL),
1568   _hot_card_cache(NULL),
1569   _g1_rem_set(NULL),
1570   _cg1r(NULL),
1571   _g1mm(NULL),
1572   _refine_cte_cl(NULL),
1573   _preserved_marks_set(true /* in_c_heap */),
1574   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1575   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1576   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1577   _humongous_reclaim_candidates(),
1578   _has_humongous_reclaim_candidates(false),
1579   _archive_allocator(NULL),
1580   _free_regions_coming(false),
1581   _gc_time_stamp(0),
1582   _summary_bytes_used(0),
1583   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1584   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1585   _expand_heap_after_alloc_failure(true),
1586   _old_marking_cycles_started(0),
1587   _old_marking_cycles_completed(0),
1588   _in_cset_fast_test(),
1589   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1590   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()) {
1591 
1592   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1593                           /* are_GC_task_threads */true,
1594                           /* are_ConcurrentGC_threads */false);
1595   _workers->initialize_workers();
1596   _verifier = new G1HeapVerifier(this);
1597 
1598   _allocator = G1Allocator::create_allocator(this);
1599 
1600   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1601 
1602   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1603 
1604   // Override the default _filler_array_max_size so that no humongous filler
1605   // objects are created.
1606   _filler_array_max_size = _humongous_object_threshold_in_words;
1607 
1608   uint n_queues = ParallelGCThreads;
1609   _task_queues = new RefToScanQueueSet(n_queues);
1610 
1611   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1612 
1613   for (uint i = 0; i < n_queues; i++) {
1614     RefToScanQueue* q = new RefToScanQueue();
1615     q->initialize();
1616     _task_queues->register_queue(i, q);
1617     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1618   }
1619 
1620   // Initialize the G1EvacuationFailureALot counters and flags.
1621   NOT_PRODUCT(reset_evacuation_should_fail();)
1622 
1623   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1624 }
1625 
1626 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1627                                                                  size_t size,
1628                                                                  size_t translation_factor) {
1629   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1630   // Allocate a new reserved space, preferring to use large pages.
1631   ReservedSpace rs(size, preferred_page_size);
1632   G1RegionToSpaceMapper* result  =
1633     G1RegionToSpaceMapper::create_mapper(rs,
1634                                          size,
1635                                          rs.alignment(),
1636                                          HeapRegion::GrainBytes,
1637                                          translation_factor,
1638                                          mtGC);
1639 
1640   os::trace_page_sizes_for_requested_size(description,
1641                                           size,
1642                                           preferred_page_size,
1643                                           rs.alignment(),
1644                                           rs.base(),
1645                                           rs.size());
1646 
1647   return result;
1648 }
1649 
1650 jint G1CollectedHeap::initialize() {
1651   CollectedHeap::pre_initialize();
1652   os::enable_vtime();
1653 
1654   // Necessary to satisfy locking discipline assertions.
1655 
1656   MutexLocker x(Heap_lock);
1657 
1658   // While there are no constraints in the GC code that HeapWordSize
1659   // be any particular value, there are multiple other areas in the
1660   // system which believe this to be true (e.g. oop->object_size in some
1661   // cases incorrectly returns the size in wordSize units rather than
1662   // HeapWordSize).
1663   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1664 
1665   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1666   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1667   size_t heap_alignment = collector_policy()->heap_alignment();
1668 
1669   // Ensure that the sizes are properly aligned.
1670   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1671   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1672   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1673 
1674   _refine_cte_cl = new RefineCardTableEntryClosure();
1675 
1676   jint ecode = JNI_OK;
1677   _cg1r = ConcurrentG1Refine::create(_refine_cte_cl, &ecode);
1678   if (_cg1r == NULL) {
1679     return ecode;
1680   }
1681 
1682   // Reserve the maximum.
1683 
1684   // When compressed oops are enabled, the preferred heap base
1685   // is calculated by subtracting the requested size from the
1686   // 32Gb boundary and using the result as the base address for
1687   // heap reservation. If the requested size is not aligned to
1688   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1689   // into the ReservedHeapSpace constructor) then the actual
1690   // base of the reserved heap may end up differing from the
1691   // address that was requested (i.e. the preferred heap base).
1692   // If this happens then we could end up using a non-optimal
1693   // compressed oops mode.
1694 
1695   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1696                                                  heap_alignment);
1697 
1698   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1699 
1700   // Create the barrier set for the entire reserved region.
1701   G1SATBCardTableLoggingModRefBS* bs
1702     = new G1SATBCardTableLoggingModRefBS(reserved_region());
1703   bs->initialize();
1704   assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1705   set_barrier_set(bs);
1706 
1707   // Create the hot card cache.
1708   _hot_card_cache = new G1HotCardCache(this);
1709 
1710   // Also create a G1 rem set.
1711   _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache);
1712 
1713   // Carve out the G1 part of the heap.
1714   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1715   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1716   G1RegionToSpaceMapper* heap_storage =
1717     G1RegionToSpaceMapper::create_mapper(g1_rs,
1718                                          g1_rs.size(),
1719                                          page_size,
1720                                          HeapRegion::GrainBytes,
1721                                          1,
1722                                          mtJavaHeap);
1723   os::trace_page_sizes("Heap",
1724                        collector_policy()->min_heap_byte_size(),
1725                        max_byte_size,
1726                        page_size,
1727                        heap_rs.base(),
1728                        heap_rs.size());
1729   heap_storage->set_mapping_changed_listener(&_listener);
1730 
1731   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1732   G1RegionToSpaceMapper* bot_storage =
1733     create_aux_memory_mapper("Block Offset Table",
1734                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1735                              G1BlockOffsetTable::heap_map_factor());
1736 
1737   ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1738   G1RegionToSpaceMapper* cardtable_storage =
1739     create_aux_memory_mapper("Card Table",
1740                              G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1741                              G1SATBCardTableLoggingModRefBS::heap_map_factor());
1742 
1743   G1RegionToSpaceMapper* card_counts_storage =
1744     create_aux_memory_mapper("Card Counts Table",
1745                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1746                              G1CardCounts::heap_map_factor());
1747 
1748   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1749   G1RegionToSpaceMapper* prev_bitmap_storage =
1750     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1751   G1RegionToSpaceMapper* next_bitmap_storage =
1752     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1753 
1754   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1755   g1_barrier_set()->initialize(cardtable_storage);
1756   // Do later initialization work for concurrent refinement.
1757   _hot_card_cache->initialize(card_counts_storage);
1758 
1759   // 6843694 - ensure that the maximum region index can fit
1760   // in the remembered set structures.
1761   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1762   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1763 
1764   g1_rem_set()->initialize(max_capacity(), max_regions());
1765 
1766   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1767   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1768   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1769             "too many cards per region");
1770 
1771   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1772 
1773   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1774 
1775   {
1776     HeapWord* start = _hrm.reserved().start();
1777     HeapWord* end = _hrm.reserved().end();
1778     size_t granularity = HeapRegion::GrainBytes;
1779 
1780     _in_cset_fast_test.initialize(start, end, granularity);
1781     _humongous_reclaim_candidates.initialize(start, end, granularity);
1782   }
1783 
1784   // Create the G1ConcurrentMark data structure and thread.
1785   // (Must do this late, so that "max_regions" is defined.)
1786   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1787   if (_cm == NULL || !_cm->completed_initialization()) {
1788     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1789     return JNI_ENOMEM;
1790   }
1791   _cmThread = _cm->cmThread();
1792 
1793   // Now expand into the initial heap size.
1794   if (!expand(init_byte_size, _workers)) {
1795     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1796     return JNI_ENOMEM;
1797   }
1798 
1799   // Perform any initialization actions delegated to the policy.
1800   g1_policy()->init(this, &_collection_set);
1801 
1802   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1803                                                SATB_Q_FL_lock,
1804                                                G1SATBProcessCompletedThreshold,
1805                                                Shared_SATB_Q_lock);
1806 
1807   JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
1808                                                 DirtyCardQ_CBL_mon,
1809                                                 DirtyCardQ_FL_lock,
1810                                                 (int)concurrent_g1_refine()->yellow_zone(),
1811                                                 (int)concurrent_g1_refine()->red_zone(),
1812                                                 Shared_DirtyCardQ_lock,
1813                                                 NULL,  // fl_owner
1814                                                 true); // init_free_ids
1815 
1816   dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
1817                                     DirtyCardQ_CBL_mon,
1818                                     DirtyCardQ_FL_lock,
1819                                     -1, // never trigger processing
1820                                     -1, // no limit on length
1821                                     Shared_DirtyCardQ_lock,
1822                                     &JavaThread::dirty_card_queue_set());
1823 
1824   // Here we allocate the dummy HeapRegion that is required by the
1825   // G1AllocRegion class.
1826   HeapRegion* dummy_region = _hrm.get_dummy_region();
1827 
1828   // We'll re-use the same region whether the alloc region will
1829   // require BOT updates or not and, if it doesn't, then a non-young
1830   // region will complain that it cannot support allocations without
1831   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1832   dummy_region->set_eden();
1833   // Make sure it's full.
1834   dummy_region->set_top(dummy_region->end());
1835   G1AllocRegion::setup(this, dummy_region);
1836 
1837   _allocator->init_mutator_alloc_region();
1838 
1839   // Do create of the monitoring and management support so that
1840   // values in the heap have been properly initialized.
1841   _g1mm = new G1MonitoringSupport(this);
1842 
1843   G1StringDedup::initialize();
1844 
1845   _preserved_marks_set.init(ParallelGCThreads);
1846 
1847   _collection_set.initialize(max_regions());
1848 
1849   return JNI_OK;
1850 }
1851 
1852 void G1CollectedHeap::stop() {
1853   // Stop all concurrent threads. We do this to make sure these threads
1854   // do not continue to execute and access resources (e.g. logging)
1855   // that are destroyed during shutdown.
1856   _cg1r->stop();
1857   _cmThread->stop();
1858   if (G1StringDedup::is_enabled()) {
1859     G1StringDedup::stop();
1860   }
1861 }
1862 
1863 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1864   return HeapRegion::max_region_size();
1865 }
1866 
1867 void G1CollectedHeap::post_initialize() {
1868   ref_processing_init();
1869 }
1870 
1871 void G1CollectedHeap::ref_processing_init() {
1872   // Reference processing in G1 currently works as follows:
1873   //
1874   // * There are two reference processor instances. One is
1875   //   used to record and process discovered references
1876   //   during concurrent marking; the other is used to
1877   //   record and process references during STW pauses
1878   //   (both full and incremental).
1879   // * Both ref processors need to 'span' the entire heap as
1880   //   the regions in the collection set may be dotted around.
1881   //
1882   // * For the concurrent marking ref processor:
1883   //   * Reference discovery is enabled at initial marking.
1884   //   * Reference discovery is disabled and the discovered
1885   //     references processed etc during remarking.
1886   //   * Reference discovery is MT (see below).
1887   //   * Reference discovery requires a barrier (see below).
1888   //   * Reference processing may or may not be MT
1889   //     (depending on the value of ParallelRefProcEnabled
1890   //     and ParallelGCThreads).
1891   //   * A full GC disables reference discovery by the CM
1892   //     ref processor and abandons any entries on it's
1893   //     discovered lists.
1894   //
1895   // * For the STW processor:
1896   //   * Non MT discovery is enabled at the start of a full GC.
1897   //   * Processing and enqueueing during a full GC is non-MT.
1898   //   * During a full GC, references are processed after marking.
1899   //
1900   //   * Discovery (may or may not be MT) is enabled at the start
1901   //     of an incremental evacuation pause.
1902   //   * References are processed near the end of a STW evacuation pause.
1903   //   * For both types of GC:
1904   //     * Discovery is atomic - i.e. not concurrent.
1905   //     * Reference discovery will not need a barrier.
1906 
1907   MemRegion mr = reserved_region();
1908 
1909   // Concurrent Mark ref processor
1910   _ref_processor_cm =
1911     new ReferenceProcessor(mr,    // span
1912                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
1913                                 // mt processing
1914                            ParallelGCThreads,
1915                                 // degree of mt processing
1916                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
1917                                 // mt discovery
1918                            MAX2(ParallelGCThreads, ConcGCThreads),
1919                                 // degree of mt discovery
1920                            false,
1921                                 // Reference discovery is not atomic
1922                            &_is_alive_closure_cm);
1923                                 // is alive closure
1924                                 // (for efficiency/performance)
1925 
1926   // STW ref processor
1927   _ref_processor_stw =
1928     new ReferenceProcessor(mr,    // span
1929                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
1930                                 // mt processing
1931                            ParallelGCThreads,
1932                                 // degree of mt processing
1933                            (ParallelGCThreads > 1),
1934                                 // mt discovery
1935                            ParallelGCThreads,
1936                                 // degree of mt discovery
1937                            true,
1938                                 // Reference discovery is atomic
1939                            &_is_alive_closure_stw);
1940                                 // is alive closure
1941                                 // (for efficiency/performance)
1942 }
1943 
1944 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1945   return _collector_policy;
1946 }
1947 
1948 size_t G1CollectedHeap::capacity() const {
1949   return _hrm.length() * HeapRegion::GrainBytes;
1950 }
1951 
1952 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
1953   hr->reset_gc_time_stamp();
1954 }
1955 
1956 #ifndef PRODUCT
1957 
1958 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
1959 private:
1960   unsigned _gc_time_stamp;
1961   bool _failures;
1962 
1963 public:
1964   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
1965     _gc_time_stamp(gc_time_stamp), _failures(false) { }
1966 
1967   virtual bool doHeapRegion(HeapRegion* hr) {
1968     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
1969     if (_gc_time_stamp != region_gc_time_stamp) {
1970       log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
1971                             region_gc_time_stamp, _gc_time_stamp);
1972       _failures = true;
1973     }
1974     return false;
1975   }
1976 
1977   bool failures() { return _failures; }
1978 };
1979 
1980 void G1CollectedHeap::check_gc_time_stamps() {
1981   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
1982   heap_region_iterate(&cl);
1983   guarantee(!cl.failures(), "all GC time stamps should have been reset");
1984 }
1985 #endif // PRODUCT
1986 
1987 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
1988   _hot_card_cache->drain(cl, worker_i);
1989 }
1990 
1991 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
1992   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1993   size_t n_completed_buffers = 0;
1994   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
1995     n_completed_buffers++;
1996   }
1997   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
1998   dcqs.clear_n_completed_buffers();
1999   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2000 }
2001 
2002 // Computes the sum of the storage used by the various regions.
2003 size_t G1CollectedHeap::used() const {
2004   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
2005   if (_archive_allocator != NULL) {
2006     result += _archive_allocator->used();
2007   }
2008   return result;
2009 }
2010 
2011 size_t G1CollectedHeap::used_unlocked() const {
2012   return _summary_bytes_used;
2013 }
2014 
2015 class SumUsedClosure: public HeapRegionClosure {
2016   size_t _used;
2017 public:
2018   SumUsedClosure() : _used(0) {}
2019   bool doHeapRegion(HeapRegion* r) {
2020     _used += r->used();
2021     return false;
2022   }
2023   size_t result() { return _used; }
2024 };
2025 
2026 size_t G1CollectedHeap::recalculate_used() const {
2027   double recalculate_used_start = os::elapsedTime();
2028 
2029   SumUsedClosure blk;
2030   heap_region_iterate(&blk);
2031 
2032   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2033   return blk.result();
2034 }
2035 
2036 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2037   switch (cause) {
2038     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
2039     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
2040     case GCCause::_update_allocation_context_stats_inc: return true;
2041     case GCCause::_wb_conc_mark:                        return true;
2042     default :                                           return false;
2043   }
2044 }
2045 
2046 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2047   switch (cause) {
2048     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2049     case GCCause::_g1_humongous_allocation: return true;
2050     default:                                return is_user_requested_concurrent_full_gc(cause);
2051   }
2052 }
2053 
2054 #ifndef PRODUCT
2055 void G1CollectedHeap::allocate_dummy_regions() {
2056   // Let's fill up most of the region
2057   size_t word_size = HeapRegion::GrainWords - 1024;
2058   // And as a result the region we'll allocate will be humongous.
