1 /*
   2  * Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/metadataOnStackMark.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "classfile/symbolTable.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc/g1/bufferingOopClosure.hpp"
  32 #include "gc/g1/concurrentG1Refine.hpp"
  33 #include "gc/g1/concurrentG1RefineThread.hpp"
  34 #include "gc/g1/concurrentMarkThread.inline.hpp"
  35 #include "gc/g1/g1Allocator.inline.hpp"
  36 #include "gc/g1/g1CollectedHeap.inline.hpp"
  37 #include "gc/g1/g1CollectionSet.hpp"
  38 #include "gc/g1/g1CollectorPolicy.hpp"
  39 #include "gc/g1/g1CollectorState.hpp"
  40 #include "gc/g1/g1EvacStats.inline.hpp"
  41 #include "gc/g1/g1GCPhaseTimes.hpp"
  42 #include "gc/g1/g1HeapSizingPolicy.hpp"
  43 #include "gc/g1/g1HeapTransition.hpp"
  44 #include "gc/g1/g1HeapVerifier.hpp"
  45 #include "gc/g1/g1HotCardCache.hpp"
  46 #include "gc/g1/g1MarkSweep.hpp"
  47 #include "gc/g1/g1OopClosures.inline.hpp"
  48 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  49 #include "gc/g1/g1Policy.hpp"
  50 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  51 #include "gc/g1/g1RemSet.inline.hpp"
  52 #include "gc/g1/g1RootClosures.hpp"
  53 #include "gc/g1/g1RootProcessor.hpp"
  54 #include "gc/g1/g1StringDedup.hpp"
  55 #include "gc/g1/g1YCTypes.hpp"
  56 #include "gc/g1/heapRegion.inline.hpp"
  57 #include "gc/g1/heapRegionRemSet.hpp"
  58 #include "gc/g1/heapRegionSet.inline.hpp"
  59 #include "gc/g1/suspendibleThreadSet.hpp"
  60 #include "gc/g1/vm_operations_g1.hpp"
  61 #include "gc/shared/gcHeapSummary.hpp"
  62 #include "gc/shared/gcId.hpp"
  63 #include "gc/shared/gcLocker.inline.hpp"
  64 #include "gc/shared/gcTimer.hpp"
  65 #include "gc/shared/gcTrace.hpp"
  66 #include "gc/shared/gcTraceTime.inline.hpp"
  67 #include "gc/shared/generationSpec.hpp"
  68 #include "gc/shared/isGCActiveMark.hpp"
  69 #include "gc/shared/preservedMarks.inline.hpp"
  70 #include "gc/shared/referenceProcessor.inline.hpp"
  71 #include "gc/shared/taskqueue.inline.hpp"
  72 #include "logging/log.hpp"
  73 #include "memory/allocation.hpp"
  74 #include "memory/iterator.hpp"
  75 #include "memory/resourceArea.hpp"
  76 #include "oops/oop.inline.hpp"
  77 #include "prims/resolvedMethodTable.hpp"
  78 #include "runtime/atomic.hpp"
  79 #include "runtime/init.hpp"
  80 #include "runtime/orderAccess.inline.hpp"
  81 #include "runtime/vmThread.hpp"
  82 #include "utilities/align.hpp"
  83 #include "utilities/globalDefinitions.hpp"
  84 #include "utilities/stack.inline.hpp"
  85 
  86 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  87 
  88 // INVARIANTS/NOTES
  89 //
  90 // All allocation activity covered by the G1CollectedHeap interface is
  91 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  92 // and allocate_new_tlab, which are the "entry" points to the
  93 // allocation code from the rest of the JVM.  (Note that this does not
  94 // apply to TLAB allocation, which is not part of this interface: it
  95 // is done by clients of this interface.)
  96 
  97 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
  98  private:
  99   size_t _num_dirtied;
 100   G1CollectedHeap* _g1h;
 101   G1SATBCardTableLoggingModRefBS* _g1_bs;
 102 
 103   HeapRegion* region_for_card(jbyte* card_ptr) const {
 104     return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
 105   }
 106 
 107   bool will_become_free(HeapRegion* hr) const {
 108     // A region will be freed by free_collection_set if the region is in the
 109     // collection set and has not had an evacuation failure.
 110     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 111   }
 112 
 113  public:
 114   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
 115     _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
 116 
 117   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 118     HeapRegion* hr = region_for_card(card_ptr);
 119 
 120     // Should only dirty cards in regions that won't be freed.
 121     if (!will_become_free(hr)) {
 122       *card_ptr = CardTableModRefBS::dirty_card_val();
 123       _num_dirtied++;
 124     }
 125 
 126     return true;
 127   }
 128 
 129   size_t num_dirtied()   const { return _num_dirtied; }
 130 };
 131 
 132 
 133 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 134   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 135 }
 136 
 137 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 138   // The from card cache is not the memory that is actually committed. So we cannot
 139   // take advantage of the zero_filled parameter.
 140   reset_from_card_cache(start_idx, num_regions);
 141 }
 142 
 143 // Returns true if the reference points to an object that
 144 // can move in an incremental collection.
 145 bool G1CollectedHeap::is_scavengable(const void* p) {
 146   HeapRegion* hr = heap_region_containing(p);
 147   return !hr->is_pinned();
 148 }
 149 
 150 // Private methods.
 151 
 152 HeapRegion*
 153 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 154   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 155   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 156     if (!_secondary_free_list.is_empty()) {
 157       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 158                                       "secondary_free_list has %u entries",
 159                                       _secondary_free_list.length());
 160       // It looks as if there are free regions available on the
 161       // secondary_free_list. Let's move them to the free_list and try
 162       // again to allocate from it.
 163       append_secondary_free_list();
 164 
 165       assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
 166              "empty we should have moved at least one entry to the free_list");
 167       HeapRegion* res = _hrm.allocate_free_region(is_old);
 168       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 169                                       "allocated " HR_FORMAT " from secondary_free_list",
 170                                       HR_FORMAT_PARAMS(res));
 171       return res;
 172     }
 173 
 174     // Wait here until we get notified either when (a) there are no
 175     // more free regions coming or (b) some regions have been moved on
 176     // the secondary_free_list.
 177     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 178   }
 179 
 180   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 181                                   "could not allocate from secondary_free_list");
 182   return NULL;
 183 }
 184 
 185 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 186   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 187          "the only time we use this to allocate a humongous region is "
 188          "when we are allocating a single humongous region");
 189 
 190   HeapRegion* res;
 191   if (G1StressConcRegionFreeing) {
 192     if (!_secondary_free_list.is_empty()) {
 193       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 194                                       "forced to look at the secondary_free_list");
 195       res = new_region_try_secondary_free_list(is_old);
 196       if (res != NULL) {
 197         return res;
 198       }
 199     }
 200   }
 201 
 202   res = _hrm.allocate_free_region(is_old);
 203 
 204   if (res == NULL) {
 205     log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 206                                     "res == NULL, trying the secondary_free_list");
 207     res = new_region_try_secondary_free_list(is_old);
 208   }
 209   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 210     // Currently, only attempts to allocate GC alloc regions set
 211     // do_expand to true. So, we should only reach here during a
 212     // safepoint. If this assumption changes we might have to
 213     // reconsider the use of _expand_heap_after_alloc_failure.
 214     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 215 
 216     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 217                               word_size * HeapWordSize);
 218 
 219     if (expand(word_size * HeapWordSize)) {
 220       // Given that expand() succeeded in expanding the heap, and we
 221       // always expand the heap by an amount aligned to the heap
 222       // region size, the free list should in theory not be empty.
 223       // In either case allocate_free_region() will check for NULL.
 224       res = _hrm.allocate_free_region(is_old);
 225     } else {
 226       _expand_heap_after_alloc_failure = false;
 227     }
 228   }
 229   return res;
 230 }
 231 
 232 HeapWord*
 233 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 234                                                            uint num_regions,
 235                                                            size_t word_size,
 236                                                            AllocationContext_t context) {
 237   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 238   assert(is_humongous(word_size), "word_size should be humongous");
 239   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 240 
 241   // Index of last region in the series.
 242   uint last = first + num_regions - 1;
 243 
 244   // We need to initialize the region(s) we just discovered. This is
 245   // a bit tricky given that it can happen concurrently with
 246   // refinement threads refining cards on these regions and
 247   // potentially wanting to refine the BOT as they are scanning
 248   // those cards (this can happen shortly after a cleanup; see CR
 249   // 6991377). So we have to set up the region(s) carefully and in
 250   // a specific order.
 251 
 252   // The word size sum of all the regions we will allocate.
 253   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 254   assert(word_size <= word_size_sum, "sanity");
 255 
 256   // This will be the "starts humongous" region.
 257   HeapRegion* first_hr = region_at(first);
 258   // The header of the new object will be placed at the bottom of
 259   // the first region.
 260   HeapWord* new_obj = first_hr->bottom();
 261   // This will be the new top of the new object.
 262   HeapWord* obj_top = new_obj + word_size;
 263 
 264   // First, we need to zero the header of the space that we will be
 265   // allocating. When we update top further down, some refinement
 266   // threads might try to scan the region. By zeroing the header we
 267   // ensure that any thread that will try to scan the region will
 268   // come across the zero klass word and bail out.
 269   //
 270   // NOTE: It would not have been correct to have used
 271   // CollectedHeap::fill_with_object() and make the space look like
 272   // an int array. The thread that is doing the allocation will
 273   // later update the object header to a potentially different array
 274   // type and, for a very short period of time, the klass and length
 275   // fields will be inconsistent. This could cause a refinement
 276   // thread to calculate the object size incorrectly.
 277   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 278 
 279   // Next, pad out the unused tail of the last region with filler
 280   // objects, for improved usage accounting.
 281   // How many words we use for filler objects.
 282   size_t word_fill_size = word_size_sum - word_size;
 283 
 284   // How many words memory we "waste" which cannot hold a filler object.
 285   size_t words_not_fillable = 0;
 286 
 287   if (word_fill_size >= min_fill_size()) {
 288     fill_with_objects(obj_top, word_fill_size);
 289   } else if (word_fill_size > 0) {
 290     // We have space to fill, but we cannot fit an object there.
