1 /*
   2  * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/metadataOnStackMark.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "classfile/symbolTable.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc/g1/bufferingOopClosure.hpp"
  32 #include "gc/g1/concurrentG1Refine.hpp"
  33 #include "gc/g1/concurrentG1RefineThread.hpp"
  34 #include "gc/g1/concurrentMarkThread.inline.hpp"
  35 #include "gc/g1/g1Allocator.inline.hpp"
  36 #include "gc/g1/g1CollectedHeap.inline.hpp"
  37 #include "gc/g1/g1CollectorPolicy.hpp"
  38 #include "gc/g1/g1CollectorState.hpp"
  39 #include "gc/g1/g1EvacStats.inline.hpp"
  40 #include "gc/g1/g1GCPhaseTimes.hpp"
  41 #include "gc/g1/g1HeapTransition.hpp"
  42 #include "gc/g1/g1HeapVerifier.hpp"
  43 #include "gc/g1/g1MarkSweep.hpp"
  44 #include "gc/g1/g1OopClosures.inline.hpp"
  45 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  46 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  47 #include "gc/g1/g1RemSet.inline.hpp"
  48 #include "gc/g1/g1RootClosures.hpp"
  49 #include "gc/g1/g1RootProcessor.hpp"
  50 #include "gc/g1/g1StringDedup.hpp"
  51 #include "gc/g1/g1YCTypes.hpp"
  52 #include "gc/g1/heapRegion.inline.hpp"
  53 #include "gc/g1/heapRegionRemSet.hpp"
  54 #include "gc/g1/heapRegionSet.inline.hpp"
  55 #include "gc/g1/suspendibleThreadSet.hpp"
  56 #include "gc/g1/vm_operations_g1.hpp"
  57 #include "gc/shared/gcHeapSummary.hpp"
  58 #include "gc/shared/gcId.hpp"
  59 #include "gc/shared/gcLocker.inline.hpp"
  60 #include "gc/shared/gcTimer.hpp"
  61 #include "gc/shared/gcTrace.hpp"
  62 #include "gc/shared/gcTraceTime.inline.hpp"
  63 #include "gc/shared/generationSpec.hpp"
  64 #include "gc/shared/isGCActiveMark.hpp"
  65 #include "gc/shared/referenceProcessor.inline.hpp"
  66 #include "gc/shared/taskqueue.inline.hpp"
  67 #include "logging/log.hpp"
  68 #include "memory/allocation.hpp"
  69 #include "memory/iterator.hpp"
  70 #include "oops/oop.inline.hpp"
  71 #include "runtime/atomic.inline.hpp"
  72 #include "runtime/init.hpp"
  73 #include "runtime/orderAccess.inline.hpp"
  74 #include "runtime/vmThread.hpp"
  75 #include "utilities/globalDefinitions.hpp"
  76 #include "utilities/stack.inline.hpp"
  77 
  78 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  79 
  80 // INVARIANTS/NOTES
  81 //
  82 // All allocation activity covered by the G1CollectedHeap interface is
  83 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  84 // and allocate_new_tlab, which are the "entry" points to the
  85 // allocation code from the rest of the JVM.  (Note that this does not
  86 // apply to TLAB allocation, which is not part of this interface: it
  87 // is done by clients of this interface.)
  88 
  89 // Local to this file.
  90 
  91 class RefineCardTableEntryClosure: public CardTableEntryClosure {
  92   bool _concurrent;
  93 public:
  94   RefineCardTableEntryClosure() : _concurrent(true) { }
  95 
  96   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
  97     bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
  98     // This path is executed by the concurrent refine or mutator threads,
  99     // concurrently, and so we do not care if card_ptr contains references
 100     // that point into the collection set.
 101     assert(!oops_into_cset, "should be");
 102 
 103     if (_concurrent && SuspendibleThreadSet::should_yield()) {
 104       // Caller will actually yield.
 105       return false;
 106     }
 107     // Otherwise, we finished successfully; return true.
 108     return true;
 109   }
 110 
 111   void set_concurrent(bool b) { _concurrent = b; }
 112 };
 113 
 114 
 115 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 116  private:
 117   size_t _num_dirtied;
 118   G1CollectedHeap* _g1h;
 119   G1SATBCardTableLoggingModRefBS* _g1_bs;
 120 
 121   HeapRegion* region_for_card(jbyte* card_ptr) const {
 122     return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
 123   }
 124 
 125   bool will_become_free(HeapRegion* hr) const {
 126     // A region will be freed by free_collection_set if the region is in the
 127     // collection set and has not had an evacuation failure.
 128     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 129   }
 130 
 131  public:
 132   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
 133     _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
 134 
 135   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 136     HeapRegion* hr = region_for_card(card_ptr);
 137 
 138     // Should only dirty cards in regions that won't be freed.
 139     if (!will_become_free(hr)) {
 140       *card_ptr = CardTableModRefBS::dirty_card_val();
 141       _num_dirtied++;
 142     }
 143 
 144     return true;
 145   }
 146 
 147   size_t num_dirtied()   const { return _num_dirtied; }
 148 };
 149 
 150 
 151 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 152   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 153 }
 154 
 155 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 156   // The from card cache is not the memory that is actually committed. So we cannot
 157   // take advantage of the zero_filled parameter.
 158   reset_from_card_cache(start_idx, num_regions);
 159 }
 160 
 161 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
 162 {
 163   // Claim the right to put the region on the dirty cards region list
 164   // by installing a self pointer.
 165   HeapRegion* next = hr->get_next_dirty_cards_region();
 166   if (next == NULL) {
 167     HeapRegion* res = (HeapRegion*)
 168       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
 169                           NULL);
 170     if (res == NULL) {
 171       HeapRegion* head;
 172       do {
 173         // Put the region to the dirty cards region list.
 174         head = _dirty_cards_region_list;
 175         next = (HeapRegion*)
 176           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
 177         if (next == head) {
 178           assert(hr->get_next_dirty_cards_region() == hr,
 179                  "hr->get_next_dirty_cards_region() != hr");
 180           if (next == NULL) {
 181             // The last region in the list points to itself.
 182             hr->set_next_dirty_cards_region(hr);
 183           } else {
 184             hr->set_next_dirty_cards_region(next);
 185           }
 186         }
 187       } while (next != head);
 188     }
 189   }
 190 }
 191 
 192 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
 193 {
 194   HeapRegion* head;
 195   HeapRegion* hr;
 196   do {
 197     head = _dirty_cards_region_list;
 198     if (head == NULL) {
 199       return NULL;
 200     }
 201     HeapRegion* new_head = head->get_next_dirty_cards_region();
 202     if (head == new_head) {
 203       // The last region.
 204       new_head = NULL;
 205     }
 206     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
 207                                           head);
 208   } while (hr != head);
 209   assert(hr != NULL, "invariant");
 210   hr->set_next_dirty_cards_region(NULL);
 211   return hr;
 212 }
 213 
 214 // Returns true if the reference points to an object that
 215 // can move in an incremental collection.
 216 bool G1CollectedHeap::is_scavengable(const void* p) {
 217   HeapRegion* hr = heap_region_containing(p);
 218   return !hr->is_pinned();
 219 }
 220 
 221 // Private methods.
 222 
 223 HeapRegion*
 224 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 225   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 226   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 227     if (!_secondary_free_list.is_empty()) {
 228       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 229                                       "secondary_free_list has %u entries",
 230                                       _secondary_free_list.length());
 231       // It looks as if there are free regions available on the
 232       // secondary_free_list. Let's move them to the free_list and try
 233       // again to allocate from it.
 234       append_secondary_free_list();
 235 
 236       assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
 237              "empty we should have moved at least one entry to the free_list");
 238       HeapRegion* res = _hrm.allocate_free_region(is_old);
 239       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 240                                       "allocated " HR_FORMAT " from secondary_free_list",
 241                                       HR_FORMAT_PARAMS(res));
 242       return res;
 243     }
 244 
 245     // Wait here until we get notified either when (a) there are no
 246     // more free regions coming or (b) some regions have been moved on
 247     // the secondary_free_list.
 248     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 249   }
 250 
 251   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 252                                   "could not allocate from secondary_free_list");
 253   return NULL;
 254 }
 255 
 256 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 257   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 258          "the only time we use this to allocate a humongous region is "
 259          "when we are allocating a single humongous region");
 260 
 261   HeapRegion* res;
 262   if (G1StressConcRegionFreeing) {
 263     if (!_secondary_free_list.is_empty()) {
 264       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 265                                       "forced to look at the secondary_free_list");
 266       res = new_region_try_secondary_free_list(is_old);
 267       if (res != NULL) {
 268         return res;
 269       }
 270     }
 271   }
 272 
 273   res = _hrm.allocate_free_region(is_old);
 274 
 275   if (res == NULL) {
 276     log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 277                                     "res == NULL, trying the secondary_free_list");
 278     res = new_region_try_secondary_free_list(is_old);
 279   }
 280   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 281     // Currently, only attempts to allocate GC alloc regions set
 282     // do_expand to true. So, we should only reach here during a
 283     // safepoint. If this assumption changes we might have to
 284     // reconsider the use of _expand_heap_after_alloc_failure.
 285     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 286 
 287     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 288                               word_size * HeapWordSize);
 289 
 290     if (expand(word_size * HeapWordSize)) {
 291       // Given that expand() succeeded in expanding the heap, and we
 292       // always expand the heap by an amount aligned to the heap
 293       // region size, the free list should in theory not be empty.
 294       // In either case allocate_free_region() will check for NULL.
 295       res = _hrm.allocate_free_region(is_old);
 296     } else {
 297       _expand_heap_after_alloc_failure = false;
 298     }
 299   }
 300   return res;
 301 }
 302 
 303 HeapWord*
 304 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 305                                                            uint num_regions,
 306                                                            size_t word_size,
 307                                                            AllocationContext_t context) {
 308   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 309   assert(is_humongous(word_size), "word_size should be humongous");
 310   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 311 
 312   // Index of last region in the series.
 313   uint last = first + num_regions - 1;
 314 
 315   // We need to initialize the region(s) we just discovered. This is
 316   // a bit tricky given that it can happen concurrently with
 317   // refinement threads refining cards on these regions and
 318   // potentially wanting to refine the BOT as they are scanning
 319   // those cards (this can happen shortly after a cleanup; see CR
 320   // 6991377). So we have to set up the region(s) carefully and in
 321   // a specific order.
 322 
 323   // The word size sum of all the regions we will allocate.
 324   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 325   assert(word_size <= word_size_sum, "sanity");
 326 
 327   // This will be the "starts humongous" region.
 328   HeapRegion* first_hr = region_at(first);
 329   // The header of the new object will be placed at the bottom of
 330   // the first region.
 331   HeapWord* new_obj = first_hr->bottom();
 332   // This will be the new top of the new object.
 333   HeapWord* obj_top = new_obj + word_size;
 334 
 335   // First, we need to zero the header of the space that we will be
 336   // allocating. When we update top further down, some refinement
 337   // threads might try to scan the region. By zeroing the header we
 338   // ensure that any thread that will try to scan the region will
 339   // come across the zero klass word and bail out.
 340   //
 341   // NOTE: It would not have been correct to have used
 342   // CollectedHeap::fill_with_object() and make the space look like
 343   // an int array. The thread that is doing the allocation will
 344   // later update the object header to a potentially different array
 345   // type and, for a very short period of time, the klass and length
 346   // fields will be inconsistent. This could cause a refinement
 347   // thread to calculate the object size incorrectly.
 348   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 349 
 350   // How many words we use for filler objects.
 351   size_t word_fill_size = word_size_sum - word_size;
 352 
 353   // How many words memory we "waste" which cannot hold a filler object.
 354   size_t words_not_fillable = 0;
 355 
 356   if (word_fill_size >= min_fill_size()) {
 357     fill_with_objects(obj_top, word_fill_size);
 358   } else if (word_fill_size > 0) {
 359     // We have space to fill, but we cannot fit an object there.
 360     words_not_fillable = word_fill_size;
 361     word_fill_size = 0;
 362   }
 363 
 364   // We will set up the first region as "starts humongous". This
 365   // will also update the BOT covering all the regions to reflect
 366   // that there is a single object that starts at the bottom of the
 367   // first region.
 368   first_hr->set_starts_humongous(obj_top, word_fill_size);
 369   first_hr->set_allocation_context(context);
 370   // Then, if there are any, we will set up the "continues
 371   // humongous" regions.
 372   HeapRegion* hr = NULL;
 373   for (uint i = first + 1; i <= last; ++i) {
 374     hr = region_at(i);
 375     hr->set_continues_humongous(first_hr);
 376     hr->set_allocation_context(context);
 377   }
 378 
 379   // Up to this point no concurrent thread would have been able to
 380   // do any scanning on any region in this series. All the top
 381   // fields still point to bottom, so the intersection between
 382   // [bottom,top] and [card_start,card_end] will be empty. Before we
 383   // update the top fields, we'll do a storestore to make sure that
 384   // no thread sees the update to top before the zeroing of the
 385   // object header and the BOT initialization.
 386   OrderAccess::storestore();
 387 
 388   // Now, we will update the top fields of the "continues humongous"
 389   // regions except the last one.
 390   for (uint i = first; i < last; ++i) {
 391     hr = region_at(i);
 392     hr->set_top(hr->end());
 393   }
 394 
 395   hr = region_at(last);
 396   // If we cannot fit a filler object, we must set top to the end
 397   // of the humongous object, otherwise we cannot iterate the heap
 398   // and the BOT will not be complete.
 399   hr->set_top(hr->end() - words_not_fillable);
 400 
 401   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 402          "obj_top should be in last region");
 403 
 404   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 405 
 406   assert(words_not_fillable == 0 ||
 407          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 408          "Miscalculation in humongous allocation");
 409 
 410   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 411 
 412   for (uint i = first; i <= last; ++i) {
 413     hr = region_at(i);
 414     _humongous_set.add(hr);
 415     _hr_printer.alloc(hr);
 416   }
 417 
 418   return new_obj;
 419 }
 420 
 421 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 422   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 423   return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 424 }
 425 
 426 // If could fit into free regions w/o expansion, try.
 427 // Otherwise, if can expand, do so.
 428 // Otherwise, if using ex regions might help, try with ex given back.
 429 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
 430   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 431 
 432   _verifier->verify_region_sets_optional();
 433 
 434   uint first = G1_NO_HRM_INDEX;
 435   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 436 
 437   if (obj_regions == 1) {
 438     // Only one region to allocate, try to use a fast path by directly allocating
 439     // from the free lists. Do not try to expand here, we will potentially do that
 440     // later.
 441     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 442     if (hr != NULL) {
 443       first = hr->hrm_index();
 444     }
 445   } else {
 446     // We can't allocate humongous regions spanning more than one region while
 447     // cleanupComplete() is running, since some of the regions we find to be
 448     // empty might not yet be added to the free list. It is not straightforward
 449     // to know in which list they are on so that we can remove them. We only
 450     // need to do this if we need to allocate more than one region to satisfy the
 451     // current humongous allocation request. If we are only allocating one region
 452     // we use the one-region region allocation code (see above), that already
 453     // potentially waits for regions from the secondary free list.
 454     wait_while_free_regions_coming();
 455     append_secondary_free_list_if_not_empty_with_lock();
 456 
 457     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 458     // are lucky enough to find some.
 459     first = _hrm.find_contiguous_only_empty(obj_regions);
 460     if (first != G1_NO_HRM_INDEX) {
 461       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 462     }
 463   }
 464 
 465   if (first == G1_NO_HRM_INDEX) {
 466     // Policy: We could not find enough regions for the humongous object in the
 467     // free list. Look through the heap to find a mix of free and uncommitted regions.
 468     // If so, try expansion.
 469     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 470     if (first != G1_NO_HRM_INDEX) {
 471       // We found something. Make sure these regions are committed, i.e. expand
 472       // the heap. Alternatively we could do a defragmentation GC.
 473       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 474                                     word_size * HeapWordSize);
 475 
 476 
 477       _hrm.expand_at(first, obj_regions);
 478       g1_policy()->record_new_heap_size(num_regions());
 479 
 480 #ifdef ASSERT
 481       for (uint i = first; i < first + obj_regions; ++i) {
 482         HeapRegion* hr = region_at(i);
 483         assert(hr->is_free(), "sanity");
 484         assert(hr->is_empty(), "sanity");
 485         assert(is_on_master_free_list(hr), "sanity");
 486       }
 487 #endif
 488       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 489     } else {
 490       // Policy: Potentially trigger a defragmentation GC.
 491     }
 492   }
 493 
 494   HeapWord* result = NULL;
 495   if (first != G1_NO_HRM_INDEX) {
 496     result = humongous_obj_allocate_initialize_regions(first, obj_regions,
 497                                                        word_size, context);
 498     assert(result != NULL, "it should always return a valid result");
 499 
 500     // A successful humongous object allocation changes the used space
 501     // information of the old generation so we need to recalculate the
 502     // sizes and update the jstat counters here.
 503     g1mm()->update_sizes();
 504   }
 505 
 506   _verifier->verify_region_sets_optional();
 507 
 508   return result;
 509 }
 510 
 511 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 512   assert_heap_not_locked_and_not_at_safepoint();
 513   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 514 
 515   uint dummy_gc_count_before;
 516   uint dummy_gclocker_retry_count = 0;
 517   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 518 }
 519 
 520 HeapWord*
 521 G1CollectedHeap::mem_allocate(size_t word_size,
 522                               bool*  gc_overhead_limit_was_exceeded) {
 523   assert_heap_not_locked_and_not_at_safepoint();
 524 
 525   // Loop until the allocation is satisfied, or unsatisfied after GC.
 526   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 527     uint gc_count_before;
 528 
 529     HeapWord* result = NULL;
 530     if (!is_humongous(word_size)) {
 531       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 532     } else {
 533       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 534     }
 535     if (result != NULL) {
 536       return result;
 537     }
 538 
 539     // Create the garbage collection operation...
 540     VM_G1CollectForAllocation op(gc_count_before, word_size);
 541     op.set_allocation_context(AllocationContext::current());
 542 
 543     // ...and get the VM thread to execute it.
 544     VMThread::execute(&op);
 545 
 546     if (op.prologue_succeeded() && op.pause_succeeded()) {
 547       // If the operation was successful we'll return the result even
 548       // if it is NULL. If the allocation attempt failed immediately
 549       // after a Full GC, it's unlikely we'll be able to allocate now.
 550       HeapWord* result = op.result();
 551       if (result != NULL && !is_humongous(word_size)) {
 552         // Allocations that take place on VM operations do not do any
 553         // card dirtying and we have to do it here. We only have to do
 554         // this for non-humongous allocations, though.
 555         dirty_young_block(result, word_size);
 556       }
 557       return result;
 558     } else {
 559       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 560         return NULL;
 561       }
 562       assert(op.result() == NULL,
 563              "the result should be NULL if the VM op did not succeed");
 564     }
 565 
 566     // Give a warning if we seem to be looping forever.
 567     if ((QueuedAllocationWarningCount > 0) &&
 568         (try_count % QueuedAllocationWarningCount == 0)) {
 569       warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
 570     }
 571   }
 572 
 573   ShouldNotReachHere();
 574   return NULL;
 575 }
 576 
 577 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 578                                                    AllocationContext_t context,
 579                                                    uint* gc_count_before_ret,
 580                                                    uint* gclocker_retry_count_ret) {
 581   // Make sure you read the note in attempt_allocation_humongous().
 582 
 583   assert_heap_not_locked_and_not_at_safepoint();
 584   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 585          "be called for humongous allocation requests");
 586 
 587   // We should only get here after the first-level allocation attempt
 588   // (attempt_allocation()) failed to allocate.
 589 
 590   // We will loop until a) we manage to successfully perform the
 591   // allocation or b) we successfully schedule a collection which
 592   // fails to perform the allocation. b) is the only case when we'll
 593   // return NULL.
 594   HeapWord* result = NULL;
 595   for (int try_count = 1; /* we'll return */; try_count += 1) {
 596     bool should_try_gc;
 597     uint gc_count_before;
 598 
 599     {
 600       MutexLockerEx x(Heap_lock);
 601       result = _allocator->attempt_allocation_locked(word_size, context);
 602       if (result != NULL) {
 603         return result;
 604       }
 605 
 606       if (GCLocker::is_active_and_needs_gc()) {
 607         if (g1_policy()->can_expand_young_list()) {
 608           // No need for an ergo verbose message here,
 609           // can_expand_young_list() does this when it returns true.
 610           result = _allocator->attempt_allocation_force(word_size, context);
 611           if (result != NULL) {
 612             return result;
 613           }
 614         }
 615         should_try_gc = false;
 616       } else {
 617         // The GCLocker may not be active but the GCLocker initiated
 618         // GC may not yet have been performed (GCLocker::needs_gc()
 619         // returns true). In this case we do not try this GC and
 620         // wait until the GCLocker initiated GC is performed, and
 621         // then retry the allocation.
 622         if (GCLocker::needs_gc()) {
 623           should_try_gc = false;
 624         } else {
 625           // Read the GC count while still holding the Heap_lock.
 626           gc_count_before = total_collections();
 627           should_try_gc = true;
 628         }
 629       }
 630     }
 631 
 632     if (should_try_gc) {
 633       bool succeeded;
 634       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 635                                    GCCause::_g1_inc_collection_pause);
 636       if (result != NULL) {
 637         assert(succeeded, "only way to get back a non-NULL result");
 638         return result;
 639       }
 640 
 641       if (succeeded) {
 642         // If we get here we successfully scheduled a collection which
 643         // failed to allocate. No point in trying to allocate
 644         // further. We'll just return NULL.
 645         MutexLockerEx x(Heap_lock);
 646         *gc_count_before_ret = total_collections();
 647         return NULL;
 648       }
 649     } else {
 650       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 651         MutexLockerEx x(Heap_lock);
 652         *gc_count_before_ret = total_collections();
 653         return NULL;
 654       }
 655       // The GCLocker is either active or the GCLocker initiated
 656       // GC has not yet been performed. Stall until it is and
 657       // then retry the allocation.
 658       GCLocker::stall_until_clear();
 659       (*gclocker_retry_count_ret) += 1;
 660     }
 661 
 662     // We can reach here if we were unsuccessful in scheduling a
 663     // collection (because another thread beat us to it) or if we were
 664     // stalled due to the GC locker. In either can we should retry the
 665     // allocation attempt in case another thread successfully
 666     // performed a collection and reclaimed enough space. We do the
 667     // first attempt (without holding the Heap_lock) here and the
 668     // follow-on attempt will be at the start of the next loop
 669     // iteration (after taking the Heap_lock).
 670     result = _allocator->attempt_allocation(word_size, context);
 671     if (result != NULL) {
 672       return result;
 673     }
 674 
 675     // Give a warning if we seem to be looping forever.