2059   guarantee(is_humongous(word_size), "sanity");
2060 
2061   // _filler_array_max_size is set to humongous object threshold
2062   // but temporarily change it to use CollectedHeap::fill_with_object().
2063   SizeTFlagSetting fs(_filler_array_max_size, word_size);
2064 
2065   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2066     // Let's use the existing mechanism for the allocation
2067     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2068                                                  AllocationContext::system());
2069     if (dummy_obj != NULL) {
2070       MemRegion mr(dummy_obj, word_size);
2071       CollectedHeap::fill_with_object(mr);
2072     } else {
2073       // If we can't allocate once, we probably cannot allocate
2074       // again. Let's get out of the loop.
2075       break;
2076     }
2077   }
2078 }
2079 #endif // !PRODUCT
2080 
2081 void G1CollectedHeap::increment_old_marking_cycles_started() {
2082   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2083          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2084          "Wrong marking cycle count (started: %d, completed: %d)",
2085          _old_marking_cycles_started, _old_marking_cycles_completed);
2086 
2087   _old_marking_cycles_started++;
2088 }
2089 
2090 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2091   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2092 
2093   // We assume that if concurrent == true, then the caller is a
2094   // concurrent thread that was joined the Suspendible Thread
2095   // Set. If there's ever a cheap way to check this, we should add an
2096   // assert here.
2097 
2098   // Given that this method is called at the end of a Full GC or of a
2099   // concurrent cycle, and those can be nested (i.e., a Full GC can
2100   // interrupt a concurrent cycle), the number of full collections
2101   // completed should be either one (in the case where there was no
2102   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2103   // behind the number of full collections started.
2104 
2105   // This is the case for the inner caller, i.e. a Full GC.
2106   assert(concurrent ||
2107          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2108          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2109          "for inner caller (Full GC): _old_marking_cycles_started = %u "
2110          "is inconsistent with _old_marking_cycles_completed = %u",
2111          _old_marking_cycles_started, _old_marking_cycles_completed);
2112 
2113   // This is the case for the outer caller, i.e. the concurrent cycle.
2114   assert(!concurrent ||
2115          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2116          "for outer caller (concurrent cycle): "
2117          "_old_marking_cycles_started = %u "
2118          "is inconsistent with _old_marking_cycles_completed = %u",
2119          _old_marking_cycles_started, _old_marking_cycles_completed);
2120 
2121   _old_marking_cycles_completed += 1;
2122 
2123   // We need to clear the "in_progress" flag in the CM thread before
2124   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2125   // is set) so that if a waiter requests another System.gc() it doesn't
2126   // incorrectly see that a marking cycle is still in progress.
2127   if (concurrent) {
2128     _cmThread->set_idle();
2129   }
2130 
2131   // This notify_all() will ensure that a thread that called
2132   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2133   // and it's waiting for a full GC to finish will be woken up. It is
2134   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2135   FullGCCount_lock->notify_all();
2136 }
2137 
2138 void G1CollectedHeap::collect(GCCause::Cause cause) {
2139   assert_heap_not_locked();
2140 
2141   uint gc_count_before;
2142   uint old_marking_count_before;
2143   uint full_gc_count_before;
2144   bool retry_gc;
2145 
2146   do {
2147     retry_gc = false;
2148 
2149     {
2150       MutexLocker ml(Heap_lock);
2151 
2152       // Read the GC count while holding the Heap_lock
2153       gc_count_before = total_collections();
2154       full_gc_count_before = total_full_collections();
2155       old_marking_count_before = _old_marking_cycles_started;
2156     }
2157 
2158     if (should_do_concurrent_full_gc(cause)) {
2159       // Schedule an initial-mark evacuation pause that will start a
2160       // concurrent cycle. We're setting word_size to 0 which means that
2161       // we are not requesting a post-GC allocation.
2162       VM_G1IncCollectionPause op(gc_count_before,
2163                                  0,     /* word_size */
2164                                  true,  /* should_initiate_conc_mark */
2165                                  g1_policy()->max_pause_time_ms(),
2166                                  cause);
2167       op.set_allocation_context(AllocationContext::current());
2168 
2169       VMThread::execute(&op);
2170       if (!op.pause_succeeded()) {
2171         if (old_marking_count_before == _old_marking_cycles_started) {
2172           retry_gc = op.should_retry_gc();
2173         } else {
2174           // A Full GC happened while we were trying to schedule the
2175           // initial-mark GC. No point in starting a new cycle given
2176           // that the whole heap was collected anyway.
2177         }
2178 
2179         if (retry_gc) {
2180           if (GCLocker::is_active_and_needs_gc()) {
2181             GCLocker::stall_until_clear();
2182           }
2183         }
2184       }
2185     } else {
2186       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2187           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2188 
2189         // Schedule a standard evacuation pause. We're setting word_size
2190         // to 0 which means that we are not requesting a post-GC allocation.
2191         VM_G1IncCollectionPause op(gc_count_before,
2192                                    0,     /* word_size */
2193                                    false, /* should_initiate_conc_mark */
2194                                    g1_policy()->max_pause_time_ms(),
2195                                    cause);
2196         VMThread::execute(&op);
2197       } else {
2198         // Schedule a Full GC.
2199         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2200         VMThread::execute(&op);
2201       }
2202     }
2203   } while (retry_gc);
2204 }
2205 
2206 bool G1CollectedHeap::is_in(const void* p) const {
2207   if (_hrm.reserved().contains(p)) {
2208     // Given that we know that p is in the reserved space,
2209     // heap_region_containing() should successfully
2210     // return the containing region.
2211     HeapRegion* hr = heap_region_containing(p);
2212     return hr->is_in(p);
2213   } else {
2214     return false;
2215   }
2216 }
2217 
2218 #ifdef ASSERT
2219 bool G1CollectedHeap::is_in_exact(const void* p) const {
2220   bool contains = reserved_region().contains(p);
2221   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2222   if (contains && available) {
2223     return true;
2224   } else {
2225     return false;
2226   }
2227 }
2228 #endif
2229 
2230 // Iteration functions.
2231 
2232 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2233 
2234 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2235   ExtendedOopClosure* _cl;
2236 public:
2237   IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2238   bool doHeapRegion(HeapRegion* r) {
2239     if (!r->is_continues_humongous()) {
2240       r->oop_iterate(_cl);
2241     }
2242     return false;
2243   }
2244 };
2245 
2246 // Iterates an ObjectClosure over all objects within a HeapRegion.
2247 
2248 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2249   ObjectClosure* _cl;
2250 public:
2251   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2252   bool doHeapRegion(HeapRegion* r) {
2253     if (!r->is_continues_humongous()) {
2254       r->object_iterate(_cl);
2255     }
2256     return false;
2257   }
2258 };
2259 
2260 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2261   IterateObjectClosureRegionClosure blk(cl);
2262   heap_region_iterate(&blk);
2263 }
2264 
2265 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2266   _hrm.iterate(cl);
2267 }
2268 
2269 void
2270 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2271                                          uint worker_id,
2272                                          HeapRegionClaimer *hrclaimer,
2273                                          bool concurrent) const {
2274   _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent);
2275 }
2276 
2277 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2278   _collection_set.iterate(cl);
2279 }
2280 
2281 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2282   _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2283 }
2284 
2285 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2286   HeapRegion* result = _hrm.next_region_in_heap(from);
2287   while (result != NULL && result->is_pinned()) {
2288     result = _hrm.next_region_in_heap(result);
2289   }
2290   return result;
2291 }
2292 
2293 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2294   HeapRegion* hr = heap_region_containing(addr);
2295   return hr->block_start(addr);
2296 }
2297 
2298 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2299   HeapRegion* hr = heap_region_containing(addr);
2300   return hr->block_size(addr);
2301 }
2302 
2303 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2304   HeapRegion* hr = heap_region_containing(addr);
2305   return hr->block_is_obj(addr);
2306 }
2307 
2308 bool G1CollectedHeap::supports_tlab_allocation() const {
2309   return true;
2310 }
2311 
2312 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2313   return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2314 }
2315 
2316 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2317   return _eden.length() * HeapRegion::GrainBytes;
2318 }
2319 
2320 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2321 // must be equal to the humongous object limit.
2322 size_t G1CollectedHeap::max_tlab_size() const {
2323   return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment);
2324 }
2325 
2326 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2327   AllocationContext_t context = AllocationContext::current();
2328   return _allocator->unsafe_max_tlab_alloc(context);
2329 }
2330 
2331 size_t G1CollectedHeap::max_capacity() const {
2332   return _hrm.reserved().byte_size();
2333 }
2334 
2335 jlong G1CollectedHeap::millis_since_last_gc() {
2336   // See the notes in GenCollectedHeap::millis_since_last_gc()
2337   // for more information about the implementation.
2338   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2339     _g1_policy->collection_pause_end_millis();
2340   if (ret_val < 0) {
2341     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2342       ". returning zero instead.", ret_val);
2343     return 0;
2344   }
2345   return ret_val;
2346 }
2347 
2348 void G1CollectedHeap::prepare_for_verify() {
2349   _verifier->prepare_for_verify();
2350 }
2351 
2352 void G1CollectedHeap::verify(VerifyOption vo) {
2353   _verifier->verify(vo);
2354 }
2355 
2356 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2357   return true;
2358 }
2359 
2360 const char* const* G1CollectedHeap::concurrent_phases() const {
2361   return _cmThread->concurrent_phases();
2362 }
2363 
2364 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2365   return _cmThread->request_concurrent_phase(phase);
2366 }
2367 
2368 class PrintRegionClosure: public HeapRegionClosure {
2369   outputStream* _st;
2370 public:
2371   PrintRegionClosure(outputStream* st) : _st(st) {}
2372   bool doHeapRegion(HeapRegion* r) {
2373     r->print_on(_st);
2374     return false;
2375   }
2376 };
2377 
2378 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2379                                        const HeapRegion* hr,
2380                                        const VerifyOption vo) const {
2381   switch (vo) {
2382   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2383   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2384   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked() && !hr->is_archive();
2385   default:                            ShouldNotReachHere();
2386   }
2387   return false; // keep some compilers happy
2388 }
2389 
2390 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2391                                        const VerifyOption vo) const {
2392   switch (vo) {
2393   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2394   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2395   case VerifyOption_G1UseMarkWord: {
2396     HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj);
2397     return !obj->is_gc_marked() && !hr->is_archive();
2398   }
2399   default:                            ShouldNotReachHere();
2400   }
2401   return false; // keep some compilers happy
2402 }
2403 
2404 void G1CollectedHeap::print_heap_regions() const {
2405   Log(gc, heap, region) log;
2406   if (log.is_trace()) {
2407     ResourceMark rm;
2408     print_regions_on(log.trace_stream());
2409   }
2410 }
2411 
2412 void G1CollectedHeap::print_on(outputStream* st) const {
2413   st->print(" %-20s", "garbage-first heap");
2414   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2415             capacity()/K, used_unlocked()/K);
2416   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
2417             p2i(_hrm.reserved().start()),
2418             p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords),
2419             p2i(_hrm.reserved().end()));
2420   st->cr();
2421   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2422   uint young_regions = young_regions_count();
2423   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2424             (size_t) young_regions * HeapRegion::GrainBytes / K);
2425   uint survivor_regions = survivor_regions_count();
2426   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2427             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2428   st->cr();
2429   MetaspaceAux::print_on(st);
2430 }
2431 
2432 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2433   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2434                "HS=humongous(starts), HC=humongous(continues), "
2435                "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2436                "AC=allocation context, "
2437                "TAMS=top-at-mark-start (previous, next)");
2438   PrintRegionClosure blk(st);
2439   heap_region_iterate(&blk);
2440 }
2441 
2442 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2443   print_on(st);
2444 
2445   // Print the per-region information.
2446   print_regions_on(st);
2447 }
2448 
2449 void G1CollectedHeap::print_on_error(outputStream* st) const {
2450   this->CollectedHeap::print_on_error(st);
2451 
2452   if (_cm != NULL) {
2453     st->cr();
2454     _cm->print_on_error(st);
2455   }
2456 }
2457 
2458 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2459   workers()->print_worker_threads_on(st);
2460   _cmThread->print_on(st);
2461   st->cr();
2462   _cm->print_worker_threads_on(st);
2463   _cg1r->print_worker_threads_on(st); // also prints the sample thread
2464   if (G1StringDedup::is_enabled()) {
2465     G1StringDedup::print_worker_threads_on(st);
2466   }
2467 }
2468 
2469 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2470   workers()->threads_do(tc);
2471   tc->do_thread(_cmThread);
2472   _cm->threads_do(tc);
2473   _cg1r->threads_do(tc); // also iterates over the sample thread
2474   if (G1StringDedup::is_enabled()) {
2475     G1StringDedup::threads_do(tc);
2476   }
2477 }
2478 
2479 void G1CollectedHeap::print_tracing_info() const {
2480   g1_rem_set()->print_summary_info();
2481   concurrent_mark()->print_summary_info();
2482 }
2483 
2484 #ifndef PRODUCT
2485 // Helpful for debugging RSet issues.
2486 
2487 class PrintRSetsClosure : public HeapRegionClosure {
2488 private:
2489   const char* _msg;
2490   size_t _occupied_sum;
2491 
2492 public:
2493   bool doHeapRegion(HeapRegion* r) {
2494     HeapRegionRemSet* hrrs = r->rem_set();
2495     size_t occupied = hrrs->occupied();
2496     _occupied_sum += occupied;
2497 
2498     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2499     if (occupied == 0) {
2500       tty->print_cr("  RSet is empty");
2501     } else {
2502       hrrs->print();
2503     }
2504     tty->print_cr("----------");
2505     return false;
2506   }
2507 
2508   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2509     tty->cr();
2510     tty->print_cr("========================================");
2511     tty->print_cr("%s", msg);
2512     tty->cr();
2513   }
2514 
2515   ~PrintRSetsClosure() {
2516     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2517     tty->print_cr("========================================");
2518     tty->cr();
2519   }
2520 };
2521 
2522 void G1CollectedHeap::print_cset_rsets() {
2523   PrintRSetsClosure cl("Printing CSet RSets");
2524   collection_set_iterate(&cl);
2525 }
2526 
2527 void G1CollectedHeap::print_all_rsets() {
2528   PrintRSetsClosure cl("Printing All RSets");;
2529   heap_region_iterate(&cl);
2530 }
2531 #endif // PRODUCT
2532 
2533 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2534 
2535   size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2536   size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2537   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2538 
2539   size_t eden_capacity_bytes =
2540     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2541 
2542   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2543   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2544                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2545 }
2546 
2547 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2548   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2549                        stats->unused(), stats->used(), stats->region_end_waste(),
2550                        stats->regions_filled(), stats->direct_allocated(),
2551                        stats->failure_used(), stats->failure_waste());
2552 }
2553 
2554 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2555   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2556   gc_tracer->report_gc_heap_summary(when, heap_summary);
2557 
2558   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2559   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2560 }
2561 
2562 G1CollectedHeap* G1CollectedHeap::heap() {
2563   CollectedHeap* heap = Universe::heap();
2564   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2565   assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2566   return (G1CollectedHeap*)heap;
2567 }
2568 
2569 void G1CollectedHeap::gc_prologue(bool full) {
2570   // always_do_update_barrier = false;
2571   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2572 
2573   // This summary needs to be printed before incrementing total collections.