 291     words_not_fillable = word_fill_size;
 292     word_fill_size = 0;
 293   }
 294 
 295   // We will set up the first region as "starts humongous". This
 296   // will also update the BOT covering all the regions to reflect
 297   // that there is a single object that starts at the bottom of the
 298   // first region.
 299   first_hr->set_starts_humongous(obj_top, word_fill_size);
 300   first_hr->set_allocation_context(context);
 301   // Then, if there are any, we will set up the "continues
 302   // humongous" regions.
 303   HeapRegion* hr = NULL;
 304   for (uint i = first + 1; i <= last; ++i) {
 305     hr = region_at(i);
 306     hr->set_continues_humongous(first_hr);
 307     hr->set_allocation_context(context);
 308   }
 309 
 310   // Up to this point no concurrent thread would have been able to
 311   // do any scanning on any region in this series. All the top
 312   // fields still point to bottom, so the intersection between
 313   // [bottom,top] and [card_start,card_end] will be empty. Before we
 314   // update the top fields, we'll do a storestore to make sure that
 315   // no thread sees the update to top before the zeroing of the
 316   // object header and the BOT initialization.
 317   OrderAccess::storestore();
 318 
 319   // Now, we will update the top fields of the "continues humongous"
 320   // regions except the last one.
 321   for (uint i = first; i < last; ++i) {
 322     hr = region_at(i);
 323     hr->set_top(hr->end());
 324   }
 325 
 326   hr = region_at(last);
 327   // If we cannot fit a filler object, we must set top to the end
 328   // of the humongous object, otherwise we cannot iterate the heap
 329   // and the BOT will not be complete.
 330   hr->set_top(hr->end() - words_not_fillable);
 331 
 332   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 333          "obj_top should be in last region");
 334 
 335   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 336 
 337   assert(words_not_fillable == 0 ||
 338          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 339          "Miscalculation in humongous allocation");
 340 
 341   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 342 
 343   for (uint i = first; i <= last; ++i) {
 344     hr = region_at(i);
 345     _humongous_set.add(hr);
 346     _hr_printer.alloc(hr);
 347   }
 348 
 349   return new_obj;
 350 }
 351 
 352 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 353   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 354   return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 355 }
 356 
 357 // If could fit into free regions w/o expansion, try.
 358 // Otherwise, if can expand, do so.
 359 // Otherwise, if using ex regions might help, try with ex given back.
 360 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
 361   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 362 
 363   _verifier->verify_region_sets_optional();
 364 
 365   uint first = G1_NO_HRM_INDEX;
 366   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 367 
 368   if (obj_regions == 1) {
 369     // Only one region to allocate, try to use a fast path by directly allocating
 370     // from the free lists. Do not try to expand here, we will potentially do that
 371     // later.
 372     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 373     if (hr != NULL) {
 374       first = hr->hrm_index();
 375     }
 376   } else {
 377     // We can't allocate humongous regions spanning more than one region while
 378     // cleanupComplete() is running, since some of the regions we find to be
 379     // empty might not yet be added to the free list. It is not straightforward
 380     // to know in which list they are on so that we can remove them. We only
 381     // need to do this if we need to allocate more than one region to satisfy the
 382     // current humongous allocation request. If we are only allocating one region
 383     // we use the one-region region allocation code (see above), that already
 384     // potentially waits for regions from the secondary free list.
 385     wait_while_free_regions_coming();
 386     append_secondary_free_list_if_not_empty_with_lock();
 387 
 388     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 389     // are lucky enough to find some.
 390     first = _hrm.find_contiguous_only_empty(obj_regions);
 391     if (first != G1_NO_HRM_INDEX) {
 392       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 393     }
 394   }
 395 
 396   if (first == G1_NO_HRM_INDEX) {
 397     // Policy: We could not find enough regions for the humongous object in the
 398     // free list. Look through the heap to find a mix of free and uncommitted regions.
 399     // If so, try expansion.
 400     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 401     if (first != G1_NO_HRM_INDEX) {
 402       // We found something. Make sure these regions are committed, i.e. expand
 403       // the heap. Alternatively we could do a defragmentation GC.
 404       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 405                                     word_size * HeapWordSize);
 406 
 407       _hrm.expand_at(first, obj_regions, workers());
 408       g1_policy()->record_new_heap_size(num_regions());
 409 
 410 #ifdef ASSERT
 411       for (uint i = first; i < first + obj_regions; ++i) {
 412         HeapRegion* hr = region_at(i);
 413         assert(hr->is_free(), "sanity");
 414         assert(hr->is_empty(), "sanity");
 415         assert(is_on_master_free_list(hr), "sanity");
 416       }
 417 #endif
 418       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 419     } else {
 420       // Policy: Potentially trigger a defragmentation GC.
 421     }
 422   }
 423 
 424   HeapWord* result = NULL;
 425   if (first != G1_NO_HRM_INDEX) {
 426     result = humongous_obj_allocate_initialize_regions(first, obj_regions,
 427                                                        word_size, context);
 428     assert(result != NULL, "it should always return a valid result");
 429 
 430     // A successful humongous object allocation changes the used space
 431     // information of the old generation so we need to recalculate the
 432     // sizes and update the jstat counters here.
 433     g1mm()->update_sizes();
 434   }
 435 
 436   _verifier->verify_region_sets_optional();
 437 
 438   return result;
 439 }
 440 
 441 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 442   assert_heap_not_locked_and_not_at_safepoint();
 443   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 444 
 445   uint dummy_gc_count_before;
 446   uint dummy_gclocker_retry_count = 0;
 447   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 448 }
 449 
 450 HeapWord*
 451 G1CollectedHeap::mem_allocate(size_t word_size,
 452                               bool*  gc_overhead_limit_was_exceeded) {
 453   assert_heap_not_locked_and_not_at_safepoint();
 454 
 455   // Loop until the allocation is satisfied, or unsatisfied after GC.
 456   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 457     uint gc_count_before;
 458 
 459     HeapWord* result = NULL;
 460     if (!is_humongous(word_size)) {
 461       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 462     } else {
 463       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 464     }
 465     if (result != NULL) {
 466       return result;
 467     }
 468 
 469     // Create the garbage collection operation...
 470     VM_G1CollectForAllocation op(gc_count_before, word_size);
 471     op.set_allocation_context(AllocationContext::current());
 472 
 473     // ...and get the VM thread to execute it.
 474     VMThread::execute(&op);
 475 
 476     if (op.prologue_succeeded() && op.pause_succeeded()) {
 477       // If the operation was successful we'll return the result even
 478       // if it is NULL. If the allocation attempt failed immediately
 479       // after a Full GC, it's unlikely we'll be able to allocate now.
 480       HeapWord* result = op.result();
 481       if (result != NULL && !is_humongous(word_size)) {
 482         // Allocations that take place on VM operations do not do any
 483         // card dirtying and we have to do it here. We only have to do
 484         // this for non-humongous allocations, though.
 485         dirty_young_block(result, word_size);
 486       }
 487       return result;
 488     } else {
 489       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 490         return NULL;
 491       }
 492       assert(op.result() == NULL,
 493              "the result should be NULL if the VM op did not succeed");
 494     }
 495 
 496     // Give a warning if we seem to be looping forever.
 497     if ((QueuedAllocationWarningCount > 0) &&
 498         (try_count % QueuedAllocationWarningCount == 0)) {
 499       log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
 500     }
 501   }
 502 
 503   ShouldNotReachHere();
 504   return NULL;
 505 }
 506 
 507 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 508                                                    AllocationContext_t context,
 509                                                    uint* gc_count_before_ret,
 510                                                    uint* gclocker_retry_count_ret) {
 511   // Make sure you read the note in attempt_allocation_humongous().
 512 
 513   assert_heap_not_locked_and_not_at_safepoint();
 514   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 515          "be called for humongous allocation requests");
 516 
 517   // We should only get here after the first-level allocation attempt
 518   // (attempt_allocation()) failed to allocate.
 519 
 520   // We will loop until a) we manage to successfully perform the
 521   // allocation or b) we successfully schedule a collection which
 522   // fails to perform the allocation. b) is the only case when we'll
 523   // return NULL.
 524   HeapWord* result = NULL;
 525   for (int try_count = 1; /* we'll return */; try_count += 1) {
 526     bool should_try_gc;
 527     uint gc_count_before;
 528 
 529     {
 530       MutexLockerEx x(Heap_lock);
 531       result = _allocator->attempt_allocation_locked(word_size, context);
 532       if (result != NULL) {
 533         return result;
 534       }
 535 
 536       if (GCLocker::is_active_and_needs_gc()) {
 537         if (g1_policy()->can_expand_young_list()) {
 538           // No need for an ergo verbose message here,
 539           // can_expand_young_list() does this when it returns true.
 540           result = _allocator->attempt_allocation_force(word_size, context);
 541           if (result != NULL) {
 542             return result;
 543           }
 544         }
 545         should_try_gc = false;
 546       } else {
 547         // The GCLocker may not be active but the GCLocker initiated
 548         // GC may not yet have been performed (GCLocker::needs_gc()
 549         // returns true). In this case we do not try this GC and
 550         // wait until the GCLocker initiated GC is performed, and
 551         // then retry the allocation.
 552         if (GCLocker::needs_gc()) {
 553           should_try_gc = false;
 554         } else {
 555           // Read the GC count while still holding the Heap_lock.
 556           gc_count_before = total_collections();
 557           should_try_gc = true;
 558         }
 559       }
 560     }
 561 
 562     if (should_try_gc) {
 563       bool succeeded;
 564       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 565                                    GCCause::_g1_inc_collection_pause);
 566       if (result != NULL) {
 567         assert(succeeded, "only way to get back a non-NULL result");
 568         return result;
 569       }
 570 
 571       if (succeeded) {
 572         // If we get here we successfully scheduled a collection which
 573         // failed to allocate. No point in trying to allocate
 574         // further. We'll just return NULL.
 575         MutexLockerEx x(Heap_lock);
 576         *gc_count_before_ret = total_collections();
 577         return NULL;
 578       }
 579     } else {
 580       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 581         MutexLockerEx x(Heap_lock);
 582         *gc_count_before_ret = total_collections();
 583         return NULL;
 584       }
 585       // The GCLocker is either active or the GCLocker initiated
 586       // GC has not yet been performed. Stall until it is and
 587       // then retry the allocation.