 676     if ((QueuedAllocationWarningCount > 0) &&
 677         (try_count % QueuedAllocationWarningCount == 0)) {
 678       warning("G1CollectedHeap::attempt_allocation_slow() "
 679               "retries %d times", try_count);
 680     }
 681   }
 682 
 683   ShouldNotReachHere();
 684   return NULL;
 685 }
 686 
 687 void G1CollectedHeap::begin_archive_alloc_range() {
 688   assert_at_safepoint(true /* should_be_vm_thread */);
 689   if (_archive_allocator == NULL) {
 690     _archive_allocator = G1ArchiveAllocator::create_allocator(this);
 691   }
 692 }
 693 
 694 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 695   // Allocations in archive regions cannot be of a size that would be considered
 696   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 697   // may be different at archive-restore time.
 698   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 699 }
 700 
 701 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 702   assert_at_safepoint(true /* should_be_vm_thread */);
 703   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 704   if (is_archive_alloc_too_large(word_size)) {
 705     return NULL;
 706   }
 707   return _archive_allocator->archive_mem_allocate(word_size);
 708 }
 709 
 710 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 711                                               size_t end_alignment_in_bytes) {
 712   assert_at_safepoint(true /* should_be_vm_thread */);
 713   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 714 
 715   // Call complete_archive to do the real work, filling in the MemRegion
 716   // array with the archive regions.
 717   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 718   delete _archive_allocator;
 719   _archive_allocator = NULL;
 720 }
 721 
 722 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 723   assert(ranges != NULL, "MemRegion array NULL");
 724   assert(count != 0, "No MemRegions provided");
 725   MemRegion reserved = _hrm.reserved();
 726   for (size_t i = 0; i < count; i++) {
 727     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 728       return false;
 729     }
 730   }
 731   return true;
 732 }
 733 
 734 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) {
 735   assert(!is_init_completed(), "Expect to be called at JVM init time");
 736   assert(ranges != NULL, "MemRegion array NULL");
 737   assert(count != 0, "No MemRegions provided");
 738   MutexLockerEx x(Heap_lock);
 739 
 740   MemRegion reserved = _hrm.reserved();
 741   HeapWord* prev_last_addr = NULL;
 742   HeapRegion* prev_last_region = NULL;
 743 
 744   // Temporarily disable pretouching of heap pages. This interface is used
 745   // when mmap'ing archived heap data in, so pre-touching is wasted.
 746   FlagSetting fs(AlwaysPreTouch, false);
 747 
 748   // Enable archive object checking in G1MarkSweep. We have to let it know
 749   // about each archive range, so that objects in those ranges aren't marked.
 750   G1MarkSweep::enable_archive_object_check();
 751 
 752   // For each specified MemRegion range, allocate the corresponding G1
 753   // regions and mark them as archive regions. We expect the ranges in
 754   // ascending starting address order, without overlap.
 755   for (size_t i = 0; i < count; i++) {
 756     MemRegion curr_range = ranges[i];
 757     HeapWord* start_address = curr_range.start();
 758     size_t word_size = curr_range.word_size();
 759     HeapWord* last_address = curr_range.last();
 760     size_t commits = 0;
 761 
 762     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 763               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 764               p2i(start_address), p2i(last_address));
 765     guarantee(start_address > prev_last_addr,
 766               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 767               p2i(start_address), p2i(prev_last_addr));
 768     prev_last_addr = last_address;
 769 
 770     // Check for ranges that start in the same G1 region in which the previous
 771     // range ended, and adjust the start address so we don't try to allocate
 772     // the same region again. If the current range is entirely within that
 773     // region, skip it, just adjusting the recorded top.
 774     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 775     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 776       start_address = start_region->end();
 777       if (start_address > last_address) {
 778         increase_used(word_size * HeapWordSize);
 779         start_region->set_top(last_address + 1);
 780         continue;
 781       }
 782       start_region->set_top(start_address);
 783       curr_range = MemRegion(start_address, last_address + 1);
 784       start_region = _hrm.addr_to_region(start_address);
 785     }
 786 
 787     // Perform the actual region allocation, exiting if it fails.
 788     // Then note how much new space we have allocated.
 789     if (!_hrm.allocate_containing_regions(curr_range, &commits)) {
 790       return false;
 791     }
 792     increase_used(word_size * HeapWordSize);
 793     if (commits != 0) {
 794       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 795                                 HeapRegion::GrainWords * HeapWordSize * commits);
 796 
 797     }
 798 
 799     // Mark each G1 region touched by the range as archive, add it to the old set,
 800     // and set the allocation context and top.
 801     HeapRegion* curr_region = _hrm.addr_to_region(start_address);
 802     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 803     prev_last_region = last_region;
 804 
 805     while (curr_region != NULL) {
 806       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 807              "Region already in use (index %u)", curr_region->hrm_index());
 808       curr_region->set_allocation_context(AllocationContext::system());
 809       curr_region->set_archive();
 810       _hr_printer.alloc(curr_region);
 811       _old_set.add(curr_region);
 812       if (curr_region != last_region) {
 813         curr_region->set_top(curr_region->end());
 814         curr_region = _hrm.next_region_in_heap(curr_region);
 815       } else {
 816         curr_region->set_top(last_address + 1);
 817         curr_region = NULL;
 818       }
 819     }
 820 
 821     // Notify mark-sweep of the archive range.
 822     G1MarkSweep::set_range_archive(curr_range, true);
 823   }
 824   return true;
 825 }
 826 
 827 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 828   assert(!is_init_completed(), "Expect to be called at JVM init time");
 829   assert(ranges != NULL, "MemRegion array NULL");
 830   assert(count != 0, "No MemRegions provided");
 831   MemRegion reserved = _hrm.reserved();
 832   HeapWord *prev_last_addr = NULL;
 833   HeapRegion* prev_last_region = NULL;
 834 
 835   // For each MemRegion, create filler objects, if needed, in the G1 regions
 836   // that contain the address range. The address range actually within the
 837   // MemRegion will not be modified. That is assumed to have been initialized
 838   // elsewhere, probably via an mmap of archived heap data.
 839   MutexLockerEx x(Heap_lock);
 840   for (size_t i = 0; i < count; i++) {
 841     HeapWord* start_address = ranges[i].start();
 842     HeapWord* last_address = ranges[i].last();
 843 
 844     assert(reserved.contains(start_address) && reserved.contains(last_address),
 845            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 846            p2i(start_address), p2i(last_address));
 847     assert(start_address > prev_last_addr,
 848            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 849            p2i(start_address), p2i(prev_last_addr));
 850 
 851     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 852     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 853     HeapWord* bottom_address = start_region->bottom();
 854 
 855     // Check for a range beginning in the same region in which the
 856     // previous one ended.
 857     if (start_region == prev_last_region) {
 858       bottom_address = prev_last_addr + 1;
 859     }
 860 
 861     // Verify that the regions were all marked as archive regions by
 862     // alloc_archive_regions.
 863     HeapRegion* curr_region = start_region;
 864     while (curr_region != NULL) {
 865       guarantee(curr_region->is_archive(),
 866                 "Expected archive region at index %u", curr_region->hrm_index());
 867       if (curr_region != last_region) {
 868         curr_region = _hrm.next_region_in_heap(curr_region);
 869       } else {
 870         curr_region = NULL;
 871       }
 872     }
 873 
 874     prev_last_addr = last_address;
 875     prev_last_region = last_region;
 876 
 877     // Fill the memory below the allocated range with dummy object(s),
 878     // if the region bottom does not match the range start, or if the previous
 879     // range ended within the same G1 region, and there is a gap.
 880     if (start_address != bottom_address) {
 881       size_t fill_size = pointer_delta(start_address, bottom_address);
 882       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 883       increase_used(fill_size * HeapWordSize);
 884     }
 885   }
 886 }
 887 
 888 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
 889                                                      uint* gc_count_before_ret,
 890                                                      uint* gclocker_retry_count_ret) {
 891   assert_heap_not_locked_and_not_at_safepoint();
 892   assert(!is_humongous(word_size), "attempt_allocation() should not "
 893          "be called for humongous allocation requests");
 894 
 895   AllocationContext_t context = AllocationContext::current();
 896   HeapWord* result = _allocator->attempt_allocation(word_size, context);
 897 
 898   if (result == NULL) {
 899     result = attempt_allocation_slow(word_size,
 900                                      context,
 901                                      gc_count_before_ret,
 902                                      gclocker_retry_count_ret);
 903   }
 904   assert_heap_not_locked();
 905   if (result != NULL) {
 906     dirty_young_block(result, word_size);
 907   }
 908   return result;
 909 }
 910 
 911 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
 912   assert(!is_init_completed(), "Expect to be called at JVM init time");
 913   assert(ranges != NULL, "MemRegion array NULL");
 914   assert(count != 0, "No MemRegions provided");
 915   MemRegion reserved = _hrm.reserved();
 916   HeapWord* prev_last_addr = NULL;
 917   HeapRegion* prev_last_region = NULL;
 918   size_t size_used = 0;
 919   size_t uncommitted_regions = 0;
 920 
 921   // For each Memregion, free the G1 regions that constitute it, and
 922   // notify mark-sweep that the range is no longer to be considered 'archive.'
 923   MutexLockerEx x(Heap_lock);
 924   for (size_t i = 0; i < count; i++) {
 925     HeapWord* start_address = ranges[i].start();
 926     HeapWord* last_address = ranges[i].last();
 927 
 928     assert(reserved.contains(start_address) && reserved.contains(last_address),
 929            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 930            p2i(start_address), p2i(last_address));
 931     assert(start_address > prev_last_addr,
 932            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 933            p2i(start_address), p2i(prev_last_addr));
 934     size_used += ranges[i].byte_size();
 935     prev_last_addr = last_address;
 936 
 937     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 938     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 939 
 940     // Check for ranges that start in the same G1 region in which the previous
 941     // range ended, and adjust the start address so we don't try to free
 942     // the same region again. If the current range is entirely within that
 943     // region, skip it.
 944     if (start_region == prev_last_region) {
 945       start_address = start_region->end();
 946       if (start_address > last_address) {
 947         continue;
 948       }
 949       start_region = _hrm.addr_to_region(start_address);
 950     }
 951     prev_last_region = last_region;
 952 
 953     // After verifying that each region was marked as an archive region by
 954     // alloc_archive_regions, set it free and empty and uncommit it.
 955     HeapRegion* curr_region = start_region;
 956     while (curr_region != NULL) {
 957       guarantee(curr_region->is_archive(),
 958                 "Expected archive region at index %u", curr_region->hrm_index());
 959       uint curr_index = curr_region->hrm_index();
 960       _old_set.remove(curr_region);
 961       curr_region->set_free();
 962       curr_region->set_top(curr_region->bottom());
 963       if (curr_region != last_region) {
 964         curr_region = _hrm.next_region_in_heap(curr_region);
 965       } else {
 966         curr_region = NULL;
 967       }
 968       _hrm.shrink_at(curr_index, 1);
 969       uncommitted_regions++;
 970     }
 971 
 972     // Notify mark-sweep that this is no longer an archive range.
 973     G1MarkSweep::set_range_archive(ranges[i], false);
 974   }
 975 
 976   if (uncommitted_regions != 0) {
 977     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 978                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 979   }
 980   decrease_used(size_used);
 981 }
 982 
 983 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
 984                                                         uint* gc_count_before_ret,
 985                                                         uint* gclocker_retry_count_ret) {
 986   // The structure of this method has a lot of similarities to
 987   // attempt_allocation_slow(). The reason these two were not merged
 988   // into a single one is that such a method would require several "if
 989   // allocation is not humongous do this, otherwise do that"
 990   // conditional paths which would obscure its flow. In fact, an early
 991   // version of this code did use a unified method which was harder to
 992   // follow and, as a result, it had subtle bugs that were hard to
 993   // track down. So keeping these two methods separate allows each to
 994   // be more readable. It will be good to keep these two in sync as
 995   // much as possible.
 996 
 997   assert_heap_not_locked_and_not_at_safepoint();
 998   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 999          "should only be called for humongous allocations");
1000 
1001   // Humongous objects can exhaust the heap quickly, so we should check if we
1002   // need to start a marking cycle at each humongous object allocation. We do
1003   // the check before we do the actual allocation. The reason for doing it
1004   // before the allocation is that we avoid having to keep track of the newly
1005   // allocated memory while we do a GC.
1006   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1007                                            word_size)) {
1008     collect(GCCause::_g1_humongous_allocation);
1009   }
1010 
1011   // We will loop until a) we manage to successfully perform the
1012   // allocation or b) we successfully schedule a collection which
1013   // fails to perform the allocation. b) is the only case when we'll
1014   // return NULL.
1015   HeapWord* result = NULL;
1016   for (int try_count = 1; /* we'll return */; try_count += 1) {
1017     bool should_try_gc;
1018     uint gc_count_before;
1019 
1020     {
1021       MutexLockerEx x(Heap_lock);
1022 
1023       // Given that humongous objects are not allocated in young
1024       // regions, we'll first try to do the allocation without doing a
1025       // collection hoping that there's enough space in the heap.
1026       result = humongous_obj_allocate(word_size, AllocationContext::current());
1027       if (result != NULL) {
1028         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
1029         g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
1030         return result;
1031       }
1032 
1033       if (GCLocker::is_active_and_needs_gc()) {
1034         should_try_gc = false;
1035       } else {
1036          // The GCLocker may not be active but the GCLocker initiated
1037         // GC may not yet have been performed (GCLocker::needs_gc()
1038         // returns true). In this case we do not try this GC and
1039         // wait until the GCLocker initiated GC is performed, and
1040         // then retry the allocation.
1041         if (GCLocker::needs_gc()) {
1042           should_try_gc = false;
1043         } else {
1044           // Read the GC count while still holding the Heap_lock.
1045           gc_count_before = total_collections();
1046           should_try_gc = true;
1047         }
1048       }
1049     }
1050 
1051     if (should_try_gc) {
1052       // If we failed to allocate the humongous object, we should try to
1053       // do a collection pause (if we're allowed) in case it reclaims
1054       // enough space for the allocation to succeed after the pause.
1055 
1056       bool succeeded;
1057       result = do_collection_pause(word_size, gc_count_before, &succeeded,
1058                                    GCCause::_g1_humongous_allocation);
1059       if (result != NULL) {
1060         assert(succeeded, "only way to get back a non-NULL result");
1061         return result;
1062       }
1063 
1064       if (succeeded) {
1065         // If we get here we successfully scheduled a collection which
1066         // failed to allocate. No point in trying to allocate
1067         // further. We'll just return NULL.
1068         MutexLockerEx x(Heap_lock);
1069         *gc_count_before_ret = total_collections();
1070         return NULL;
1071       }
1072     } else {
1073       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1074         MutexLockerEx x(Heap_lock);
1075         *gc_count_before_ret = total_collections();
1076         return NULL;
1077       }
1078       // The GCLocker is either active or the GCLocker initiated
1079       // GC has not yet been performed. Stall until it is and
1080       // then retry the allocation.
1081       GCLocker::stall_until_clear();
1082       (*gclocker_retry_count_ret) += 1;
1083     }
1084 
1085     // We can reach here if we were unsuccessful in scheduling a
1086     // collection (because another thread beat us to it) or if we were
1087     // stalled due to the GC locker. In either can we should retry the
1088     // allocation attempt in case another thread successfully
1089     // performed a collection and reclaimed enough space.  Give a
1090     // warning if we seem to be looping forever.
1091 
1092     if ((QueuedAllocationWarningCount > 0) &&
1093         (try_count % QueuedAllocationWarningCount == 0)) {
1094       warning("G1CollectedHeap::attempt_allocation_humongous() "
1095               "retries %d times", try_count);
1096     }
1097   }
1098 
1099   ShouldNotReachHere();
1100   return NULL;
1101 }
1102 
1103 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1104                                                            AllocationContext_t context,
1105                                                            bool expect_null_mutator_alloc_region) {
1106   assert_at_safepoint(true /* should_be_vm_thread */);
1107   assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1108          "the current alloc region was unexpectedly found to be non-NULL");
1109 
1110   if (!is_humongous(word_size)) {
1111     return _allocator->attempt_allocation_locked(word_size, context);
1112   } else {
1113     HeapWord* result = humongous_obj_allocate(word_size, context);
1114     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1115       collector_state()->set_initiate_conc_mark_if_possible(true);
1116     }
1117     return result;
1118   }
1119 
1120   ShouldNotReachHere();
1121 }
1122 
1123 class PostMCRemSetClearClosure: public HeapRegionClosure {
1124   G1CollectedHeap* _g1h;
1125   ModRefBarrierSet* _mr_bs;
1126 public:
1127   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1128     _g1h(g1h), _mr_bs(mr_bs) {}
1129 
1130   bool doHeapRegion(HeapRegion* r) {
1131     HeapRegionRemSet* hrrs = r->rem_set();
1132 
1133     _g1h->reset_gc_time_stamps(r);
1134 
1135     if (r->is_continues_humongous()) {
1136       // We'll assert that the strong code root list and RSet is empty
1137       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1138       assert(hrrs->occupied() == 0, "RSet should be empty");
1139     } else {
1140       hrrs->clear();
1141     }
1142     // You might think here that we could clear just the cards
1143     // corresponding to the used region.  But no: if we leave a dirty card
1144     // in a region we might allocate into, then it would prevent that card
1145     // from being enqueued, and cause it to be missed.
1146     // Re: the performance cost: we shouldn't be doing full GC anyway!
1147     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1148 
1149     return false;
1150   }
1151 };
1152 
1153 void G1CollectedHeap::clear_rsets_post_compaction() {
1154   PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1155   heap_region_iterate(&rs_clear);
1156 }
1157 
1158 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1159   G1CollectedHeap*   _g1h;
1160   UpdateRSOopClosure _cl;
1161 public:
1162   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) :
1163     _cl(g1->g1_rem_set(), worker_i),
1164     _g1h(g1)
1165   { }
1166 
1167   bool doHeapRegion(HeapRegion* r) {
1168     if (!r->is_continues_humongous()) {
1169       _cl.set_from(r);
1170       r->oop_iterate(&_cl);
1171     }
1172     return false;
1173   }
1174 };
1175 
1176 class ParRebuildRSTask: public AbstractGangTask {
1177   G1CollectedHeap* _g1;
1178   HeapRegionClaimer _hrclaimer;
1179 
1180 public:
1181   ParRebuildRSTask(G1CollectedHeap* g1) :
1182       AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {}
1183 
1184   void work(uint worker_id) {
1185     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1186     _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer);
1187   }
1188 };
1189 
1190 class PostCompactionPrinterClosure: public HeapRegionClosure {
1191 private:
1192   G1HRPrinter* _hr_printer;
1193 public:
1194   bool doHeapRegion(HeapRegion* hr) {
1195     assert(!hr->is_young(), "not expecting to find young regions");
1196     _hr_printer->post_compaction(hr);
1197     return false;
1198   }
1199 
1200   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1201     : _hr_printer(hr_printer) { }
1202 };
1203 
1204 void G1CollectedHeap::print_hrm_post_compaction() {
1205   if (_hr_printer.is_active()) {
1206     PostCompactionPrinterClosure cl(hr_printer());
1207     heap_region_iterate(&cl);
1208   }
1209 
1210 }
1211 
1212 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1213                                          bool clear_all_soft_refs) {
1214   assert_at_safepoint(true /* should_be_vm_thread */);
1215 
1216   if (GCLocker::check_active_before_gc()) {
1217     return false;
1218   }
1219 
1220   STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1221   gc_timer->register_gc_start();
1222 
1223   SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1224   GCIdMark gc_id_mark;
1225   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1226 
1227   SvcGCMarker sgcm(SvcGCMarker::FULL);
1228   ResourceMark rm;
1229 
1230   print_heap_before_gc();
1231   trace_heap_before_gc(gc_tracer);
1232 
1233   size_t metadata_prev_used = MetaspaceAux::used_bytes();
1234 
1235   _verifier->verify_region_sets_optional();
1236 
1237   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1238                            collector_policy()->should_clear_all_soft_refs();
1239 
1240   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1241 
1242   {
1243     IsGCActiveMark x;
1244 
1245     // Timing
1246     assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1247     GCTraceCPUTime tcpu;
1248 
1249     {
1250       GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1251       TraceCollectorStats tcs(g1mm()->full_collection_counters());
1252       TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1253 
1254       G1HeapTransition heap_transition(this);
1255       g1_policy()->record_full_collection_start();
1256 
1257       // Note: When we have a more flexible GC logging framework that
1258       // allows us to add optional attributes to a GC log record we
1259       // could consider timing and reporting how long we wait in the
1260       // following two methods.
1261       wait_while_free_regions_coming();
1262       // If we start the compaction before the CM threads finish
1263       // scanning the root regions we might trip them over as we'll
1264       // be moving objects / updating references. So let's wait until
1265       // they are done. By telling them to abort, they should complete
1266       // early.
1267       _cm->root_regions()->abort();
1268       _cm->root_regions()->wait_until_scan_finished();
1269       append_secondary_free_list_if_not_empty_with_lock();
1270 
1271       gc_prologue(true);
1272       increment_total_collections(true /* full gc */);
1273       increment_old_marking_cycles_started();
1274 
1275       assert(used() == recalculate_used(), "Should be equal");
1276 
1277       _verifier->verify_before_gc();
1278 
1279       _verifier->check_bitmaps("Full GC Start");
1280       pre_full_gc_dump(gc_timer);
1281 
1282 #if defined(COMPILER2) || INCLUDE_JVMCI
1283       DerivedPointerTable::clear();
1284 #endif
1285 
1286       // Disable discovery and empty the discovered lists
1287       // for the CM ref processor.
1288       ref_processor_cm()->disable_discovery();
1289       ref_processor_cm()->abandon_partial_discovery();
1290       ref_processor_cm()->verify_no_references_recorded();
1291 
1292       // Abandon current iterations of concurrent marking and concurrent
1293       // refinement, if any are in progress.
1294       concurrent_mark()->abort();
1295 
1296       // Make sure we'll choose a new allocation region afterwards.
1297       _allocator->release_mutator_alloc_region();
1298       _allocator->abandon_gc_alloc_regions();
1299       g1_rem_set()->cleanupHRRS();
1300 
1301       // We may have added regions to the current incremental collection
1302       // set between the last GC or pause and now. We need to clear the
1303       // incremental collection set and then start rebuilding it afresh
1304       // after this full GC.
1305       abandon_collection_set(g1_policy()->inc_cset_head());
1306       g1_policy()->clear_incremental_cset();
1307       g1_policy()->stop_incremental_cset_building();
1308 
1309       tear_down_region_sets(false /* free_list_only */);
1310       collector_state()->set_gcs_are_young(true);
1311 
1312       // See the comments in g1CollectedHeap.hpp and
1313       // G1CollectedHeap::ref_processing_init() about
1314       // how reference processing currently works in G1.
1315 
1316       // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1317       ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1318 
1319       // Temporarily clear the STW ref processor's _is_alive_non_header field.
1320       ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1321 
1322       ref_processor_stw()->enable_discovery();
1323       ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1324 
1325       // Do collection work
1326       {
1327         HandleMark hm;  // Discard invalid handles created during gc
1328         G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1329       }
1330 
1331       assert(num_free_regions() == 0, "we should not have added any free regions");
1332       rebuild_region_sets(false /* free_list_only */);
1333 
1334       // Enqueue any discovered reference objects that have
1335       // not been removed from the discovered lists.