2574   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2575 
2576   // Update common counters.
2577   increment_total_collections(full /* full gc */);
2578   if (full) {
2579     increment_old_marking_cycles_started();
2580     reset_gc_time_stamp();
2581   } else {
2582     increment_gc_time_stamp();
2583   }
2584 
2585   // Fill TLAB's and such
2586   double start = os::elapsedTime();
2587   accumulate_statistics_all_tlabs();
2588   ensure_parsability(true);
2589   g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2590 }
2591 
2592 void G1CollectedHeap::gc_epilogue(bool full) {
2593   // Update common counters.
2594   if (full) {
2595     // Update the number of full collections that have been completed.
2596     increment_old_marking_cycles_completed(false /* concurrent */);
2597   }
2598 
2599   // We are at the end of the GC. Total collections has already been increased.
2600   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2601 
2602   // FIXME: what is this about?
2603   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2604   // is set.
2605 #if defined(COMPILER2) || INCLUDE_JVMCI
2606   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2607 #endif
2608   // always_do_update_barrier = true;
2609 
2610   double start = os::elapsedTime();
2611   resize_all_tlabs();
2612   g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2613 
2614   allocation_context_stats().update(full);
2615 
2616   MemoryService::track_memory_usage();
2617   // We have just completed a GC. Update the soft reference
2618   // policy with the new heap occupancy
2619   Universe::update_heap_info_at_gc();
2620 }
2621 
2622 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2623                                                uint gc_count_before,
2624                                                bool* succeeded,
2625                                                GCCause::Cause gc_cause) {
2626   assert_heap_not_locked_and_not_at_safepoint();
2627   VM_G1IncCollectionPause op(gc_count_before,
2628                              word_size,
2629                              false, /* should_initiate_conc_mark */
2630                              g1_policy()->max_pause_time_ms(),
2631                              gc_cause);
2632 
2633   op.set_allocation_context(AllocationContext::current());
2634   VMThread::execute(&op);
2635 
2636   HeapWord* result = op.result();
2637   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2638   assert(result == NULL || ret_succeeded,
2639          "the result should be NULL if the VM did not succeed");
2640   *succeeded = ret_succeeded;
2641 
2642   assert_heap_not_locked();
2643   return result;
2644 }
2645 
2646 void
2647 G1CollectedHeap::doConcurrentMark() {
2648   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2649   if (!_cmThread->in_progress()) {
2650     _cmThread->set_started();
2651     CGC_lock->notify();
2652   }
2653 }
2654 
2655 size_t G1CollectedHeap::pending_card_num() {
2656   size_t extra_cards = 0;
2657   JavaThread *curr = Threads::first();
2658   while (curr != NULL) {
2659     DirtyCardQueue& dcq = curr->dirty_card_queue();
2660     extra_cards += dcq.size();
2661     curr = curr->next();
2662   }
2663   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2664   size_t buffer_size = dcqs.buffer_size();
2665   size_t buffer_num = dcqs.completed_buffers_num();
2666 
2667   return buffer_size * buffer_num + extra_cards;
2668 }
2669 
2670 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2671  private:
2672   size_t _total_humongous;
2673   size_t _candidate_humongous;
2674 
2675   DirtyCardQueue _dcq;
2676 
2677   // We don't nominate objects with many remembered set entries, on
2678   // the assumption that such objects are likely still live.
2679   bool is_remset_small(HeapRegion* region) const {
2680     HeapRegionRemSet* const rset = region->rem_set();
2681     return G1EagerReclaimHumongousObjectsWithStaleRefs
2682       ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2683       : rset->is_empty();
2684   }
2685 
2686   bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2687     assert(region->is_starts_humongous(), "Must start a humongous object");
2688 
2689     oop obj = oop(region->bottom());
2690 
2691     // Dead objects cannot be eager reclaim candidates. Due to class
2692     // unloading it is unsafe to query their classes so we return early.
2693     if (heap->is_obj_dead(obj, region)) {
2694       return false;
2695     }
2696 
2697     // Candidate selection must satisfy the following constraints
2698     // while concurrent marking is in progress:
2699     //
2700     // * In order to maintain SATB invariants, an object must not be
2701     // reclaimed if it was allocated before the start of marking and
2702     // has not had its references scanned.  Such an object must have
2703     // its references (including type metadata) scanned to ensure no
2704     // live objects are missed by the marking process.  Objects
2705     // allocated after the start of concurrent marking don't need to
2706     // be scanned.
2707     //
2708     // * An object must not be reclaimed if it is on the concurrent
2709     // mark stack.  Objects allocated after the start of concurrent
2710     // marking are never pushed on the mark stack.
2711     //
2712     // Nominating only objects allocated after the start of concurrent
2713     // marking is sufficient to meet both constraints.  This may miss
2714     // some objects that satisfy the constraints, but the marking data
2715     // structures don't support efficiently performing the needed
2716     // additional tests or scrubbing of the mark stack.
2717     //
2718     // However, we presently only nominate is_typeArray() objects.
2719     // A humongous object containing references induces remembered
2720     // set entries on other regions.  In order to reclaim such an
2721     // object, those remembered sets would need to be cleaned up.
2722     //
2723     // We also treat is_typeArray() objects specially, allowing them
2724     // to be reclaimed even if allocated before the start of
2725     // concurrent mark.  For this we rely on mark stack insertion to
2726     // exclude is_typeArray() objects, preventing reclaiming an object
2727     // that is in the mark stack.  We also rely on the metadata for
2728     // such objects to be built-in and so ensured to be kept live.
2729     // Frequent allocation and drop of large binary blobs is an
2730     // important use case for eager reclaim, and this special handling
2731     // may reduce needed headroom.
2732 
2733     return obj->is_typeArray() && is_remset_small(region);
2734   }
2735 
2736  public:
2737   RegisterHumongousWithInCSetFastTestClosure()
2738   : _total_humongous(0),
2739     _candidate_humongous(0),
2740     _dcq(&JavaThread::dirty_card_queue_set()) {
2741   }
2742 
2743   virtual bool doHeapRegion(HeapRegion* r) {
2744     if (!r->is_starts_humongous()) {
2745       return false;
2746     }
2747     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2748 
2749     bool is_candidate = humongous_region_is_candidate(g1h, r);
2750     uint rindex = r->hrm_index();
2751     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2752     if (is_candidate) {
2753       _candidate_humongous++;
2754       g1h->register_humongous_region_with_cset(rindex);
2755       // Is_candidate already filters out humongous object with large remembered sets.
2756       // If we have a humongous object with a few remembered sets, we simply flush these
2757       // remembered set entries into the DCQS. That will result in automatic
2758       // re-evaluation of their remembered set entries during the following evacuation
2759       // phase.
2760       if (!r->rem_set()->is_empty()) {
2761         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2762                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2763         G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
2764         HeapRegionRemSetIterator hrrs(r->rem_set());
2765         size_t card_index;
2766         while (hrrs.has_next(card_index)) {
2767           jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
2768           // The remembered set might contain references to already freed
2769           // regions. Filter out such entries to avoid failing card table
2770           // verification.
2771           if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
2772             if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
2773               *card_ptr = CardTableModRefBS::dirty_card_val();
2774               _dcq.enqueue(card_ptr);
2775             }
2776           }
2777         }
2778         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2779                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2780                hrrs.n_yielded(), r->rem_set()->occupied());
2781         r->rem_set()->clear_locked();
2782       }
2783       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2784     }
2785     _total_humongous++;
2786 
2787     return false;
2788   }
2789 
2790   size_t total_humongous() const { return _total_humongous; }
2791   size_t candidate_humongous() const { return _candidate_humongous; }
2792 
2793   void flush_rem_set_entries() { _dcq.flush(); }
2794 };
2795 
2796 void G1CollectedHeap::register_humongous_regions_with_cset() {
2797   if (!G1EagerReclaimHumongousObjects) {
2798     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2799     return;
2800   }
2801   double time = os::elapsed_counter();
2802 
2803   // Collect reclaim candidate information and register candidates with cset.
2804   RegisterHumongousWithInCSetFastTestClosure cl;
2805   heap_region_iterate(&cl);
2806 
2807   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2808   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2809                                                                   cl.total_humongous(),
2810                                                                   cl.candidate_humongous());
2811   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2812 
2813   // Finally flush all remembered set entries to re-check into the global DCQS.
2814   cl.flush_rem_set_entries();
2815 }
2816 
2817 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2818   public:
2819     bool doHeapRegion(HeapRegion* hr) {
2820       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2821         hr->verify_rem_set();
2822       }
2823       return false;
2824     }
2825 };
2826 
2827 uint G1CollectedHeap::num_task_queues() const {
2828   return _task_queues->size();
2829 }
2830 
2831 #if TASKQUEUE_STATS
2832 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2833   st->print_raw_cr("GC Task Stats");
2834   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2835   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2836 }
2837 
2838 void G1CollectedHeap::print_taskqueue_stats() const {
2839   if (!log_is_enabled(Trace, gc, task, stats)) {
2840     return;
2841   }
2842   Log(gc, task, stats) log;
2843   ResourceMark rm;
2844   outputStream* st = log.trace_stream();
2845 
2846   print_taskqueue_stats_hdr(st);
2847 
2848   TaskQueueStats totals;
2849   const uint n = num_task_queues();
2850   for (uint i = 0; i < n; ++i) {
2851     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2852     totals += task_queue(i)->stats;
2853   }
2854   st->print_raw("tot "); totals.print(st); st->cr();
2855 
2856   DEBUG_ONLY(totals.verify());
2857 }
2858 
2859 void G1CollectedHeap::reset_taskqueue_stats() {
2860   const uint n = num_task_queues();
2861   for (uint i = 0; i < n; ++i) {
2862     task_queue(i)->stats.reset();
2863   }
2864 }
2865 #endif // TASKQUEUE_STATS
2866 
2867 void G1CollectedHeap::wait_for_root_region_scanning() {
2868   double scan_wait_start = os::elapsedTime();
2869   // We have to wait until the CM threads finish scanning the
2870   // root regions as it's the only way to ensure that all the
2871   // objects on them have been correctly scanned before we start
2872   // moving them during the GC.
2873   bool waited = _cm->root_regions()->wait_until_scan_finished();
2874   double wait_time_ms = 0.0;
2875   if (waited) {
2876     double scan_wait_end = os::elapsedTime();
2877     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2878   }
2879   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2880 }
2881 
2882 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2883 private:
2884   G1HRPrinter* _hr_printer;
2885 public:
2886   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2887 
2888   virtual bool doHeapRegion(HeapRegion* r) {
2889     _hr_printer->cset(r);
2890     return false;
2891   }
2892 };
2893 
2894 void G1CollectedHeap::start_new_collection_set() {
2895   collection_set()->start_incremental_building();
2896 
2897   clear_cset_fast_test();
2898 
2899   guarantee(_eden.length() == 0, "eden should have been cleared");
2900   g1_policy()->transfer_survivors_to_cset(survivor());
2901 }
2902 
2903 bool
2904 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2905   assert_at_safepoint(true /* should_be_vm_thread */);
2906   guarantee(!is_gc_active(), "collection is not reentrant");
2907 
2908   if (GCLocker::check_active_before_gc()) {
2909     return false;
2910   }
2911 
2912   _gc_timer_stw->register_gc_start();
2913 
2914   GCIdMark gc_id_mark;
2915   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2916 
2917   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2918   ResourceMark rm;
2919 
2920   g1_policy()->note_gc_start();
2921 
2922   wait_for_root_region_scanning();
2923 
2924   print_heap_before_gc();
2925   print_heap_regions();
2926   trace_heap_before_gc(_gc_tracer_stw);
2927 
2928   _verifier->verify_region_sets_optional();
2929   _verifier->verify_dirty_young_regions();
2930 
2931   // We should not be doing initial mark unless the conc mark thread is running
2932   if (!_cmThread->should_terminate()) {
2933     // This call will decide whether this pause is an initial-mark
2934     // pause. If it is, during_initial_mark_pause() will return true
2935     // for the duration of this pause.
2936     g1_policy()->decide_on_conc_mark_initiation();
2937   }
2938 
2939   // We do not allow initial-mark to be piggy-backed on a mixed GC.
2940   assert(!collector_state()->during_initial_mark_pause() ||
2941           collector_state()->gcs_are_young(), "sanity");
2942 
2943   // We also do not allow mixed GCs during marking.
2944   assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
2945 
2946   // Record whether this pause is an initial mark. When the current
2947   // thread has completed its logging output and it's safe to signal
2948   // the CM thread, the flag's value in the policy has been reset.
2949   bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
2950 
2951   // Inner scope for scope based logging, timers, and stats collection
2952   {
2953     EvacuationInfo evacuation_info;
2954 
2955     if (collector_state()->during_initial_mark_pause()) {
2956       // We are about to start a marking cycle, so we increment the
2957       // full collection counter.
2958       increment_old_marking_cycles_started();
2959       _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2960     }
2961 
2962     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2963 
2964     GCTraceCPUTime tcpu;
2965 
2966     FormatBuffer<> gc_string("Pause ");
2967     if (collector_state()->during_initial_mark_pause()) {
2968       gc_string.append("Initial Mark");
2969     } else if (collector_state()->gcs_are_young()) {
2970       gc_string.append("Young");
2971     } else {
2972       gc_string.append("Mixed");
2973     }
2974     GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2975 
2976     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2977                                                                   workers()->active_workers(),
2978                                                                   Threads::number_of_non_daemon_threads());
2979     workers()->update_active_workers(active_workers);
2980     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2981 
2982     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2983     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
2984 
2985     // If the secondary_free_list is not empty, append it to the
2986     // free_list. No need to wait for the cleanup operation to finish;
2987     // the region allocation code will check the secondary_free_list
2988     // and wait if necessary. If the G1StressConcRegionFreeing flag is
2989     // set, skip this step so that the region allocation code has to
2990     // get entries from the secondary_free_list.
2991     if (!G1StressConcRegionFreeing) {
2992       append_secondary_free_list_if_not_empty_with_lock();
2993     }
2994 
2995     G1HeapTransition heap_transition(this);
2996     size_t heap_used_bytes_before_gc = used();
2997 
2998     // Don't dynamically change the number of GC threads this early.  A value of
2999     // 0 is used to indicate serial work.  When parallel work is done,
3000     // it will be set.