 588       GCLocker::stall_until_clear();
 589       (*gclocker_retry_count_ret) += 1;
 590     }
 591 
 592     // We can reach here if we were unsuccessful in scheduling a
 593     // collection (because another thread beat us to it) or if we were
 594     // stalled due to the GC locker. In either can we should retry the
 595     // allocation attempt in case another thread successfully
 596     // performed a collection and reclaimed enough space. We do the
 597     // first attempt (without holding the Heap_lock) here and the
 598     // follow-on attempt will be at the start of the next loop
 599     // iteration (after taking the Heap_lock).
 600     result = _allocator->attempt_allocation(word_size, context);
 601     if (result != NULL) {
 602       return result;
 603     }
 604 
 605     // Give a warning if we seem to be looping forever.
 606     if ((QueuedAllocationWarningCount > 0) &&
 607         (try_count % QueuedAllocationWarningCount == 0)) {
 608       log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
 609                       "retries %d times", try_count);
 610     }
 611   }
 612 
 613   ShouldNotReachHere();
 614   return NULL;
 615 }
 616 
 617 void G1CollectedHeap::begin_archive_alloc_range() {
 618   assert_at_safepoint(true /* should_be_vm_thread */);
 619   if (_archive_allocator == NULL) {
 620     _archive_allocator = G1ArchiveAllocator::create_allocator(this);
 621   }
 622 }
 623 
 624 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 625   // Allocations in archive regions cannot be of a size that would be considered
 626   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 627   // may be different at archive-restore time.
 628   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 629 }
 630 
 631 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 632   assert_at_safepoint(true /* should_be_vm_thread */);
 633   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 634   if (is_archive_alloc_too_large(word_size)) {
 635     return NULL;
 636   }
 637   return _archive_allocator->archive_mem_allocate(word_size);
 638 }
 639 
 640 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 641                                               size_t end_alignment_in_bytes) {
 642   assert_at_safepoint(true /* should_be_vm_thread */);
 643   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 644 
 645   // Call complete_archive to do the real work, filling in the MemRegion
 646   // array with the archive regions.
 647   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 648   delete _archive_allocator;
 649   _archive_allocator = NULL;
 650 }
 651 
 652 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 653   assert(ranges != NULL, "MemRegion array NULL");
 654   assert(count != 0, "No MemRegions provided");
 655   MemRegion reserved = _hrm.reserved();
 656   for (size_t i = 0; i < count; i++) {
 657     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 658       return false;
 659     }
 660   }
 661   return true;
 662 }
 663 
 664 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) {
 665   assert(!is_init_completed(), "Expect to be called at JVM init time");
 666   assert(ranges != NULL, "MemRegion array NULL");
 667   assert(count != 0, "No MemRegions provided");
 668   MutexLockerEx x(Heap_lock);
 669 
 670   MemRegion reserved = _hrm.reserved();
 671   HeapWord* prev_last_addr = NULL;
 672   HeapRegion* prev_last_region = NULL;
 673 
 674   // Temporarily disable pretouching of heap pages. This interface is used
 675   // when mmap'ing archived heap data in, so pre-touching is wasted.
 676   FlagSetting fs(AlwaysPreTouch, false);
 677 
 678   // Enable archive object checking used by G1MarkSweep. We have to let it know
 679   // about each archive range, so that objects in those ranges aren't marked.
 680   G1ArchiveAllocator::enable_archive_object_check();
 681 
 682   // For each specified MemRegion range, allocate the corresponding G1
 683   // regions and mark them as archive regions. We expect the ranges in
 684   // ascending starting address order, without overlap.
 685   for (size_t i = 0; i < count; i++) {
 686     MemRegion curr_range = ranges[i];
 687     HeapWord* start_address = curr_range.start();
 688     size_t word_size = curr_range.word_size();
 689     HeapWord* last_address = curr_range.last();
 690     size_t commits = 0;
 691 
 692     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 693               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 694               p2i(start_address), p2i(last_address));
 695     guarantee(start_address > prev_last_addr,
 696               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 697               p2i(start_address), p2i(prev_last_addr));
 698     prev_last_addr = last_address;
 699 
 700     // Check for ranges that start in the same G1 region in which the previous
 701     // range ended, and adjust the start address so we don't try to allocate
 702     // the same region again. If the current range is entirely within that
 703     // region, skip it, just adjusting the recorded top.
 704     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 705     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 706       start_address = start_region->end();
 707       if (start_address > last_address) {
 708         increase_used(word_size * HeapWordSize);
 709         start_region->set_top(last_address + 1);
 710         continue;
 711       }
 712       start_region->set_top(start_address);
 713       curr_range = MemRegion(start_address, last_address + 1);
 714       start_region = _hrm.addr_to_region(start_address);
 715     }
 716 
 717     // Perform the actual region allocation, exiting if it fails.
 718     // Then note how much new space we have allocated.
 719     if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
 720       return false;
 721     }
 722     increase_used(word_size * HeapWordSize);
 723     if (commits != 0) {
 724       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 725                                 HeapRegion::GrainWords * HeapWordSize * commits);
 726 
 727     }
 728 
 729     // Mark each G1 region touched by the range as archive, add it to the old set,
 730     // and set the allocation context and top.
 731     HeapRegion* curr_region = _hrm.addr_to_region(start_address);
 732     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 733     prev_last_region = last_region;
 734 
 735     while (curr_region != NULL) {
 736       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 737              "Region already in use (index %u)", curr_region->hrm_index());
 738       curr_region->set_allocation_context(AllocationContext::system());
 739       curr_region->set_archive();
 740       _hr_printer.alloc(curr_region);
 741       _old_set.add(curr_region);
 742       if (curr_region != last_region) {
 743         curr_region->set_top(curr_region->end());
 744         curr_region = _hrm.next_region_in_heap(curr_region);
 745       } else {
 746         curr_region->set_top(last_address + 1);
 747         curr_region = NULL;
 748       }
 749     }
 750 
 751     // Notify mark-sweep of the archive range.
 752     G1ArchiveAllocator::set_range_archive(curr_range, true);
 753   }
 754   return true;
 755 }
 756 
 757 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 758   assert(!is_init_completed(), "Expect to be called at JVM init time");
 759   assert(ranges != NULL, "MemRegion array NULL");
 760   assert(count != 0, "No MemRegions provided");
 761   MemRegion reserved = _hrm.reserved();
 762   HeapWord *prev_last_addr = NULL;
 763   HeapRegion* prev_last_region = NULL;
 764 
 765   // For each MemRegion, create filler objects, if needed, in the G1 regions
 766   // that contain the address range. The address range actually within the
 767   // MemRegion will not be modified. That is assumed to have been initialized
 768   // elsewhere, probably via an mmap of archived heap data.
 769   MutexLockerEx x(Heap_lock);
 770   for (size_t i = 0; i < count; i++) {
 771     HeapWord* start_address = ranges[i].start();
 772     HeapWord* last_address = ranges[i].last();
 773 
 774     assert(reserved.contains(start_address) && reserved.contains(last_address),
 775            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 776            p2i(start_address), p2i(last_address));
 777     assert(start_address > prev_last_addr,
 778            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 779            p2i(start_address), p2i(prev_last_addr));
 780 
 781     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 782     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 783     HeapWord* bottom_address = start_region->bottom();
 784 
 785     // Check for a range beginning in the same region in which the
 786     // previous one ended.
 787     if (start_region == prev_last_region) {
 788       bottom_address = prev_last_addr + 1;
 789     }
 790 
 791     // Verify that the regions were all marked as archive regions by
 792     // alloc_archive_regions.
 793     HeapRegion* curr_region = start_region;
 794     while (curr_region != NULL) {
 795       guarantee(curr_region->is_archive(),
 796                 "Expected archive region at index %u", curr_region->hrm_index());
 797       if (curr_region != last_region) {
 798         curr_region = _hrm.next_region_in_heap(curr_region);
 799       } else {
 800         curr_region = NULL;
 801       }
 802     }
 803 
 804     prev_last_addr = last_address;
 805     prev_last_region = last_region;
 806 
 807     // Fill the memory below the allocated range with dummy object(s),
 808     // if the region bottom does not match the range start, or if the previous
 809     // range ended within the same G1 region, and there is a gap.
 810     if (start_address != bottom_address) {
 811       size_t fill_size = pointer_delta(start_address, bottom_address);
 812       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 813       increase_used(fill_size * HeapWordSize);
 814     }
 815   }
 816 }
 817 
 818 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
 819                                                      uint* gc_count_before_ret,
 820                                                      uint* gclocker_retry_count_ret) {
 821   assert_heap_not_locked_and_not_at_safepoint();
 822   assert(!is_humongous(word_size), "attempt_allocation() should not "
 823          "be called for humongous allocation requests");
 824 
 825   AllocationContext_t context = AllocationContext::current();
 826   HeapWord* result = _allocator->attempt_allocation(word_size, context);
 827 
 828   if (result == NULL) {
 829     result = attempt_allocation_slow(word_size,
 830                                      context,
 831                                      gc_count_before_ret,
 832                                      gclocker_retry_count_ret);
 833   }
 834   assert_heap_not_locked();
 835   if (result != NULL) {
 836     dirty_young_block(result, word_size);
 837   }
 838   return result;
 839 }
 840 
 841 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
 842   assert(!is_init_completed(), "Expect to be called at JVM init time");
 843   assert(ranges != NULL, "MemRegion array NULL");
 844   assert(count != 0, "No MemRegions provided");
 845   MemRegion reserved = _hrm.reserved();
 846   HeapWord* prev_last_addr = NULL;
 847   HeapRegion* prev_last_region = NULL;
 848   size_t size_used = 0;
 849   size_t uncommitted_regions = 0;
 850 
 851   // For each Memregion, free the G1 regions that constitute it, and
 852   // notify mark-sweep that the range is no longer to be considered 'archive.'