1336       ref_processor_stw()->enqueue_discovered_references();
1337 
1338 #if defined(COMPILER2) || INCLUDE_JVMCI
1339       DerivedPointerTable::update_pointers();
1340 #endif
1341 
1342       MemoryService::track_memory_usage();
1343 
1344       assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1345       ref_processor_stw()->verify_no_references_recorded();
1346 
1347       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1348       ClassLoaderDataGraph::purge();
1349       MetaspaceAux::verify_metrics();
1350 
1351       // Note: since we've just done a full GC, concurrent
1352       // marking is no longer active. Therefore we need not
1353       // re-enable reference discovery for the CM ref processor.
1354       // That will be done at the start of the next marking cycle.
1355       assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1356       ref_processor_cm()->verify_no_references_recorded();
1357 
1358       reset_gc_time_stamp();
1359       // Since everything potentially moved, we will clear all remembered
1360       // sets, and clear all cards.  Later we will rebuild remembered
1361       // sets. We will also reset the GC time stamps of the regions.
1362       clear_rsets_post_compaction();
1363       check_gc_time_stamps();
1364 
1365       resize_if_necessary_after_full_collection();
1366 
1367       // We should do this after we potentially resize the heap so
1368       // that all the COMMIT / UNCOMMIT events are generated before
1369       // the compaction events.
1370       print_hrm_post_compaction();
1371 
1372       G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1373       if (hot_card_cache->use_cache()) {
1374         hot_card_cache->reset_card_counts();
1375         hot_card_cache->reset_hot_cache();
1376       }
1377 
1378       // Rebuild remembered sets of all regions.
1379       uint n_workers =
1380         AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1381                                                 workers()->active_workers(),
1382                                                 Threads::number_of_non_daemon_threads());
1383       workers()->set_active_workers(n_workers);
1384 
1385       ParRebuildRSTask rebuild_rs_task(this);
1386       workers()->run_task(&rebuild_rs_task);
1387 
1388       // Rebuild the strong code root lists for each region
1389       rebuild_strong_code_roots();
1390 
1391       if (true) { // FIXME
1392         MetaspaceGC::compute_new_size();
1393       }
1394 
1395 #ifdef TRACESPINNING
1396       ParallelTaskTerminator::print_termination_counts();
1397 #endif
1398 
1399       // Discard all rset updates
1400       JavaThread::dirty_card_queue_set().abandon_logs();
1401       assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1402 
1403       _young_list->reset_sampled_info();
1404       // At this point there should be no regions in the
1405       // entire heap tagged as young.
1406       assert(check_young_list_empty(true /* check_heap */),
1407              "young list should be empty at this point");
1408 
1409       // Update the number of full collections that have been completed.
1410       increment_old_marking_cycles_completed(false /* concurrent */);
1411 
1412       _hrm.verify_optional();
1413       _verifier->verify_region_sets_optional();
1414 
1415       _verifier->verify_after_gc();
1416 
1417       // Clear the previous marking bitmap, if needed for bitmap verification.
1418       // Note we cannot do this when we clear the next marking bitmap in
1419       // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1420       // objects marked during a full GC against the previous bitmap.
1421       // But we need to clear it before calling check_bitmaps below since
1422       // the full GC has compacted objects and updated TAMS but not updated
1423       // the prev bitmap.
1424       if (G1VerifyBitmaps) {
1425         ((G1CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1426       }
1427       _verifier->check_bitmaps("Full GC End");
1428 
1429       // Start a new incremental collection set for the next pause
1430       assert(g1_policy()->collection_set() == NULL, "must be");
1431       g1_policy()->start_incremental_cset_building();
1432 
1433       clear_cset_fast_test();
1434 
1435       _allocator->init_mutator_alloc_region();
1436 
1437       g1_policy()->record_full_collection_end();
1438 
1439       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1440       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1441       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1442       // before any GC notifications are raised.
1443       g1mm()->update_sizes();
1444 
1445       gc_epilogue(true);
1446 
1447       heap_transition.print();
1448 
1449       print_heap_after_gc();
1450       trace_heap_after_gc(gc_tracer);
1451 
1452       post_full_gc_dump(gc_timer);
1453     }
1454 
1455     gc_timer->register_gc_end();
1456     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1457   }
1458 
1459   return true;
1460 }
1461 
1462 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1463   // Currently, there is no facility in the do_full_collection(bool) API to notify
1464   // the caller that the collection did not succeed (e.g., because it was locked
1465   // out by the GC locker). So, right now, we'll ignore the return value.
1466   bool dummy = do_full_collection(true,                /* explicit_gc */
1467                                   clear_all_soft_refs);
1468 }
1469 
1470 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1471   // Include bytes that will be pre-allocated to support collections, as "used".
1472   const size_t used_after_gc = used();
1473   const size_t capacity_after_gc = capacity();
1474   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1475 
1476   // This is enforced in arguments.cpp.
1477   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1478          "otherwise the code below doesn't make sense");
1479 
1480   // We don't have floating point command-line arguments
1481   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1482   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1483   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1484   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1485 
1486   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1487   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1488 
1489   // We have to be careful here as these two calculations can overflow
1490   // 32-bit size_t's.
1491   double used_after_gc_d = (double) used_after_gc;
1492   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1493   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1494 
1495   // Let's make sure that they are both under the max heap size, which
1496   // by default will make them fit into a size_t.
1497   double desired_capacity_upper_bound = (double) max_heap_size;
1498   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1499                                     desired_capacity_upper_bound);
1500   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1501                                     desired_capacity_upper_bound);
1502 
1503   // We can now safely turn them into size_t's.
1504   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1505   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1506 
1507   // This assert only makes sense here, before we adjust them
1508   // with respect to the min and max heap size.
1509   assert(minimum_desired_capacity <= maximum_desired_capacity,
1510          "minimum_desired_capacity = " SIZE_FORMAT ", "
1511          "maximum_desired_capacity = " SIZE_FORMAT,
1512          minimum_desired_capacity, maximum_desired_capacity);
1513 
1514   // Should not be greater than the heap max size. No need to adjust
1515   // it with respect to the heap min size as it's a lower bound (i.e.,
1516   // we'll try to make the capacity larger than it, not smaller).
1517   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1518   // Should not be less than the heap min size. No need to adjust it
1519   // with respect to the heap max size as it's an upper bound (i.e.,
1520   // we'll try to make the capacity smaller than it, not greater).
1521   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1522 
1523   if (capacity_after_gc < minimum_desired_capacity) {
1524     // Don't expand unless it's significant
1525     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1526 
1527     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1528                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1529                               capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1530 
1531     expand(expand_bytes);
1532 
1533     // No expansion, now see if we want to shrink
1534   } else if (capacity_after_gc > maximum_desired_capacity) {
1535     // Capacity too large, compute shrinking size
1536     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1537 
1538     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1539                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1540                               capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1541 
1542     shrink(shrink_bytes);
1543   }
1544 }
1545 
1546 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1547                                                             AllocationContext_t context,
1548                                                             bool do_gc,
1549                                                             bool clear_all_soft_refs,
1550                                                             bool expect_null_mutator_alloc_region,
1551                                                             bool* gc_succeeded) {
1552   *gc_succeeded = true;
1553   // Let's attempt the allocation first.
1554   HeapWord* result =
1555     attempt_allocation_at_safepoint(word_size,
1556                                     context,
1557                                     expect_null_mutator_alloc_region);
1558   if (result != NULL) {
1559     assert(*gc_succeeded, "sanity");
1560     return result;
1561   }
1562 
1563   // In a G1 heap, we're supposed to keep allocation from failing by
1564   // incremental pauses.  Therefore, at least for now, we'll favor
1565   // expansion over collection.  (This might change in the future if we can
1566   // do something smarter than full collection to satisfy a failed alloc.)
1567   result = expand_and_allocate(word_size, context);
1568   if (result != NULL) {
1569     assert(*gc_succeeded, "sanity");
1570     return result;
1571   }
1572 
1573   if (do_gc) {
1574     // Expansion didn't work, we'll try to do a Full GC.
1575     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1576                                        clear_all_soft_refs);
1577   }
1578 
1579   return NULL;
1580 }
1581 
1582 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1583                                                      AllocationContext_t context,
1584                                                      bool* succeeded) {
1585   assert_at_safepoint(true /* should_be_vm_thread */);
1586 
1587   // Attempts to allocate followed by Full GC.
1588   HeapWord* result =
1589     satisfy_failed_allocation_helper(word_size,
1590                                      context,
1591                                      true,  /* do_gc */
1592                                      false, /* clear_all_soft_refs */
1593                                      false, /* expect_null_mutator_alloc_region */
1594                                      succeeded);
1595 
1596   if (result != NULL || !*succeeded) {
1597     return result;
1598   }
1599 
1600   // Attempts to allocate followed by Full GC that will collect all soft references.
1601   result = satisfy_failed_allocation_helper(word_size,
1602                                             context,
1603                                             true, /* do_gc */
1604                                             true, /* clear_all_soft_refs */
1605                                             true, /* expect_null_mutator_alloc_region */
1606                                             succeeded);
1607 
1608   if (result != NULL || !*succeeded) {
1609     return result;
1610   }
1611 
1612   // Attempts to allocate, no GC
1613   result = satisfy_failed_allocation_helper(word_size,
1614                                             context,
1615                                             false, /* do_gc */
1616                                             false, /* clear_all_soft_refs */
1617                                             true,  /* expect_null_mutator_alloc_region */
1618                                             succeeded);
1619 
1620   if (result != NULL) {
1621     assert(*succeeded, "sanity");
1622     return result;
1623   }
1624 
1625   assert(!collector_policy()->should_clear_all_soft_refs(),
1626          "Flag should have been handled and cleared prior to this point");
1627 
1628   // What else?  We might try synchronous finalization later.  If the total
1629   // space available is large enough for the allocation, then a more
1630   // complete compaction phase than we've tried so far might be
1631   // appropriate.
1632   assert(*succeeded, "sanity");
1633   return NULL;
1634 }
1635 
1636 // Attempting to expand the heap sufficiently
1637 // to support an allocation of the given "word_size".  If
1638 // successful, perform the allocation and return the address of the
1639 // allocated block, or else "NULL".
1640 
1641 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1642   assert_at_safepoint(true /* should_be_vm_thread */);
1643 
1644   _verifier->verify_region_sets_optional();
1645 
1646   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1647   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1648                             word_size * HeapWordSize);
1649 
1650 
1651   if (expand(expand_bytes)) {
1652     _hrm.verify_optional();
1653     _verifier->verify_region_sets_optional();
1654     return attempt_allocation_at_safepoint(word_size,
1655                                            context,
1656                                            false /* expect_null_mutator_alloc_region */);
1657   }
1658   return NULL;
1659 }
1660 
1661 bool G1CollectedHeap::expand(size_t expand_bytes, double* expand_time_ms) {
1662   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1663   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1664                                        HeapRegion::GrainBytes);
1665 
1666   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount:" SIZE_FORMAT "B expansion amount:" SIZE_FORMAT "B",
1667                             expand_bytes, aligned_expand_bytes);
1668 
1669   if (is_maximal_no_gc()) {
1670     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1671     return false;
1672   }
1673 
1674   double expand_heap_start_time_sec = os::elapsedTime();
1675   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1676   assert(regions_to_expand > 0, "Must expand by at least one region");
1677 
1678   uint expanded_by = _hrm.expand_by(regions_to_expand);
1679   if (expand_time_ms != NULL) {
1680     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1681   }
1682 
1683   if (expanded_by > 0) {
1684     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1685     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1686     g1_policy()->record_new_heap_size(num_regions());
1687   } else {
1688     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1689 
1690     // The expansion of the virtual storage space was unsuccessful.
1691     // Let's see if it was because we ran out of swap.
1692     if (G1ExitOnExpansionFailure &&
1693         _hrm.available() >= regions_to_expand) {
1694       // We had head room...
1695       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1696     }
1697   }
1698   return regions_to_expand > 0;
1699 }
1700 
1701 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1702   size_t aligned_shrink_bytes =
1703     ReservedSpace::page_align_size_down(shrink_bytes);
1704   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1705                                          HeapRegion::GrainBytes);
1706   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1707 
1708   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1709   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1710 
1711 
1712   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",
1713                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1714   if (num_regions_removed > 0) {
1715     g1_policy()->record_new_heap_size(num_regions());
1716   } else {
1717     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1718   }
1719 }
1720 
1721 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1722   _verifier->verify_region_sets_optional();
1723 
1724   // We should only reach here at the end of a Full GC which means we
1725   // should not not be holding to any GC alloc regions. The method
1726   // below will make sure of that and do any remaining clean up.
1727   _allocator->abandon_gc_alloc_regions();
1728 
1729   // Instead of tearing down / rebuilding the free lists here, we
1730   // could instead use the remove_all_pending() method on free_list to
1731   // remove only the ones that we need to remove.
1732   tear_down_region_sets(true /* free_list_only */);
1733   shrink_helper(shrink_bytes);
1734   rebuild_region_sets(true /* free_list_only */);
1735 
1736   _hrm.verify_optional();
1737   _verifier->verify_region_sets_optional();
1738 }
1739 
1740 // Public methods.
1741 
1742 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1743   CollectedHeap(),
1744   _g1_policy(policy_),
1745   _dirty_card_queue_set(false),
1746   _is_alive_closure_cm(this),
1747   _is_alive_closure_stw(this),
1748   _ref_processor_cm(NULL),
1749   _ref_processor_stw(NULL),
1750   _bot(NULL),
1751   _cg1r(NULL),
1752   _g1mm(NULL),
1753   _refine_cte_cl(NULL),
1754   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1755   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1756   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1757   _humongous_reclaim_candidates(),
1758   _has_humongous_reclaim_candidates(false),
1759   _archive_allocator(NULL),
1760   _free_regions_coming(false),
1761   _young_list(new YoungList(this)),
1762   _gc_time_stamp(0),
1763   _summary_bytes_used(0),
1764   _survivor_evac_stats(YoungPLABSize, PLABWeight),
1765   _old_evac_stats(OldPLABSize, PLABWeight),
1766   _expand_heap_after_alloc_failure(true),
1767   _old_marking_cycles_started(0),
1768   _old_marking_cycles_completed(0),
1769   _heap_summary_sent(false),
1770   _in_cset_fast_test(),
1771   _dirty_cards_region_list(NULL),
1772   _worker_cset_start_region(NULL),
1773   _worker_cset_start_region_time_stamp(NULL),
1774   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1775   _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1776   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1777   _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1778 
1779   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1780                           /* are_GC_task_threads */true,
1781                           /* are_ConcurrentGC_threads */false);
1782   _workers->initialize_workers();
1783   _verifier = new G1HeapVerifier(this);
1784 
1785   _allocator = G1Allocator::create_allocator(this);
1786   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1787 
1788   // Override the default _filler_array_max_size so that no humongous filler
1789   // objects are created.
1790   _filler_array_max_size = _humongous_object_threshold_in_words;
1791 
1792   uint n_queues = ParallelGCThreads;
1793   _task_queues = new RefToScanQueueSet(n_queues);
1794 
1795   _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1796   _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC);
1797   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1798 
1799   for (uint i = 0; i < n_queues; i++) {
1800     RefToScanQueue* q = new RefToScanQueue();
1801     q->initialize();
1802     _task_queues->register_queue(i, q);
1803     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1804   }
1805   clear_cset_start_regions();
1806 
1807   // Initialize the G1EvacuationFailureALot counters and flags.
1808   NOT_PRODUCT(reset_evacuation_should_fail();)
1809 
1810   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1811 }
1812 
1813 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1814                                                                  size_t size,
1815                                                                  size_t translation_factor) {
1816   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1817   // Allocate a new reserved space, preferring to use large pages.
1818   ReservedSpace rs(size, preferred_page_size);
1819   G1RegionToSpaceMapper* result  =
1820     G1RegionToSpaceMapper::create_mapper(rs,
1821                                          size,
1822                                          rs.alignment(),
1823                                          HeapRegion::GrainBytes,
1824                                          translation_factor,
1825                                          mtGC);
1826   if (TracePageSizes) {
1827     tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT,
1828                   description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size);
1829   }
1830   return result;
1831 }
1832 
1833 jint G1CollectedHeap::initialize() {
1834   CollectedHeap::pre_initialize();
1835   os::enable_vtime();
1836 
1837   // Necessary to satisfy locking discipline assertions.
1838 
1839   MutexLocker x(Heap_lock);
1840 
1841   // While there are no constraints in the GC code that HeapWordSize
1842   // be any particular value, there are multiple other areas in the
1843   // system which believe this to be true (e.g. oop->object_size in some
1844   // cases incorrectly returns the size in wordSize units rather than
1845   // HeapWordSize).
1846   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1847 
1848   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1849   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1850   size_t heap_alignment = collector_policy()->heap_alignment();
1851 
1852   // Ensure that the sizes are properly aligned.
1853   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1854   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1855   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1856 
1857   _refine_cte_cl = new RefineCardTableEntryClosure();
1858 
1859   jint ecode = JNI_OK;
1860   _cg1r = ConcurrentG1Refine::create(this, _refine_cte_cl, &ecode);
1861   if (_cg1r == NULL) {
1862     return ecode;
1863   }
1864 
1865   // Reserve the maximum.
1866 
1867   // When compressed oops are enabled, the preferred heap base
1868   // is calculated by subtracting the requested size from the
1869   // 32Gb boundary and using the result as the base address for
1870   // heap reservation. If the requested size is not aligned to
1871   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1872   // into the ReservedHeapSpace constructor) then the actual
1873   // base of the reserved heap may end up differing from the
1874   // address that was requested (i.e. the preferred heap base).
1875   // If this happens then we could end up using a non-optimal
1876   // compressed oops mode.
1877 
1878   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1879                                                  heap_alignment);
1880 
1881   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1882 
1883   // Create the barrier set for the entire reserved region.
1884   G1SATBCardTableLoggingModRefBS* bs
1885     = new G1SATBCardTableLoggingModRefBS(reserved_region());
1886   bs->initialize();
1887   assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1888   set_barrier_set(bs);
1889 
1890   // Also create a G1 rem set.
1891   _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1892 
1893   // Carve out the G1 part of the heap.
1894   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1895   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1896   G1RegionToSpaceMapper* heap_storage =
1897     G1RegionToSpaceMapper::create_mapper(g1_rs,
1898                                          g1_rs.size(),
1899                                          page_size,
1900                                          HeapRegion::GrainBytes,
1901                                          1,
1902                                          mtJavaHeap);
1903   os::trace_page_sizes("G1 Heap", collector_policy()->min_heap_byte_size(),
1904                        max_byte_size, page_size,
1905                        heap_rs.base(),
1906                        heap_rs.size());
1907   heap_storage->set_mapping_changed_listener(&_listener);
1908 
1909   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1910   G1RegionToSpaceMapper* bot_storage =
1911     create_aux_memory_mapper("Block offset table",
1912                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1913                              G1BlockOffsetTable::heap_map_factor());
1914 
1915   ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1916   G1RegionToSpaceMapper* cardtable_storage =
1917     create_aux_memory_mapper("Card table",
1918                              G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1919                              G1SATBCardTableLoggingModRefBS::heap_map_factor());
1920 
1921   G1RegionToSpaceMapper* card_counts_storage =
1922     create_aux_memory_mapper("Card counts table",
1923                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1924                              G1CardCounts::heap_map_factor());
1925 
1926   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1927   G1RegionToSpaceMapper* prev_bitmap_storage =
1928     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1929   G1RegionToSpaceMapper* next_bitmap_storage =
1930     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1931 
1932   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1933   g1_barrier_set()->initialize(cardtable_storage);
1934    // Do later initialization work for concurrent refinement.
1935   _cg1r->init(card_counts_storage);
1936 
1937   // 6843694 - ensure that the maximum region index can fit
1938   // in the remembered set structures.
1939   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1940   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1941 
1942   G1RemSet::initialize(max_regions());
1943 
1944   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1945   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1946   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1947             "too many cards per region");
1948 
1949   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1950 
1951   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1952 
1953   {
1954     HeapWord* start = _hrm.reserved().start();
1955     HeapWord* end = _hrm.reserved().end();
1956     size_t granularity = HeapRegion::GrainBytes;
1957 
1958     _in_cset_fast_test.initialize(start, end, granularity);
1959     _humongous_reclaim_candidates.initialize(start, end, granularity);
1960   }
1961 
1962   // Create the G1ConcurrentMark data structure and thread.
1963   // (Must do this late, so that "max_regions" is defined.)
1964   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1965   if (_cm == NULL || !_cm->completed_initialization()) {
1966     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1967     return JNI_ENOMEM;
1968   }
1969   _cmThread = _cm->cmThread();
1970 
1971   // Now expand into the initial heap size.
1972   if (!expand(init_byte_size)) {
1973     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1974     return JNI_ENOMEM;
1975   }
1976 
1977   // Perform any initialization actions delegated to the policy.
1978   g1_policy()->init();
1979 
1980   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1981                                                SATB_Q_FL_lock,
1982                                                G1SATBProcessCompletedThreshold,
1983                                                Shared_SATB_Q_lock);
1984 
1985   JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
1986                                                 DirtyCardQ_CBL_mon,
1987                                                 DirtyCardQ_FL_lock,
1988                                                 concurrent_g1_refine()->yellow_zone(),
1989                                                 concurrent_g1_refine()->red_zone(),
1990                                                 Shared_DirtyCardQ_lock,
1991                                                 NULL,  // fl_owner
1992                                                 true); // init_free_ids
1993 
1994   dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
1995                                     DirtyCardQ_CBL_mon,
1996                                     DirtyCardQ_FL_lock,
1997                                     -1, // never trigger processing
1998                                     -1, // no limit on length
1999                                     Shared_DirtyCardQ_lock,
2000                                     &JavaThread::dirty_card_queue_set());
2001 
2002   // Here we allocate the dummy HeapRegion that is required by the
2003   // G1AllocRegion class.
2004   HeapRegion* dummy_region = _hrm.get_dummy_region();
2005 
2006   // We'll re-use the same region whether the alloc region will
2007   // require BOT updates or not and, if it doesn't, then a non-young
2008   // region will complain that it cannot support allocations without
2009   // BOT updates. So we'll tag the dummy region as eden to avoid that.
2010   dummy_region->set_eden();
2011   // Make sure it's full.
2012   dummy_region->set_top(dummy_region->end());
2013   G1AllocRegion::setup(this, dummy_region);
2014 
2015   _allocator->init_mutator_alloc_region();
2016 
2017   // Do create of the monitoring and management support so that
2018   // values in the heap have been properly initialized.