3001 
3002     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3003       IsGCActiveMark x;
3004 
3005       gc_prologue(false);
3006 
3007       if (VerifyRememberedSets) {
3008         log_info(gc, verify)("[Verifying RemSets before GC]");
3009         VerifyRegionRemSetClosure v_cl;
3010         heap_region_iterate(&v_cl);
3011       }
3012 
3013       _verifier->verify_before_gc();
3014 
3015       _verifier->check_bitmaps("GC Start");
3016 
3017 #if defined(COMPILER2) || INCLUDE_JVMCI
3018       DerivedPointerTable::clear();
3019 #endif
3020 
3021       // Please see comment in g1CollectedHeap.hpp and
3022       // G1CollectedHeap::ref_processing_init() to see how
3023       // reference processing currently works in G1.
3024 
3025       // Enable discovery in the STW reference processor
3026       if (g1_policy()->should_process_references()) {
3027         ref_processor_stw()->enable_discovery();
3028       } else {
3029         ref_processor_stw()->disable_discovery();
3030       }
3031 
3032       {
3033         // We want to temporarily turn off discovery by the
3034         // CM ref processor, if necessary, and turn it back on
3035         // on again later if we do. Using a scoped
3036         // NoRefDiscovery object will do this.
3037         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3038 
3039         // Forget the current alloc region (we might even choose it to be part
3040         // of the collection set!).
3041         _allocator->release_mutator_alloc_region();
3042 
3043         // This timing is only used by the ergonomics to handle our pause target.
3044         // It is unclear why this should not include the full pause. We will
3045         // investigate this in CR 7178365.
3046         //
3047         // Preserving the old comment here if that helps the investigation:
3048         //
3049         // The elapsed time induced by the start time below deliberately elides
3050         // the possible verification above.
3051         double sample_start_time_sec = os::elapsedTime();
3052 
3053         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3054 
3055         if (collector_state()->during_initial_mark_pause()) {
3056           concurrent_mark()->checkpointRootsInitialPre();
3057         }
3058 
3059         g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
3060 
3061         evacuation_info.set_collectionset_regions(collection_set()->region_length());
3062 
3063         // Make sure the remembered sets are up to date. This needs to be
3064         // done before register_humongous_regions_with_cset(), because the
3065         // remembered sets are used there to choose eager reclaim candidates.
3066         // If the remembered sets are not up to date we might miss some
3067         // entries that need to be handled.
3068         g1_rem_set()->cleanupHRRS();
3069 
3070         register_humongous_regions_with_cset();
3071 
3072         assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3073 
3074         // We call this after finalize_cset() to
3075         // ensure that the CSet has been finalized.
3076         _cm->verify_no_cset_oops();
3077 
3078         if (_hr_printer.is_active()) {
3079           G1PrintCollectionSetClosure cl(&_hr_printer);
3080           _collection_set.iterate(&cl);
3081         }
3082 
3083         // Initialize the GC alloc regions.
3084         _allocator->init_gc_alloc_regions(evacuation_info);
3085 
3086         G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3087         pre_evacuate_collection_set();
3088 
3089         // Actually do the work...
3090         evacuate_collection_set(evacuation_info, &per_thread_states);
3091 
3092         post_evacuate_collection_set(evacuation_info, &per_thread_states);
3093 
3094         const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3095         free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
3096 
3097         eagerly_reclaim_humongous_regions();
3098 
3099         record_obj_copy_mem_stats();
3100         _survivor_evac_stats.adjust_desired_plab_sz();
3101         _old_evac_stats.adjust_desired_plab_sz();
3102 
3103         double start = os::elapsedTime();
3104         start_new_collection_set();
3105         g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
3106 
3107         if (evacuation_failed()) {
3108           set_used(recalculate_used());
3109           if (_archive_allocator != NULL) {
3110             _archive_allocator->clear_used();
3111           }
3112           for (uint i = 0; i < ParallelGCThreads; i++) {
3113             if (_evacuation_failed_info_array[i].has_failed()) {
3114               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3115             }
3116           }
3117         } else {
3118           // The "used" of the the collection set have already been subtracted
3119           // when they were freed.  Add in the bytes evacuated.
3120           increase_used(g1_policy()->bytes_copied_during_gc());
3121         }
3122 
3123         if (collector_state()->during_initial_mark_pause()) {
3124           // We have to do this before we notify the CM threads that
3125           // they can start working to make sure that all the
3126           // appropriate initialization is done on the CM object.
3127           concurrent_mark()->checkpointRootsInitialPost();
3128           collector_state()->set_mark_in_progress(true);
3129           // Note that we don't actually trigger the CM thread at
3130           // this point. We do that later when we're sure that
3131           // the current thread has completed its logging output.
3132         }
3133 
3134         allocate_dummy_regions();
3135 
3136         _allocator->init_mutator_alloc_region();
3137 
3138         {
3139           size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3140           if (expand_bytes > 0) {
3141             size_t bytes_before = capacity();
3142             // No need for an ergo logging here,
3143             // expansion_amount() does this when it returns a value > 0.
3144             double expand_ms;
3145             if (!expand(expand_bytes, _workers, &expand_ms)) {
3146               // We failed to expand the heap. Cannot do anything about it.
3147             }
3148             g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3149           }
3150         }
3151 
3152         // We redo the verification but now wrt to the new CSet which
3153         // has just got initialized after the previous CSet was freed.
3154         _cm->verify_no_cset_oops();
3155 
3156         // This timing is only used by the ergonomics to handle our pause target.
3157         // It is unclear why this should not include the full pause. We will
3158         // investigate this in CR 7178365.
3159         double sample_end_time_sec = os::elapsedTime();
3160         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3161         size_t total_cards_scanned = per_thread_states.total_cards_scanned();
3162         g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3163 
3164         evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3165         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3166 
3167         // In prepare_for_verify() below we'll need to scan the deferred
3168         // update buffers to bring the RSets up-to-date if
3169         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3170         // the update buffers we'll probably need to scan cards on the
3171         // regions we just allocated to (i.e., the GC alloc
3172         // regions). However, during the last GC we called
3173         // set_saved_mark() on all the GC alloc regions, so card
3174         // scanning might skip the [saved_mark_word()...top()] area of
3175         // those regions (i.e., the area we allocated objects into
3176         // during the last GC). But it shouldn't. Given that
3177         // saved_mark_word() is conditional on whether the GC time stamp
3178         // on the region is current or not, by incrementing the GC time
3179         // stamp here we invalidate all the GC time stamps on all the
3180         // regions and saved_mark_word() will simply return top() for
3181         // all the regions. This is a nicer way of ensuring this rather
3182         // than iterating over the regions and fixing them. In fact, the
3183         // GC time stamp increment here also ensures that
3184         // saved_mark_word() will return top() between pauses, i.e.,
3185         // during concurrent refinement. So we don't need the
3186         // is_gc_active() check to decided which top to use when
3187         // scanning cards (see CR 7039627).
3188         increment_gc_time_stamp();
3189 
3190         if (VerifyRememberedSets) {
3191           log_info(gc, verify)("[Verifying RemSets after GC]");
3192           VerifyRegionRemSetClosure v_cl;
3193           heap_region_iterate(&v_cl);
3194         }
3195 
3196         _verifier->verify_after_gc();
3197         _verifier->check_bitmaps("GC End");
3198 
3199         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3200         ref_processor_stw()->verify_no_references_recorded();
3201 
3202         // CM reference discovery will be re-enabled if necessary.
3203       }
3204 
3205 #ifdef TRACESPINNING
3206       ParallelTaskTerminator::print_termination_counts();
3207 #endif
3208 
3209       gc_epilogue(false);
3210     }
3211 
3212     // Print the remainder of the GC log output.
3213     if (evacuation_failed()) {
3214       log_info(gc)("To-space exhausted");
3215     }
3216 
3217     g1_policy()->print_phases();
3218     heap_transition.print();
3219 
3220     // It is not yet to safe to tell the concurrent mark to
3221     // start as we have some optional output below. We don't want the
3222     // output from the concurrent mark thread interfering with this
3223     // logging output either.
3224 
3225     _hrm.verify_optional();
3226     _verifier->verify_region_sets_optional();
3227 
3228     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3229     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3230 
3231     print_heap_after_gc();
3232     print_heap_regions();
3233     trace_heap_after_gc(_gc_tracer_stw);
3234 
3235     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3236     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3237     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3238     // before any GC notifications are raised.
3239     g1mm()->update_sizes();
3240 
3241     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3242     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3243     _gc_timer_stw->register_gc_end();
3244     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3245   }
3246   // It should now be safe to tell the concurrent mark thread to start
3247   // without its logging output interfering with the logging output
3248   // that came from the pause.
3249 
3250   if (should_start_conc_mark) {
3251     // CAUTION: after the doConcurrentMark() call below,
3252     // the concurrent marking thread(s) could be running
3253     // concurrently with us. Make sure that anything after
3254     // this point does not assume that we are the only GC thread
3255     // running. Note: of course, the actual marking work will
3256     // not start until the safepoint itself is released in
3257     // SuspendibleThreadSet::desynchronize().
3258     doConcurrentMark();
3259   }
3260 
3261   return true;
3262 }
3263 
3264 void G1CollectedHeap::remove_self_forwarding_pointers() {
3265   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3266   workers()->run_task(&rsfp_task);
3267 }
3268 
3269 void G1CollectedHeap::restore_after_evac_failure() {
3270   double remove_self_forwards_start = os::elapsedTime();
3271 
3272   remove_self_forwarding_pointers();
3273   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3274   _preserved_marks_set.restore(&task_executor);
3275 
3276   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3277 }
3278 
3279 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3280   if (!_evacuation_failed) {
3281     _evacuation_failed = true;
3282   }
3283 
3284   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3285   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3286 }
3287 
3288 bool G1ParEvacuateFollowersClosure::offer_termination() {
3289   G1ParScanThreadState* const pss = par_scan_state();
3290   start_term_time();
3291   const bool res = terminator()->offer_termination();
3292   end_term_time();
3293   return res;
3294 }
3295 
3296 void G1ParEvacuateFollowersClosure::do_void() {
3297   G1ParScanThreadState* const pss = par_scan_state();
3298   pss->trim_queue();
3299   do {
3300     pss->steal_and_trim_queue(queues());
3301   } while (!offer_termination());
3302 }
3303 
3304 class G1ParTask : public AbstractGangTask {
3305 protected:
3306   G1CollectedHeap*         _g1h;
3307   G1ParScanThreadStateSet* _pss;
3308   RefToScanQueueSet*       _queues;
3309   G1RootProcessor*         _root_processor;
3310   ParallelTaskTerminator   _terminator;
3311   uint                     _n_workers;
3312 
3313 public:
3314   G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3315     : AbstractGangTask("G1 collection"),
3316       _g1h(g1h),
3317       _pss(per_thread_states),
3318       _queues(task_queues),
3319       _root_processor(root_processor),
3320       _terminator(n_workers, _queues),
3321       _n_workers(n_workers)
3322   {}
3323 
3324   void work(uint worker_id) {
3325     if (worker_id >= _n_workers) return;  // no work needed this round
3326 
3327     double start_sec = os::elapsedTime();
3328     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3329 
3330     {
3331       ResourceMark rm;
3332       HandleMark   hm;
3333 
3334       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
3335 
3336       G1ParScanThreadState*           pss = _pss->state_for_worker(worker_id);
3337       pss->set_ref_processor(rp);
3338 
3339       double start_strong_roots_sec = os::elapsedTime();
3340 
3341       _root_processor->evacuate_roots(pss->closures(), worker_id);
3342 
3343       G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss);
3344 
3345       // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3346       // treating the nmethods visited to act as roots for concurrent marking.
3347       // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3348       // objects copied by the current evacuation.
3349       size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl,
3350                                                                              pss->closures()->weak_codeblobs(),
3351                                                                              worker_id);
3352 
3353       _pss->add_cards_scanned(worker_id, cards_scanned);
3354 
3355       double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3356 
3357       double term_sec = 0.0;
3358       size_t evac_term_attempts = 0;
3359       {
3360         double start = os::elapsedTime();
3361         G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3362         evac.do_void();
3363 
3364         evac_term_attempts = evac.term_attempts();
3365         term_sec = evac.term_time();
3366         double elapsed_sec = os::elapsedTime() - start;
3367         _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3368         _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3369         _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3370       }
3371 
3372       assert(pss->queue_is_empty(), "should be empty");
3373 
3374       if (log_is_enabled(Debug, gc, task, stats)) {
3375         MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3376         size_t lab_waste;
3377         size_t lab_undo_waste;
3378         pss->waste(lab_waste, lab_undo_waste);
3379         _g1h->print_termination_stats(worker_id,
3380                                       (os::elapsedTime() - start_sec) * 1000.0,   /* elapsed time */
3381                                       strong_roots_sec * 1000.0,                  /* strong roots time */
3382                                       term_sec * 1000.0,                          /* evac term time */
3383                                       evac_term_attempts,                         /* evac term attempts */
3384                                       lab_waste,                                  /* alloc buffer waste */
3385                                       lab_undo_waste                              /* undo waste */
3386                                       );
3387       }
3388 
3389       // Close the inner scope so that the ResourceMark and HandleMark
3390       // destructors are executed here and are included as part of the
3391       // "GC Worker Time".
3392     }
3393     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3394   }
3395 };
3396 
3397 void G1CollectedHeap::print_termination_stats_hdr() {
3398   log_debug(gc, task, stats)("GC Termination Stats");
3399   log_debug(gc, task, stats)("     elapsed  --strong roots-- -------termination------- ------waste (KiB)------");
3400   log_debug(gc, task, stats)("thr     ms        ms      %%        ms      %%    attempts  total   alloc    undo");
3401   log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3402 }
3403 
3404 void G1CollectedHeap::print_termination_stats(uint worker_id,
3405                                               double elapsed_ms,
3406                                               double strong_roots_ms,
3407                                               double term_ms,
3408                                               size_t term_attempts,
3409                                               size_t alloc_buffer_waste,
3410                                               size_t undo_waste) const {
3411   log_debug(gc, task, stats)
3412               ("%3d %9.2f %9.2f %6.2f "
3413                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3414                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3415                worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3416                term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3417                (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3418                alloc_buffer_waste * HeapWordSize / K,
3419                undo_waste * HeapWordSize / K);
3420 }
3421 
3422 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3423 private:
3424   BoolObjectClosure* _is_alive;
3425   G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3426 
3427   int _initial_string_table_size;
3428   int _initial_symbol_table_size;
3429 
3430   bool  _process_strings;
3431   int _strings_processed;
3432   int _strings_removed;
3433 
3434   bool  _process_symbols;
3435   int _symbols_processed;
3436   int _symbols_removed;
3437 
3438   bool _process_string_dedup;
3439 
3440 public:
3441   G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3442     AbstractGangTask("String/Symbol Unlinking"),
3443     _is_alive(is_alive),
3444     _dedup_closure(is_alive, NULL, false),
3445     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3446     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3447     _process_string_dedup(process_string_dedup) {
3448 
3449     _initial_string_table_size = StringTable::the_table()->table_size();
3450     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3451     if (process_strings) {
3452       StringTable::clear_parallel_claimed_index();
3453     }
3454     if (process_symbols) {
3455       SymbolTable::clear_parallel_claimed_index();
3456     }
3457   }
3458 
3459   ~G1StringAndSymbolCleaningTask() {
3460     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3461               "claim value %d after unlink less than initial string table size %d",
3462               StringTable::parallel_claimed_index(), _initial_string_table_size);
3463     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3464               "claim value %d after unlink less than initial symbol table size %d",
3465               SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3466 
3467     log_info(gc, stringtable)(
3468         "Cleaned string and symbol table, "
3469         "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3470         "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3471         strings_processed(), strings_removed(),
3472         symbols_processed(), symbols_removed());
3473   }
3474 
3475   void work(uint worker_id) {
3476     int strings_processed = 0;
3477     int strings_removed = 0;
3478     int symbols_processed = 0;
3479     int symbols_removed = 0;
3480     if (_process_strings) {
3481       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3482       Atomic::add(strings_processed, &_strings_processed);
3483       Atomic::add(strings_removed, &_strings_removed);
3484     }
3485     if (_process_symbols) {
3486       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3487       Atomic::add(symbols_processed, &_symbols_processed);
3488       Atomic::add(symbols_removed, &_symbols_removed);
3489     }
3490     if (_process_string_dedup) {
3491       G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3492     }
3493   }
3494 
3495   size_t strings_processed() const { return (size_t)_strings_processed; }
3496   size_t strings_removed()   const { return (size_t)_strings_removed; }
3497 
3498   size_t symbols_processed() const { return (size_t)_symbols_processed; }
3499   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
3500 };
3501 
3502 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3503 private:
3504   static Monitor* _lock;
3505 
3506   BoolObjectClosure* const _is_alive;
3507   const bool               _unloading_occurred;
3508   const uint               _num_workers;
3509 
3510   // Variables used to claim nmethods.