 853   MutexLockerEx x(Heap_lock);
 854   for (size_t i = 0; i < count; i++) {
 855     HeapWord* start_address = ranges[i].start();
 856     HeapWord* last_address = ranges[i].last();
 857 
 858     assert(reserved.contains(start_address) && reserved.contains(last_address),
 859            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 860            p2i(start_address), p2i(last_address));
 861     assert(start_address > prev_last_addr,
 862            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 863            p2i(start_address), p2i(prev_last_addr));
 864     size_used += ranges[i].byte_size();
 865     prev_last_addr = last_address;
 866 
 867     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 868     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 869 
 870     // Check for ranges that start in the same G1 region in which the previous
 871     // range ended, and adjust the start address so we don't try to free
 872     // the same region again. If the current range is entirely within that
 873     // region, skip it.
 874     if (start_region == prev_last_region) {
 875       start_address = start_region->end();
 876       if (start_address > last_address) {
 877         continue;
 878       }
 879       start_region = _hrm.addr_to_region(start_address);
 880     }
 881     prev_last_region = last_region;
 882 
 883     // After verifying that each region was marked as an archive region by
 884     // alloc_archive_regions, set it free and empty and uncommit it.
 885     HeapRegion* curr_region = start_region;
 886     while (curr_region != NULL) {
 887       guarantee(curr_region->is_archive(),
 888                 "Expected archive region at index %u", curr_region->hrm_index());
 889       uint curr_index = curr_region->hrm_index();
 890       _old_set.remove(curr_region);
 891       curr_region->set_free();
 892       curr_region->set_top(curr_region->bottom());
 893       if (curr_region != last_region) {
 894         curr_region = _hrm.next_region_in_heap(curr_region);
 895       } else {
 896         curr_region = NULL;
 897       }
 898       _hrm.shrink_at(curr_index, 1);
 899       uncommitted_regions++;
 900     }
 901 
 902     // Notify mark-sweep that this is no longer an archive range.
 903     G1ArchiveAllocator::set_range_archive(ranges[i], false);
 904   }
 905 
 906   if (uncommitted_regions != 0) {
 907     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 908                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 909   }
 910   decrease_used(size_used);
 911 }
 912 
 913 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
 914                                                         uint* gc_count_before_ret,
 915                                                         uint* gclocker_retry_count_ret) {
 916   // The structure of this method has a lot of similarities to
 917   // attempt_allocation_slow(). The reason these two were not merged
 918   // into a single one is that such a method would require several "if
 919   // allocation is not humongous do this, otherwise do that"
 920   // conditional paths which would obscure its flow. In fact, an early
 921   // version of this code did use a unified method which was harder to
 922   // follow and, as a result, it had subtle bugs that were hard to
 923   // track down. So keeping these two methods separate allows each to
 924   // be more readable. It will be good to keep these two in sync as
 925   // much as possible.
 926 
 927   assert_heap_not_locked_and_not_at_safepoint();
 928   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 929          "should only be called for humongous allocations");
 930 
 931   // Humongous objects can exhaust the heap quickly, so we should check if we
 932   // need to start a marking cycle at each humongous object allocation. We do
 933   // the check before we do the actual allocation. The reason for doing it
 934   // before the allocation is that we avoid having to keep track of the newly
 935   // allocated memory while we do a GC.
 936   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
 937                                            word_size)) {
 938     collect(GCCause::_g1_humongous_allocation);
 939   }
 940 
 941   // We will loop until a) we manage to successfully perform the
 942   // allocation or b) we successfully schedule a collection which
 943   // fails to perform the allocation. b) is the only case when we'll
 944   // return NULL.
 945   HeapWord* result = NULL;
 946   for (int try_count = 1; /* we'll return */; try_count += 1) {
 947     bool should_try_gc;
 948     uint gc_count_before;
 949 
 950     {
 951       MutexLockerEx x(Heap_lock);
 952 
 953       // Given that humongous objects are not allocated in young
 954       // regions, we'll first try to do the allocation without doing a
 955       // collection hoping that there's enough space in the heap.
 956       result = humongous_obj_allocate(word_size, AllocationContext::current());
 957       if (result != NULL) {
 958         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 959         g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 960         return result;
 961       }
 962 
 963       if (GCLocker::is_active_and_needs_gc()) {
 964         should_try_gc = false;
 965       } else {
 966          // The GCLocker may not be active but the GCLocker initiated
 967         // GC may not yet have been performed (GCLocker::needs_gc()
 968         // returns true). In this case we do not try this GC and
 969         // wait until the GCLocker initiated GC is performed, and
 970         // then retry the allocation.
 971         if (GCLocker::needs_gc()) {
 972           should_try_gc = false;
 973         } else {
 974           // Read the GC count while still holding the Heap_lock.
 975           gc_count_before = total_collections();
 976           should_try_gc = true;
 977         }
 978       }
 979     }
 980 
 981     if (should_try_gc) {
 982       // If we failed to allocate the humongous object, we should try to
 983       // do a collection pause (if we're allowed) in case it reclaims
 984       // enough space for the allocation to succeed after the pause.
 985 
 986       bool succeeded;
 987       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 988                                    GCCause::_g1_humongous_allocation);
 989       if (result != NULL) {
 990         assert(succeeded, "only way to get back a non-NULL result");
 991         return result;
 992       }
 993 
 994       if (succeeded) {
 995         // If we get here we successfully scheduled a collection which
 996         // failed to allocate. No point in trying to allocate
 997         // further. We'll just return NULL.
 998         MutexLockerEx x(Heap_lock);
 999         *gc_count_before_ret = total_collections();
1000         return NULL;
1001       }
1002     } else {
1003       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1004         MutexLockerEx x(Heap_lock);
1005         *gc_count_before_ret = total_collections();
1006         return NULL;
1007       }
1008       // The GCLocker is either active or the GCLocker initiated
1009       // GC has not yet been performed. Stall until it is and
1010       // then retry the allocation.
1011       GCLocker::stall_until_clear();
1012       (*gclocker_retry_count_ret) += 1;
1013     }
1014 
1015     // We can reach here if we were unsuccessful in scheduling a
1016     // collection (because another thread beat us to it) or if we were
1017     // stalled due to the GC locker. In either can we should retry the
1018     // allocation attempt in case another thread successfully
1019     // performed a collection and reclaimed enough space.  Give a
1020     // warning if we seem to be looping forever.
1021 
1022     if ((QueuedAllocationWarningCount > 0) &&
1023         (try_count % QueuedAllocationWarningCount == 0)) {
1024       log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
1025                       "retries %d times", try_count);
1026     }
1027   }
1028 
1029   ShouldNotReachHere();
1030   return NULL;
1031 }
1032 
1033 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1034                                                            AllocationContext_t context,
1035                                                            bool expect_null_mutator_alloc_region) {
1036   assert_at_safepoint(true /* should_be_vm_thread */);
1037   assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1038          "the current alloc region was unexpectedly found to be non-NULL");
1039 
1040   if (!is_humongous(word_size)) {
1041     return _allocator->attempt_allocation_locked(word_size, context);
1042   } else {
1043     HeapWord* result = humongous_obj_allocate(word_size, context);
1044     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1045       collector_state()->set_initiate_conc_mark_if_possible(true);
1046     }
1047     return result;
1048   }
1049 
1050   ShouldNotReachHere();
1051 }
1052 
1053 class PostMCRemSetClearClosure: public HeapRegionClosure {
1054   G1CollectedHeap* _g1h;
1055   ModRefBarrierSet* _mr_bs;
1056 public:
1057   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1058     _g1h(g1h), _mr_bs(mr_bs) {}
1059 
1060   bool doHeapRegion(HeapRegion* r) {
1061     HeapRegionRemSet* hrrs = r->rem_set();
1062 
1063     _g1h->reset_gc_time_stamps(r);
1064 
1065     if (r->is_continues_humongous()) {
1066       // We'll assert that the strong code root list and RSet is empty
1067       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1068       assert(hrrs->occupied() == 0, "RSet should be empty");
1069     } else {
1070       hrrs->clear();
1071     }
1072     // You might think here that we could clear just the cards
1073     // corresponding to the used region.  But no: if we leave a dirty card
1074     // in a region we might allocate into, then it would prevent that card
1075     // from being enqueued, and cause it to be missed.
1076     // Re: the performance cost: we shouldn't be doing full GC anyway!
1077     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1078 
1079     return false;
1080   }
1081 };
1082 
1083 void G1CollectedHeap::clear_rsets_post_compaction() {
1084   PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1085   heap_region_iterate(&rs_clear);
1086 }
1087 
1088 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1089   G1CollectedHeap*   _g1h;
1090   RebuildRSOopClosure _cl;
1091 public:
1092   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) :
1093     _cl(g1->g1_rem_set(), worker_i),
1094     _g1h(g1)
1095   { }
1096 
1097   bool doHeapRegion(HeapRegion* r) {
1098     if (!r->is_continues_humongous()) {
1099       _cl.set_from(r);
1100       r->oop_iterate(&_cl);
1101     }
1102     return false;
1103   }
1104 };
1105 
1106 class ParRebuildRSTask: public AbstractGangTask {
1107   G1CollectedHeap* _g1;
1108   HeapRegionClaimer _hrclaimer;
1109 
1110 public:
1111   ParRebuildRSTask(G1CollectedHeap* g1) :
1112       AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {}
1113 
1114   void work(uint worker_id) {
1115     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1116     _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer);
1117   }
1118 };
1119 
1120 class PostCompactionPrinterClosure: public HeapRegionClosure {
1121 private:
1122   G1HRPrinter* _hr_printer;
1123 public:
1124   bool doHeapRegion(HeapRegion* hr) {
1125     assert(!hr->is_young(), "not expecting to find young regions");
1126     _hr_printer->post_compaction(hr);
1127     return false;
1128   }
1129 
1130   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1131     : _hr_printer(hr_printer) { }
1132 };
1133 
1134 void G1CollectedHeap::print_hrm_post_compaction() {
1135   if (_hr_printer.is_active()) {
1136     PostCompactionPrinterClosure cl(hr_printer());
1137     heap_region_iterate(&cl);
1138   }
1139 
1140 }
1141 
1142 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1143                                          bool clear_all_soft_refs) {
1144   assert_at_safepoint(true /* should_be_vm_thread */);
1145 
1146   if (GCLocker::check_active_before_gc()) {
1147     return false;
1148   }
1149 
1150   STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1151   gc_timer->register_gc_start();
1152 
1153   SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1154   GCIdMark gc_id_mark;
1155   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1156 
1157   SvcGCMarker sgcm(SvcGCMarker::FULL);
1158   ResourceMark rm;
1159 
1160   print_heap_before_gc();
1161   print_heap_regions();
1162   trace_heap_before_gc(gc_tracer);
1163 
1164   size_t metadata_prev_used = MetaspaceAux::used_bytes();
1165 
1166   _verifier->verify_region_sets_optional();
1167 
1168   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1169                            collector_policy()->should_clear_all_soft_refs();
1170 
1171   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1172 
1173   {
1174     IsGCActiveMark x;
1175 
1176     // Timing
1177     assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1178     GCTraceCPUTime tcpu;
1179 
1180     {
1181       GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1182       TraceCollectorStats tcs(g1mm()->full_collection_counters());
1183       TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1184 
1185       G1HeapTransition heap_transition(this);
1186       g1_policy()->record_full_collection_start();
1187 
1188       // Note: When we have a more flexible GC logging framework that
1189       // allows us to add optional attributes to a GC log record we
1190       // could consider timing and reporting how long we wait in the
1191       // following two methods.