2019   _g1mm = new G1MonitoringSupport(this);
2020 
2021   G1StringDedup::initialize();
2022 
2023   _preserved_objs = NEW_C_HEAP_ARRAY(OopAndMarkOopStack, ParallelGCThreads, mtGC);
2024   for (uint i = 0; i < ParallelGCThreads; i++) {
2025     new (&_preserved_objs[i]) OopAndMarkOopStack();
2026   }
2027 
2028   return JNI_OK;
2029 }
2030 
2031 void G1CollectedHeap::stop() {
2032   // Stop all concurrent threads. We do this to make sure these threads
2033   // do not continue to execute and access resources (e.g. logging)
2034   // that are destroyed during shutdown.
2035   _cg1r->stop();
2036   _cmThread->stop();
2037   if (G1StringDedup::is_enabled()) {
2038     G1StringDedup::stop();
2039   }
2040 }
2041 
2042 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2043   return HeapRegion::max_region_size();
2044 }
2045 
2046 void G1CollectedHeap::post_initialize() {
2047   CollectedHeap::post_initialize();
2048   ref_processing_init();
2049 }
2050 
2051 void G1CollectedHeap::ref_processing_init() {
2052   // Reference processing in G1 currently works as follows:
2053   //
2054   // * There are two reference processor instances. One is
2055   //   used to record and process discovered references
2056   //   during concurrent marking; the other is used to
2057   //   record and process references during STW pauses
2058   //   (both full and incremental).
2059   // * Both ref processors need to 'span' the entire heap as
2060   //   the regions in the collection set may be dotted around.
2061   //
2062   // * For the concurrent marking ref processor:
2063   //   * Reference discovery is enabled at initial marking.
2064   //   * Reference discovery is disabled and the discovered
2065   //     references processed etc during remarking.
2066   //   * Reference discovery is MT (see below).
2067   //   * Reference discovery requires a barrier (see below).
2068   //   * Reference processing may or may not be MT
2069   //     (depending on the value of ParallelRefProcEnabled
2070   //     and ParallelGCThreads).
2071   //   * A full GC disables reference discovery by the CM
2072   //     ref processor and abandons any entries on it's
2073   //     discovered lists.
2074   //
2075   // * For the STW processor:
2076   //   * Non MT discovery is enabled at the start of a full GC.
2077   //   * Processing and enqueueing during a full GC is non-MT.
2078   //   * During a full GC, references are processed after marking.
2079   //
2080   //   * Discovery (may or may not be MT) is enabled at the start
2081   //     of an incremental evacuation pause.
2082   //   * References are processed near the end of a STW evacuation pause.
2083   //   * For both types of GC:
2084   //     * Discovery is atomic - i.e. not concurrent.
2085   //     * Reference discovery will not need a barrier.
2086 
2087   MemRegion mr = reserved_region();
2088 
2089   // Concurrent Mark ref processor
2090   _ref_processor_cm =
2091     new ReferenceProcessor(mr,    // span
2092                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2093                                 // mt processing
2094                            ParallelGCThreads,
2095                                 // degree of mt processing
2096                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2097                                 // mt discovery
2098                            MAX2(ParallelGCThreads, ConcGCThreads),
2099                                 // degree of mt discovery
2100                            false,
2101                                 // Reference discovery is not atomic
2102                            &_is_alive_closure_cm);
2103                                 // is alive closure
2104                                 // (for efficiency/performance)
2105 
2106   // STW ref processor
2107   _ref_processor_stw =
2108     new ReferenceProcessor(mr,    // span
2109                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2110                                 // mt processing
2111                            ParallelGCThreads,
2112                                 // degree of mt processing
2113                            (ParallelGCThreads > 1),
2114                                 // mt discovery
2115                            ParallelGCThreads,
2116                                 // degree of mt discovery
2117                            true,
2118                                 // Reference discovery is atomic
2119                            &_is_alive_closure_stw);
2120                                 // is alive closure
2121                                 // (for efficiency/performance)
2122 }
2123 
2124 CollectorPolicy* G1CollectedHeap::collector_policy() const {
2125   return g1_policy();
2126 }
2127 
2128 size_t G1CollectedHeap::capacity() const {
2129   return _hrm.length() * HeapRegion::GrainBytes;
2130 }
2131 
2132 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2133   hr->reset_gc_time_stamp();
2134 }
2135 
2136 #ifndef PRODUCT
2137 
2138 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2139 private:
2140   unsigned _gc_time_stamp;
2141   bool _failures;
2142 
2143 public:
2144   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2145     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2146 
2147   virtual bool doHeapRegion(HeapRegion* hr) {
2148     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2149     if (_gc_time_stamp != region_gc_time_stamp) {
2150       log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
2151                             region_gc_time_stamp, _gc_time_stamp);
2152       _failures = true;
2153     }
2154     return false;
2155   }
2156 
2157   bool failures() { return _failures; }
2158 };
2159 
2160 void G1CollectedHeap::check_gc_time_stamps() {
2161   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2162   heap_region_iterate(&cl);
2163   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2164 }
2165 #endif // PRODUCT
2166 
2167 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
2168   _cg1r->hot_card_cache()->drain(cl, worker_i);
2169 }
2170 
2171 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
2172   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2173   size_t n_completed_buffers = 0;
2174   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2175     n_completed_buffers++;
2176   }
2177   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2178   dcqs.clear_n_completed_buffers();
2179   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2180 }
2181 
2182 // Computes the sum of the storage used by the various regions.
2183 size_t G1CollectedHeap::used() const {
2184   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
2185   if (_archive_allocator != NULL) {
2186     result += _archive_allocator->used();
2187   }
2188   return result;
2189 }
2190 
2191 size_t G1CollectedHeap::used_unlocked() const {
2192   return _summary_bytes_used;
2193 }
2194 
2195 class SumUsedClosure: public HeapRegionClosure {
2196   size_t _used;
2197 public:
2198   SumUsedClosure() : _used(0) {}
2199   bool doHeapRegion(HeapRegion* r) {
2200     _used += r->used();
2201     return false;
2202   }
2203   size_t result() { return _used; }
2204 };
2205 
2206 size_t G1CollectedHeap::recalculate_used() const {
2207   double recalculate_used_start = os::elapsedTime();
2208 
2209   SumUsedClosure blk;
2210   heap_region_iterate(&blk);
2211 
2212   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2213   return blk.result();
2214 }
2215 
2216 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2217   switch (cause) {
2218     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
2219     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
2220     case GCCause::_update_allocation_context_stats_inc: return true;
2221     case GCCause::_wb_conc_mark:                        return true;
2222     default :                                           return false;
2223   }
2224 }
2225 
2226 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2227   switch (cause) {
2228     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2229     case GCCause::_g1_humongous_allocation: return true;
2230     default:                                return is_user_requested_concurrent_full_gc(cause);
2231   }
2232 }
2233 
2234 #ifndef PRODUCT
2235 void G1CollectedHeap::allocate_dummy_regions() {
2236   // Let's fill up most of the region
2237   size_t word_size = HeapRegion::GrainWords - 1024;
2238   // And as a result the region we'll allocate will be humongous.
2239   guarantee(is_humongous(word_size), "sanity");
2240 
2241   // _filler_array_max_size is set to humongous object threshold
2242   // but temporarily change it to use CollectedHeap::fill_with_object().
2243   SizeTFlagSetting fs(_filler_array_max_size, word_size);
2244 
2245   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2246     // Let's use the existing mechanism for the allocation
2247     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2248                                                  AllocationContext::system());
2249     if (dummy_obj != NULL) {
2250       MemRegion mr(dummy_obj, word_size);
2251       CollectedHeap::fill_with_object(mr);
2252     } else {
2253       // If we can't allocate once, we probably cannot allocate
2254       // again. Let's get out of the loop.
2255       break;
2256     }
2257   }
2258 }
2259 #endif // !PRODUCT
2260 
2261 void G1CollectedHeap::increment_old_marking_cycles_started() {
2262   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2263          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2264          "Wrong marking cycle count (started: %d, completed: %d)",
2265          _old_marking_cycles_started, _old_marking_cycles_completed);
2266 
2267   _old_marking_cycles_started++;
2268 }
2269 
2270 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2271   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2272 
2273   // We assume that if concurrent == true, then the caller is a
2274   // concurrent thread that was joined the Suspendible Thread
2275   // Set. If there's ever a cheap way to check this, we should add an
2276   // assert here.
2277 
2278   // Given that this method is called at the end of a Full GC or of a
2279   // concurrent cycle, and those can be nested (i.e., a Full GC can
2280   // interrupt a concurrent cycle), the number of full collections
2281   // completed should be either one (in the case where there was no
2282   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2283   // behind the number of full collections started.
2284 
2285   // This is the case for the inner caller, i.e. a Full GC.
2286   assert(concurrent ||
2287          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2288          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2289          "for inner caller (Full GC): _old_marking_cycles_started = %u "
2290          "is inconsistent with _old_marking_cycles_completed = %u",
2291          _old_marking_cycles_started, _old_marking_cycles_completed);
2292 
2293   // This is the case for the outer caller, i.e. the concurrent cycle.
2294   assert(!concurrent ||
2295          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2296          "for outer caller (concurrent cycle): "
2297          "_old_marking_cycles_started = %u "
2298          "is inconsistent with _old_marking_cycles_completed = %u",
2299          _old_marking_cycles_started, _old_marking_cycles_completed);
2300 
2301   _old_marking_cycles_completed += 1;
2302 
2303   // We need to clear the "in_progress" flag in the CM thread before
2304   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2305   // is set) so that if a waiter requests another System.gc() it doesn't
2306   // incorrectly see that a marking cycle is still in progress.
2307   if (concurrent) {
2308     _cmThread->set_idle();
2309   }
2310 
2311   // This notify_all() will ensure that a thread that called
2312   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2313   // and it's waiting for a full GC to finish will be woken up. It is
2314   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2315   FullGCCount_lock->notify_all();
2316 }
2317 
2318 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2319   GCIdMarkAndRestore conc_gc_id_mark;
2320   collector_state()->set_concurrent_cycle_started(true);
2321   _gc_timer_cm->register_gc_start(start_time);
2322 
2323   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2324   trace_heap_before_gc(_gc_tracer_cm);
2325   _cmThread->set_gc_id(GCId::current());
2326 }
2327 
2328 void G1CollectedHeap::register_concurrent_cycle_end() {
2329   if (collector_state()->concurrent_cycle_started()) {
2330     GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id());
2331     if (_cm->has_aborted()) {
2332       _gc_tracer_cm->report_concurrent_mode_failure();
2333     }
2334 
2335     _gc_timer_cm->register_gc_end();
2336     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2337 
2338     // Clear state variables to prepare for the next concurrent cycle.
2339     collector_state()->set_concurrent_cycle_started(false);
2340     _heap_summary_sent = false;
2341   }
2342 }
2343 
2344 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2345   if (collector_state()->concurrent_cycle_started()) {
2346     // This function can be called when:
2347     //  the cleanup pause is run
2348     //  the concurrent cycle is aborted before the cleanup pause.
2349     //  the concurrent cycle is aborted after the cleanup pause,
2350     //   but before the concurrent cycle end has been registered.
2351     // Make sure that we only send the heap information once.
2352     if (!_heap_summary_sent) {
2353       GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id());
2354       trace_heap_after_gc(_gc_tracer_cm);
2355       _heap_summary_sent = true;
2356     }
2357   }
2358 }
2359 
2360 void G1CollectedHeap::collect(GCCause::Cause cause) {
2361   assert_heap_not_locked();
2362 
2363   uint gc_count_before;
2364   uint old_marking_count_before;
2365   uint full_gc_count_before;
2366   bool retry_gc;
2367 
2368   do {
2369     retry_gc = false;
2370 
2371     {
2372       MutexLocker ml(Heap_lock);
2373 
2374       // Read the GC count while holding the Heap_lock
2375       gc_count_before = total_collections();
2376       full_gc_count_before = total_full_collections();
2377       old_marking_count_before = _old_marking_cycles_started;
2378     }
2379 
2380     if (should_do_concurrent_full_gc(cause)) {
2381       // Schedule an initial-mark evacuation pause that will start a
2382       // concurrent cycle. We're setting word_size to 0 which means that
2383       // we are not requesting a post-GC allocation.
2384       VM_G1IncCollectionPause op(gc_count_before,
2385                                  0,     /* word_size */
2386                                  true,  /* should_initiate_conc_mark */
2387                                  g1_policy()->max_pause_time_ms(),
2388                                  cause);
2389       op.set_allocation_context(AllocationContext::current());
2390 
2391       VMThread::execute(&op);
2392       if (!op.pause_succeeded()) {
2393         if (old_marking_count_before == _old_marking_cycles_started) {
2394           retry_gc = op.should_retry_gc();
2395         } else {
2396           // A Full GC happened while we were trying to schedule the
2397           // initial-mark GC. No point in starting a new cycle given
2398           // that the whole heap was collected anyway.
2399         }
2400 
2401         if (retry_gc) {
2402           if (GCLocker::is_active_and_needs_gc()) {
2403             GCLocker::stall_until_clear();
2404           }
2405         }
2406       }
2407     } else {
2408       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2409           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2410 
2411         // Schedule a standard evacuation pause. We're setting word_size
2412         // to 0 which means that we are not requesting a post-GC allocation.
2413         VM_G1IncCollectionPause op(gc_count_before,
2414                                    0,     /* word_size */
2415                                    false, /* should_initiate_conc_mark */
2416                                    g1_policy()->max_pause_time_ms(),
2417                                    cause);
2418         VMThread::execute(&op);
2419       } else {
2420         // Schedule a Full GC.
2421         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2422         VMThread::execute(&op);
2423       }
2424     }
2425   } while (retry_gc);
2426 }
2427 
2428 bool G1CollectedHeap::is_in(const void* p) const {
2429   if (_hrm.reserved().contains(p)) {
2430     // Given that we know that p is in the reserved space,
2431     // heap_region_containing() should successfully
2432     // return the containing region.
2433     HeapRegion* hr = heap_region_containing(p);
2434     return hr->is_in(p);
2435   } else {
2436     return false;
2437   }
2438 }
2439 
2440 #ifdef ASSERT
2441 bool G1CollectedHeap::is_in_exact(const void* p) const {
2442   bool contains = reserved_region().contains(p);
2443   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2444   if (contains && available) {
2445     return true;
2446   } else {
2447     return false;
2448   }
2449 }
2450 #endif
2451 
2452 bool G1CollectedHeap::obj_in_cs(oop obj) {
2453   HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj);
2454   return r != NULL && r->in_collection_set();
2455 }
2456 
2457 // Iteration functions.
2458 
2459 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2460 
2461 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2462   ExtendedOopClosure* _cl;
2463 public:
2464   IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2465   bool doHeapRegion(HeapRegion* r) {
2466     if (!r->is_continues_humongous()) {
2467       r->oop_iterate(_cl);
2468     }
2469     return false;
2470   }
2471 };
2472 
2473 // Iterates an ObjectClosure over all objects within a HeapRegion.
2474 
2475 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2476   ObjectClosure* _cl;
2477 public:
2478   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2479   bool doHeapRegion(HeapRegion* r) {
2480     if (!r->is_continues_humongous()) {
2481       r->object_iterate(_cl);
2482     }
2483     return false;
2484   }
2485 };
2486 
2487 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2488   IterateObjectClosureRegionClosure blk(cl);
2489   heap_region_iterate(&blk);
2490 }
2491 
2492 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2493   _hrm.iterate(cl);
2494 }
2495 
2496 void
2497 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2498                                          uint worker_id,
2499                                          HeapRegionClaimer *hrclaimer,
2500                                          bool concurrent) const {
2501   _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent);
2502 }
2503 
2504 // Clear the cached CSet starting regions and (more importantly)
2505 // the time stamps. Called when we reset the GC time stamp.
2506 void G1CollectedHeap::clear_cset_start_regions() {
2507   assert(_worker_cset_start_region != NULL, "sanity");
2508   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2509 
2510   for (uint i = 0; i < ParallelGCThreads; i++) {
2511     _worker_cset_start_region[i] = NULL;
2512     _worker_cset_start_region_time_stamp[i] = 0;
2513   }
2514 }
2515 
2516 // Given the id of a worker, obtain or calculate a suitable
2517 // starting region for iterating over the current collection set.
2518 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2519   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2520 
2521   HeapRegion* result = NULL;
2522   unsigned gc_time_stamp = get_gc_time_stamp();
2523 
2524   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2525     // Cached starting region for current worker was set
2526     // during the current pause - so it's valid.
2527     // Note: the cached starting heap region may be NULL
2528     // (when the collection set is empty).
2529     result = _worker_cset_start_region[worker_i];
2530     assert(result == NULL || result->in_collection_set(), "sanity");
2531     return result;
2532   }
2533 
2534   // The cached entry was not valid so let's calculate
2535   // a suitable starting heap region for this worker.
2536 
2537   // We want the parallel threads to start their collection
2538   // set iteration at different collection set regions to
2539   // avoid contention.
2540   // If we have:
2541   //          n collection set regions
2542   //          p threads
2543   // Then thread t will start at region floor ((t * n) / p)
2544 
2545   result = g1_policy()->collection_set();
2546   uint cs_size = g1_policy()->cset_region_length();
2547   uint active_workers = workers()->active_workers();
2548 
2549   uint end_ind   = (cs_size * worker_i) / active_workers;
2550   uint start_ind = 0;
2551 
2552   if (worker_i > 0 &&
2553       _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2554     // Previous workers starting region is valid
2555     // so let's iterate from there
2556     start_ind = (cs_size * (worker_i - 1)) / active_workers;
2557     OrderAccess::loadload();
2558     result = _worker_cset_start_region[worker_i - 1];
2559   }
2560 
2561   for (uint i = start_ind; i < end_ind; i++) {
2562     result = result->next_in_collection_set();
2563   }
2564 
2565   // Note: the calculated starting heap region may be NULL
2566   // (when the collection set is empty).
2567   assert(result == NULL || result->in_collection_set(), "sanity");
2568   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2569          "should be updated only once per pause");
2570   _worker_cset_start_region[worker_i] = result;
2571   OrderAccess::storestore();
2572   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2573   return result;
2574 }
2575 
2576 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2577   HeapRegion* r = g1_policy()->collection_set();
2578   while (r != NULL) {
2579     HeapRegion* next = r->next_in_collection_set();
2580     if (cl->doHeapRegion(r)) {
2581       cl->incomplete();
2582       return;
2583     }
2584     r = next;
2585   }
2586 }
2587 
2588 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2589                                                   HeapRegionClosure *cl) {
2590   if (r == NULL) {
2591     // The CSet is empty so there's nothing to do.
2592     return;
2593   }
2594 
2595   assert(r->in_collection_set(),
2596          "Start region must be a member of the collection set.");
2597   HeapRegion* cur = r;
2598   while (cur != NULL) {
2599     HeapRegion* next = cur->next_in_collection_set();
2600     if (cl->doHeapRegion(cur) && false) {
2601       cl->incomplete();
2602       return;
2603     }
2604     cur = next;
2605   }
2606   cur = g1_policy()->collection_set();
2607   while (cur != r) {
2608     HeapRegion* next = cur->next_in_collection_set();
2609     if (cl->doHeapRegion(cur) && false) {
2610       cl->incomplete();
2611       return;
2612     }
2613     cur = next;
2614   }
2615 }
2616 
2617 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2618   HeapRegion* result = _hrm.next_region_in_heap(from);
2619   while (result != NULL && result->is_pinned()) {
2620     result = _hrm.next_region_in_heap(result);
2621   }
2622   return result;
2623 }
2624 
2625 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2626   HeapRegion* hr = heap_region_containing(addr);
2627   return hr->block_start(addr);
2628 }
2629 
2630 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2631   HeapRegion* hr = heap_region_containing(addr);
2632   return hr->block_size(addr);
2633 }
2634 
2635 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2636   HeapRegion* hr = heap_region_containing(addr);
2637   return hr->block_is_obj(addr);
2638 }
2639 
2640 bool G1CollectedHeap::supports_tlab_allocation() const {
2641   return true;
2642 }
2643 
2644 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2645   return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2646 }
2647 
2648 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2649   return young_list()->eden_used_bytes();
2650 }
2651 
2652 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2653 // must be equal to the humongous object limit.
2654 size_t G1CollectedHeap::max_tlab_size() const {
2655   return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment);
2656 }
2657 
2658 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2659   AllocationContext_t context = AllocationContext::current();
2660   return _allocator->unsafe_max_tlab_alloc(context);
2661 }
2662 
2663 size_t G1CollectedHeap::max_capacity() const {
2664   return _hrm.reserved().byte_size();
2665 }
2666 
2667 jlong G1CollectedHeap::millis_since_last_gc() {
2668   // assert(false, "NYI");
2669   return 0;
2670 }
2671 
2672 void G1CollectedHeap::prepare_for_verify() {
2673   _verifier->prepare_for_verify();
2674 }
2675 
2676 void G1CollectedHeap::verify(VerifyOption vo) {
2677   _verifier->verify(vo);
2678 }
2679 
2680 class PrintRegionClosure: public HeapRegionClosure {
2681   outputStream* _st;
2682 public:
2683   PrintRegionClosure(outputStream* st) : _st(st) {}
2684   bool doHeapRegion(HeapRegion* r) {
2685     r->print_on(_st);
2686     return false;
2687   }
2688 };
2689 
2690 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2691                                        const HeapRegion* hr,
2692                                        const VerifyOption vo) const {
2693   switch (vo) {
2694   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2695   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2696   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked() && !hr->is_archive();
2697   default:                            ShouldNotReachHere();
2698   }
2699   return false; // keep some compilers happy
2700 }
2701 
2702 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2703                                        const VerifyOption vo) const {
2704   switch (vo) {
2705   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2706   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2707   case VerifyOption_G1UseMarkWord: {
2708     HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj);
2709     return !obj->is_gc_marked() && !hr->is_archive();
2710   }
2711   default:                            ShouldNotReachHere();
2712   }
2713   return false; // keep some compilers happy
2714 }
2715 
2716 void G1CollectedHeap::print_on(outputStream* st) const {
2717   st->print(" %-20s", "garbage-first heap");
2718   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2719             capacity()/K, used_unlocked()/K);
2720   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
2721             p2i(_hrm.reserved().start()),
2722             p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords),
2723             p2i(_hrm.reserved().end()));
2724   st->cr();
2725   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2726   uint young_regions = _young_list->length();
2727   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2728             (size_t) young_regions * HeapRegion::GrainBytes / K);
2729   uint survivor_regions = g1_policy()->recorded_survivor_regions();
2730   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2731             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2732   st->cr();
2733   MetaspaceAux::print_on(st);
2734 }
2735 
2736 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2737   print_on(st);
2738 
2739   // Print the per-region information.