3511   CompiledMethod* _first_nmethod;
3512   volatile CompiledMethod* _claimed_nmethod;
3513 
3514   // The list of nmethods that need to be processed by the second pass.
3515   volatile CompiledMethod* _postponed_list;
3516   volatile uint            _num_entered_barrier;
3517 
3518  public:
3519   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3520       _is_alive(is_alive),
3521       _unloading_occurred(unloading_occurred),
3522       _num_workers(num_workers),
3523       _first_nmethod(NULL),
3524       _claimed_nmethod(NULL),
3525       _postponed_list(NULL),
3526       _num_entered_barrier(0)
3527   {
3528     CompiledMethod::increase_unloading_clock();
3529     // Get first alive nmethod
3530     CompiledMethodIterator iter = CompiledMethodIterator();
3531     if(iter.next_alive()) {
3532       _first_nmethod = iter.method();
3533     }
3534     _claimed_nmethod = (volatile CompiledMethod*)_first_nmethod;
3535   }
3536 
3537   ~G1CodeCacheUnloadingTask() {
3538     CodeCache::verify_clean_inline_caches();
3539 
3540     CodeCache::set_needs_cache_clean(false);
3541     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3542 
3543     CodeCache::verify_icholder_relocations();
3544   }
3545 
3546  private:
3547   void add_to_postponed_list(CompiledMethod* nm) {
3548       CompiledMethod* old;
3549       do {
3550         old = (CompiledMethod*)_postponed_list;
3551         nm->set_unloading_next(old);
3552       } while ((CompiledMethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
3553   }
3554 
3555   void clean_nmethod(CompiledMethod* nm) {
3556     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3557 
3558     if (postponed) {
3559       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3560       add_to_postponed_list(nm);
3561     }
3562 
3563     // Mark that this thread has been cleaned/unloaded.
3564     // After this call, it will be safe to ask if this nmethod was unloaded or not.
3565     nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3566   }
3567 
3568   void clean_nmethod_postponed(CompiledMethod* nm) {
3569     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3570   }
3571 
3572   static const int MaxClaimNmethods = 16;
3573 
3574   void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3575     CompiledMethod* first;
3576     CompiledMethodIterator last;
3577 
3578     do {
3579       *num_claimed_nmethods = 0;
3580 
3581       first = (CompiledMethod*)_claimed_nmethod;
3582       last = CompiledMethodIterator(first);
3583 
3584       if (first != NULL) {
3585 
3586         for (int i = 0; i < MaxClaimNmethods; i++) {
3587           if (!last.next_alive()) {
3588             break;
3589           }
3590           claimed_nmethods[i] = last.method();
3591           (*num_claimed_nmethods)++;
3592         }
3593       }
3594 
3595     } while ((CompiledMethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
3596   }
3597 
3598   CompiledMethod* claim_postponed_nmethod() {
3599     CompiledMethod* claim;
3600     CompiledMethod* next;
3601 
3602     do {
3603       claim = (CompiledMethod*)_postponed_list;
3604       if (claim == NULL) {
3605         return NULL;
3606       }
3607 
3608       next = claim->unloading_next();
3609 
3610     } while ((CompiledMethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
3611 
3612     return claim;
3613   }
3614 
3615  public:
3616   // Mark that we're done with the first pass of nmethod cleaning.
3617   void barrier_mark(uint worker_id) {
3618     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3619     _num_entered_barrier++;
3620     if (_num_entered_barrier == _num_workers) {
3621       ml.notify_all();
3622     }
3623   }
3624 
3625   // See if we have to wait for the other workers to
3626   // finish their first-pass nmethod cleaning work.
3627   void barrier_wait(uint worker_id) {
3628     if (_num_entered_barrier < _num_workers) {
3629       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3630       while (_num_entered_barrier < _num_workers) {
3631           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3632       }
3633     }
3634   }
3635 
3636   // Cleaning and unloading of nmethods. Some work has to be postponed
3637   // to the second pass, when we know which nmethods survive.
3638   void work_first_pass(uint worker_id) {
3639     // The first nmethods is claimed by the first worker.
3640     if (worker_id == 0 && _first_nmethod != NULL) {
3641       clean_nmethod(_first_nmethod);
3642       _first_nmethod = NULL;
3643     }
3644 
3645     int num_claimed_nmethods;
3646     CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3647 
3648     while (true) {
3649       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3650 
3651       if (num_claimed_nmethods == 0) {
3652         break;
3653       }
3654 
3655       for (int i = 0; i < num_claimed_nmethods; i++) {
3656         clean_nmethod(claimed_nmethods[i]);
3657       }
3658     }
3659   }
3660 
3661   void work_second_pass(uint worker_id) {
3662     CompiledMethod* nm;
3663     // Take care of postponed nmethods.
3664     while ((nm = claim_postponed_nmethod()) != NULL) {
3665       clean_nmethod_postponed(nm);
3666     }
3667   }
3668 };
3669 
3670 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3671 
3672 class G1KlassCleaningTask : public StackObj {
3673   BoolObjectClosure*                      _is_alive;
3674   volatile jint                           _clean_klass_tree_claimed;
3675   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3676 
3677  public:
3678   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3679       _is_alive(is_alive),
3680       _clean_klass_tree_claimed(0),
3681       _klass_iterator() {
3682   }
3683 
3684  private:
3685   bool claim_clean_klass_tree_task() {
3686     if (_clean_klass_tree_claimed) {
3687       return false;
3688     }
3689 
3690     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
3691   }
3692 
3693   InstanceKlass* claim_next_klass() {
3694     Klass* klass;
3695     do {
3696       klass =_klass_iterator.next_klass();
3697     } while (klass != NULL && !klass->is_instance_klass());
3698 
3699     // this can be null so don't call InstanceKlass::cast
3700     return static_cast<InstanceKlass*>(klass);
3701   }
3702 
3703 public:
3704 
3705   void clean_klass(InstanceKlass* ik) {
3706     ik->clean_weak_instanceklass_links(_is_alive);
3707   }
3708 
3709   void work() {
3710     ResourceMark rm;
3711 
3712     // One worker will clean the subklass/sibling klass tree.
3713     if (claim_clean_klass_tree_task()) {
3714       Klass::clean_subklass_tree(_is_alive);
3715     }
3716 
3717     // All workers will help cleaning the classes,
3718     InstanceKlass* klass;
3719     while ((klass = claim_next_klass()) != NULL) {
3720       clean_klass(klass);
3721     }
3722   }
3723 };
3724 
3725 class G1ResolvedMethodCleaningTask : public StackObj {
3726   BoolObjectClosure* _is_alive;
3727   volatile jint      _resolved_method_task_claimed;
3728 public:
3729   G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) :
3730       _is_alive(is_alive), _resolved_method_task_claimed(0) {}
3731 
3732   bool claim_resolved_method_task() {
3733     if (_resolved_method_task_claimed) {
3734       return false;
3735     }
3736     return Atomic::cmpxchg(1, (jint*)&_resolved_method_task_claimed, 0) == 0;
3737   }
3738 
3739   // These aren't big, one thread can do it all.
3740   void work() {
3741     if (claim_resolved_method_task()) {
3742       ResolvedMethodTable::unlink(_is_alive);
3743     }
3744   }
3745 };
3746 
3747 
3748 // To minimize the remark pause times, the tasks below are done in parallel.
3749 class G1ParallelCleaningTask : public AbstractGangTask {
3750 private:
3751   G1StringAndSymbolCleaningTask _string_symbol_task;
3752   G1CodeCacheUnloadingTask      _code_cache_task;
3753   G1KlassCleaningTask           _klass_cleaning_task;
3754   G1ResolvedMethodCleaningTask  _resolved_method_cleaning_task;
3755 
3756 public:
3757   // The constructor is run in the VMThread.
3758   G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3759       AbstractGangTask("Parallel Cleaning"),
3760       _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3761       _code_cache_task(num_workers, is_alive, unloading_occurred),
3762       _klass_cleaning_task(is_alive),
3763       _resolved_method_cleaning_task(is_alive) {
3764   }
3765 
3766   // The parallel work done by all worker threads.
3767   void work(uint worker_id) {
3768     // Do first pass of code cache cleaning.
3769     _code_cache_task.work_first_pass(worker_id);
3770 
3771     // Let the threads mark that the first pass is done.
3772     _code_cache_task.barrier_mark(worker_id);
3773 
3774     // Clean the Strings and Symbols.
3775     _string_symbol_task.work(worker_id);
3776 
3777     // Clean unreferenced things in the ResolvedMethodTable
3778     _resolved_method_cleaning_task.work();
3779 
3780     // Wait for all workers to finish the first code cache cleaning pass.
3781     _code_cache_task.barrier_wait(worker_id);
3782 
3783     // Do the second code cache cleaning work, which realize on
3784     // the liveness information gathered during the first pass.
3785     _code_cache_task.work_second_pass(worker_id);
3786 
3787     // Clean all klasses that were not unloaded.
3788     _klass_cleaning_task.work();
3789   }
3790 };
3791 
3792 
3793 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3794                                         bool class_unloading_occurred) {
3795   uint n_workers = workers()->active_workers();
3796 
3797   G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3798   workers()->run_task(&g1_unlink_task);
3799 }
3800 
3801 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3802                                        bool process_strings,
3803                                        bool process_symbols,
3804                                        bool process_string_dedup) {
3805   if (!process_strings && !process_symbols && !process_string_dedup) {
3806     // Nothing to clean.
3807     return;
3808   }
3809 
3810   G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3811   workers()->run_task(&g1_unlink_task);
3812 
3813 }
3814 
3815 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3816  private:
3817   DirtyCardQueueSet* _queue;
3818   G1CollectedHeap* _g1h;
3819  public:
3820   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3821     _queue(queue), _g1h(g1h) { }
3822 
3823   virtual void work(uint worker_id) {
3824     G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3825     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3826 
3827     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3828     _queue->par_apply_closure_to_all_completed_buffers(&cl);
3829 
3830     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3831   }
3832 };
3833 
3834 void G1CollectedHeap::redirty_logged_cards() {
3835   double redirty_logged_cards_start = os::elapsedTime();
3836 
3837   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3838   dirty_card_queue_set().reset_for_par_iteration();
3839   workers()->run_task(&redirty_task);
3840 
3841   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
3842   dcq.merge_bufferlists(&dirty_card_queue_set());
3843   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3844 
3845   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3846 }
3847 
3848 // Weak Reference Processing support
3849 
3850 // An always "is_alive" closure that is used to preserve referents.
3851 // If the object is non-null then it's alive.  Used in the preservation
3852 // of referent objects that are pointed to by reference objects
3853 // discovered by the CM ref processor.
3854 class G1AlwaysAliveClosure: public BoolObjectClosure {
3855   G1CollectedHeap* _g1;
3856 public:
3857   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3858   bool do_object_b(oop p) {
3859     if (p != NULL) {
3860       return true;
3861     }
3862     return false;
3863   }
3864 };
3865 
3866 bool G1STWIsAliveClosure::do_object_b(oop p) {
3867   // An object is reachable if it is outside the collection set,
3868   // or is inside and copied.
3869   return !_g1->is_in_cset(p) || p->is_forwarded();
3870 }
3871 
3872 // Non Copying Keep Alive closure
3873 class G1KeepAliveClosure: public OopClosure {
3874   G1CollectedHeap* _g1;
3875 public:
3876   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3877   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3878   void do_oop(oop* p) {
3879     oop obj = *p;
3880     assert(obj != NULL, "the caller should have filtered out NULL values");
3881 
3882     const InCSetState cset_state = _g1->in_cset_state(obj);
3883     if (!cset_state.is_in_cset_or_humongous()) {
3884       return;
3885     }
3886     if (cset_state.is_in_cset()) {
3887       assert( obj->is_forwarded(), "invariant" );
3888       *p = obj->forwardee();
3889     } else {
3890       assert(!obj->is_forwarded(), "invariant" );
3891       assert(cset_state.is_humongous(),
3892              "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3893       _g1->set_humongous_is_live(obj);
3894     }
3895   }
3896 };
3897 
3898 // Copying Keep Alive closure - can be called from both
3899 // serial and parallel code as long as different worker
3900 // threads utilize different G1ParScanThreadState instances
3901 // and different queues.
3902 
3903 class G1CopyingKeepAliveClosure: public OopClosure {
3904   G1CollectedHeap*         _g1h;
3905   OopClosure*              _copy_non_heap_obj_cl;
3906   G1ParScanThreadState*    _par_scan_state;
3907 
3908 public:
3909   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3910                             OopClosure* non_heap_obj_cl,
3911                             G1ParScanThreadState* pss):
3912     _g1h(g1h),
3913     _copy_non_heap_obj_cl(non_heap_obj_cl),
3914     _par_scan_state(pss)
3915   {}
3916 
3917   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3918   virtual void do_oop(      oop* p) { do_oop_work(p); }
3919 
3920   template <class T> void do_oop_work(T* p) {
3921     oop obj = oopDesc::load_decode_heap_oop(p);
3922 
3923     if (_g1h->is_in_cset_or_humongous(obj)) {
3924       // If the referent object has been forwarded (either copied
3925       // to a new location or to itself in the event of an
3926       // evacuation failure) then we need to update the reference
3927       // field and, if both reference and referent are in the G1
3928       // heap, update the RSet for the referent.
3929       //
3930       // If the referent has not been forwarded then we have to keep
3931       // it alive by policy. Therefore we have copy the referent.
3932       //
3933       // If the reference field is in the G1 heap then we can push
3934       // on the PSS queue. When the queue is drained (after each
3935       // phase of reference processing) the object and it's followers
3936       // will be copied, the reference field set to point to the
3937       // new location, and the RSet updated. Otherwise we need to
3938       // use the the non-heap or metadata closures directly to copy
3939       // the referent object and update the pointer, while avoiding
3940       // updating the RSet.