1192       wait_while_free_regions_coming();
1193       // If we start the compaction before the CM threads finish
1194       // scanning the root regions we might trip them over as we'll
1195       // be moving objects / updating references. So let's wait until
1196       // they are done. By telling them to abort, they should complete
1197       // early.
1198       _cm->root_regions()->abort();
1199       _cm->root_regions()->wait_until_scan_finished();
1200       append_secondary_free_list_if_not_empty_with_lock();
1201 
1202       gc_prologue(true);
1203       increment_total_collections(true /* full gc */);
1204       increment_old_marking_cycles_started();
1205 
1206       assert(used() == recalculate_used(), "Should be equal");
1207 
1208       _verifier->verify_before_gc();
1209 
1210       _verifier->check_bitmaps("Full GC Start");
1211       pre_full_gc_dump(gc_timer);
1212 
1213 #if defined(COMPILER2) || INCLUDE_JVMCI
1214       DerivedPointerTable::clear();
1215 #endif
1216 
1217       // Disable discovery and empty the discovered lists
1218       // for the CM ref processor.
1219       ref_processor_cm()->disable_discovery();
1220       ref_processor_cm()->abandon_partial_discovery();
1221       ref_processor_cm()->verify_no_references_recorded();
1222 
1223       // Abandon current iterations of concurrent marking and concurrent
1224       // refinement, if any are in progress.
1225       concurrent_mark()->abort();
1226 
1227       // Make sure we'll choose a new allocation region afterwards.
1228       _allocator->release_mutator_alloc_region();
1229       _allocator->abandon_gc_alloc_regions();
1230       g1_rem_set()->cleanupHRRS();
1231 
1232       // We may have added regions to the current incremental collection
1233       // set between the last GC or pause and now. We need to clear the
1234       // incremental collection set and then start rebuilding it afresh
1235       // after this full GC.
1236       abandon_collection_set(collection_set());
1237 
1238       tear_down_region_sets(false /* free_list_only */);
1239       collector_state()->set_gcs_are_young(true);
1240 
1241       // See the comments in g1CollectedHeap.hpp and
1242       // G1CollectedHeap::ref_processing_init() about
1243       // how reference processing currently works in G1.
1244 
1245       // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1246       ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1247 
1248       // Temporarily clear the STW ref processor's _is_alive_non_header field.
1249       ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1250 
1251       ref_processor_stw()->enable_discovery();
1252       ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1253 
1254       // Do collection work
1255       {
1256         HandleMark hm;  // Discard invalid handles created during gc
1257         G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1258       }
1259 
1260       assert(num_free_regions() == 0, "we should not have added any free regions");
1261       rebuild_region_sets(false /* free_list_only */);
1262 
1263       // Enqueue any discovered reference objects that have
1264       // not been removed from the discovered lists.
1265       ref_processor_stw()->enqueue_discovered_references();
1266 
1267 #if defined(COMPILER2) || INCLUDE_JVMCI
1268       DerivedPointerTable::update_pointers();
1269 #endif
1270 
1271       MemoryService::track_memory_usage();
1272 
1273       assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1274       ref_processor_stw()->verify_no_references_recorded();
1275 
1276       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1277       ClassLoaderDataGraph::purge();
1278       MetaspaceAux::verify_metrics();
1279 
1280       // Note: since we've just done a full GC, concurrent
1281       // marking is no longer active. Therefore we need not
1282       // re-enable reference discovery for the CM ref processor.
1283       // That will be done at the start of the next marking cycle.
1284       assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1285       ref_processor_cm()->verify_no_references_recorded();
1286 
1287       reset_gc_time_stamp();
1288       // Since everything potentially moved, we will clear all remembered
1289       // sets, and clear all cards.  Later we will rebuild remembered
1290       // sets. We will also reset the GC time stamps of the regions.
1291       clear_rsets_post_compaction();
1292       check_gc_time_stamps();
1293 
1294       resize_if_necessary_after_full_collection();
1295 
1296       // We should do this after we potentially resize the heap so
1297       // that all the COMMIT / UNCOMMIT events are generated before
1298       // the compaction events.
1299       print_hrm_post_compaction();
1300 
1301       if (_hot_card_cache->use_cache()) {
1302         _hot_card_cache->reset_card_counts();
1303         _hot_card_cache->reset_hot_cache();
1304       }
1305 
1306       // Rebuild remembered sets of all regions.
1307       uint n_workers =
1308         AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1309                                                 workers()->active_workers(),
1310                                                 Threads::number_of_non_daemon_threads());
1311       workers()->update_active_workers(n_workers);
1312       log_info(gc,task)("Using %u workers of %u to rebuild remembered set", n_workers, workers()->total_workers());
1313 
1314       ParRebuildRSTask rebuild_rs_task(this);
1315       workers()->run_task(&rebuild_rs_task);
1316 
1317       // Rebuild the strong code root lists for each region
1318       rebuild_strong_code_roots();
1319 
1320       if (true) { // FIXME
1321         MetaspaceGC::compute_new_size();
1322       }
1323 
1324 #ifdef TRACESPINNING
1325       ParallelTaskTerminator::print_termination_counts();
1326 #endif
1327 
1328       // Discard all rset updates
1329       JavaThread::dirty_card_queue_set().abandon_logs();
1330       assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1331 
1332       // At this point there should be no regions in the
1333       // entire heap tagged as young.
1334       assert(check_young_list_empty(), "young list should be empty at this point");
1335 
1336       // Update the number of full collections that have been completed.
1337       increment_old_marking_cycles_completed(false /* concurrent */);
1338 
1339       _hrm.verify_optional();
1340       _verifier->verify_region_sets_optional();
1341 
1342       _verifier->verify_after_gc();
1343 
1344       // Clear the previous marking bitmap, if needed for bitmap verification.
1345       // Note we cannot do this when we clear the next marking bitmap in
1346       // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1347       // objects marked during a full GC against the previous bitmap.
1348       // But we need to clear it before calling check_bitmaps below since
1349       // the full GC has compacted objects and updated TAMS but not updated
1350       // the prev bitmap.
1351       if (G1VerifyBitmaps) {
1352         GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1353         _cm->clear_prev_bitmap(workers());
1354       }
1355       _verifier->check_bitmaps("Full GC End");
1356 
1357       start_new_collection_set();
1358 
1359       _allocator->init_mutator_alloc_region();
1360 
1361       g1_policy()->record_full_collection_end();
1362 
1363       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1364       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1365       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1366       // before any GC notifications are raised.
1367       g1mm()->update_sizes();
1368 
1369       gc_epilogue(true);
1370 
1371       heap_transition.print();
1372 
1373       print_heap_after_gc();
1374       print_heap_regions();
1375       trace_heap_after_gc(gc_tracer);
1376 
1377       post_full_gc_dump(gc_timer);
1378     }
1379 
1380     gc_timer->register_gc_end();
1381     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1382   }
1383 
1384   return true;
1385 }
1386 
1387 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1388   // Currently, there is no facility in the do_full_collection(bool) API to notify
1389   // the caller that the collection did not succeed (e.g., because it was locked
1390   // out by the GC locker). So, right now, we'll ignore the return value.
1391   bool dummy = do_full_collection(true,                /* explicit_gc */
1392                                   clear_all_soft_refs);
1393 }
1394 
1395 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1396   // Include bytes that will be pre-allocated to support collections, as "used".
1397   const size_t used_after_gc = used();
1398   const size_t capacity_after_gc = capacity();
1399   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1400 
1401   // This is enforced in arguments.cpp.
1402   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1403          "otherwise the code below doesn't make sense");
1404 
1405   // We don't have floating point command-line arguments
1406   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1407   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1408   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1409   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1410 
1411   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1412   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1413 
1414   // We have to be careful here as these two calculations can overflow
1415   // 32-bit size_t's.
1416   double used_after_gc_d = (double) used_after_gc;
1417   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1418   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1419 
1420   // Let's make sure that they are both under the max heap size, which
1421   // by default will make them fit into a size_t.
1422   double desired_capacity_upper_bound = (double) max_heap_size;
1423   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1424                                     desired_capacity_upper_bound);
1425   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1426                                     desired_capacity_upper_bound);
1427 
1428   // We can now safely turn them into size_t's.
1429   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1430   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1431 
1432   // This assert only makes sense here, before we adjust them
1433   // with respect to the min and max heap size.
1434   assert(minimum_desired_capacity <= maximum_desired_capacity,
1435          "minimum_desired_capacity = " SIZE_FORMAT ", "
1436          "maximum_desired_capacity = " SIZE_FORMAT,
1437          minimum_desired_capacity, maximum_desired_capacity);
1438 
1439   // Should not be greater than the heap max size. No need to adjust
1440   // it with respect to the heap min size as it's a lower bound (i.e.,
1441   // we'll try to make the capacity larger than it, not smaller).
1442   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1443   // Should not be less than the heap min size. No need to adjust it
1444   // with respect to the heap max size as it's an upper bound (i.e.,
1445   // we'll try to make the capacity smaller than it, not greater).