2740   st->cr();
2741   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2742                "HS=humongous(starts), HC=humongous(continues), "
2743                "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2744                "AC=allocation context, "
2745                "TAMS=top-at-mark-start (previous, next)");
2746   PrintRegionClosure blk(st);
2747   heap_region_iterate(&blk);
2748 }
2749 
2750 void G1CollectedHeap::print_on_error(outputStream* st) const {
2751   this->CollectedHeap::print_on_error(st);
2752 
2753   if (_cm != NULL) {
2754     st->cr();
2755     _cm->print_on_error(st);
2756   }
2757 }
2758 
2759 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2760   workers()->print_worker_threads_on(st);
2761   _cmThread->print_on(st);
2762   st->cr();
2763   _cm->print_worker_threads_on(st);
2764   _cg1r->print_worker_threads_on(st);
2765   if (G1StringDedup::is_enabled()) {
2766     G1StringDedup::print_worker_threads_on(st);
2767   }
2768 }
2769 
2770 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2771   workers()->threads_do(tc);
2772   tc->do_thread(_cmThread);
2773   _cg1r->threads_do(tc);
2774   if (G1StringDedup::is_enabled()) {
2775     G1StringDedup::threads_do(tc);
2776   }
2777 }
2778 
2779 void G1CollectedHeap::print_tracing_info() const {
2780   g1_rem_set()->print_summary_info();
2781   concurrent_mark()->print_summary_info();
2782   g1_policy()->print_yg_surv_rate_info();
2783 }
2784 
2785 #ifndef PRODUCT
2786 // Helpful for debugging RSet issues.
2787 
2788 class PrintRSetsClosure : public HeapRegionClosure {
2789 private:
2790   const char* _msg;
2791   size_t _occupied_sum;
2792 
2793 public:
2794   bool doHeapRegion(HeapRegion* r) {
2795     HeapRegionRemSet* hrrs = r->rem_set();
2796     size_t occupied = hrrs->occupied();
2797     _occupied_sum += occupied;
2798 
2799     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2800     if (occupied == 0) {
2801       tty->print_cr("  RSet is empty");
2802     } else {
2803       hrrs->print();
2804     }
2805     tty->print_cr("----------");
2806     return false;
2807   }
2808 
2809   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2810     tty->cr();
2811     tty->print_cr("========================================");
2812     tty->print_cr("%s", msg);
2813     tty->cr();
2814   }
2815 
2816   ~PrintRSetsClosure() {
2817     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2818     tty->print_cr("========================================");
2819     tty->cr();
2820   }
2821 };
2822 
2823 void G1CollectedHeap::print_cset_rsets() {
2824   PrintRSetsClosure cl("Printing CSet RSets");
2825   collection_set_iterate(&cl);
2826 }
2827 
2828 void G1CollectedHeap::print_all_rsets() {
2829   PrintRSetsClosure cl("Printing All RSets");;
2830   heap_region_iterate(&cl);
2831 }
2832 #endif // PRODUCT
2833 
2834 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2835   YoungList* young_list = heap()->young_list();
2836 
2837   size_t eden_used_bytes = young_list->eden_used_bytes();
2838   size_t survivor_used_bytes = young_list->survivor_used_bytes();
2839 
2840   size_t eden_capacity_bytes =
2841     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2842 
2843   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2844   return G1HeapSummary(heap_summary, used(), eden_used_bytes, eden_capacity_bytes, survivor_used_bytes, num_regions());
2845 }
2846 
2847 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2848   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2849                        stats->unused(), stats->used(), stats->region_end_waste(),
2850                        stats->regions_filled(), stats->direct_allocated(),
2851                        stats->failure_used(), stats->failure_waste());
2852 }
2853 
2854 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2855   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2856   gc_tracer->report_gc_heap_summary(when, heap_summary);
2857 
2858   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2859   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2860 }
2861 
2862 
2863 G1CollectedHeap* G1CollectedHeap::heap() {
2864   CollectedHeap* heap = Universe::heap();
2865   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2866   assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2867   return (G1CollectedHeap*)heap;
2868 }
2869 
2870 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
2871   // always_do_update_barrier = false;
2872   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2873   // Fill TLAB's and such
2874   accumulate_statistics_all_tlabs();
2875   ensure_parsability(true);
2876 
2877   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2878 }
2879 
2880 void G1CollectedHeap::gc_epilogue(bool full) {
2881   // we are at the end of the GC. Total collections has already been increased.
2882   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2883 
2884   // FIXME: what is this about?
2885   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2886   // is set.
2887 #if defined(COMPILER2) || INCLUDE_JVMCI
2888   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2889 #endif
2890   // always_do_update_barrier = true;
2891 
2892   resize_all_tlabs();
2893   allocation_context_stats().update(full);
2894 
2895   // We have just completed a GC. Update the soft reference
2896   // policy with the new heap occupancy
2897   Universe::update_heap_info_at_gc();
2898 }
2899 
2900 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2901                                                uint gc_count_before,
2902                                                bool* succeeded,
2903                                                GCCause::Cause gc_cause) {
2904   assert_heap_not_locked_and_not_at_safepoint();
2905   VM_G1IncCollectionPause op(gc_count_before,
2906                              word_size,
2907                              false, /* should_initiate_conc_mark */
2908                              g1_policy()->max_pause_time_ms(),
2909                              gc_cause);
2910 
2911   op.set_allocation_context(AllocationContext::current());
2912   VMThread::execute(&op);
2913 
2914   HeapWord* result = op.result();
2915   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2916   assert(result == NULL || ret_succeeded,
2917          "the result should be NULL if the VM did not succeed");
2918   *succeeded = ret_succeeded;
2919 
2920   assert_heap_not_locked();
2921   return result;
2922 }
2923 
2924 void
2925 G1CollectedHeap::doConcurrentMark() {
2926   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2927   if (!_cmThread->in_progress()) {
2928     _cmThread->set_started();
2929     CGC_lock->notify();
2930   }
2931 }
2932 
2933 size_t G1CollectedHeap::pending_card_num() {
2934   size_t extra_cards = 0;
2935   JavaThread *curr = Threads::first();
2936   while (curr != NULL) {
2937     DirtyCardQueue& dcq = curr->dirty_card_queue();
2938     extra_cards += dcq.size();
2939     curr = curr->next();
2940   }
2941   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2942   size_t buffer_size = dcqs.buffer_size();
2943   size_t buffer_num = dcqs.completed_buffers_num();
2944 
2945   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
2946   // in bytes - not the number of 'entries'. We need to convert
2947   // into a number of cards.
2948   return (buffer_size * buffer_num + extra_cards) / oopSize;
2949 }
2950 
2951 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2952  private:
2953   size_t _total_humongous;
2954   size_t _candidate_humongous;
2955 
2956   DirtyCardQueue _dcq;
2957 
2958   // We don't nominate objects with many remembered set entries, on
2959   // the assumption that such objects are likely still live.
2960   bool is_remset_small(HeapRegion* region) const {
2961     HeapRegionRemSet* const rset = region->rem_set();
2962     return G1EagerReclaimHumongousObjectsWithStaleRefs
2963       ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2964       : rset->is_empty();
2965   }
2966 
2967   bool is_typeArray_region(HeapRegion* region) const {
2968     return oop(region->bottom())->is_typeArray();
2969   }
2970 
2971   bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2972     assert(region->is_starts_humongous(), "Must start a humongous object");
2973 
2974     // Candidate selection must satisfy the following constraints
2975     // while concurrent marking is in progress:
2976     //
2977     // * In order to maintain SATB invariants, an object must not be
2978     // reclaimed if it was allocated before the start of marking and
2979     // has not had its references scanned.  Such an object must have
2980     // its references (including type metadata) scanned to ensure no
2981     // live objects are missed by the marking process.  Objects
2982     // allocated after the start of concurrent marking don't need to
2983     // be scanned.
2984     //
2985     // * An object must not be reclaimed if it is on the concurrent
2986     // mark stack.  Objects allocated after the start of concurrent
2987     // marking are never pushed on the mark stack.
2988     //
2989     // Nominating only objects allocated after the start of concurrent
2990     // marking is sufficient to meet both constraints.  This may miss
2991     // some objects that satisfy the constraints, but the marking data
2992     // structures don't support efficiently performing the needed
2993     // additional tests or scrubbing of the mark stack.
2994     //
2995     // However, we presently only nominate is_typeArray() objects.
2996     // A humongous object containing references induces remembered
2997     // set entries on other regions.  In order to reclaim such an
2998     // object, those remembered sets would need to be cleaned up.
2999     //
3000     // We also treat is_typeArray() objects specially, allowing them
3001     // to be reclaimed even if allocated before the start of
3002     // concurrent mark.  For this we rely on mark stack insertion to
3003     // exclude is_typeArray() objects, preventing reclaiming an object
3004     // that is in the mark stack.  We also rely on the metadata for
3005     // such objects to be built-in and so ensured to be kept live.
3006     // Frequent allocation and drop of large binary blobs is an
3007     // important use case for eager reclaim, and this special handling
3008     // may reduce needed headroom.
3009 
3010     return is_typeArray_region(region) && is_remset_small(region);
3011   }
3012 
3013  public:
3014   RegisterHumongousWithInCSetFastTestClosure()
3015   : _total_humongous(0),
3016     _candidate_humongous(0),
3017     _dcq(&JavaThread::dirty_card_queue_set()) {
3018   }
3019 
3020   virtual bool doHeapRegion(HeapRegion* r) {
3021     if (!r->is_starts_humongous()) {
3022       return false;
3023     }
3024     G1CollectedHeap* g1h = G1CollectedHeap::heap();
3025 
3026     bool is_candidate = humongous_region_is_candidate(g1h, r);
3027     uint rindex = r->hrm_index();
3028     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
3029     if (is_candidate) {
3030       _candidate_humongous++;
3031       g1h->register_humongous_region_with_cset(rindex);
3032       // Is_candidate already filters out humongous object with large remembered sets.
3033       // If we have a humongous object with a few remembered sets, we simply flush these
3034       // remembered set entries into the DCQS. That will result in automatic
3035       // re-evaluation of their remembered set entries during the following evacuation
3036       // phase.
3037       if (!r->rem_set()->is_empty()) {
3038         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
3039                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
3040         G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
3041         HeapRegionRemSetIterator hrrs(r->rem_set());
3042         size_t card_index;
3043         while (hrrs.has_next(card_index)) {
3044           jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
3045           // The remembered set might contain references to already freed
3046           // regions. Filter out such entries to avoid failing card table
3047           // verification.
3048           if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
3049             if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
3050               *card_ptr = CardTableModRefBS::dirty_card_val();
3051               _dcq.enqueue(card_ptr);
3052             }
3053           }
3054         }
3055         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
3056                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
3057                hrrs.n_yielded(), r->rem_set()->occupied());
3058         r->rem_set()->clear_locked();
3059       }
3060       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
3061     }
3062     _total_humongous++;
3063 
3064     return false;
3065   }
3066 
3067   size_t total_humongous() const { return _total_humongous; }
3068   size_t candidate_humongous() const { return _candidate_humongous; }
3069 
3070   void flush_rem_set_entries() { _dcq.flush(); }
3071 };
3072 
3073 void G1CollectedHeap::register_humongous_regions_with_cset() {
3074   if (!G1EagerReclaimHumongousObjects) {
3075     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
3076     return;
3077   }
3078   double time = os::elapsed_counter();
3079 
3080   // Collect reclaim candidate information and register candidates with cset.
3081   RegisterHumongousWithInCSetFastTestClosure cl;
3082   heap_region_iterate(&cl);
3083 
3084   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
3085   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
3086                                                                   cl.total_humongous(),
3087                                                                   cl.candidate_humongous());
3088   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3089 
3090   // Finally flush all remembered set entries to re-check into the global DCQS.
3091   cl.flush_rem_set_entries();
3092 }
3093 
3094 class VerifyRegionRemSetClosure : public HeapRegionClosure {
3095   public:
3096     bool doHeapRegion(HeapRegion* hr) {
3097       if (!hr->is_archive() && !hr->is_continues_humongous()) {
3098         hr->verify_rem_set();
3099       }
3100       return false;
3101     }
3102 };
3103 
3104 #ifdef ASSERT
3105 class VerifyCSetClosure: public HeapRegionClosure {
3106 public:
3107   bool doHeapRegion(HeapRegion* hr) {
3108     // Here we check that the CSet region's RSet is ready for parallel
3109     // iteration. The fields that we'll verify are only manipulated
3110     // when the region is part of a CSet and is collected. Afterwards,
3111     // we reset these fields when we clear the region's RSet (when the
3112     // region is freed) so they are ready when the region is
3113     // re-allocated. The only exception to this is if there's an
3114     // evacuation failure and instead of freeing the region we leave
3115     // it in the heap. In that case, we reset these fields during
3116     // evacuation failure handling.
3117     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3118 
3119     // Here's a good place to add any other checks we'd like to
3120     // perform on CSet regions.
3121     return false;
3122   }
3123 };
3124 #endif // ASSERT
3125 
3126 uint G1CollectedHeap::num_task_queues() const {
3127   return _task_queues->size();
3128 }
3129 
3130 #if TASKQUEUE_STATS
3131 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3132   st->print_raw_cr("GC Task Stats");
3133   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3134   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3135 }
3136 
3137 void G1CollectedHeap::print_taskqueue_stats() const {
3138   if (!log_develop_is_enabled(Trace, gc, task, stats)) {
3139     return;
3140   }
3141   LogHandle(gc, task, stats) log;
3142   ResourceMark rm;
3143   outputStream* st = log.trace_stream();
3144 
3145   print_taskqueue_stats_hdr(st);
3146 
3147   TaskQueueStats totals;
3148   const uint n = num_task_queues();
3149   for (uint i = 0; i < n; ++i) {
3150     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
3151     totals += task_queue(i)->stats;
3152   }
3153   st->print_raw("tot "); totals.print(st); st->cr();
3154 
3155   DEBUG_ONLY(totals.verify());
3156 }
3157 
3158 void G1CollectedHeap::reset_taskqueue_stats() {
3159   const uint n = num_task_queues();
3160   for (uint i = 0; i < n; ++i) {
3161     task_queue(i)->stats.reset();
3162   }
3163 }
3164 #endif // TASKQUEUE_STATS
3165 
3166 void G1CollectedHeap::wait_for_root_region_scanning() {
3167   double scan_wait_start = os::elapsedTime();
3168   // We have to wait until the CM threads finish scanning the
3169   // root regions as it's the only way to ensure that all the
3170   // objects on them have been correctly scanned before we start
3171   // moving them during the GC.
3172   bool waited = _cm->root_regions()->wait_until_scan_finished();
3173   double wait_time_ms = 0.0;
3174   if (waited) {
3175     double scan_wait_end = os::elapsedTime();
3176     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3177   }
3178   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3179 }
3180 
3181 bool
3182 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3183   assert_at_safepoint(true /* should_be_vm_thread */);
3184   guarantee(!is_gc_active(), "collection is not reentrant");
3185 
3186   if (GCLocker::check_active_before_gc()) {
3187     return false;
3188   }
3189 
3190   _gc_timer_stw->register_gc_start();
3191 
3192   GCIdMark gc_id_mark;
3193   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3194 
3195   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3196   ResourceMark rm;
3197 
3198   wait_for_root_region_scanning();
3199 
3200   print_heap_before_gc();
3201   trace_heap_before_gc(_gc_tracer_stw);
3202 
3203   _verifier->verify_region_sets_optional();
3204   _verifier->verify_dirty_young_regions();
3205 
3206   // This call will decide whether this pause is an initial-mark
3207   // pause. If it is, during_initial_mark_pause() will return true
3208   // for the duration of this pause.
3209   g1_policy()->decide_on_conc_mark_initiation();
3210 
3211   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3212   assert(!collector_state()->during_initial_mark_pause() ||
3213           collector_state()->gcs_are_young(), "sanity");
3214 
3215   // We also do not allow mixed GCs during marking.
3216   assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
3217 
3218   // Record whether this pause is an initial mark. When the current
3219   // thread has completed its logging output and it's safe to signal
3220   // the CM thread, the flag's value in the policy has been reset.
3221   bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
3222 
3223   // Inner scope for scope based logging, timers, and stats collection
3224   {
3225     EvacuationInfo evacuation_info;
3226 
3227     if (collector_state()->during_initial_mark_pause()) {
3228       // We are about to start a marking cycle, so we increment the
3229       // full collection counter.
3230       increment_old_marking_cycles_started();
3231       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3232     }
3233 
3234     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
3235 
3236     GCTraceCPUTime tcpu;
3237 
3238     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
3239                                                                   workers()->active_workers(),
3240                                                                   Threads::number_of_non_daemon_threads());
3241     workers()->set_active_workers(active_workers);
3242     FormatBuffer<> gc_string("Pause ");
3243     if (collector_state()->during_initial_mark_pause()) {
3244       gc_string.append("Initial Mark");
3245     } else if (collector_state()->gcs_are_young()) {
3246       gc_string.append("Young");
3247     } else {
3248       gc_string.append("Mixed");
3249     }
3250     GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
3251 
3252     g1_policy()->note_gc_start(active_workers);
3253 
3254     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3255     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3256 
3257     // If the secondary_free_list is not empty, append it to the
3258     // free_list. No need to wait for the cleanup operation to finish;
3259     // the region allocation code will check the secondary_free_list
3260     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3261     // set, skip this step so that the region allocation code has to
3262     // get entries from the secondary_free_list.
3263     if (!G1StressConcRegionFreeing) {
3264       append_secondary_free_list_if_not_empty_with_lock();
3265     }
3266 
3267     G1HeapTransition heap_transition(this);
3268     size_t heap_used_bytes_before_gc = used();
3269 
3270     assert(check_young_list_well_formed(), "young list should be well formed");
3271 
3272     // Don't dynamically change the number of GC threads this early.  A value of
3273     // 0 is used to indicate serial work.  When parallel work is done,
3274     // it will be set.
3275 
3276     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3277       IsGCActiveMark x;
3278 
3279       gc_prologue(false);
3280       increment_total_collections(false /* full gc */);
3281       increment_gc_time_stamp();
3282 
3283       if (VerifyRememberedSets) {
3284         log_info(gc, verify)("[Verifying RemSets before GC]");
3285         VerifyRegionRemSetClosure v_cl;
3286         heap_region_iterate(&v_cl);
3287       }
3288 
3289       _verifier->verify_before_gc();
3290 
3291       _verifier->check_bitmaps("GC Start");
3292 
3293 #if defined(COMPILER2) || INCLUDE_JVMCI
3294       DerivedPointerTable::clear();
3295 #endif
3296 
3297       // Please see comment in g1CollectedHeap.hpp and
3298       // G1CollectedHeap::ref_processing_init() to see how
3299       // reference processing currently works in G1.
3300 
3301       // Enable discovery in the STW reference processor
3302       if (g1_policy()->should_process_references()) {
3303         ref_processor_stw()->enable_discovery();
3304       } else {
3305         ref_processor_stw()->disable_discovery();
3306       }
3307 
3308       {
3309         // We want to temporarily turn off discovery by the
3310         // CM ref processor, if necessary, and turn it back on
3311         // on again later if we do. Using a scoped
3312         // NoRefDiscovery object will do this.
3313         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3314 
3315         // Forget the current alloc region (we might even choose it to be part
3316         // of the collection set!).
3317         _allocator->release_mutator_alloc_region();
3318 
3319         // This timing is only used by the ergonomics to handle our pause target.
3320         // It is unclear why this should not include the full pause. We will
3321         // investigate this in CR 7178365.
3322         //
3323         // Preserving the old comment here if that helps the investigation:
3324         //
3325         // The elapsed time induced by the start time below deliberately elides
3326         // the possible verification above.
3327         double sample_start_time_sec = os::elapsedTime();
3328 
3329         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3330 
3331         if (collector_state()->during_initial_mark_pause()) {
3332           concurrent_mark()->checkpointRootsInitialPre();
3333         }
3334 
3335         double time_remaining_ms = g1_policy()->finalize_young_cset_part(target_pause_time_ms);
3336         g1_policy()->finalize_old_cset_part(time_remaining_ms);
3337 
3338         evacuation_info.set_collectionset_regions(g1_policy()->cset_region_length());
3339 
3340         // Make sure the remembered sets are up to date. This needs to be
3341         // done before register_humongous_regions_with_cset(), because the
3342         // remembered sets are used there to choose eager reclaim candidates.
3343         // If the remembered sets are not up to date we might miss some
3344         // entries that need to be handled.
3345         g1_rem_set()->cleanupHRRS();
3346 
3347         register_humongous_regions_with_cset();
3348 
3349         assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3350 
3351         _cm->note_start_of_gc();
3352         // We call this after finalize_cset() to
3353         // ensure that the CSet has been finalized.
3354         _cm->verify_no_cset_oops();
3355 
3356         if (_hr_printer.is_active()) {
3357           HeapRegion* hr = g1_policy()->collection_set();
3358           while (hr != NULL) {
3359             _hr_printer.cset(hr);
3360             hr = hr->next_in_collection_set();
3361           }
3362         }
3363 
3364 #ifdef ASSERT
3365         VerifyCSetClosure cl;
3366         collection_set_iterate(&cl);
3367 #endif // ASSERT
3368 
3369         // Initialize the GC alloc regions.
3370         _allocator->init_gc_alloc_regions(evacuation_info);
3371 
3372         G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), g1_policy()->young_cset_region_length());
3373         pre_evacuate_collection_set();
3374 
3375         // Actually do the work...
3376         evacuate_collection_set(evacuation_info, &per_thread_states);
3377 
3378         post_evacuate_collection_set(evacuation_info, &per_thread_states);
3379 
3380         const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3381         free_collection_set(g1_policy()->collection_set(), evacuation_info, surviving_young_words);
3382 
3383         eagerly_reclaim_humongous_regions();
3384 
3385         g1_policy()->clear_collection_set();
3386 
3387         // Start a new incremental collection set for the next pause.
3388         g1_policy()->start_incremental_cset_building();
3389 
3390         clear_cset_fast_test();
3391 
3392         _young_list->reset_sampled_info();
3393 
3394         // Don't check the whole heap at this point as the
3395         // GC alloc regions from this pause have been tagged
3396         // as survivors and moved on to the survivor list.
3397         // Survivor regions will fail the !is_young() check.
3398         assert(check_young_list_empty(false /* check_heap */),
3399           "young list should be empty");
3400 
3401         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3402                                              _young_list->first_survivor_region(),
3403                                              _young_list->last_survivor_region());
3404 
3405         _young_list->reset_auxilary_lists();
3406 
3407         if (evacuation_failed()) {
3408           set_used(recalculate_used());
3409           if (_archive_allocator != NULL) {
3410             _archive_allocator->clear_used();
3411           }
3412           for (uint i = 0; i < ParallelGCThreads; i++) {
3413             if (_evacuation_failed_info_array[i].has_failed()) {
3414               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3415             }
3416           }
3417         } else {
3418           // The "used" of the the collection set have already been subtracted
3419           // when they were freed.  Add in the bytes evacuated.
3420           increase_used(g1_policy()->bytes_copied_during_gc());
3421         }
3422 
3423         if (collector_state()->during_initial_mark_pause()) {
3424           // We have to do this before we notify the CM threads that
3425           // they can start working to make sure that all the
3426           // appropriate initialization is done on the CM object.
3427           concurrent_mark()->checkpointRootsInitialPost();
3428           collector_state()->set_mark_in_progress(true);
3429           // Note that we don't actually trigger the CM thread at
3430           // this point. We do that later when we're sure that
3431           // the current thread has completed its logging output.