3941 
3942       if (_g1h->is_in_g1_reserved(p)) {
3943         _par_scan_state->push_on_queue(p);
3944       } else {
3945         assert(!Metaspace::contains((const void*)p),
3946                "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3947         _copy_non_heap_obj_cl->do_oop(p);
3948       }
3949     }
3950   }
3951 };
3952 
3953 // Serial drain queue closure. Called as the 'complete_gc'
3954 // closure for each discovered list in some of the
3955 // reference processing phases.
3956 
3957 class G1STWDrainQueueClosure: public VoidClosure {
3958 protected:
3959   G1CollectedHeap* _g1h;
3960   G1ParScanThreadState* _par_scan_state;
3961 
3962   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3963 
3964 public:
3965   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3966     _g1h(g1h),
3967     _par_scan_state(pss)
3968   { }
3969 
3970   void do_void() {
3971     G1ParScanThreadState* const pss = par_scan_state();
3972     pss->trim_queue();
3973   }
3974 };
3975 
3976 // Parallel Reference Processing closures
3977 
3978 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3979 // processing during G1 evacuation pauses.
3980 
3981 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3982 private:
3983   G1CollectedHeap*          _g1h;
3984   G1ParScanThreadStateSet*  _pss;
3985   RefToScanQueueSet*        _queues;
3986   WorkGang*                 _workers;
3987   uint                      _active_workers;
3988 
3989 public:
3990   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3991                            G1ParScanThreadStateSet* per_thread_states,
3992                            WorkGang* workers,
3993                            RefToScanQueueSet *task_queues,
3994                            uint n_workers) :
3995     _g1h(g1h),
3996     _pss(per_thread_states),
3997     _queues(task_queues),
3998     _workers(workers),
3999     _active_workers(n_workers)
4000   {
4001     g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
4002   }
4003 
4004   // Executes the given task using concurrent marking worker threads.
4005   virtual void execute(ProcessTask& task);
4006   virtual void execute(EnqueueTask& task);
4007 };
4008 
4009 // Gang task for possibly parallel reference processing
4010 
4011 class G1STWRefProcTaskProxy: public AbstractGangTask {
4012   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
4013   ProcessTask&     _proc_task;
4014   G1CollectedHeap* _g1h;
4015   G1ParScanThreadStateSet* _pss;
4016   RefToScanQueueSet* _task_queues;
4017   ParallelTaskTerminator* _terminator;
4018 
4019 public:
4020   G1STWRefProcTaskProxy(ProcessTask& proc_task,
4021                         G1CollectedHeap* g1h,
4022                         G1ParScanThreadStateSet* per_thread_states,
4023                         RefToScanQueueSet *task_queues,
4024                         ParallelTaskTerminator* terminator) :
4025     AbstractGangTask("Process reference objects in parallel"),
4026     _proc_task(proc_task),
4027     _g1h(g1h),
4028     _pss(per_thread_states),
4029     _task_queues(task_queues),
4030     _terminator(terminator)
4031   {}
4032 
4033   virtual void work(uint worker_id) {
4034     // The reference processing task executed by a single worker.
4035     ResourceMark rm;
4036     HandleMark   hm;
4037 
4038     G1STWIsAliveClosure is_alive(_g1h);
4039 
4040     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4041     pss->set_ref_processor(NULL);
4042 
4043     // Keep alive closure.
4044     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4045 
4046     // Complete GC closure
4047     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
4048 
4049     // Call the reference processing task's work routine.
4050     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
4051 
4052     // Note we cannot assert that the refs array is empty here as not all
4053     // of the processing tasks (specifically phase2 - pp2_work) execute
4054     // the complete_gc closure (which ordinarily would drain the queue) so
4055     // the queue may not be empty.
4056   }
4057 };
4058 
4059 // Driver routine for parallel reference processing.
4060 // Creates an instance of the ref processing gang
4061 // task and has the worker threads execute it.
4062 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4063   assert(_workers != NULL, "Need parallel worker threads.");
4064 
4065   ParallelTaskTerminator terminator(_active_workers, _queues);
4066   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4067 
4068   _workers->run_task(&proc_task_proxy);
4069 }
4070 
4071 // Gang task for parallel reference enqueueing.
4072 
4073 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4074   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4075   EnqueueTask& _enq_task;
4076 
4077 public:
4078   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4079     AbstractGangTask("Enqueue reference objects in parallel"),
4080     _enq_task(enq_task)
4081   { }
4082 
4083   virtual void work(uint worker_id) {
4084     _enq_task.work(worker_id);
4085   }
4086 };
4087 
4088 // Driver routine for parallel reference enqueueing.
4089 // Creates an instance of the ref enqueueing gang
4090 // task and has the worker threads execute it.
4091 
4092 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4093   assert(_workers != NULL, "Need parallel worker threads.");
4094 
4095   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4096 
4097   _workers->run_task(&enq_task_proxy);
4098 }
4099 
4100 // End of weak reference support closures
4101 
4102 // Abstract task used to preserve (i.e. copy) any referent objects
4103 // that are in the collection set and are pointed to by reference
4104 // objects discovered by the CM ref processor.
4105 
4106 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4107 protected:
4108   G1CollectedHeap*         _g1h;
4109   G1ParScanThreadStateSet* _pss;
4110   RefToScanQueueSet*       _queues;
4111   ParallelTaskTerminator   _terminator;
4112   uint                     _n_workers;
4113 
4114 public:
4115   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4116     AbstractGangTask("ParPreserveCMReferents"),
4117     _g1h(g1h),
4118     _pss(per_thread_states),
4119     _queues(task_queues),
4120     _terminator(workers, _queues),
4121     _n_workers(workers)
4122   {
4123     g1h->ref_processor_cm()->set_active_mt_degree(workers);
4124   }
4125 
4126   void work(uint worker_id) {
4127     G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4128 
4129     ResourceMark rm;
4130     HandleMark   hm;
4131 
4132     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4133     pss->set_ref_processor(NULL);
4134     assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4135 
4136     // Is alive closure
4137     G1AlwaysAliveClosure always_alive(_g1h);
4138 
4139     // Copying keep alive closure. Applied to referent objects that need
4140     // to be copied.
4141     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4142 
4143     ReferenceProcessor* rp = _g1h->ref_processor_cm();
4144 
4145     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4146     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4147 
4148     // limit is set using max_num_q() - which was set using ParallelGCThreads.
4149     // So this must be true - but assert just in case someone decides to
4150     // change the worker ids.
4151     assert(worker_id < limit, "sanity");
4152     assert(!rp->discovery_is_atomic(), "check this code");
4153 
4154     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4155     for (uint idx = worker_id; idx < limit; idx += stride) {
4156       DiscoveredList& ref_list = rp->discovered_refs()[idx];
4157 
4158       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4159       while (iter.has_next()) {
4160         // Since discovery is not atomic for the CM ref processor, we
4161         // can see some null referent objects.
4162         iter.load_ptrs(DEBUG_ONLY(true));
4163         oop ref = iter.obj();
4164 
4165         // This will filter nulls.
4166         if (iter.is_referent_alive()) {
4167           iter.make_referent_alive();
4168         }
4169         iter.move_to_next();
4170       }
4171     }
4172 
4173     // Drain the queue - which may cause stealing
4174     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4175     drain_queue.do_void();
4176     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4177     assert(pss->queue_is_empty(), "should be");
4178   }
4179 };
4180 
4181 void G1CollectedHeap::process_weak_jni_handles() {
4182   double ref_proc_start = os::elapsedTime();
4183 
4184   G1STWIsAliveClosure is_alive(this);
4185   G1KeepAliveClosure keep_alive(this);
4186   JNIHandles::weak_oops_do(&is_alive, &keep_alive);
4187 
4188   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4189   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4190 }
4191 
4192 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4193   // Any reference objects, in the collection set, that were 'discovered'
4194   // by the CM ref processor should have already been copied (either by
4195   // applying the external root copy closure to the discovered lists, or
4196   // by following an RSet entry).
4197   //
4198   // But some of the referents, that are in the collection set, that these
4199   // reference objects point to may not have been copied: the STW ref
4200   // processor would have seen that the reference object had already
4201   // been 'discovered' and would have skipped discovering the reference,
4202   // but would not have treated the reference object as a regular oop.
4203   // As a result the copy closure would not have been applied to the
4204   // referent object.
4205   //
4206   // We need to explicitly copy these referent objects - the references
4207   // will be processed at the end of remarking.
4208   //
4209   // We also need to do this copying before we process the reference
4210   // objects discovered by the STW ref processor in case one of these
4211   // referents points to another object which is also referenced by an
4212   // object discovered by the STW ref processor.
4213   double preserve_cm_referents_time = 0.0;
4214 
4215   // To avoid spawning task when there is no work to do, check that
4216   // a concurrent cycle is active and that some references have been
4217   // discovered.
4218   if (concurrent_mark()->cmThread()->during_cycle() &&
4219       ref_processor_cm()->has_discovered_references()) {
4220     double preserve_cm_referents_start = os::elapsedTime();
4221     uint no_of_gc_workers = workers()->active_workers();
4222     G1ParPreserveCMReferentsTask keep_cm_referents(this,
4223                                                    per_thread_states,
4224                                                    no_of_gc_workers,
4225                                                    _task_queues);
4226     workers()->run_task(&keep_cm_referents);
4227     preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4228   }
4229 
4230   g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4231 }
4232 
4233 // Weak Reference processing during an evacuation pause (part 1).
4234 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4235   double ref_proc_start = os::elapsedTime();
4236 
4237   ReferenceProcessor* rp = _ref_processor_stw;
4238   assert(rp->discovery_enabled(), "should have been enabled");
4239 
4240   // Closure to test whether a referent is alive.
4241   G1STWIsAliveClosure is_alive(this);
4242 
4243   // Even when parallel reference processing is enabled, the processing
4244   // of JNI refs is serial and performed serially by the current thread
4245   // rather than by a worker. The following PSS will be used for processing
4246   // JNI refs.
4247 
4248   // Use only a single queue for this PSS.
4249   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
4250   pss->set_ref_processor(NULL);
4251   assert(pss->queue_is_empty(), "pre-condition");
4252 
4253   // Keep alive closure.
4254   G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4255 
4256   // Serial Complete GC closure
4257   G1STWDrainQueueClosure drain_queue(this, pss);
4258 
4259   // Setup the soft refs policy...
4260   rp->setup_policy(false);
4261 
4262   ReferenceProcessorStats stats;
4263   if (!rp->processing_is_mt()) {
4264     // Serial reference processing...
4265     stats = rp->process_discovered_references(&is_alive,
4266                                               &keep_alive,
4267                                               &drain_queue,
4268                                               NULL,
4269                                               _gc_timer_stw);
4270   } else {
4271     uint no_of_gc_workers = workers()->active_workers();
4272 
4273     // Parallel reference processing
4274     assert(no_of_gc_workers <= rp->max_num_q(),
4275            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4276            no_of_gc_workers,  rp->max_num_q());
4277 
4278     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4279     stats = rp->process_discovered_references(&is_alive,
4280                                               &keep_alive,
4281                                               &drain_queue,
4282                                               &par_task_executor,
4283                                               _gc_timer_stw);
4284   }
4285 
4286   _gc_tracer_stw->report_gc_reference_stats(stats);
4287 
4288   // We have completed copying any necessary live referent objects.
4289   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4290 
4291   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4292   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4293 }
4294 
4295 // Weak Reference processing during an evacuation pause (part 2).
4296 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4297   double ref_enq_start = os::elapsedTime();
4298 
4299   ReferenceProcessor* rp = _ref_processor_stw;
4300   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4301 
4302   // Now enqueue any remaining on the discovered lists on to
4303   // the pending list.
4304   if (!rp->processing_is_mt()) {
4305     // Serial reference processing...
4306     rp->enqueue_discovered_references();
4307   } else {
4308     // Parallel reference enqueueing
4309 
4310     uint n_workers = workers()->active_workers();
4311 
4312     assert(n_workers <= rp->max_num_q(),
4313            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4314            n_workers,  rp->max_num_q());
4315 
4316     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4317     rp->enqueue_discovered_references(&par_task_executor);
4318   }
4319 
4320   rp->verify_no_references_recorded();
4321   assert(!rp->discovery_enabled(), "should have been disabled");
4322 
4323   // FIXME
4324   // CM's reference processing also cleans up the string and symbol tables.
4325   // Should we do that here also? We could, but it is a serial operation
4326   // and could significantly increase the pause time.
4327 
4328   double ref_enq_time = os::elapsedTime() - ref_enq_start;
4329   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4330 }
4331 
4332 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4333   double merge_pss_time_start = os::elapsedTime();
4334   per_thread_states->flush();
4335   g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4336 }
4337 
4338 void G1CollectedHeap::pre_evacuate_collection_set() {
4339   _expand_heap_after_alloc_failure = true;
4340   _evacuation_failed = false;
4341 
4342   // Disable the hot card cache.
4343   _hot_card_cache->reset_hot_cache_claimed_index();
4344   _hot_card_cache->set_use_cache(false);
4345 
4346   g1_rem_set()->prepare_for_oops_into_collection_set_do();
4347   _preserved_marks_set.assert_empty();
4348 
4349   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4350 
4351   // InitialMark needs claim bits to keep track of the marked-through CLDs.
4352   if (collector_state()->during_initial_mark_pause()) {
4353     double start_clear_claimed_marks = os::elapsedTime();
4354 
4355     ClassLoaderDataGraph::clear_claimed_marks();
4356 
4357     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
4358     phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
4359   }
4360 }
4361 
4362 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4363   // Should G1EvacuationFailureALot be in effect for this GC?
4364   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4365 
4366   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4367 
4368   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4369 
4370   double start_par_time_sec = os::elapsedTime();
4371   double end_par_time_sec;
4372 
4373   {
4374     const uint n_workers = workers()->active_workers();
4375     G1RootProcessor root_processor(this, n_workers);
4376     G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4377 
4378     print_termination_stats_hdr();
4379 
4380     workers()->run_task(&g1_par_task);
4381     end_par_time_sec = os::elapsedTime();
4382 
4383     // Closing the inner scope will execute the destructor
4384     // for the G1RootProcessor object. We record the current
4385     // elapsed time before closing the scope so that time
4386     // taken for the destructor is NOT included in the
4387     // reported parallel time.
4388   }
4389 
4390   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4391   phase_times->record_par_time(par_time_ms);
4392 
4393   double code_root_fixup_time_ms =
4394         (os::elapsedTime() - end_par_time_sec) * 1000.0;
4395   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4396 }
4397 
4398 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4399   // Process any discovered reference objects - we have
4400   // to do this _before_ we retire the GC alloc regions
4401   // as we may have to copy some 'reachable' referent
4402   // objects (and their reachable sub-graphs) that were
4403   // not copied during the pause.
4404   if (g1_policy()->should_process_references()) {
4405     preserve_cm_referents(per_thread_states);
4406     process_discovered_references(per_thread_states);
4407   } else {
4408     ref_processor_stw()->verify_no_references_recorded();
4409     process_weak_jni_handles();
4410   }
4411 
4412   if (G1StringDedup::is_enabled()) {
4413     double fixup_start = os::elapsedTime();
4414 
4415     G1STWIsAliveClosure is_alive(this);
4416     G1KeepAliveClosure keep_alive(this);
4417     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4418 
4419     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4420     g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4421   }
4422 
4423   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4424 
4425   if (evacuation_failed()) {
4426     restore_after_evac_failure();
4427 
4428     // Reset the G1EvacuationFailureALot counters and flags
4429     // Note: the values are reset only when an actual
4430     // evacuation failure occurs.