1446   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1447 
1448   if (capacity_after_gc < minimum_desired_capacity) {
1449     // Don't expand unless it's significant
1450     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1451 
1452     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1453                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1454                               capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1455 
1456     expand(expand_bytes, _workers);
1457 
1458     // No expansion, now see if we want to shrink
1459   } else if (capacity_after_gc > maximum_desired_capacity) {
1460     // Capacity too large, compute shrinking size
1461     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1462 
1463     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1464                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1465                               capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1466 
1467     shrink(shrink_bytes);
1468   }
1469 }
1470 
1471 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1472                                                             AllocationContext_t context,
1473                                                             bool do_gc,
1474                                                             bool clear_all_soft_refs,
1475                                                             bool expect_null_mutator_alloc_region,
1476                                                             bool* gc_succeeded) {
1477   *gc_succeeded = true;
1478   // Let's attempt the allocation first.
1479   HeapWord* result =
1480     attempt_allocation_at_safepoint(word_size,
1481                                     context,
1482                                     expect_null_mutator_alloc_region);
1483   if (result != NULL) {
1484     assert(*gc_succeeded, "sanity");
1485     return result;
1486   }
1487 
1488   // In a G1 heap, we're supposed to keep allocation from failing by
1489   // incremental pauses.  Therefore, at least for now, we'll favor
1490   // expansion over collection.  (This might change in the future if we can
1491   // do something smarter than full collection to satisfy a failed alloc.)
1492   result = expand_and_allocate(word_size, context);
1493   if (result != NULL) {
1494     assert(*gc_succeeded, "sanity");
1495     return result;
1496   }
1497 
1498   if (do_gc) {
1499     // Expansion didn't work, we'll try to do a Full GC.
1500     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1501                                        clear_all_soft_refs);
1502   }
1503 
1504   return NULL;
1505 }
1506 
1507 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1508                                                      AllocationContext_t context,
1509                                                      bool* succeeded) {
1510   assert_at_safepoint(true /* should_be_vm_thread */);
1511 
1512   // Attempts to allocate followed by Full GC.
1513   HeapWord* result =
1514     satisfy_failed_allocation_helper(word_size,
1515                                      context,
1516                                      true,  /* do_gc */
1517                                      false, /* clear_all_soft_refs */
1518                                      false, /* expect_null_mutator_alloc_region */
1519                                      succeeded);
1520 
1521   if (result != NULL || !*succeeded) {
1522     return result;
1523   }
1524 
1525   // Attempts to allocate followed by Full GC that will collect all soft references.
1526   result = satisfy_failed_allocation_helper(word_size,
1527                                             context,
1528                                             true, /* do_gc */
1529                                             true, /* clear_all_soft_refs */
1530                                             true, /* expect_null_mutator_alloc_region */
1531                                             succeeded);
1532 
1533   if (result != NULL || !*succeeded) {
1534     return result;
1535   }
1536 
1537   // Attempts to allocate, no GC
1538   result = satisfy_failed_allocation_helper(word_size,
1539                                             context,
1540                                             false, /* do_gc */
1541                                             false, /* clear_all_soft_refs */
1542                                             true,  /* expect_null_mutator_alloc_region */
1543                                             succeeded);
1544 
1545   if (result != NULL) {
1546     assert(*succeeded, "sanity");
1547     return result;
1548   }
1549 
1550   assert(!collector_policy()->should_clear_all_soft_refs(),
1551          "Flag should have been handled and cleared prior to this point");
1552 
1553   // What else?  We might try synchronous finalization later.  If the total
1554   // space available is large enough for the allocation, then a more
1555   // complete compaction phase than we've tried so far might be
1556   // appropriate.
1557   assert(*succeeded, "sanity");
1558   return NULL;
1559 }
1560 
1561 // Attempting to expand the heap sufficiently
1562 // to support an allocation of the given "word_size".  If
1563 // successful, perform the allocation and return the address of the
1564 // allocated block, or else "NULL".
1565 
1566 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1567   assert_at_safepoint(true /* should_be_vm_thread */);
1568 
1569   _verifier->verify_region_sets_optional();
1570 
1571   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1572   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1573                             word_size * HeapWordSize);
1574 
1575 
1576   if (expand(expand_bytes, _workers)) {
1577     _hrm.verify_optional();
1578     _verifier->verify_region_sets_optional();
1579     return attempt_allocation_at_safepoint(word_size,
1580                                            context,
1581                                            false /* expect_null_mutator_alloc_region */);
1582   }
1583   return NULL;
1584 }
1585 
1586 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1587   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1588   aligned_expand_bytes = align_up(aligned_expand_bytes,
1589                                        HeapRegion::GrainBytes);
1590 
1591   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1592                             expand_bytes, aligned_expand_bytes);
1593 
1594   if (is_maximal_no_gc()) {
1595     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1596     return false;
1597   }
1598 
1599   double expand_heap_start_time_sec = os::elapsedTime();
1600   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1601   assert(regions_to_expand > 0, "Must expand by at least one region");
1602 
1603   uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1604   if (expand_time_ms != NULL) {
1605     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1606   }
1607 
1608   if (expanded_by > 0) {
1609     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1610     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1611     g1_policy()->record_new_heap_size(num_regions());
1612   } else {
1613     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1614 
1615     // The expansion of the virtual storage space was unsuccessful.
1616     // Let's see if it was because we ran out of swap.
1617     if (G1ExitOnExpansionFailure &&
1618         _hrm.available() >= regions_to_expand) {
1619       // We had head room...
1620       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1621     }
1622   }
1623   return regions_to_expand > 0;
1624 }
1625 
1626 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1627   size_t aligned_shrink_bytes =
1628     ReservedSpace::page_align_size_down(shrink_bytes);
1629   aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1630                                          HeapRegion::GrainBytes);
1631   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1632 
1633   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1634   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1635 
1636 
1637   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",
1638                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1639   if (num_regions_removed > 0) {
1640     g1_policy()->record_new_heap_size(num_regions());
1641   } else {
1642     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1643   }
1644 }
1645 
1646 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1647   _verifier->verify_region_sets_optional();
1648 
1649   // We should only reach here at the end of a Full GC which means we
1650   // should not not be holding to any GC alloc regions. The method
1651   // below will make sure of that and do any remaining clean up.
1652   _allocator->abandon_gc_alloc_regions();
1653 
1654   // Instead of tearing down / rebuilding the free lists here, we
1655   // could instead use the remove_all_pending() method on free_list to
1656   // remove only the ones that we need to remove.
1657   tear_down_region_sets(true /* free_list_only */);
1658   shrink_helper(shrink_bytes);
1659   rebuild_region_sets(true /* free_list_only */);
1660 
1661   _hrm.verify_optional();
1662   _verifier->verify_region_sets_optional();
1663 }
1664 
1665 // Public methods.
1666 
1667 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1668   CollectedHeap(),
1669   _collector_policy(collector_policy),
1670   _g1_policy(create_g1_policy()),
1671   _collection_set(this, _g1_policy),
1672   _dirty_card_queue_set(false),
1673   _is_alive_closure_cm(this),
1674   _is_alive_closure_stw(this),
1675   _ref_processor_cm(NULL),
1676   _ref_processor_stw(NULL),
1677   _bot(NULL),
1678   _hot_card_cache(NULL),
1679   _g1_rem_set(NULL),
1680   _cg1r(NULL),
1681   _g1mm(NULL),
1682   _preserved_marks_set(true /* in_c_heap */),
1683   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1684   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1685   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1686   _humongous_reclaim_candidates(),
1687   _has_humongous_reclaim_candidates(false),
1688   _archive_allocator(NULL),
1689   _free_regions_coming(false),
1690   _gc_time_stamp(0),
1691   _summary_bytes_used(0),
1692   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1693   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1694   _expand_heap_after_alloc_failure(true),
1695   _old_marking_cycles_started(0),
1696   _old_marking_cycles_completed(0),
1697   _in_cset_fast_test(),
1698   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1699   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()) {
1700 
1701   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1702                           /* are_GC_task_threads */true,
1703                           /* are_ConcurrentGC_threads */false);
1704   _workers->initialize_workers();
1705   _verifier = new G1HeapVerifier(this);
1706 
1707   _allocator = G1Allocator::create_allocator(this);
1708 
1709   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1710 
1711   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1712 
1713   // Override the default _filler_array_max_size so that no humongous filler
1714   // objects are created.
1715   _filler_array_max_size = _humongous_object_threshold_in_words;
1716 
1717   uint n_queues = ParallelGCThreads;
1718   _task_queues = new RefToScanQueueSet(n_queues);
1719 
1720   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1721 
1722   for (uint i = 0; i < n_queues; i++) {
1723     RefToScanQueue* q = new RefToScanQueue();
1724     q->initialize();
1725     _task_queues->register_queue(i, q);
1726     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1727   }
1728 
1729   // Initialize the G1EvacuationFailureALot counters and flags.
1730   NOT_PRODUCT(reset_evacuation_should_fail();)
1731 
1732   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1733 }
1734 
1735 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1736                                                                  size_t size,
1737                                                                  size_t translation_factor) {
1738   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1739   // Allocate a new reserved space, preferring to use large pages.
1740   ReservedSpace rs(size, preferred_page_size);
1741   G1RegionToSpaceMapper* result  =
1742     G1RegionToSpaceMapper::create_mapper(rs,
1743                                          size,
1744                                          rs.alignment(),
1745                                          HeapRegion::GrainBytes,
1746                                          translation_factor,
1747                                          mtGC);
1748 
1749   os::trace_page_sizes_for_requested_size(description,
1750                                           size,
1751                                           preferred_page_size,
1752                                           rs.alignment(),
1753                                           rs.base(),
1754                                           rs.size());
1755 
1756   return result;
1757 }
1758 
1759 jint G1CollectedHeap::initialize_concurrent_refinement() {
1760   jint ecode = JNI_OK;
1761   _cg1r = ConcurrentG1Refine::create(&ecode);
1762   return ecode;
1763 }
1764 
1765 jint G1CollectedHeap::initialize() {
1766   CollectedHeap::pre_initialize();
1767   os::enable_vtime();
1768 
1769   // Necessary to satisfy locking discipline assertions.