3432         }
3433 
3434         allocate_dummy_regions();
3435 
3436         _allocator->init_mutator_alloc_region();
3437 
3438         {
3439           size_t expand_bytes = g1_policy()->expansion_amount();
3440           if (expand_bytes > 0) {
3441             size_t bytes_before = capacity();
3442             // No need for an ergo logging here,
3443             // expansion_amount() does this when it returns a value > 0.
3444             double expand_ms;
3445             if (!expand(expand_bytes, &expand_ms)) {
3446               // We failed to expand the heap. Cannot do anything about it.
3447             }
3448             g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3449           }
3450         }
3451 
3452         // We redo the verification but now wrt to the new CSet which
3453         // has just got initialized after the previous CSet was freed.
3454         _cm->verify_no_cset_oops();
3455         _cm->note_end_of_gc();
3456 
3457         // This timing is only used by the ergonomics to handle our pause target.
3458         // It is unclear why this should not include the full pause. We will
3459         // investigate this in CR 7178365.
3460         double sample_end_time_sec = os::elapsedTime();
3461         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3462         size_t total_cards_scanned = per_thread_states.total_cards_scanned();
3463         g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3464 
3465         evacuation_info.set_collectionset_used_before(g1_policy()->collection_set_bytes_used_before());
3466         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3467 
3468         MemoryService::track_memory_usage();
3469 
3470         // In prepare_for_verify() below we'll need to scan the deferred
3471         // update buffers to bring the RSets up-to-date if
3472         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3473         // the update buffers we'll probably need to scan cards on the
3474         // regions we just allocated to (i.e., the GC alloc
3475         // regions). However, during the last GC we called
3476         // set_saved_mark() on all the GC alloc regions, so card
3477         // scanning might skip the [saved_mark_word()...top()] area of
3478         // those regions (i.e., the area we allocated objects into
3479         // during the last GC). But it shouldn't. Given that
3480         // saved_mark_word() is conditional on whether the GC time stamp
3481         // on the region is current or not, by incrementing the GC time
3482         // stamp here we invalidate all the GC time stamps on all the
3483         // regions and saved_mark_word() will simply return top() for
3484         // all the regions. This is a nicer way of ensuring this rather
3485         // than iterating over the regions and fixing them. In fact, the
3486         // GC time stamp increment here also ensures that
3487         // saved_mark_word() will return top() between pauses, i.e.,
3488         // during concurrent refinement. So we don't need the
3489         // is_gc_active() check to decided which top to use when
3490         // scanning cards (see CR 7039627).
3491         increment_gc_time_stamp();
3492 
3493         if (VerifyRememberedSets) {
3494           log_info(gc, verify)("[Verifying RemSets after GC]");
3495           VerifyRegionRemSetClosure v_cl;
3496           heap_region_iterate(&v_cl);
3497         }
3498 
3499         _verifier->verify_after_gc();
3500         _verifier->check_bitmaps("GC End");
3501 
3502         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3503         ref_processor_stw()->verify_no_references_recorded();
3504 
3505         // CM reference discovery will be re-enabled if necessary.
3506       }
3507 
3508 #ifdef TRACESPINNING
3509       ParallelTaskTerminator::print_termination_counts();
3510 #endif
3511 
3512       gc_epilogue(false);
3513     }
3514 
3515     // Print the remainder of the GC log output.
3516     if (evacuation_failed()) {
3517       log_info(gc)("To-space exhausted");
3518     }
3519 
3520     g1_policy()->print_phases();
3521     heap_transition.print();
3522 
3523     // It is not yet to safe to tell the concurrent mark to
3524     // start as we have some optional output below. We don't want the
3525     // output from the concurrent mark thread interfering with this
3526     // logging output either.
3527 
3528     _hrm.verify_optional();
3529     _verifier->verify_region_sets_optional();
3530 
3531     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3532     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3533 
3534     print_heap_after_gc();
3535     trace_heap_after_gc(_gc_tracer_stw);
3536 
3537     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3538     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3539     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3540     // before any GC notifications are raised.
3541     g1mm()->update_sizes();
3542 
3543     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3544     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3545     _gc_timer_stw->register_gc_end();
3546     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3547   }
3548   // It should now be safe to tell the concurrent mark thread to start
3549   // without its logging output interfering with the logging output
3550   // that came from the pause.
3551 
3552   if (should_start_conc_mark) {
3553     // CAUTION: after the doConcurrentMark() call below,
3554     // the concurrent marking thread(s) could be running
3555     // concurrently with us. Make sure that anything after
3556     // this point does not assume that we are the only GC thread
3557     // running. Note: of course, the actual marking work will
3558     // not start until the safepoint itself is released in
3559     // SuspendibleThreadSet::desynchronize().
3560     doConcurrentMark();
3561   }
3562 
3563   return true;
3564 }
3565 
3566 void G1CollectedHeap::restore_preserved_marks() {
3567   G1RestorePreservedMarksTask rpm_task(_preserved_objs);
3568   workers()->run_task(&rpm_task);
3569 }
3570 
3571 void G1CollectedHeap::remove_self_forwarding_pointers() {
3572   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3573   workers()->run_task(&rsfp_task);
3574 }
3575 
3576 void G1CollectedHeap::restore_after_evac_failure() {
3577   double remove_self_forwards_start = os::elapsedTime();
3578 
3579   remove_self_forwarding_pointers();
3580   restore_preserved_marks();
3581 
3582   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3583 }
3584 
3585 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3586   if (!_evacuation_failed) {
3587     _evacuation_failed = true;
3588   }
3589 
3590   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3591 
3592   // We want to call the "for_promotion_failure" version only in the
3593   // case of a promotion failure.
3594   if (m->must_be_preserved_for_promotion_failure(obj)) {
3595     OopAndMarkOop elem(obj, m);
3596     _preserved_objs[worker_id].push(elem);
3597   }
3598 }
3599 
3600 bool G1ParEvacuateFollowersClosure::offer_termination() {
3601   G1ParScanThreadState* const pss = par_scan_state();
3602   start_term_time();
3603   const bool res = terminator()->offer_termination();
3604   end_term_time();
3605   return res;
3606 }
3607 
3608 void G1ParEvacuateFollowersClosure::do_void() {
3609   G1ParScanThreadState* const pss = par_scan_state();
3610   pss->trim_queue();
3611   do {
3612     pss->steal_and_trim_queue(queues());
3613   } while (!offer_termination());
3614 }
3615 
3616 class G1ParTask : public AbstractGangTask {
3617 protected:
3618   G1CollectedHeap*         _g1h;
3619   G1ParScanThreadStateSet* _pss;
3620   RefToScanQueueSet*       _queues;
3621   G1RootProcessor*         _root_processor;
3622   ParallelTaskTerminator   _terminator;
3623   uint                     _n_workers;
3624 
3625 public:
3626   G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3627     : AbstractGangTask("G1 collection"),
3628       _g1h(g1h),
3629       _pss(per_thread_states),
3630       _queues(task_queues),
3631       _root_processor(root_processor),
3632       _terminator(n_workers, _queues),
3633       _n_workers(n_workers)
3634   {}
3635 
3636   void work(uint worker_id) {
3637     if (worker_id >= _n_workers) return;  // no work needed this round
3638 
3639     double start_sec = os::elapsedTime();
3640     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3641 
3642     {
3643       ResourceMark rm;
3644       HandleMark   hm;
3645 
3646       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
3647 
3648       G1ParScanThreadState*           pss = _pss->state_for_worker(worker_id);
3649       pss->set_ref_processor(rp);
3650 
3651       double start_strong_roots_sec = os::elapsedTime();
3652 
3653       _root_processor->evacuate_roots(pss->closures(), worker_id);
3654 
3655       G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss);
3656 
3657       // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3658       // treating the nmethods visited to act as roots for concurrent marking.
3659       // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3660       // objects copied by the current evacuation.
3661       size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl,
3662                                                                              pss->closures()->weak_codeblobs(),
3663                                                                              worker_id);
3664 
3665       _pss->add_cards_scanned(worker_id, cards_scanned);
3666 
3667       double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3668 
3669       double term_sec = 0.0;
3670       size_t evac_term_attempts = 0;
3671       {
3672         double start = os::elapsedTime();
3673         G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3674         evac.do_void();
3675 
3676         evac_term_attempts = evac.term_attempts();
3677         term_sec = evac.term_time();
3678         double elapsed_sec = os::elapsedTime() - start;
3679         _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3680         _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3681         _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3682       }
3683 
3684       assert(pss->queue_is_empty(), "should be empty");
3685 
3686       if (log_is_enabled(Debug, gc, task, stats)) {
3687         MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3688         size_t lab_waste;
3689         size_t lab_undo_waste;
3690         pss->waste(lab_waste, lab_undo_waste);
3691         _g1h->print_termination_stats(worker_id,
3692                                       (os::elapsedTime() - start_sec) * 1000.0,   /* elapsed time */
3693                                       strong_roots_sec * 1000.0,                  /* strong roots time */
3694                                       term_sec * 1000.0,                          /* evac term time */
3695                                       evac_term_attempts,                         /* evac term attempts */
3696                                       lab_waste,                                  /* alloc buffer waste */
3697                                       lab_undo_waste                              /* undo waste */
3698                                       );
3699       }
3700 
3701       // Close the inner scope so that the ResourceMark and HandleMark
3702       // destructors are executed here and are included as part of the
3703       // "GC Worker Time".
3704     }
3705     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3706   }
3707 };
3708 
3709 void G1CollectedHeap::print_termination_stats_hdr() {
3710   log_debug(gc, task, stats)("GC Termination Stats");
3711   log_debug(gc, task, stats)("     elapsed  --strong roots-- -------termination------- ------waste (KiB)------");
3712   log_debug(gc, task, stats)("thr     ms        ms      %%        ms      %%    attempts  total   alloc    undo");
3713   log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3714 }
3715 
3716 void G1CollectedHeap::print_termination_stats(uint worker_id,
3717                                               double elapsed_ms,
3718                                               double strong_roots_ms,
3719                                               double term_ms,
3720                                               size_t term_attempts,
3721                                               size_t alloc_buffer_waste,
3722                                               size_t undo_waste) const {
3723   log_debug(gc, task, stats)
3724               ("%3d %9.2f %9.2f %6.2f "
3725                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3726                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3727                worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3728                term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3729                (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3730                alloc_buffer_waste * HeapWordSize / K,
3731                undo_waste * HeapWordSize / K);
3732 }
3733 
3734 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
3735 private:
3736   BoolObjectClosure* _is_alive;
3737   int _initial_string_table_size;
3738   int _initial_symbol_table_size;
3739 
3740   bool  _process_strings;
3741   int _strings_processed;
3742   int _strings_removed;
3743 
3744   bool  _process_symbols;
3745   int _symbols_processed;
3746   int _symbols_removed;
3747 
3748 public:
3749   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
3750     AbstractGangTask("String/Symbol Unlinking"),
3751     _is_alive(is_alive),
3752     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3753     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
3754 
3755     _initial_string_table_size = StringTable::the_table()->table_size();
3756     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3757     if (process_strings) {
3758       StringTable::clear_parallel_claimed_index();
3759     }
3760     if (process_symbols) {
3761       SymbolTable::clear_parallel_claimed_index();
3762     }
3763   }
3764 
3765   ~G1StringSymbolTableUnlinkTask() {
3766     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3767               "claim value %d after unlink less than initial string table size %d",
3768               StringTable::parallel_claimed_index(), _initial_string_table_size);
3769     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3770               "claim value %d after unlink less than initial symbol table size %d",
3771               SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3772 
3773     log_debug(gc, stringdedup)("Cleaned string and symbol table, "
3774                                "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3775                                "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3776                                strings_processed(), strings_removed(),
3777                                symbols_processed(), symbols_removed());
3778   }
3779 
3780   void work(uint worker_id) {
3781     int strings_processed = 0;
3782     int strings_removed = 0;
3783     int symbols_processed = 0;
3784     int symbols_removed = 0;
3785     if (_process_strings) {
3786       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3787       Atomic::add(strings_processed, &_strings_processed);
3788       Atomic::add(strings_removed, &_strings_removed);
3789     }
3790     if (_process_symbols) {
3791       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3792       Atomic::add(symbols_processed, &_symbols_processed);
3793       Atomic::add(symbols_removed, &_symbols_removed);
3794     }
3795   }
3796 
3797   size_t strings_processed() const { return (size_t)_strings_processed; }
3798   size_t strings_removed()   const { return (size_t)_strings_removed; }
3799 
3800   size_t symbols_processed() const { return (size_t)_symbols_processed; }
3801   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
3802 };
3803 
3804 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3805 private:
3806   static Monitor* _lock;
3807 
3808   BoolObjectClosure* const _is_alive;
3809   const bool               _unloading_occurred;
3810   const uint               _num_workers;
3811 
3812   // Variables used to claim nmethods.
3813   nmethod* _first_nmethod;
3814   volatile nmethod* _claimed_nmethod;
3815 
3816   // The list of nmethods that need to be processed by the second pass.
3817   volatile nmethod* _postponed_list;
3818   volatile uint     _num_entered_barrier;
3819 
3820  public:
3821   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3822       _is_alive(is_alive),
3823       _unloading_occurred(unloading_occurred),
3824       _num_workers(num_workers),
3825       _first_nmethod(NULL),
3826       _claimed_nmethod(NULL),
3827       _postponed_list(NULL),
3828       _num_entered_barrier(0)
3829   {
3830     nmethod::increase_unloading_clock();
3831     // Get first alive nmethod
3832     NMethodIterator iter = NMethodIterator();
3833     if(iter.next_alive()) {
3834       _first_nmethod = iter.method();
3835     }
3836     _claimed_nmethod = (volatile nmethod*)_first_nmethod;
3837   }
3838 
3839   ~G1CodeCacheUnloadingTask() {
3840     CodeCache::verify_clean_inline_caches();
3841 
3842     CodeCache::set_needs_cache_clean(false);
3843     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3844 
3845     CodeCache::verify_icholder_relocations();
3846   }
3847 
3848  private:
3849   void add_to_postponed_list(nmethod* nm) {
3850       nmethod* old;
3851       do {
3852         old = (nmethod*)_postponed_list;
3853         nm->set_unloading_next(old);
3854       } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
3855   }
3856 
3857   void clean_nmethod(nmethod* nm) {
3858     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3859 
3860     if (postponed) {
3861       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3862       add_to_postponed_list(nm);
3863     }
3864 
3865     // Mark that this thread has been cleaned/unloaded.
3866     // After this call, it will be safe to ask if this nmethod was unloaded or not.
3867     nm->set_unloading_clock(nmethod::global_unloading_clock());
3868   }
3869 
3870   void clean_nmethod_postponed(nmethod* nm) {
3871     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3872   }
3873 
3874   static const int MaxClaimNmethods = 16;
3875 
3876   void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
3877     nmethod* first;
3878     NMethodIterator last;
3879 
3880     do {
3881       *num_claimed_nmethods = 0;
3882 
3883       first = (nmethod*)_claimed_nmethod;
3884       last = NMethodIterator(first);
3885 
3886       if (first != NULL) {
3887 
3888         for (int i = 0; i < MaxClaimNmethods; i++) {
3889           if (!last.next_alive()) {
3890             break;
3891           }
3892           claimed_nmethods[i] = last.method();
3893           (*num_claimed_nmethods)++;
3894         }
3895       }
3896 
3897     } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
3898   }
3899 
3900   nmethod* claim_postponed_nmethod() {
3901     nmethod* claim;
3902     nmethod* next;
3903 
3904     do {
3905       claim = (nmethod*)_postponed_list;
3906       if (claim == NULL) {
3907         return NULL;
3908       }
3909 
3910       next = claim->unloading_next();
3911 
3912     } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
3913 
3914     return claim;
3915   }
3916 
3917  public:
3918   // Mark that we're done with the first pass of nmethod cleaning.
3919   void barrier_mark(uint worker_id) {
3920     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3921     _num_entered_barrier++;
3922     if (_num_entered_barrier == _num_workers) {
3923       ml.notify_all();
3924     }
3925   }
3926 
3927   // See if we have to wait for the other workers to
3928   // finish their first-pass nmethod cleaning work.
3929   void barrier_wait(uint worker_id) {
3930     if (_num_entered_barrier < _num_workers) {
3931       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3932       while (_num_entered_barrier < _num_workers) {
3933           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3934       }
3935     }
3936   }
3937 
3938   // Cleaning and unloading of nmethods. Some work has to be postponed
3939   // to the second pass, when we know which nmethods survive.
3940   void work_first_pass(uint worker_id) {
3941     // The first nmethods is claimed by the first worker.
3942     if (worker_id == 0 && _first_nmethod != NULL) {
3943       clean_nmethod(_first_nmethod);
3944       _first_nmethod = NULL;
3945     }
3946 
3947     int num_claimed_nmethods;
3948     nmethod* claimed_nmethods[MaxClaimNmethods];
3949 
3950     while (true) {
3951       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3952 
3953       if (num_claimed_nmethods == 0) {
3954         break;
3955       }
3956 
3957       for (int i = 0; i < num_claimed_nmethods; i++) {
3958         clean_nmethod(claimed_nmethods[i]);
3959       }
3960     }
3961   }
3962 
3963   void work_second_pass(uint worker_id) {
3964     nmethod* nm;
3965     // Take care of postponed nmethods.
3966     while ((nm = claim_postponed_nmethod()) != NULL) {
3967       clean_nmethod_postponed(nm);
3968     }
3969   }
3970 };
3971 
3972 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3973 
3974 class G1KlassCleaningTask : public StackObj {
3975   BoolObjectClosure*                      _is_alive;
3976   volatile jint                           _clean_klass_tree_claimed;
3977   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3978 
3979  public:
3980   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3981       _is_alive(is_alive),
3982       _clean_klass_tree_claimed(0),
3983       _klass_iterator() {
3984   }
3985 
3986  private:
3987   bool claim_clean_klass_tree_task() {
3988     if (_clean_klass_tree_claimed) {
3989       return false;
3990     }
3991 
3992     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
3993   }
3994 
3995   InstanceKlass* claim_next_klass() {
3996     Klass* klass;
3997     do {
3998       klass =_klass_iterator.next_klass();
3999     } while (klass != NULL && !klass->is_instance_klass());
4000 
4001     // this can be null so don't call InstanceKlass::cast
4002     return static_cast<InstanceKlass*>(klass);
4003   }
4004 
4005 public:
4006 
4007   void clean_klass(InstanceKlass* ik) {
4008     ik->clean_weak_instanceklass_links(_is_alive);
4009   }
4010 
4011   void work() {
4012     ResourceMark rm;
4013 
4014     // One worker will clean the subklass/sibling klass tree.
4015     if (claim_clean_klass_tree_task()) {
4016       Klass::clean_subklass_tree(_is_alive);
4017     }
4018 
4019     // All workers will help cleaning the classes,
4020     InstanceKlass* klass;
4021     while ((klass = claim_next_klass()) != NULL) {
4022       clean_klass(klass);
4023     }
4024   }
4025 };
4026 
4027 // To minimize the remark pause times, the tasks below are done in parallel.
4028 class G1ParallelCleaningTask : public AbstractGangTask {
4029 private:
4030   G1StringSymbolTableUnlinkTask _string_symbol_task;
4031   G1CodeCacheUnloadingTask      _code_cache_task;
4032   G1KlassCleaningTask           _klass_cleaning_task;
4033 
4034 public:
4035   // The constructor is run in the VMThread.
4036   G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
4037       AbstractGangTask("Parallel Cleaning"),
4038       _string_symbol_task(is_alive, process_strings, process_symbols),
4039       _code_cache_task(num_workers, is_alive, unloading_occurred),
4040       _klass_cleaning_task(is_alive) {
4041   }
4042 
4043   // The parallel work done by all worker threads.
4044   void work(uint worker_id) {
4045     // Do first pass of code cache cleaning.
4046     _code_cache_task.work_first_pass(worker_id);
4047 
4048     // Let the threads mark that the first pass is done.
4049     _code_cache_task.barrier_mark(worker_id);
4050 
4051     // Clean the Strings and Symbols.
4052     _string_symbol_task.work(worker_id);
4053 
4054     // Wait for all workers to finish the first code cache cleaning pass.
4055     _code_cache_task.barrier_wait(worker_id);
4056 
4057     // Do the second code cache cleaning work, which realize on
4058     // the liveness information gathered during the first pass.
4059     _code_cache_task.work_second_pass(worker_id);
4060 
4061     // Clean all klasses that were not unloaded.
4062     _klass_cleaning_task.work();
4063   }
4064 };
4065 
4066 
4067 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
4068                                         bool process_strings,
4069                                         bool process_symbols,
4070                                         bool class_unloading_occurred) {
4071   uint n_workers = workers()->active_workers();
4072 
4073   G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
4074                                         n_workers, class_unloading_occurred);
4075   workers()->run_task(&g1_unlink_task);
4076 }
4077 
4078 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
4079                                                      bool process_strings, bool process_symbols) {
4080   {
4081     G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
4082     workers()->run_task(&g1_unlink_task);
4083   }
4084 
4085   if (G1StringDedup::is_enabled()) {
4086     G1StringDedup::unlink(is_alive);
4087   }
4088 }
4089 
4090 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
4091  private:
4092   DirtyCardQueueSet* _queue;
4093   G1CollectedHeap* _g1h;
4094  public:
4095   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
4096     _queue(queue), _g1h(g1h) { }
4097 
4098   virtual void work(uint worker_id) {
4099     G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
4100     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
4101 
4102     RedirtyLoggedCardTableEntryClosure cl(_g1h);
4103     _queue->par_apply_closure_to_all_completed_buffers(&cl);
4104 
4105     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
4106   }
4107 };
4108 
4109 void G1CollectedHeap::redirty_logged_cards() {
4110   double redirty_logged_cards_start = os::elapsedTime();
4111 
4112   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
4113   dirty_card_queue_set().reset_for_par_iteration();
4114   workers()->run_task(&redirty_task);
4115 
4116   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
4117   dcq.merge_bufferlists(&dirty_card_queue_set());
4118   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
4119 
4120   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
4121 }
4122 
4123 // Weak Reference Processing support
4124 
4125 // An always "is_alive" closure that is used to preserve referents.
4126 // If the object is non-null then it's alive.  Used in the preservation
4127 // of referent objects that are pointed to by reference objects
4128 // discovered by the CM ref processor.
4129 class G1AlwaysAliveClosure: public BoolObjectClosure {
4130   G1CollectedHeap* _g1;
4131 public:
4132   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4133   bool do_object_b(oop p) {
4134     if (p != NULL) {
4135       return true;
4136     }
4137     return false;
4138   }
4139 };
4140 
4141 bool G1STWIsAliveClosure::do_object_b(oop p) {
4142   // An object is reachable if it is outside the collection set,
4143   // or is inside and copied.