4431     NOT_PRODUCT(reset_evacuation_should_fail();)
4432   }
4433 
4434   _preserved_marks_set.assert_empty();
4435 
4436   // Enqueue any remaining references remaining on the STW
4437   // reference processor's discovered lists. We need to do
4438   // this after the card table is cleaned (and verified) as
4439   // the act of enqueueing entries on to the pending list
4440   // will log these updates (and dirty their associated
4441   // cards). We need these updates logged to update any
4442   // RSets.
4443   if (g1_policy()->should_process_references()) {
4444     enqueue_discovered_references(per_thread_states);
4445   } else {
4446     g1_policy()->phase_times()->record_ref_enq_time(0);
4447   }
4448 
4449   _allocator->release_gc_alloc_regions(evacuation_info);
4450 
4451   merge_per_thread_state_info(per_thread_states);
4452 
4453   // Reset and re-enable the hot card cache.
4454   // Note the counts for the cards in the regions in the
4455   // collection set are reset when the collection set is freed.
4456   _hot_card_cache->reset_hot_cache();
4457   _hot_card_cache->set_use_cache(true);
4458 
4459   purge_code_root_memory();
4460 
4461   redirty_logged_cards();
4462 #if defined(COMPILER2) || INCLUDE_JVMCI
4463   double start = os::elapsedTime();
4464   DerivedPointerTable::update_pointers();
4465   g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4466 #endif
4467   g1_policy()->print_age_table();
4468 }
4469 
4470 void G1CollectedHeap::record_obj_copy_mem_stats() {
4471   g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4472 
4473   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4474                                                create_g1_evac_summary(&_old_evac_stats));
4475 }
4476 
4477 void G1CollectedHeap::free_region(HeapRegion* hr,
4478                                   FreeRegionList* free_list,
4479                                   bool skip_remset,
4480                                   bool skip_hot_card_cache,
4481                                   bool locked) {
4482   assert(!hr->is_free(), "the region should not be free");
4483   assert(!hr->is_empty(), "the region should not be empty");
4484   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4485   assert(free_list != NULL, "pre-condition");
4486 
4487   if (G1VerifyBitmaps) {
4488     MemRegion mr(hr->bottom(), hr->end());
4489     concurrent_mark()->clearRangePrevBitmap(mr);
4490   }
4491 
4492   // Clear the card counts for this region.
4493   // Note: we only need to do this if the region is not young
4494   // (since we don't refine cards in young regions).
4495   if (!skip_hot_card_cache && !hr->is_young()) {
4496     _hot_card_cache->reset_card_counts(hr);
4497   }
4498   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4499   free_list->add_ordered(hr);
4500 }
4501 
4502 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4503                                             FreeRegionList* free_list,
4504                                             bool skip_remset) {
4505   assert(hr->is_humongous(), "this is only for humongous regions");
4506   assert(free_list != NULL, "pre-condition");
4507   hr->clear_humongous();
4508   free_region(hr, free_list, skip_remset);
4509 }
4510 
4511 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4512                                            const uint humongous_regions_removed) {
4513   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4514     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4515     _old_set.bulk_remove(old_regions_removed);
4516     _humongous_set.bulk_remove(humongous_regions_removed);
4517   }
4518 
4519 }
4520 
4521 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4522   assert(list != NULL, "list can't be null");
4523   if (!list->is_empty()) {
4524     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4525     _hrm.insert_list_into_free_list(list);
4526   }
4527 }
4528 
4529 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4530   decrease_used(bytes);
4531 }
4532 
4533 class G1ParScrubRemSetTask: public AbstractGangTask {
4534 protected:
4535   G1RemSet* _g1rs;
4536   HeapRegionClaimer _hrclaimer;
4537 
4538 public:
4539   G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
4540     AbstractGangTask("G1 ScrubRS"),
4541     _g1rs(g1_rs),
4542     _hrclaimer(num_workers) {
4543   }
4544 
4545   void work(uint worker_id) {
4546     _g1rs->scrub(worker_id, &_hrclaimer);
4547   }
4548 };
4549 
4550 void G1CollectedHeap::scrub_rem_set() {
4551   uint num_workers = workers()->active_workers();
4552   G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
4553   workers()->run_task(&g1_par_scrub_rs_task);
4554 }
4555 
4556 class G1FreeCollectionSetTask : public AbstractGangTask {
4557 private:
4558 
4559   // Closure applied to all regions in the collection set to do work that needs to
4560   // be done serially in a single thread.
4561   class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4562   private:
4563     EvacuationInfo* _evacuation_info;
4564     const size_t* _surviving_young_words;
4565 
4566     // Bytes used in successfully evacuated regions before the evacuation.
4567     size_t _before_used_bytes;
4568     // Bytes used in unsucessfully evacuated regions before the evacuation
4569     size_t _after_used_bytes;
4570 
4571     size_t _bytes_allocated_in_old_since_last_gc;
4572 
4573     size_t _failure_used_words;
4574     size_t _failure_waste_words;
4575 
4576     FreeRegionList _local_free_list;
4577   public:
4578     G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4579       HeapRegionClosure(),
4580       _evacuation_info(evacuation_info),
4581       _surviving_young_words(surviving_young_words),
4582       _before_used_bytes(0),
4583       _after_used_bytes(0),
4584       _bytes_allocated_in_old_since_last_gc(0),
4585       _failure_used_words(0),
4586       _failure_waste_words(0),
4587       _local_free_list("Local Region List for CSet Freeing") {
4588     }
4589 
4590     virtual bool doHeapRegion(HeapRegion* r) {
4591       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4592 
4593       assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4594       g1h->clear_in_cset(r);
4595 
4596       if (r->is_young()) {
4597         assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4598                "Young index %d is wrong for region %u of type %s with %u young regions",
4599                r->young_index_in_cset(),
4600                r->hrm_index(),
4601                r->get_type_str(),
4602                g1h->collection_set()->young_region_length());
4603         size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4604         r->record_surv_words_in_group(words_survived);
4605       }
4606 
4607       if (!r->evacuation_failed()) {
4608         assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4609         _before_used_bytes += r->used();
4610         g1h->free_region(r,
4611                          &_local_free_list,
4612                          true, /* skip_remset */
4613                          true, /* skip_hot_card_cache */
4614                          true  /* locked */);
4615       } else {
4616         r->uninstall_surv_rate_group();
4617         r->set_young_index_in_cset(-1);
4618         r->set_evacuation_failed(false);
4619         // When moving a young gen region to old gen, we "allocate" that whole region
4620         // there. This is in addition to any already evacuated objects. Notify the
4621         // policy about that.
4622         // Old gen regions do not cause an additional allocation: both the objects
4623         // still in the region and the ones already moved are accounted for elsewhere.
4624         if (r->is_young()) {
4625           _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4626         }
4627         // The region is now considered to be old.
4628         r->set_old();
4629         // Do some allocation statistics accounting. Regions that failed evacuation
4630         // are always made old, so there is no need to update anything in the young
4631         // gen statistics, but we need to update old gen statistics.
4632         size_t used_words = r->marked_bytes() / HeapWordSize;
4633 
4634         _failure_used_words += used_words;
4635         _failure_waste_words += HeapRegion::GrainWords - used_words;
4636 
4637         g1h->old_set_add(r);
4638         _after_used_bytes += r->used();
4639       }
4640       return false;
4641     }
4642 
4643     void complete_work() {
4644       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4645 
4646       _evacuation_info->set_regions_freed(_local_free_list.length());
4647       _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4648 
4649       g1h->prepend_to_freelist(&_local_free_list);
4650       g1h->decrement_summary_bytes(_before_used_bytes);
4651 
4652       G1Policy* policy = g1h->g1_policy();
4653       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4654 
4655       g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4656     }
4657   };
4658 
4659   G1CollectionSet* _collection_set;
4660   G1SerialFreeCollectionSetClosure _cl;
4661   const size_t* _surviving_young_words;
4662 
4663   size_t _rs_lengths;
4664 
4665   volatile jint _serial_work_claim;
4666 
4667   struct WorkItem {
4668     uint region_idx;
4669     bool is_young;
4670     bool evacuation_failed;
4671 
4672     WorkItem(HeapRegion* r) {
4673       region_idx = r->hrm_index();
4674       is_young = r->is_young();
4675       evacuation_failed = r->evacuation_failed();
4676     }
4677   };
4678 
4679   volatile size_t _parallel_work_claim;
4680   size_t _num_work_items;
4681   WorkItem* _work_items;
4682 
4683   void do_serial_work() {
4684     // Need to grab the lock to be allowed to modify the old region list.
4685     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4686     _collection_set->iterate(&_cl);
4687   }
4688 
4689   void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4690     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4691 
4692     HeapRegion* r = g1h->region_at(region_idx);
4693     assert(!g1h->is_on_master_free_list(r), "sanity");
4694 
4695     Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4696 
4697     if (!is_young) {
4698       g1h->_hot_card_cache->reset_card_counts(r);
4699     }
4700 
4701     if (!evacuation_failed) {
4702       r->rem_set()->clear_locked();
4703     }
4704   }
4705 
4706   class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4707   private:
4708     size_t _cur_idx;
4709     WorkItem* _work_items;
4710   public:
4711     G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4712 
4713     virtual bool doHeapRegion(HeapRegion* r) {
4714       _work_items[_cur_idx++] = WorkItem(r);
4715       return false;
4716     }
4717   };
4718 
4719   void prepare_work() {
4720     G1PrepareFreeCollectionSetClosure cl(_work_items);
4721     _collection_set->iterate(&cl);
4722   }
4723 
4724   void complete_work() {
4725     _cl.complete_work();
4726 
4727     G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4728     policy->record_max_rs_lengths(_rs_lengths);
4729     policy->cset_regions_freed();
4730   }
4731 public:
4732   G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4733     AbstractGangTask("G1 Free Collection Set"),
4734     _cl(evacuation_info, surviving_young_words),
4735     _collection_set(collection_set),
4736     _surviving_young_words(surviving_young_words),
4737     _serial_work_claim(0),
4738     _rs_lengths(0),
4739     _parallel_work_claim(0),
4740     _num_work_items(collection_set->region_length()),
4741     _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4742     prepare_work();
4743   }
4744 
4745   ~G1FreeCollectionSetTask() {
4746     complete_work();
4747     FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4748   }
4749 
4750   // Chunk size for work distribution. The chosen value has been determined experimentally
4751   // to be a good tradeoff between overhead and achievable parallelism.
4752   static uint chunk_size() { return 32; }
4753 
4754   virtual void work(uint worker_id) {
4755     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4756 
4757     // Claim serial work.
4758     if (_serial_work_claim == 0) {
4759       jint value = Atomic::add(1, &_serial_work_claim) - 1;
4760       if (value == 0) {
4761         double serial_time = os::elapsedTime();
4762         do_serial_work();
4763         timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4764       }
4765     }
4766 
4767     // Start parallel work.
4768     double young_time = 0.0;
4769     bool has_young_time = false;
4770     double non_young_time = 0.0;
4771     bool has_non_young_time = false;
4772 
4773     while (true) {
4774       size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4775       size_t cur = end - chunk_size();
4776 
4777       if (cur >= _num_work_items) {
4778         break;
4779       }
4780 
4781       double start_time = os::elapsedTime();
4782 
4783       end = MIN2(end, _num_work_items);
4784 
4785       for (; cur < end; cur++) {
4786         bool is_young = _work_items[cur].is_young;
4787 
4788         do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4789 
4790         double end_time = os::elapsedTime();
4791         double time_taken = end_time - start_time;
4792         if (is_young) {
4793           young_time += time_taken;
4794           has_young_time = true;
4795         } else {
4796           non_young_time += time_taken;
4797           has_non_young_time = true;
4798         }
4799         start_time = end_time;
4800       }
4801     }
4802 
4803     if (has_young_time) {
4804       timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4805     }
4806     if (has_non_young_time) {
4807       timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time);
4808     }
4809   }
4810 };
4811 
4812 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4813   _eden.clear();
4814 
4815   double free_cset_start_time = os::elapsedTime();
4816 
4817   {
4818     uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4819     uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4820 
4821     G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4822 
4823     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4824                         cl.name(),
4825                         num_workers,
4826                         _collection_set.region_length());
4827     workers()->run_task(&cl, num_workers);
4828   }
4829   g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4830 
4831   collection_set->clear();
4832 }
4833 
4834 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4835  private:
4836   FreeRegionList* _free_region_list;
4837   HeapRegionSet* _proxy_set;
4838   uint _humongous_objects_reclaimed;
4839   uint _humongous_regions_reclaimed;
4840   size_t _freed_bytes;
4841  public:
4842 
4843   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4844     _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4845   }
4846 
4847   virtual bool doHeapRegion(HeapRegion* r) {
4848     if (!r->is_starts_humongous()) {
4849       return false;
4850     }
4851 
4852     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4853 
4854     oop obj = (oop)r->bottom();
4855     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
4856 
4857     // The following checks whether the humongous object is live are sufficient.
4858     // The main additional check (in addition to having a reference from the roots
4859     // or the young gen) is whether the humongous object has a remembered set entry.
4860     //
4861     // A humongous object cannot be live if there is no remembered set for it
4862     // because:
4863     // - there can be no references from within humongous starts regions referencing
4864     // the object because we never allocate other objects into them.
4865     // (I.e. there are no intra-region references that may be missed by the
4866     // remembered set)
4867     // - as soon there is a remembered set entry to the humongous starts region
4868     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4869     // until the end of a concurrent mark.
4870     //
4871     // It is not required to check whether the object has been found dead by marking
4872     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4873     // all objects allocated during that time are considered live.
4874     // SATB marking is even more conservative than the remembered set.
4875     // So if at this point in the collection there is no remembered set entry,
4876     // nobody has a reference to it.
4877     // At the start of collection we flush all refinement logs, and remembered sets
4878     // are completely up-to-date wrt to references to the humongous object.
4879     //
4880     // Other implementation considerations:
4881     // - never consider object arrays at this time because they would pose
4882     // considerable effort for cleaning up the the remembered sets. This is
4883     // required because stale remembered sets might reference locations that
4884     // are currently allocated into.
4885     uint region_idx = r->hrm_index();
4886     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4887         !r->rem_set()->is_empty()) {
4888       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",
4889                                region_idx,
4890                                (size_t)obj->size() * HeapWordSize,
4891                                p2i(r->bottom()),
4892                                r->rem_set()->occupied(),
4893                                r->rem_set()->strong_code_roots_list_length(),
4894                                next_bitmap->isMarked(r->bottom()),
4895                                g1h->is_humongous_reclaim_candidate(region_idx),
4896                                obj->is_typeArray()
4897                               );
4898       return false;
4899     }
4900 
4901     guarantee(obj->is_typeArray(),
4902               "Only eagerly reclaiming type arrays is supported, but the object "
4903               PTR_FORMAT " is not.", p2i(r->bottom()));
4904 
4905     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",
4906                              region_idx,
4907                              (size_t)obj->size() * HeapWordSize,
4908                              p2i(r->bottom()),
4909                              r->rem_set()->occupied(),
4910                              r->rem_set()->strong_code_roots_list_length(),
4911                              next_bitmap->isMarked(r->bottom()),
4912                              g1h->is_humongous_reclaim_candidate(region_idx),
4913                              obj->is_typeArray()
4914                             );
4915 
4916     // Need to clear mark bit of the humongous object if already set.