1770 
1771   MutexLocker x(Heap_lock);
1772 
1773   // While there are no constraints in the GC code that HeapWordSize
1774   // be any particular value, there are multiple other areas in the
1775   // system which believe this to be true (e.g. oop->object_size in some
1776   // cases incorrectly returns the size in wordSize units rather than
1777   // HeapWordSize).
1778   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1779 
1780   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1781   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1782   size_t heap_alignment = collector_policy()->heap_alignment();
1783 
1784   // Ensure that the sizes are properly aligned.
1785   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1786   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1787   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1788 
1789   // Reserve the maximum.
1790 
1791   // When compressed oops are enabled, the preferred heap base
1792   // is calculated by subtracting the requested size from the
1793   // 32Gb boundary and using the result as the base address for
1794   // heap reservation. If the requested size is not aligned to
1795   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1796   // into the ReservedHeapSpace constructor) then the actual
1797   // base of the reserved heap may end up differing from the
1798   // address that was requested (i.e. the preferred heap base).
1799   // If this happens then we could end up using a non-optimal
1800   // compressed oops mode.
1801 
1802   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1803                                                  heap_alignment);
1804 
1805   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1806 
1807   // Create the barrier set for the entire reserved region.
1808   G1SATBCardTableLoggingModRefBS* bs
1809     = new G1SATBCardTableLoggingModRefBS(reserved_region());
1810   bs->initialize();
1811   assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1812   set_barrier_set(bs);
1813 
1814   // Create the hot card cache.
1815   _hot_card_cache = new G1HotCardCache(this);
1816 
1817   // Carve out the G1 part of the heap.
1818   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1819   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1820   G1RegionToSpaceMapper* heap_storage =
1821     G1RegionToSpaceMapper::create_mapper(g1_rs,
1822                                          g1_rs.size(),
1823                                          page_size,
1824                                          HeapRegion::GrainBytes,
1825                                          1,
1826                                          mtJavaHeap);
1827   os::trace_page_sizes("Heap",
1828                        collector_policy()->min_heap_byte_size(),
1829                        max_byte_size,
1830                        page_size,
1831                        heap_rs.base(),
1832                        heap_rs.size());
1833   heap_storage->set_mapping_changed_listener(&_listener);
1834 
1835   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1836   G1RegionToSpaceMapper* bot_storage =
1837     create_aux_memory_mapper("Block Offset Table",
1838                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1839                              G1BlockOffsetTable::heap_map_factor());
1840 
1841   ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1842   G1RegionToSpaceMapper* cardtable_storage =
1843     create_aux_memory_mapper("Card Table",
1844                              G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1845                              G1SATBCardTableLoggingModRefBS::heap_map_factor());
1846 
1847   G1RegionToSpaceMapper* card_counts_storage =
1848     create_aux_memory_mapper("Card Counts Table",
1849                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1850                              G1CardCounts::heap_map_factor());
1851 
1852   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1853   G1RegionToSpaceMapper* prev_bitmap_storage =
1854     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1855   G1RegionToSpaceMapper* next_bitmap_storage =
1856     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1857 
1858   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1859   g1_barrier_set()->initialize(cardtable_storage);
1860   // Do later initialization work for concurrent refinement.
1861   _hot_card_cache->initialize(card_counts_storage);
1862 
1863   // 6843694 - ensure that the maximum region index can fit
1864   // in the remembered set structures.
1865   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1866   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1867 
1868   // Also create a G1 rem set.
1869   _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache);
1870   _g1_rem_set->initialize(max_capacity(), max_regions());
1871 
1872   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1873   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1874   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1875             "too many cards per region");
1876 
1877   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1878 
1879   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1880 
1881   {
1882     HeapWord* start = _hrm.reserved().start();
1883     HeapWord* end = _hrm.reserved().end();
1884     size_t granularity = HeapRegion::GrainBytes;
1885 
1886     _in_cset_fast_test.initialize(start, end, granularity);
1887     _humongous_reclaim_candidates.initialize(start, end, granularity);
1888   }
1889 
1890   // Create the G1ConcurrentMark data structure and thread.
1891   // (Must do this late, so that "max_regions" is defined.)
1892   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1893   if (_cm == NULL || !_cm->completed_initialization()) {
1894     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1895     return JNI_ENOMEM;
1896   }
1897   _cmThread = _cm->cmThread();
1898 
1899   // Now expand into the initial heap size.
1900   if (!expand(init_byte_size, _workers)) {
1901     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1902     return JNI_ENOMEM;
1903   }
1904 
1905   // Perform any initialization actions delegated to the policy.
1906   g1_policy()->init(this, &_collection_set);
1907 
1908   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1909                                                SATB_Q_FL_lock,
1910                                                G1SATBProcessCompletedThreshold,
1911                                                Shared_SATB_Q_lock);
1912 
1913   jint ecode = initialize_concurrent_refinement();
1914   if (ecode != JNI_OK) {
1915     return ecode;
1916   }
1917 
1918   JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1919                                                 DirtyCardQ_FL_lock,
1920                                                 (int)concurrent_g1_refine()->yellow_zone(),
1921                                                 (int)concurrent_g1_refine()->red_zone(),
1922                                                 Shared_DirtyCardQ_lock,
1923                                                 NULL,  // fl_owner
1924                                                 true); // init_free_ids
1925 
1926   dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1927                                     DirtyCardQ_FL_lock,
1928                                     -1, // never trigger processing
1929                                     -1, // no limit on length
1930                                     Shared_DirtyCardQ_lock,
1931                                     &JavaThread::dirty_card_queue_set());
1932 
1933   // Here we allocate the dummy HeapRegion that is required by the
1934   // G1AllocRegion class.
1935   HeapRegion* dummy_region = _hrm.get_dummy_region();
1936 
1937   // We'll re-use the same region whether the alloc region will
1938   // require BOT updates or not and, if it doesn't, then a non-young
1939   // region will complain that it cannot support allocations without
1940   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1941   dummy_region->set_eden();
1942   // Make sure it's full.
1943   dummy_region->set_top(dummy_region->end());
1944   G1AllocRegion::setup(this, dummy_region);
1945 
1946   _allocator->init_mutator_alloc_region();
1947 
1948   // Do create of the monitoring and management support so that
1949   // values in the heap have been properly initialized.
1950   _g1mm = new G1MonitoringSupport(this);
1951 
1952   G1StringDedup::initialize();
1953 
1954   _preserved_marks_set.init(ParallelGCThreads);
1955 
1956   _collection_set.initialize(max_regions());
1957 
1958   return JNI_OK;
1959 }
1960 
1961 void G1CollectedHeap::stop() {
1962   // Stop all concurrent threads. We do this to make sure these threads
1963   // do not continue to execute and access resources (e.g. logging)
1964   // that are destroyed during shutdown.
1965   _cg1r->stop();
1966   _cmThread->stop();
1967   if (G1StringDedup::is_enabled()) {
1968     G1StringDedup::stop();
1969   }
1970 }
1971 
1972 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1973   return HeapRegion::max_region_size();
1974 }
1975 
1976 void G1CollectedHeap::post_initialize() {
1977   ref_processing_init();
1978 }
1979 
1980 void G1CollectedHeap::ref_processing_init() {
1981   // Reference processing in G1 currently works as follows:
1982   //
1983   // * There are two reference processor instances. One is
1984   //   used to record and process discovered references
1985   //   during concurrent marking; the other is used to
1986   //   record and process references during STW pauses
1987   //   (both full and incremental).
1988   // * Both ref processors need to 'span' the entire heap as
1989   //   the regions in the collection set may be dotted around.
1990   //
1991   // * For the concurrent marking ref processor:
1992   //   * Reference discovery is enabled at initial marking.
1993   //   * Reference discovery is disabled and the discovered
1994   //     references processed etc during remarking.
1995   //   * Reference discovery is MT (see below).
1996   //   * Reference discovery requires a barrier (see below).
1997   //   * Reference processing may or may not be MT
1998   //     (depending on the value of ParallelRefProcEnabled
1999   //     and ParallelGCThreads).
2000   //   * A full GC disables reference discovery by the CM
2001   //     ref processor and abandons any entries on it's
2002   //     discovered lists.
2003   //
2004   // * For the STW processor:
2005   //   * Non MT discovery is enabled at the start of a full GC.
2006   //   * Processing and enqueueing during a full GC is non-MT.
2007   //   * During a full GC, references are processed after marking.
2008   //
2009   //   * Discovery (may or may not be MT) is enabled at the start
2010   //     of an incremental evacuation pause.
2011   //   * References are processed near the end of a STW evacuation pause.
2012   //   * For both types of GC:
2013   //     * Discovery is atomic - i.e. not concurrent.
2014   //     * Reference discovery will not need a barrier.
2015 
2016   MemRegion mr = reserved_region();
2017 
2018   // Concurrent Mark ref processor
2019   _ref_processor_cm =
2020     new ReferenceProcessor(mr,    // span
2021                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2022                                 // mt processing
2023                            ParallelGCThreads,
2024                                 // degree of mt processing
2025                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2026                                 // mt discovery
2027                            MAX2(ParallelGCThreads, ConcGCThreads),
2028                                 // degree of mt discovery
2029                            false,
2030                                 // Reference discovery is not atomic
2031                            &_is_alive_closure_cm);
2032                                 // is alive closure
2033                                 // (for efficiency/performance)
2034 
2035   // STW ref processor
2036   _ref_processor_stw =
2037     new ReferenceProcessor(mr,    // span
2038                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2039                                 // mt processing
2040                            ParallelGCThreads,
2041                                 // degree of mt processing
2042                            (ParallelGCThreads > 1),
2043                                 // mt discovery
2044                            ParallelGCThreads,
2045                                 // degree of mt discovery
2046                            true,
2047                                 // Reference discovery is atomic
2048                            &_is_alive_closure_stw);
2049                                 // is alive closure
2050                                 // (for efficiency/performance)
2051 }
2052 
2053 CollectorPolicy* G1CollectedHeap::collector_policy() const {
2054   return _collector_policy;
2055 }
2056 
2057 size_t G1CollectedHeap::capacity() const {
2058   return _hrm.length() * HeapRegion::GrainBytes;
2059 }
2060 
2061 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2062   hr->reset_gc_time_stamp();
2063 }
2064 
2065 #ifndef PRODUCT
2066 
2067 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2068 private:
2069   unsigned _gc_time_stamp;
2070   bool _failures;
2071 
2072 public:
2073   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2074     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2075 
2076   virtual bool doHeapRegion(HeapRegion* hr) {
2077     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2078     if (_gc_time_stamp != region_gc_time_stamp) {
2079       log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
2080                             region_gc_time_stamp, _gc_time_stamp);
2081       _failures = true;
2082     }
2083     return false;
2084   }
2085 
2086   bool failures() { return _failures; }
2087 };
2088 
2089 void G1CollectedHeap::check_gc_time_stamps() {
2090   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2091   heap_region_iterate(&cl);
2092   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2093 }
2094 #endif // PRODUCT
2095 
2096 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
2097   _hot_card_cache->drain(cl, worker_i);
2098 }
2099 
2100 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
2101   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2102   size_t n_completed_buffers = 0;
2103   while (dcqs.apply_closure_during_gc(cl, worker_i)) {
2104     n_completed_buffers++;
2105   }
2106   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2107   dcqs.clear_n_completed_buffers();
2108   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2109 }
2110 
2111 // Computes the sum of the storage used by the various regions.