4144   return !_g1->is_in_cset(p) || p->is_forwarded();
4145 }
4146 
4147 // Non Copying Keep Alive closure
4148 class G1KeepAliveClosure: public OopClosure {
4149   G1CollectedHeap* _g1;
4150 public:
4151   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4152   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
4153   void do_oop(oop* p) {
4154     oop obj = *p;
4155     assert(obj != NULL, "the caller should have filtered out NULL values");
4156 
4157     const InCSetState cset_state = _g1->in_cset_state(obj);
4158     if (!cset_state.is_in_cset_or_humongous()) {
4159       return;
4160     }
4161     if (cset_state.is_in_cset()) {
4162       assert( obj->is_forwarded(), "invariant" );
4163       *p = obj->forwardee();
4164     } else {
4165       assert(!obj->is_forwarded(), "invariant" );
4166       assert(cset_state.is_humongous(),
4167              "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
4168       _g1->set_humongous_is_live(obj);
4169     }
4170   }
4171 };
4172 
4173 // Copying Keep Alive closure - can be called from both
4174 // serial and parallel code as long as different worker
4175 // threads utilize different G1ParScanThreadState instances
4176 // and different queues.
4177 
4178 class G1CopyingKeepAliveClosure: public OopClosure {
4179   G1CollectedHeap*         _g1h;
4180   OopClosure*              _copy_non_heap_obj_cl;
4181   G1ParScanThreadState*    _par_scan_state;
4182 
4183 public:
4184   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
4185                             OopClosure* non_heap_obj_cl,
4186                             G1ParScanThreadState* pss):
4187     _g1h(g1h),
4188     _copy_non_heap_obj_cl(non_heap_obj_cl),
4189     _par_scan_state(pss)
4190   {}
4191 
4192   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
4193   virtual void do_oop(      oop* p) { do_oop_work(p); }
4194 
4195   template <class T> void do_oop_work(T* p) {
4196     oop obj = oopDesc::load_decode_heap_oop(p);
4197 
4198     if (_g1h->is_in_cset_or_humongous(obj)) {
4199       // If the referent object has been forwarded (either copied
4200       // to a new location or to itself in the event of an
4201       // evacuation failure) then we need to update the reference
4202       // field and, if both reference and referent are in the G1
4203       // heap, update the RSet for the referent.
4204       //
4205       // If the referent has not been forwarded then we have to keep
4206       // it alive by policy. Therefore we have copy the referent.
4207       //
4208       // If the reference field is in the G1 heap then we can push
4209       // on the PSS queue. When the queue is drained (after each
4210       // phase of reference processing) the object and it's followers
4211       // will be copied, the reference field set to point to the
4212       // new location, and the RSet updated. Otherwise we need to
4213       // use the the non-heap or metadata closures directly to copy
4214       // the referent object and update the pointer, while avoiding
4215       // updating the RSet.
4216 
4217       if (_g1h->is_in_g1_reserved(p)) {
4218         _par_scan_state->push_on_queue(p);
4219       } else {
4220         assert(!Metaspace::contains((const void*)p),
4221                "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
4222         _copy_non_heap_obj_cl->do_oop(p);
4223       }
4224     }
4225   }
4226 };
4227 
4228 // Serial drain queue closure. Called as the 'complete_gc'
4229 // closure for each discovered list in some of the
4230 // reference processing phases.
4231 
4232 class G1STWDrainQueueClosure: public VoidClosure {
4233 protected:
4234   G1CollectedHeap* _g1h;
4235   G1ParScanThreadState* _par_scan_state;
4236 
4237   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4238 
4239 public:
4240   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
4241     _g1h(g1h),
4242     _par_scan_state(pss)
4243   { }
4244 
4245   void do_void() {
4246     G1ParScanThreadState* const pss = par_scan_state();
4247     pss->trim_queue();
4248   }
4249 };
4250 
4251 // Parallel Reference Processing closures
4252 
4253 // Implementation of AbstractRefProcTaskExecutor for parallel reference
4254 // processing during G1 evacuation pauses.
4255 
4256 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
4257 private:
4258   G1CollectedHeap*          _g1h;
4259   G1ParScanThreadStateSet*  _pss;
4260   RefToScanQueueSet*        _queues;
4261   WorkGang*                 _workers;
4262   uint                      _active_workers;
4263 
4264 public:
4265   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
4266                            G1ParScanThreadStateSet* per_thread_states,
4267                            WorkGang* workers,
4268                            RefToScanQueueSet *task_queues,
4269                            uint n_workers) :
4270     _g1h(g1h),
4271     _pss(per_thread_states),
4272     _queues(task_queues),
4273     _workers(workers),
4274     _active_workers(n_workers)
4275   {
4276     assert(n_workers > 0, "shouldn't call this otherwise");
4277   }
4278 
4279   // Executes the given task using concurrent marking worker threads.
4280   virtual void execute(ProcessTask& task);
4281   virtual void execute(EnqueueTask& task);
4282 };
4283 
4284 // Gang task for possibly parallel reference processing
4285 
4286 class G1STWRefProcTaskProxy: public AbstractGangTask {
4287   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
4288   ProcessTask&     _proc_task;
4289   G1CollectedHeap* _g1h;
4290   G1ParScanThreadStateSet* _pss;
4291   RefToScanQueueSet* _task_queues;
4292   ParallelTaskTerminator* _terminator;
4293 
4294 public:
4295   G1STWRefProcTaskProxy(ProcessTask& proc_task,
4296                         G1CollectedHeap* g1h,
4297                         G1ParScanThreadStateSet* per_thread_states,
4298                         RefToScanQueueSet *task_queues,
4299                         ParallelTaskTerminator* terminator) :
4300     AbstractGangTask("Process reference objects in parallel"),
4301     _proc_task(proc_task),
4302     _g1h(g1h),
4303     _pss(per_thread_states),
4304     _task_queues(task_queues),
4305     _terminator(terminator)
4306   {}
4307 
4308   virtual void work(uint worker_id) {
4309     // The reference processing task executed by a single worker.
4310     ResourceMark rm;
4311     HandleMark   hm;
4312 
4313     G1STWIsAliveClosure is_alive(_g1h);
4314 
4315     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4316     pss->set_ref_processor(NULL);
4317 
4318     // Keep alive closure.
4319     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4320 
4321     // Complete GC closure
4322     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
4323 
4324     // Call the reference processing task's work routine.
4325     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
4326 
4327     // Note we cannot assert that the refs array is empty here as not all
4328     // of the processing tasks (specifically phase2 - pp2_work) execute
4329     // the complete_gc closure (which ordinarily would drain the queue) so
4330     // the queue may not be empty.
4331   }
4332 };
4333 
4334 // Driver routine for parallel reference processing.
4335 // Creates an instance of the ref processing gang
4336 // task and has the worker threads execute it.
4337 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4338   assert(_workers != NULL, "Need parallel worker threads.");
4339 
4340   ParallelTaskTerminator terminator(_active_workers, _queues);
4341   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4342 
4343   _workers->run_task(&proc_task_proxy);
4344 }
4345 
4346 // Gang task for parallel reference enqueueing.
4347 
4348 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4349   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4350   EnqueueTask& _enq_task;
4351 
4352 public:
4353   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4354     AbstractGangTask("Enqueue reference objects in parallel"),
4355     _enq_task(enq_task)
4356   { }
4357 
4358   virtual void work(uint worker_id) {
4359     _enq_task.work(worker_id);
4360   }
4361 };
4362 
4363 // Driver routine for parallel reference enqueueing.
4364 // Creates an instance of the ref enqueueing gang
4365 // task and has the worker threads execute it.
4366 
4367 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4368   assert(_workers != NULL, "Need parallel worker threads.");
4369 
4370   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4371 
4372   _workers->run_task(&enq_task_proxy);
4373 }
4374 
4375 // End of weak reference support closures
4376 
4377 // Abstract task used to preserve (i.e. copy) any referent objects
4378 // that are in the collection set and are pointed to by reference
4379 // objects discovered by the CM ref processor.
4380 
4381 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4382 protected:
4383   G1CollectedHeap*         _g1h;
4384   G1ParScanThreadStateSet* _pss;
4385   RefToScanQueueSet*       _queues;
4386   ParallelTaskTerminator   _terminator;
4387   uint                     _n_workers;
4388 
4389 public:
4390   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4391     AbstractGangTask("ParPreserveCMReferents"),
4392     _g1h(g1h),
4393     _pss(per_thread_states),
4394     _queues(task_queues),
4395     _terminator(workers, _queues),
4396     _n_workers(workers)
4397   { }
4398 
4399   void work(uint worker_id) {
4400     ResourceMark rm;
4401     HandleMark   hm;
4402 
4403     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4404     pss->set_ref_processor(NULL);
4405     assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4406 
4407     // Is alive closure
4408     G1AlwaysAliveClosure always_alive(_g1h);
4409 
4410     // Copying keep alive closure. Applied to referent objects that need
4411     // to be copied.
4412     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4413 
4414     ReferenceProcessor* rp = _g1h->ref_processor_cm();
4415 
4416     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4417     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4418 
4419     // limit is set using max_num_q() - which was set using ParallelGCThreads.
4420     // So this must be true - but assert just in case someone decides to
4421     // change the worker ids.
4422     assert(worker_id < limit, "sanity");
4423     assert(!rp->discovery_is_atomic(), "check this code");
4424 
4425     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4426     for (uint idx = worker_id; idx < limit; idx += stride) {
4427       DiscoveredList& ref_list = rp->discovered_refs()[idx];
4428 
4429       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4430       while (iter.has_next()) {
4431         // Since discovery is not atomic for the CM ref processor, we
4432         // can see some null referent objects.
4433         iter.load_ptrs(DEBUG_ONLY(true));
4434         oop ref = iter.obj();
4435 
4436         // This will filter nulls.
4437         if (iter.is_referent_alive()) {
4438           iter.make_referent_alive();
4439         }
4440         iter.move_to_next();
4441       }
4442     }
4443 
4444     // Drain the queue - which may cause stealing
4445     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4446     drain_queue.do_void();
4447     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4448     assert(pss->queue_is_empty(), "should be");
4449   }
4450 };
4451 
4452 void G1CollectedHeap::process_weak_jni_handles() {
4453   double ref_proc_start = os::elapsedTime();
4454 
4455   G1STWIsAliveClosure is_alive(this);
4456   G1KeepAliveClosure keep_alive(this);
4457   JNIHandles::weak_oops_do(&is_alive, &keep_alive);
4458 
4459   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4460   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4461 }
4462 
4463 // Weak Reference processing during an evacuation pause (part 1).
4464 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4465   double ref_proc_start = os::elapsedTime();
4466 
4467   ReferenceProcessor* rp = _ref_processor_stw;
4468   assert(rp->discovery_enabled(), "should have been enabled");
4469 
4470   // Any reference objects, in the collection set, that were 'discovered'
4471   // by the CM ref processor should have already been copied (either by
4472   // applying the external root copy closure to the discovered lists, or
4473   // by following an RSet entry).
4474   //
4475   // But some of the referents, that are in the collection set, that these
4476   // reference objects point to may not have been copied: the STW ref
4477   // processor would have seen that the reference object had already
4478   // been 'discovered' and would have skipped discovering the reference,
4479   // but would not have treated the reference object as a regular oop.
4480   // As a result the copy closure would not have been applied to the
4481   // referent object.
4482   //
4483   // We need to explicitly copy these referent objects - the references
4484   // will be processed at the end of remarking.
4485   //
4486   // We also need to do this copying before we process the reference
4487   // objects discovered by the STW ref processor in case one of these
4488   // referents points to another object which is also referenced by an
4489   // object discovered by the STW ref processor.
4490 
4491   uint no_of_gc_workers = workers()->active_workers();
4492 
4493   G1ParPreserveCMReferentsTask keep_cm_referents(this,
4494                                                  per_thread_states,
4495                                                  no_of_gc_workers,
4496                                                  _task_queues);
4497 
4498   workers()->run_task(&keep_cm_referents);
4499 
4500   // Closure to test whether a referent is alive.
4501   G1STWIsAliveClosure is_alive(this);
4502 
4503   // Even when parallel reference processing is enabled, the processing
4504   // of JNI refs is serial and performed serially by the current thread
4505   // rather than by a worker. The following PSS will be used for processing
4506   // JNI refs.
4507 
4508   // Use only a single queue for this PSS.
4509   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
4510   pss->set_ref_processor(NULL);
4511   assert(pss->queue_is_empty(), "pre-condition");
4512 
4513   // Keep alive closure.
4514   G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4515 
4516   // Serial Complete GC closure
4517   G1STWDrainQueueClosure drain_queue(this, pss);
4518 
4519   // Setup the soft refs policy...
4520   rp->setup_policy(false);
4521 
4522   ReferenceProcessorStats stats;
4523   if (!rp->processing_is_mt()) {
4524     // Serial reference processing...
4525     stats = rp->process_discovered_references(&is_alive,
4526                                               &keep_alive,
4527                                               &drain_queue,
4528                                               NULL,
4529                                               _gc_timer_stw);
4530   } else {
4531     // Parallel reference processing
4532     assert(rp->num_q() == no_of_gc_workers, "sanity");
4533     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
4534 
4535     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4536     stats = rp->process_discovered_references(&is_alive,
4537                                               &keep_alive,
4538                                               &drain_queue,
4539                                               &par_task_executor,
4540                                               _gc_timer_stw);
4541   }
4542 
4543   _gc_tracer_stw->report_gc_reference_stats(stats);
4544 
4545   // We have completed copying any necessary live referent objects.
4546   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4547 
4548   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4549   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4550 }
4551 
4552 // Weak Reference processing during an evacuation pause (part 2).
4553 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4554   double ref_enq_start = os::elapsedTime();
4555 
4556   ReferenceProcessor* rp = _ref_processor_stw;
4557   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4558 
4559   // Now enqueue any remaining on the discovered lists on to
4560   // the pending list.
4561   if (!rp->processing_is_mt()) {
4562     // Serial reference processing...
4563     rp->enqueue_discovered_references();
4564   } else {
4565     // Parallel reference enqueueing
4566 
4567     uint n_workers = workers()->active_workers();
4568 
4569     assert(rp->num_q() == n_workers, "sanity");
4570     assert(n_workers <= rp->max_num_q(), "sanity");
4571 
4572     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4573     rp->enqueue_discovered_references(&par_task_executor);
4574   }
4575 
4576   rp->verify_no_references_recorded();
4577   assert(!rp->discovery_enabled(), "should have been disabled");
4578 
4579   // FIXME
4580   // CM's reference processing also cleans up the string and symbol tables.
4581   // Should we do that here also? We could, but it is a serial operation
4582   // and could significantly increase the pause time.
4583 
4584   double ref_enq_time = os::elapsedTime() - ref_enq_start;
4585   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4586 }
4587 
4588 void G1CollectedHeap::pre_evacuate_collection_set() {
4589   _expand_heap_after_alloc_failure = true;
4590   _evacuation_failed = false;
4591 
4592   // Disable the hot card cache.
4593   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
4594   hot_card_cache->reset_hot_cache_claimed_index();
4595   hot_card_cache->set_use_cache(false);
4596 
4597   g1_rem_set()->prepare_for_oops_into_collection_set_do();
4598 }
4599 
4600 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4601   // Should G1EvacuationFailureALot be in effect for this GC?
4602   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4603 
4604   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4605   double start_par_time_sec = os::elapsedTime();
4606   double end_par_time_sec;
4607 
4608   {
4609     const uint n_workers = workers()->active_workers();
4610     G1RootProcessor root_processor(this, n_workers);
4611     G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4612     // InitialMark needs claim bits to keep track of the marked-through CLDs.
4613     if (collector_state()->during_initial_mark_pause()) {
4614       ClassLoaderDataGraph::clear_claimed_marks();
4615     }
4616 
4617     print_termination_stats_hdr();
4618 
4619     workers()->run_task(&g1_par_task);
4620     end_par_time_sec = os::elapsedTime();
4621 
4622     // Closing the inner scope will execute the destructor
4623     // for the G1RootProcessor object. We record the current
4624     // elapsed time before closing the scope so that time
4625     // taken for the destructor is NOT included in the
4626     // reported parallel time.
4627   }
4628 
4629   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4630 
4631   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4632   phase_times->record_par_time(par_time_ms);
4633 
4634   double code_root_fixup_time_ms =
4635         (os::elapsedTime() - end_par_time_sec) * 1000.0;
4636   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4637 }
4638 
4639 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4640   // Process any discovered reference objects - we have
4641   // to do this _before_ we retire the GC alloc regions
4642   // as we may have to copy some 'reachable' referent
4643   // objects (and their reachable sub-graphs) that were
4644   // not copied during the pause.
4645   if (g1_policy()->should_process_references()) {
4646     process_discovered_references(per_thread_states);
4647   } else {
4648     ref_processor_stw()->verify_no_references_recorded();
4649     process_weak_jni_handles();
4650   }
4651 
4652   if (G1StringDedup::is_enabled()) {
4653     double fixup_start = os::elapsedTime();
4654 
4655     G1STWIsAliveClosure is_alive(this);
4656     G1KeepAliveClosure keep_alive(this);
4657     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4658 
4659     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4660     g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4661   }
4662 
4663   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4664 
4665   if (evacuation_failed()) {
4666     restore_after_evac_failure();
4667 
4668     // Reset the G1EvacuationFailureALot counters and flags
4669     // Note: the values are reset only when an actual
4670     // evacuation failure occurs.
4671     NOT_PRODUCT(reset_evacuation_should_fail();)
4672   }
4673 
4674   // Enqueue any remaining references remaining on the STW
4675   // reference processor's discovered lists. We need to do
4676   // this after the card table is cleaned (and verified) as
4677   // the act of enqueueing entries on to the pending list
4678   // will log these updates (and dirty their associated
4679   // cards). We need these updates logged to update any
4680   // RSets.
4681   if (g1_policy()->should_process_references()) {
4682     enqueue_discovered_references(per_thread_states);
4683   } else {
4684     g1_policy()->phase_times()->record_ref_enq_time(0);
4685   }
4686 
4687   _allocator->release_gc_alloc_regions(evacuation_info);
4688 
4689   per_thread_states->flush();
4690 
4691   record_obj_copy_mem_stats();
4692 
4693   _survivor_evac_stats.adjust_desired_plab_sz();
4694   _old_evac_stats.adjust_desired_plab_sz();
4695 
4696   // Reset and re-enable the hot card cache.
4697   // Note the counts for the cards in the regions in the
4698   // collection set are reset when the collection set is freed.
4699   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
4700   hot_card_cache->reset_hot_cache();
4701   hot_card_cache->set_use_cache(true);
4702 
4703   purge_code_root_memory();
4704 
4705   redirty_logged_cards();
4706 #if defined(COMPILER2) || INCLUDE_JVMCI
4707   DerivedPointerTable::update_pointers();
4708 #endif
4709 }
4710 
4711 void G1CollectedHeap::record_obj_copy_mem_stats() {
4712   g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4713 
4714   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4715                                                create_g1_evac_summary(&_old_evac_stats));
4716 }
4717 
4718 void G1CollectedHeap::free_region(HeapRegion* hr,
4719                                   FreeRegionList* free_list,
4720                                   bool par,
4721                                   bool locked) {
4722   assert(!hr->is_free(), "the region should not be free");
4723   assert(!hr->is_empty(), "the region should not be empty");
4724   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4725   assert(free_list != NULL, "pre-condition");
4726 
4727   if (G1VerifyBitmaps) {
4728     MemRegion mr(hr->bottom(), hr->end());
4729     concurrent_mark()->clearRangePrevBitmap(mr);
4730   }
4731 
4732   // Clear the card counts for this region.
4733   // Note: we only need to do this if the region is not young
4734   // (since we don't refine cards in young regions).
4735   if (!hr->is_young()) {
4736     _cg1r->hot_card_cache()->reset_card_counts(hr);
4737   }
4738   hr->hr_clear(par, true /* clear_space */, locked /* locked */);
4739   free_list->add_ordered(hr);
4740 }
4741 
4742 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4743                                             FreeRegionList* free_list,
4744                                             bool par) {
4745   assert(hr->is_humongous(), "this is only for humongous regions");
4746   assert(free_list != NULL, "pre-condition");
4747   hr->clear_humongous();
4748   free_region(hr, free_list, par);
4749 }
4750 
4751 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4752                                            const uint humongous_regions_removed) {
4753   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4754     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4755     _old_set.bulk_remove(old_regions_removed);
4756     _humongous_set.bulk_remove(humongous_regions_removed);
4757   }
4758 
4759 }
4760 
4761 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4762   assert(list != NULL, "list can't be null");
4763   if (!list->is_empty()) {
4764     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4765     _hrm.insert_list_into_free_list(list);
4766   }
4767 }
4768 
4769 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4770   decrease_used(bytes);
4771 }
4772 
4773 class G1ParCleanupCTTask : public AbstractGangTask {
4774   G1SATBCardTableModRefBS* _ct_bs;
4775   G1CollectedHeap* _g1h;
4776   HeapRegion* volatile _su_head;
4777 public:
4778   G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
4779                      G1CollectedHeap* g1h) :
4780     AbstractGangTask("G1 Par Cleanup CT Task"),
4781     _ct_bs(ct_bs), _g1h(g1h) { }
4782 
4783   void work(uint worker_id) {
4784     HeapRegion* r;
4785     while (r = _g1h->pop_dirty_cards_region()) {
4786       clear_cards(r);
4787     }
4788   }
4789 
4790   void clear_cards(HeapRegion* r) {
4791     // Cards of the survivors should have already been dirtied.
4792     if (!r->is_survivor()) {
4793       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
4794     }
4795   }
4796 };
4797 
4798 class G1ParScrubRemSetTask: public AbstractGangTask {
4799 protected:
4800   G1RemSet* _g1rs;
4801   BitMap* _region_bm;
4802   BitMap* _card_bm;
4803   HeapRegionClaimer _hrclaimer;
4804 
4805 public:
4806   G1ParScrubRemSetTask(G1RemSet* g1_rs, BitMap* region_bm, BitMap* card_bm, uint num_workers) :
4807     AbstractGangTask("G1 ScrubRS"),
4808     _g1rs(g1_rs),
4809     _region_bm(region_bm),
4810     _card_bm(card_bm),
4811     _hrclaimer(num_workers) {
4812   }
4813 
4814   void work(uint worker_id) {
4815     _g1rs->scrub(_region_bm, _card_bm, worker_id, &_hrclaimer);
4816   }
4817 };
4818 
4819 void G1CollectedHeap::scrub_rem_set(BitMap* region_bm, BitMap* card_bm) {
4820   uint num_workers = workers()->active_workers();
4821   G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), region_bm, card_bm, num_workers);
4822   workers()->run_task(&g1_par_scrub_rs_task);
4823 }
4824 
4825 void G1CollectedHeap::cleanUpCardTable() {
4826   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
4827   double start = os::elapsedTime();
4828 
4829   {
4830     // Iterate over the dirty cards region list.