4917     if (next_bitmap->isMarked(r->bottom())) {
4918       next_bitmap->clear(r->bottom());
4919     }
4920     _humongous_objects_reclaimed++;
4921     do {
4922       HeapRegion* next = g1h->next_region_in_humongous(r);
4923       _freed_bytes += r->used();
4924       r->set_containing_set(NULL);
4925       _humongous_regions_reclaimed++;
4926       g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ );
4927       r = next;
4928     } while (r != NULL);
4929 
4930     return false;
4931   }
4932 
4933   uint humongous_objects_reclaimed() {
4934     return _humongous_objects_reclaimed;
4935   }
4936 
4937   uint humongous_regions_reclaimed() {
4938     return _humongous_regions_reclaimed;
4939   }
4940 
4941   size_t bytes_freed() const {
4942     return _freed_bytes;
4943   }
4944 };
4945 
4946 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4947   assert_at_safepoint(true);
4948 
4949   if (!G1EagerReclaimHumongousObjects ||
4950       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4951     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4952     return;
4953   }
4954 
4955   double start_time = os::elapsedTime();
4956 
4957   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4958 
4959   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4960   heap_region_iterate(&cl);
4961 
4962   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4963 
4964   G1HRPrinter* hrp = hr_printer();
4965   if (hrp->is_active()) {
4966     FreeRegionListIterator iter(&local_cleanup_list);
4967     while (iter.more_available()) {
4968       HeapRegion* hr = iter.get_next();
4969       hrp->cleanup(hr);
4970     }
4971   }
4972 
4973   prepend_to_freelist(&local_cleanup_list);
4974   decrement_summary_bytes(cl.bytes_freed());
4975 
4976   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4977                                                                     cl.humongous_objects_reclaimed());
4978 }
4979 
4980 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4981 public:
4982   virtual bool doHeapRegion(HeapRegion* r) {
4983     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4984     G1CollectedHeap::heap()->clear_in_cset(r);
4985     r->set_young_index_in_cset(-1);
4986     return false;
4987   }
4988 };
4989 
4990 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4991   G1AbandonCollectionSetClosure cl;
4992   collection_set->iterate(&cl);
4993 
4994   collection_set->clear();
4995   collection_set->stop_incremental_building();
4996 }
4997 
4998 void G1CollectedHeap::set_free_regions_coming() {
4999   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
5000 
5001   assert(!free_regions_coming(), "pre-condition");
5002   _free_regions_coming = true;
5003 }
5004 
5005 void G1CollectedHeap::reset_free_regions_coming() {
5006   assert(free_regions_coming(), "pre-condition");
5007 
5008   {
5009     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5010     _free_regions_coming = false;
5011     SecondaryFreeList_lock->notify_all();
5012   }
5013 
5014   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
5015 }
5016 
5017 void G1CollectedHeap::wait_while_free_regions_coming() {
5018   // Most of the time we won't have to wait, so let's do a quick test
5019   // first before we take the lock.
5020   if (!free_regions_coming()) {
5021     return;
5022   }
5023 
5024   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
5025 
5026   {
5027     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5028     while (free_regions_coming()) {
5029       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5030     }
5031   }
5032 
5033   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
5034 }
5035 
5036 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
5037   return _allocator->is_retained_old_region(hr);
5038 }
5039 
5040 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5041   _eden.add(hr);
5042   _g1_policy->set_region_eden(hr);
5043 }
5044 
5045 #ifdef ASSERT
5046 
5047 class NoYoungRegionsClosure: public HeapRegionClosure {
5048 private:
5049   bool _success;
5050 public:
5051   NoYoungRegionsClosure() : _success(true) { }
5052   bool doHeapRegion(HeapRegion* r) {
5053     if (r->is_young()) {
5054       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5055                             p2i(r->bottom()), p2i(r->end()));
5056       _success = false;
5057     }
5058     return false;
5059   }
5060   bool success() { return _success; }
5061 };
5062 
5063 bool G1CollectedHeap::check_young_list_empty() {
5064   bool ret = (young_regions_count() == 0);
5065 
5066   NoYoungRegionsClosure closure;
5067   heap_region_iterate(&closure);
5068   ret = ret && closure.success();
5069 
5070   return ret;
5071 }
5072 
5073 #endif // ASSERT
5074 
5075 class TearDownRegionSetsClosure : public HeapRegionClosure {
5076 private:
5077   HeapRegionSet *_old_set;
5078 
5079 public:
5080   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5081 
5082   bool doHeapRegion(HeapRegion* r) {
5083     if (r->is_old()) {
5084       _old_set->remove(r);
5085     } else if(r->is_young()) {
5086       r->uninstall_surv_rate_group();
5087     } else {
5088       // We ignore free regions, we'll empty the free list afterwards.
5089       // We ignore humongous regions, we're not tearing down the
5090       // humongous regions set.
5091       assert(r->is_free() || r->is_humongous(),
5092              "it cannot be another type");
5093     }
5094     return false;
5095   }
5096 
5097   ~TearDownRegionSetsClosure() {
5098     assert(_old_set->is_empty(), "post-condition");
5099   }
5100 };
5101 
5102 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5103   assert_at_safepoint(true /* should_be_vm_thread */);
5104 
5105   if (!free_list_only) {
5106     TearDownRegionSetsClosure cl(&_old_set);
5107     heap_region_iterate(&cl);
5108 
5109     // Note that emptying the _young_list is postponed and instead done as
5110     // the first step when rebuilding the regions sets again. The reason for
5111     // this is that during a full GC string deduplication needs to know if
5112     // a collected region was young or old when the full GC was initiated.
5113   }
5114   _hrm.remove_all_free_regions();
5115 }
5116 
5117 void G1CollectedHeap::increase_used(size_t bytes) {
5118   _summary_bytes_used += bytes;
5119 }
5120 
5121 void G1CollectedHeap::decrease_used(size_t bytes) {
5122   assert(_summary_bytes_used >= bytes,
5123          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5124          _summary_bytes_used, bytes);
5125   _summary_bytes_used -= bytes;
5126 }
5127 
5128 void G1CollectedHeap::set_used(size_t bytes) {
5129   _summary_bytes_used = bytes;
5130 }
5131 
5132 class RebuildRegionSetsClosure : public HeapRegionClosure {
5133 private:
5134   bool            _free_list_only;
5135   HeapRegionSet*   _old_set;
5136   HeapRegionManager*   _hrm;
5137   size_t          _total_used;
5138 
5139 public:
5140   RebuildRegionSetsClosure(bool free_list_only,
5141                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
5142     _free_list_only(free_list_only),
5143     _old_set(old_set), _hrm(hrm), _total_used(0) {
5144     assert(_hrm->num_free_regions() == 0, "pre-condition");
5145     if (!free_list_only) {
5146       assert(_old_set->is_empty(), "pre-condition");
5147     }
5148   }
5149 
5150   bool doHeapRegion(HeapRegion* r) {
5151     if (r->is_empty()) {
5152       // Add free regions to the free list
5153       r->set_free();
5154       r->set_allocation_context(AllocationContext::system());
5155       _hrm->insert_into_free_list(r);
5156     } else if (!_free_list_only) {
5157 
5158       if (r->is_humongous()) {
5159         // We ignore humongous regions. We left the humongous set unchanged.
5160       } else {
5161         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
5162         // We now consider all regions old, so register as such. Leave
5163         // archive regions set that way, however, while still adding
5164         // them to the old set.
5165         if (!r->is_archive()) {
5166           r->set_old();
5167         }
5168         _old_set->add(r);
5169       }
5170       _total_used += r->used();
5171     }
5172 
5173     return false;
5174   }
5175 
5176   size_t total_used() {
5177     return _total_used;
5178   }
5179 };
5180 
5181 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5182   assert_at_safepoint(true /* should_be_vm_thread */);
5183 
5184   if (!free_list_only) {
5185     _eden.clear();
5186     _survivor.clear();
5187   }
5188 
5189   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5190   heap_region_iterate(&cl);
5191 
5192   if (!free_list_only) {
5193     set_used(cl.total_used());
5194     if (_archive_allocator != NULL) {
5195       _archive_allocator->clear_used();
5196     }
5197   }
5198   assert(used_unlocked() == recalculate_used(),
5199          "inconsistent used_unlocked(), "
5200          "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5201          used_unlocked(), recalculate_used());
5202 }
5203 
5204 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
5205   _refine_cte_cl->set_concurrent(concurrent);
5206 }
5207 
5208 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5209   HeapRegion* hr = heap_region_containing(p);
5210   return hr->is_in(p);
5211 }
5212 
5213 // Methods for the mutator alloc region
5214 
5215 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5216                                                       bool force) {
5217   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5218   bool should_allocate = g1_policy()->should_allocate_mutator_region();
5219   if (force || should_allocate) {
5220     HeapRegion* new_alloc_region = new_region(word_size,
5221                                               false /* is_old */,
5222                                               false /* do_expand */);
5223     if (new_alloc_region != NULL) {
5224       set_region_short_lived_locked(new_alloc_region);
5225       _hr_printer.alloc(new_alloc_region, !should_allocate);
5226       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5227       return new_alloc_region;
5228     }
5229   }
5230   return NULL;
5231 }
5232 
5233 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5234                                                   size_t allocated_bytes) {
5235   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5236   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5237 
5238   collection_set()->add_eden_region(alloc_region);
5239   increase_used(allocated_bytes);
5240   _hr_printer.retire(alloc_region);
5241   // We update the eden sizes here, when the region is retired,
5242   // instead of when it's allocated, since this is the point that its
5243   // used space has been recored in _summary_bytes_used.
5244   g1mm()->update_eden_size();
5245 }
5246 
5247 // Methods for the GC alloc regions
5248 
5249 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
5250   if (dest.is_old()) {
5251     return true;
5252   } else {
5253     return survivor_regions_count() < g1_policy()->max_survivor_regions();
5254   }
5255 }
5256 
5257 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
5258   assert(FreeList_lock->owned_by_self(), "pre-condition");
5259 
5260   if (!has_more_regions(dest)) {
5261     return NULL;
5262   }
5263 
5264   const bool is_survivor = dest.is_young();
5265 
5266   HeapRegion* new_alloc_region = new_region(word_size,
5267                                             !is_survivor,
5268                                             true /* do_expand */);
5269   if (new_alloc_region != NULL) {
5270     // We really only need to do this for old regions given that we
5271     // should never scan survivors. But it doesn't hurt to do it
5272     // for survivors too.
5273     new_alloc_region->record_timestamp();
5274     if (is_survivor) {
5275       new_alloc_region->set_survivor();
5276       _survivor.add(new_alloc_region);
5277       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5278     } else {
5279       new_alloc_region->set_old();
5280       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5281     }
5282     _hr_printer.alloc(new_alloc_region);
5283     bool during_im = collector_state()->during_initial_mark_pause();
5284     new_alloc_region->note_start_of_copying(during_im);
5285     return new_alloc_region;
5286   }
5287   return NULL;
5288 }
5289 
5290 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5291                                              size_t allocated_bytes,
5292                                              InCSetState dest) {
5293   bool during_im = collector_state()->during_initial_mark_pause();
5294   alloc_region->note_end_of_copying(during_im);
5295   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5296   if (dest.is_old()) {
5297     _old_set.add(alloc_region);
5298   }
5299   _hr_printer.retire(alloc_region);
5300 }
5301 
5302 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5303   bool expanded = false;
5304   uint index = _hrm.find_highest_free(&expanded);
5305 
5306   if (index != G1_NO_HRM_INDEX) {
5307     if (expanded) {
5308       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5309                                 HeapRegion::GrainWords * HeapWordSize);
5310     }
5311     _hrm.allocate_free_regions_starting_at(index, 1);
5312     return region_at(index);
5313   }
5314   return NULL;
5315 }
5316 
5317 // Optimized nmethod scanning
5318 
5319 class RegisterNMethodOopClosure: public OopClosure {
5320   G1CollectedHeap* _g1h;
5321   nmethod* _nm;
5322 
5323   template <class T> void do_oop_work(T* p) {
5324     T heap_oop = oopDesc::load_heap_oop(p);
5325     if (!oopDesc::is_null(heap_oop)) {
5326       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5327       HeapRegion* hr = _g1h->heap_region_containing(obj);
5328       assert(!hr->is_continues_humongous(),
5329              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5330              " starting at " HR_FORMAT,
5331              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5332 
5333       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5334       hr->add_strong_code_root_locked(_nm);
5335     }
5336   }
5337 
5338 public:
5339   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5340     _g1h(g1h), _nm(nm) {}
5341 
5342   void do_oop(oop* p)       { do_oop_work(p); }
5343   void do_oop(narrowOop* p) { do_oop_work(p); }
5344 };
5345 
5346 class UnregisterNMethodOopClosure: public OopClosure {
5347   G1CollectedHeap* _g1h;
5348   nmethod* _nm;
5349 
5350   template <class T> void do_oop_work(T* p) {
5351     T heap_oop = oopDesc::load_heap_oop(p);
5352     if (!oopDesc::is_null(heap_oop)) {
5353       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5354       HeapRegion* hr = _g1h->heap_region_containing(obj);
5355       assert(!hr->is_continues_humongous(),
5356              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5357              " starting at " HR_FORMAT,
5358              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5359 
5360       hr->remove_strong_code_root(_nm);
5361     }
5362   }
5363 
5364 public:
5365   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5366     _g1h(g1h), _nm(nm) {}
5367 
5368   void do_oop(oop* p)       { do_oop_work(p); }
5369   void do_oop(narrowOop* p) { do_oop_work(p); }
5370 };
5371 
5372 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5373   CollectedHeap::register_nmethod(nm);
5374 
5375   guarantee(nm != NULL, "sanity");
5376   RegisterNMethodOopClosure reg_cl(this, nm);
5377   nm->oops_do(&reg_cl);
5378 }
5379 
5380 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5381   CollectedHeap::unregister_nmethod(nm);
5382 
5383   guarantee(nm != NULL, "sanity");
5384   UnregisterNMethodOopClosure reg_cl(this, nm);
5385   nm->oops_do(&reg_cl, true);
5386 }
5387 
5388 void G1CollectedHeap::purge_code_root_memory() {
5389   double purge_start = os::elapsedTime();
5390   G1CodeRootSet::purge();
5391   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5392   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5393 }
5394 
5395 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5396   G1CollectedHeap* _g1h;
5397 
5398 public:
5399   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5400     _g1h(g1h) {}
5401 
5402   void do_code_blob(CodeBlob* cb) {
5403     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5404     if (nm == NULL) {
5405       return;
5406     }
5407 
5408     if (ScavengeRootsInCode) {
5409       _g1h->register_nmethod(nm);
5410     }
5411   }
5412 };
5413 
5414 void G1CollectedHeap::rebuild_strong_code_roots() {
5415   RebuildStrongCodeRootClosure blob_cl(this);
5416   CodeCache::blobs_do(&blob_cl);
5417 }