4831     G1ParCleanupCTTask cleanup_task(ct_bs, this);
4832 
4833     workers()->run_task(&cleanup_task);
4834 #ifndef PRODUCT
4835     _verifier->verify_card_table_cleanup();
4836 #endif
4837   }
4838 
4839   double elapsed = os::elapsedTime() - start;
4840   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
4841 }
4842 
4843 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4844   size_t pre_used = 0;
4845   FreeRegionList local_free_list("Local List for CSet Freeing");
4846 
4847   double young_time_ms     = 0.0;
4848   double non_young_time_ms = 0.0;
4849 
4850   // Since the collection set is a superset of the the young list,
4851   // all we need to do to clear the young list is clear its
4852   // head and length, and unlink any young regions in the code below
4853   _young_list->clear();
4854 
4855   G1CollectorPolicy* policy = g1_policy();
4856 
4857   double start_sec = os::elapsedTime();
4858   bool non_young = true;
4859 
4860   HeapRegion* cur = cs_head;
4861   int age_bound = -1;
4862   size_t rs_lengths = 0;
4863 
4864   while (cur != NULL) {
4865     assert(!is_on_master_free_list(cur), "sanity");
4866     if (non_young) {
4867       if (cur->is_young()) {
4868         double end_sec = os::elapsedTime();
4869         double elapsed_ms = (end_sec - start_sec) * 1000.0;
4870         non_young_time_ms += elapsed_ms;
4871 
4872         start_sec = os::elapsedTime();
4873         non_young = false;
4874       }
4875     } else {
4876       if (!cur->is_young()) {
4877         double end_sec = os::elapsedTime();
4878         double elapsed_ms = (end_sec - start_sec) * 1000.0;
4879         young_time_ms += elapsed_ms;
4880 
4881         start_sec = os::elapsedTime();
4882         non_young = true;
4883       }
4884     }
4885 
4886     rs_lengths += cur->rem_set()->occupied_locked();
4887 
4888     HeapRegion* next = cur->next_in_collection_set();
4889     assert(cur->in_collection_set(), "bad CS");
4890     cur->set_next_in_collection_set(NULL);
4891     clear_in_cset(cur);
4892 
4893     if (cur->is_young()) {
4894       int index = cur->young_index_in_cset();
4895       assert(index != -1, "invariant");
4896       assert((uint) index < policy->young_cset_region_length(), "invariant");
4897       size_t words_survived = surviving_young_words[index];
4898       cur->record_surv_words_in_group(words_survived);
4899 
4900       // At this point the we have 'popped' cur from the collection set
4901       // (linked via next_in_collection_set()) but it is still in the
4902       // young list (linked via next_young_region()). Clear the
4903       // _next_young_region field.
4904       cur->set_next_young_region(NULL);
4905     } else {
4906       int index = cur->young_index_in_cset();
4907       assert(index == -1, "invariant");
4908     }
4909 
4910     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
4911             (!cur->is_young() && cur->young_index_in_cset() == -1),
4912             "invariant" );
4913 
4914     if (!cur->evacuation_failed()) {
4915       MemRegion used_mr = cur->used_region();
4916 
4917       // And the region is empty.
4918       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
4919       pre_used += cur->used();
4920       free_region(cur, &local_free_list, false /* par */, true /* locked */);
4921     } else {
4922       cur->uninstall_surv_rate_group();
4923       if (cur->is_young()) {
4924         cur->set_young_index_in_cset(-1);
4925       }
4926       cur->set_evacuation_failed(false);
4927       // When moving a young gen region to old gen, we "allocate" that whole region
4928       // there. This is in addition to any already evacuated objects. Notify the
4929       // policy about that.
4930       // Old gen regions do not cause an additional allocation: both the objects
4931       // still in the region and the ones already moved are accounted for elsewhere.
4932       if (cur->is_young()) {
4933         policy->add_bytes_allocated_in_old_since_last_gc(HeapRegion::GrainBytes);
4934       }
4935       // The region is now considered to be old.
4936       cur->set_old();
4937       // Do some allocation statistics accounting. Regions that failed evacuation
4938       // are always made old, so there is no need to update anything in the young
4939       // gen statistics, but we need to update old gen statistics.
4940       size_t used_words = cur->marked_bytes() / HeapWordSize;
4941       _old_evac_stats.add_failure_used_and_waste(used_words, HeapRegion::GrainWords - used_words);
4942       _old_set.add(cur);
4943       evacuation_info.increment_collectionset_used_after(cur->used());
4944     }
4945     cur = next;
4946   }
4947 
4948   evacuation_info.set_regions_freed(local_free_list.length());
4949   policy->record_max_rs_lengths(rs_lengths);
4950   policy->cset_regions_freed();
4951 
4952   double end_sec = os::elapsedTime();
4953   double elapsed_ms = (end_sec - start_sec) * 1000.0;
4954 
4955   if (non_young) {
4956     non_young_time_ms += elapsed_ms;
4957   } else {
4958     young_time_ms += elapsed_ms;
4959   }
4960 
4961   prepend_to_freelist(&local_free_list);
4962   decrement_summary_bytes(pre_used);
4963   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
4964   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
4965 }
4966 
4967 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4968  private:
4969   FreeRegionList* _free_region_list;
4970   HeapRegionSet* _proxy_set;
4971   uint _humongous_regions_removed;
4972   size_t _freed_bytes;
4973  public:
4974 
4975   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4976     _free_region_list(free_region_list), _humongous_regions_removed(0), _freed_bytes(0) {
4977   }
4978 
4979   virtual bool doHeapRegion(HeapRegion* r) {
4980     if (!r->is_starts_humongous()) {
4981       return false;
4982     }
4983 
4984     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4985 
4986     oop obj = (oop)r->bottom();
4987     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
4988 
4989     // The following checks whether the humongous object is live are sufficient.
4990     // The main additional check (in addition to having a reference from the roots
4991     // or the young gen) is whether the humongous object has a remembered set entry.
4992     //
4993     // A humongous object cannot be live if there is no remembered set for it
4994     // because:
4995     // - there can be no references from within humongous starts regions referencing
4996     // the object because we never allocate other objects into them.
4997     // (I.e. there are no intra-region references that may be missed by the
4998     // remembered set)
4999     // - as soon there is a remembered set entry to the humongous starts region
5000     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
5001     // until the end of a concurrent mark.
5002     //
5003     // It is not required to check whether the object has been found dead by marking
5004     // or not, in fact it would prevent reclamation within a concurrent cycle, as
5005     // all objects allocated during that time are considered live.
5006     // SATB marking is even more conservative than the remembered set.
5007     // So if at this point in the collection there is no remembered set entry,
5008     // nobody has a reference to it.
5009     // At the start of collection we flush all refinement logs, and remembered sets
5010     // are completely up-to-date wrt to references to the humongous object.
5011     //
5012     // Other implementation considerations:
5013     // - never consider object arrays at this time because they would pose
5014     // considerable effort for cleaning up the the remembered sets. This is
5015     // required because stale remembered sets might reference locations that
5016     // are currently allocated into.
5017     uint region_idx = r->hrm_index();
5018     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
5019         !r->rem_set()->is_empty()) {
5020       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",
5021                                region_idx,
5022                                (size_t)obj->size() * HeapWordSize,
5023                                p2i(r->bottom()),
5024                                r->rem_set()->occupied(),
5025                                r->rem_set()->strong_code_roots_list_length(),
5026                                next_bitmap->isMarked(r->bottom()),
5027                                g1h->is_humongous_reclaim_candidate(region_idx),
5028                                obj->is_typeArray()
5029                               );
5030       return false;
5031     }
5032 
5033     guarantee(obj->is_typeArray(),
5034               "Only eagerly reclaiming type arrays is supported, but the object "
5035               PTR_FORMAT " is not.", p2i(r->bottom()));
5036 
5037     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",
5038                              region_idx,
5039                              (size_t)obj->size() * HeapWordSize,
5040                              p2i(r->bottom()),
5041                              r->rem_set()->occupied(),
5042                              r->rem_set()->strong_code_roots_list_length(),
5043                              next_bitmap->isMarked(r->bottom()),
5044                              g1h->is_humongous_reclaim_candidate(region_idx),
5045                              obj->is_typeArray()
5046                             );
5047 
5048     // Need to clear mark bit of the humongous object if already set.
5049     if (next_bitmap->isMarked(r->bottom())) {
5050       next_bitmap->clear(r->bottom());
5051     }
5052     do {
5053       HeapRegion* next = g1h->next_region_in_humongous(r);
5054       _freed_bytes += r->used();
5055       r->set_containing_set(NULL);
5056       _humongous_regions_removed++;
5057       g1h->free_humongous_region(r, _free_region_list, false);
5058       r = next;
5059     } while (r != NULL);
5060 
5061     return false;
5062   }
5063 
5064   uint humongous_free_count() {
5065     return _humongous_regions_removed;
5066   }
5067 
5068   size_t bytes_freed() const {
5069     return _freed_bytes;
5070   }
5071 };
5072 
5073 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
5074   assert_at_safepoint(true);
5075 
5076   if (!G1EagerReclaimHumongousObjects ||
5077       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
5078     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
5079     return;
5080   }
5081 
5082   double start_time = os::elapsedTime();
5083 
5084   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
5085 
5086   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
5087   heap_region_iterate(&cl);
5088 
5089   remove_from_old_sets(0, cl.humongous_free_count());
5090 
5091   G1HRPrinter* hrp = hr_printer();
5092   if (hrp->is_active()) {
5093     FreeRegionListIterator iter(&local_cleanup_list);
5094     while (iter.more_available()) {
5095       HeapRegion* hr = iter.get_next();
5096       hrp->cleanup(hr);
5097     }
5098   }
5099 
5100   prepend_to_freelist(&local_cleanup_list);
5101   decrement_summary_bytes(cl.bytes_freed());
5102 
5103   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
5104                                                                     cl.humongous_free_count());
5105 }
5106 
5107 // This routine is similar to the above but does not record
5108 // any policy statistics or update free lists; we are abandoning
5109 // the current incremental collection set in preparation of a
5110 // full collection. After the full GC we will start to build up
5111 // the incremental collection set again.
5112 // This is only called when we're doing a full collection
5113 // and is immediately followed by the tearing down of the young list.
5114 
5115 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
5116   HeapRegion* cur = cs_head;
5117 
5118   while (cur != NULL) {
5119     HeapRegion* next = cur->next_in_collection_set();
5120     assert(cur->in_collection_set(), "bad CS");
5121     cur->set_next_in_collection_set(NULL);
5122     clear_in_cset(cur);
5123     cur->set_young_index_in_cset(-1);
5124     cur = next;
5125   }
5126 }
5127 
5128 void G1CollectedHeap::set_free_regions_coming() {
5129   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
5130 
5131   assert(!free_regions_coming(), "pre-condition");
5132   _free_regions_coming = true;
5133 }
5134 
5135 void G1CollectedHeap::reset_free_regions_coming() {
5136   assert(free_regions_coming(), "pre-condition");
5137 
5138   {
5139     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5140     _free_regions_coming = false;
5141     SecondaryFreeList_lock->notify_all();
5142   }
5143 
5144   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
5145 }
5146 
5147 void G1CollectedHeap::wait_while_free_regions_coming() {
5148   // Most of the time we won't have to wait, so let's do a quick test
5149   // first before we take the lock.
5150   if (!free_regions_coming()) {
5151     return;
5152   }
5153 
5154   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
5155 
5156   {
5157     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5158     while (free_regions_coming()) {
5159       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5160     }
5161   }
5162 
5163   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
5164 }
5165 
5166 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
5167   return _allocator->is_retained_old_region(hr);
5168 }
5169 
5170 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5171   _young_list->push_region(hr);
5172 }
5173 
5174 class NoYoungRegionsClosure: public HeapRegionClosure {
5175 private:
5176   bool _success;
5177 public:
5178   NoYoungRegionsClosure() : _success(true) { }
5179   bool doHeapRegion(HeapRegion* r) {
5180     if (r->is_young()) {
5181       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5182                             p2i(r->bottom()), p2i(r->end()));
5183       _success = false;
5184     }
5185     return false;
5186   }
5187   bool success() { return _success; }
5188 };
5189 
5190 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
5191   bool ret = _young_list->check_list_empty(check_sample);
5192 
5193   if (check_heap) {
5194     NoYoungRegionsClosure closure;
5195     heap_region_iterate(&closure);
5196     ret = ret && closure.success();
5197   }
5198 
5199   return ret;
5200 }
5201 
5202 class TearDownRegionSetsClosure : public HeapRegionClosure {
5203 private:
5204   HeapRegionSet *_old_set;
5205 
5206 public:
5207   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5208 
5209   bool doHeapRegion(HeapRegion* r) {
5210     if (r->is_old()) {
5211       _old_set->remove(r);
5212     } else {
5213       // We ignore free regions, we'll empty the free list afterwards.
5214       // We ignore young regions, we'll empty the young list afterwards.
5215       // We ignore humongous regions, we're not tearing down the
5216       // humongous regions set.
5217       assert(r->is_free() || r->is_young() || r->is_humongous(),
5218              "it cannot be another type");
5219     }
5220     return false;
5221   }
5222 
5223   ~TearDownRegionSetsClosure() {
5224     assert(_old_set->is_empty(), "post-condition");
5225   }
5226 };
5227 
5228 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5229   assert_at_safepoint(true /* should_be_vm_thread */);
5230 
5231   if (!free_list_only) {
5232     TearDownRegionSetsClosure cl(&_old_set);
5233     heap_region_iterate(&cl);
5234 
5235     // Note that emptying the _young_list is postponed and instead done as
5236     // the first step when rebuilding the regions sets again. The reason for
5237     // this is that during a full GC string deduplication needs to know if
5238     // a collected region was young or old when the full GC was initiated.
5239   }
5240   _hrm.remove_all_free_regions();
5241 }
5242 
5243 void G1CollectedHeap::increase_used(size_t bytes) {
5244   _summary_bytes_used += bytes;
5245 }
5246 
5247 void G1CollectedHeap::decrease_used(size_t bytes) {
5248   assert(_summary_bytes_used >= bytes,
5249          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5250          _summary_bytes_used, bytes);
5251   _summary_bytes_used -= bytes;
5252 }
5253 
5254 void G1CollectedHeap::set_used(size_t bytes) {
5255   _summary_bytes_used = bytes;
5256 }
5257 
5258 class RebuildRegionSetsClosure : public HeapRegionClosure {
5259 private:
5260   bool            _free_list_only;
5261   HeapRegionSet*   _old_set;
5262   HeapRegionManager*   _hrm;
5263   size_t          _total_used;
5264 
5265 public:
5266   RebuildRegionSetsClosure(bool free_list_only,
5267                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
5268     _free_list_only(free_list_only),
5269     _old_set(old_set), _hrm(hrm), _total_used(0) {
5270     assert(_hrm->num_free_regions() == 0, "pre-condition");
5271     if (!free_list_only) {
5272       assert(_old_set->is_empty(), "pre-condition");
5273     }
5274   }
5275 
5276   bool doHeapRegion(HeapRegion* r) {
5277     if (r->is_empty()) {
5278       // Add free regions to the free list
5279       r->set_free();
5280       r->set_allocation_context(AllocationContext::system());
5281       _hrm->insert_into_free_list(r);
5282     } else if (!_free_list_only) {
5283       assert(!r->is_young(), "we should not come across young regions");
5284 
5285       if (r->is_humongous()) {
5286         // We ignore humongous regions. We left the humongous set unchanged.
5287       } else {
5288         // Objects that were compacted would have ended up on regions
5289         // that were previously old or free.  Archive regions (which are
5290         // old) will not have been touched.
5291         assert(r->is_free() || r->is_old(), "invariant");
5292         // We now consider them old, so register as such. Leave
5293         // archive regions set that way, however, while still adding
5294         // them to the old set.
5295         if (!r->is_archive()) {
5296           r->set_old();
5297         }
5298         _old_set->add(r);
5299       }
5300       _total_used += r->used();
5301     }
5302 
5303     return false;
5304   }
5305 
5306   size_t total_used() {
5307     return _total_used;
5308   }
5309 };
5310 
5311 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5312   assert_at_safepoint(true /* should_be_vm_thread */);
5313 
5314   if (!free_list_only) {
5315     _young_list->empty_list();
5316   }
5317 
5318   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5319   heap_region_iterate(&cl);
5320 
5321   if (!free_list_only) {
5322     set_used(cl.total_used());
5323     if (_archive_allocator != NULL) {
5324       _archive_allocator->clear_used();
5325     }
5326   }
5327   assert(used_unlocked() == recalculate_used(),
5328          "inconsistent used_unlocked(), "
5329          "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5330          used_unlocked(), recalculate_used());
5331 }
5332 
5333 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
5334   _refine_cte_cl->set_concurrent(concurrent);
5335 }
5336 
5337 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5338   HeapRegion* hr = heap_region_containing(p);
5339   return hr->is_in(p);
5340 }
5341 
5342 // Methods for the mutator alloc region
5343 
5344 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5345                                                       bool force) {
5346   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5347   assert(!force || g1_policy()->can_expand_young_list(),
5348          "if force is true we should be able to expand the young list");
5349   bool young_list_full = g1_policy()->is_young_list_full();
5350   if (force || !young_list_full) {
5351     HeapRegion* new_alloc_region = new_region(word_size,
5352                                               false /* is_old */,
5353                                               false /* do_expand */);
5354     if (new_alloc_region != NULL) {
5355       set_region_short_lived_locked(new_alloc_region);
5356       _hr_printer.alloc(new_alloc_region, young_list_full);
5357       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5358       return new_alloc_region;
5359     }
5360   }
5361   return NULL;
5362 }
5363 
5364 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5365                                                   size_t allocated_bytes) {
5366   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5367   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5368 
5369   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
5370   increase_used(allocated_bytes);
5371   _hr_printer.retire(alloc_region);
5372   // We update the eden sizes here, when the region is retired,
5373   // instead of when it's allocated, since this is the point that its
5374   // used space has been recored in _summary_bytes_used.
5375   g1mm()->update_eden_size();
5376 }
5377 
5378 // Methods for the GC alloc regions
5379 
5380 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
5381                                                  uint count,
5382                                                  InCSetState dest) {
5383   assert(FreeList_lock->owned_by_self(), "pre-condition");
5384 
5385   if (count < g1_policy()->max_regions(dest)) {
5386     const bool is_survivor = (dest.is_young());
5387     HeapRegion* new_alloc_region = new_region(word_size,
5388                                               !is_survivor,
5389                                               true /* do_expand */);
5390     if (new_alloc_region != NULL) {
5391       // We really only need to do this for old regions given that we
5392       // should never scan survivors. But it doesn't hurt to do it
5393       // for survivors too.
5394       new_alloc_region->record_timestamp();
5395       if (is_survivor) {
5396         new_alloc_region->set_survivor();
5397         _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5398       } else {
5399         new_alloc_region->set_old();
5400         _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5401       }
5402       _hr_printer.alloc(new_alloc_region);
5403       bool during_im = collector_state()->during_initial_mark_pause();
5404       new_alloc_region->note_start_of_copying(during_im);
5405       return new_alloc_region;
5406     }
5407   }
5408   return NULL;
5409 }
5410 
5411 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5412                                              size_t allocated_bytes,
5413                                              InCSetState dest) {
5414   bool during_im = collector_state()->during_initial_mark_pause();
5415   alloc_region->note_end_of_copying(during_im);
5416   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5417   if (dest.is_young()) {
5418     young_list()->add_survivor_region(alloc_region);
5419   } else {
5420     _old_set.add(alloc_region);
5421   }
5422   _hr_printer.retire(alloc_region);
5423 }
5424 
5425 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5426   bool expanded = false;
5427   uint index = _hrm.find_highest_free(&expanded);
5428 
5429   if (index != G1_NO_HRM_INDEX) {
5430     if (expanded) {
5431       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5432                                 HeapRegion::GrainWords * HeapWordSize);
5433     }
5434     _hrm.allocate_free_regions_starting_at(index, 1);
5435     return region_at(index);
5436   }
5437   return NULL;
5438 }
5439 
5440 // Optimized nmethod scanning
5441 
5442 class RegisterNMethodOopClosure: public OopClosure {
5443   G1CollectedHeap* _g1h;
5444   nmethod* _nm;
5445 
5446   template <class T> void do_oop_work(T* p) {
5447     T heap_oop = oopDesc::load_heap_oop(p);
5448     if (!oopDesc::is_null(heap_oop)) {
5449       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5450       HeapRegion* hr = _g1h->heap_region_containing(obj);
5451       assert(!hr->is_continues_humongous(),
5452              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5453              " starting at " HR_FORMAT,
5454              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5455 
5456       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5457       hr->add_strong_code_root_locked(_nm);
5458     }
5459   }
5460 
5461 public:
5462   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5463     _g1h(g1h), _nm(nm) {}
5464 
5465   void do_oop(oop* p)       { do_oop_work(p); }
5466   void do_oop(narrowOop* p) { do_oop_work(p); }
5467 };
5468 
5469 class UnregisterNMethodOopClosure: public OopClosure {
5470   G1CollectedHeap* _g1h;
5471   nmethod* _nm;
5472 
5473   template <class T> void do_oop_work(T* p) {
5474     T heap_oop = oopDesc::load_heap_oop(p);
5475     if (!oopDesc::is_null(heap_oop)) {
5476       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5477       HeapRegion* hr = _g1h->heap_region_containing(obj);
5478       assert(!hr->is_continues_humongous(),
5479              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5480              " starting at " HR_FORMAT,
5481              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5482 
5483       hr->remove_strong_code_root(_nm);
5484     }
5485   }
5486 
5487 public:
5488   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5489     _g1h(g1h), _nm(nm) {}
5490 
5491   void do_oop(oop* p)       { do_oop_work(p); }
5492   void do_oop(narrowOop* p) { do_oop_work(p); }
5493 };
5494 
5495 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5496   CollectedHeap::register_nmethod(nm);
5497 
5498   guarantee(nm != NULL, "sanity");
5499   RegisterNMethodOopClosure reg_cl(this, nm);
5500   nm->oops_do(&reg_cl);
5501 }
5502 
5503 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5504   CollectedHeap::unregister_nmethod(nm);
5505 
5506   guarantee(nm != NULL, "sanity");
5507   UnregisterNMethodOopClosure reg_cl(this, nm);
5508   nm->oops_do(&reg_cl, true);
5509 }
5510 
5511 void G1CollectedHeap::purge_code_root_memory() {
5512   double purge_start = os::elapsedTime();
5513   G1CodeRootSet::purge();
5514   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5515   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5516 }
5517 
5518 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5519   G1CollectedHeap* _g1h;
5520 
5521 public:
5522   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5523     _g1h(g1h) {}
5524 
5525   void do_code_blob(CodeBlob* cb) {
5526     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5527     if (nm == NULL) {
5528       return;
5529     }
5530 
5531     if (ScavengeRootsInCode) {
5532       _g1h->register_nmethod(nm);
5533     }
5534   }
5535 };
5536 
5537 void G1CollectedHeap::rebuild_strong_code_roots() {
5538   RebuildStrongCodeRootClosure blob_cl(this);
5539   CodeCache::blobs_do(&blob_cl);
5540 }