2112 size_t G1CollectedHeap::used() const {
2113   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
2114   if (_archive_allocator != NULL) {
2115     result += _archive_allocator->used();
2116   }
2117   return result;
2118 }
2119 
2120 size_t G1CollectedHeap::used_unlocked() const {
2121   return _summary_bytes_used;
2122 }
2123 
2124 class SumUsedClosure: public HeapRegionClosure {
2125   size_t _used;
2126 public:
2127   SumUsedClosure() : _used(0) {}
2128   bool doHeapRegion(HeapRegion* r) {
2129     _used += r->used();
2130     return false;
2131   }
2132   size_t result() { return _used; }
2133 };
2134 
2135 size_t G1CollectedHeap::recalculate_used() const {
2136   double recalculate_used_start = os::elapsedTime();
2137 
2138   SumUsedClosure blk;
2139   heap_region_iterate(&blk);
2140 
2141   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2142   return blk.result();
2143 }
2144 
2145 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2146   switch (cause) {
2147     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
2148     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
2149     case GCCause::_update_allocation_context_stats_inc: return true;
2150     case GCCause::_wb_conc_mark:                        return true;
2151     default :                                           return false;
2152   }
2153 }
2154 
2155 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2156   switch (cause) {
2157     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2158     case GCCause::_g1_humongous_allocation: return true;
2159     default:                                return is_user_requested_concurrent_full_gc(cause);
2160   }
2161 }
2162 
2163 #ifndef PRODUCT
2164 void G1CollectedHeap::allocate_dummy_regions() {
2165   // Let's fill up most of the region
2166   size_t word_size = HeapRegion::GrainWords - 1024;
2167   // And as a result the region we'll allocate will be humongous.
2168   guarantee(is_humongous(word_size), "sanity");
2169 
2170   // _filler_array_max_size is set to humongous object threshold
2171   // but temporarily change it to use CollectedHeap::fill_with_object().
2172   SizeTFlagSetting fs(_filler_array_max_size, word_size);
2173 
2174   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2175     // Let's use the existing mechanism for the allocation
2176     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2177                                                  AllocationContext::system());
2178     if (dummy_obj != NULL) {
2179       MemRegion mr(dummy_obj, word_size);
2180       CollectedHeap::fill_with_object(mr);
2181     } else {
2182       // If we can't allocate once, we probably cannot allocate
2183       // again. Let's get out of the loop.
2184       break;
2185     }
2186   }
2187 }
2188 #endif // !PRODUCT
2189 
2190 void G1CollectedHeap::increment_old_marking_cycles_started() {
2191   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2192          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2193          "Wrong marking cycle count (started: %d, completed: %d)",
2194          _old_marking_cycles_started, _old_marking_cycles_completed);
2195 
2196   _old_marking_cycles_started++;
2197 }
2198 
2199 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2200   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2201 
2202   // We assume that if concurrent == true, then the caller is a
2203   // concurrent thread that was joined the Suspendible Thread
2204   // Set. If there's ever a cheap way to check this, we should add an
2205   // assert here.
2206 
2207   // Given that this method is called at the end of a Full GC or of a
2208   // concurrent cycle, and those can be nested (i.e., a Full GC can
2209   // interrupt a concurrent cycle), the number of full collections
2210   // completed should be either one (in the case where there was no
2211   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2212   // behind the number of full collections started.
2213 
2214   // This is the case for the inner caller, i.e. a Full GC.
2215   assert(concurrent ||
2216          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2217          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2218          "for inner caller (Full GC): _old_marking_cycles_started = %u "
2219          "is inconsistent with _old_marking_cycles_completed = %u",
2220          _old_marking_cycles_started, _old_marking_cycles_completed);
2221 
2222   // This is the case for the outer caller, i.e. the concurrent cycle.
2223   assert(!concurrent ||
2224          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2225          "for outer caller (concurrent cycle): "
2226          "_old_marking_cycles_started = %u "
2227          "is inconsistent with _old_marking_cycles_completed = %u",
2228          _old_marking_cycles_started, _old_marking_cycles_completed);
2229 
2230   _old_marking_cycles_completed += 1;
2231 
2232   // We need to clear the "in_progress" flag in the CM thread before
2233   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2234   // is set) so that if a waiter requests another System.gc() it doesn't
2235   // incorrectly see that a marking cycle is still in progress.
2236   if (concurrent) {
2237     _cmThread->set_idle();
2238   }
2239 
2240   // This notify_all() will ensure that a thread that called
2241   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2242   // and it's waiting for a full GC to finish will be woken up. It is
2243   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2244   FullGCCount_lock->notify_all();
2245 }
2246 
2247 void G1CollectedHeap::collect(GCCause::Cause cause) {
2248   assert_heap_not_locked();
2249 
2250   uint gc_count_before;
2251   uint old_marking_count_before;
2252   uint full_gc_count_before;
2253   bool retry_gc;
2254 
2255   do {
2256     retry_gc = false;
2257 
2258     {
2259       MutexLocker ml(Heap_lock);
2260 
2261       // Read the GC count while holding the Heap_lock
2262       gc_count_before = total_collections();
2263       full_gc_count_before = total_full_collections();
2264       old_marking_count_before = _old_marking_cycles_started;
2265     }
2266 
2267     if (should_do_concurrent_full_gc(cause)) {
2268       // Schedule an initial-mark evacuation pause that will start a
2269       // concurrent cycle. We're setting word_size to 0 which means that
2270       // we are not requesting a post-GC allocation.
2271       VM_G1IncCollectionPause op(gc_count_before,
2272                                  0,     /* word_size */
2273                                  true,  /* should_initiate_conc_mark */
2274                                  g1_policy()->max_pause_time_ms(),
2275                                  cause);
2276       op.set_allocation_context(AllocationContext::current());
2277 
2278       VMThread::execute(&op);
2279       if (!op.pause_succeeded()) {
2280         if (old_marking_count_before == _old_marking_cycles_started) {
2281           retry_gc = op.should_retry_gc();
2282         } else {
2283           // A Full GC happened while we were trying to schedule the
2284           // initial-mark GC. No point in starting a new cycle given
2285           // that the whole heap was collected anyway.
2286         }
2287 
2288         if (retry_gc) {
2289           if (GCLocker::is_active_and_needs_gc()) {
2290             GCLocker::stall_until_clear();
2291           }
2292         }
2293       }
2294     } else {
2295       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2296           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2297 
2298         // Schedule a standard evacuation pause. We're setting word_size
2299         // to 0 which means that we are not requesting a post-GC allocation.
2300         VM_G1IncCollectionPause op(gc_count_before,
2301                                    0,     /* word_size */
2302                                    false, /* should_initiate_conc_mark */
2303                                    g1_policy()->max_pause_time_ms(),
2304                                    cause);
2305         VMThread::execute(&op);
2306       } else {
2307         // Schedule a Full GC.
2308         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2309         VMThread::execute(&op);
2310       }
2311     }
2312   } while (retry_gc);
2313 }
2314 
2315 bool G1CollectedHeap::is_in(const void* p) const {
2316   if (_hrm.reserved().contains(p)) {
2317     // Given that we know that p is in the reserved space,
2318     // heap_region_containing() should successfully
2319     // return the containing region.
2320     HeapRegion* hr = heap_region_containing(p);
2321     return hr->is_in(p);
2322   } else {
2323     return false;
2324   }
2325 }
2326 
2327 #ifdef ASSERT
2328 bool G1CollectedHeap::is_in_exact(const void* p) const {
2329   bool contains = reserved_region().contains(p);
2330   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2331   if (contains && available) {
2332     return true;
2333   } else {
2334     return false;
2335   }
2336 }
2337 #endif
2338 
2339 // Iteration functions.
2340 
2341 // Iterates an ObjectClosure over all objects within a HeapRegion.
2342 
2343 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2344   ObjectClosure* _cl;
2345 public:
2346   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2347   bool doHeapRegion(HeapRegion* r) {
2348     if (!r->is_continues_humongous()) {
2349       r->object_iterate(_cl);
2350     }
2351     return false;
2352   }
2353 };
2354 
2355 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2356   IterateObjectClosureRegionClosure blk(cl);
2357   heap_region_iterate(&blk);
2358 }
2359 
2360 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2361   _hrm.iterate(cl);
2362 }
2363 
2364 void G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2365                                               uint worker_id,
2366                                               HeapRegionClaimer *hrclaimer) const {
2367   _hrm.par_iterate(cl, worker_id, hrclaimer);
2368 }
2369 
2370 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2371   _collection_set.iterate(cl);
2372 }
2373 
2374 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2375   _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2376 }
2377 
2378 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2379   HeapRegion* result = _hrm.next_region_in_heap(from);
2380   while (result != NULL && result->is_pinned()) {
2381     result = _hrm.next_region_in_heap(result);
2382   }
2383   return result;
2384 }
2385 
2386 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2387   HeapRegion* hr = heap_region_containing(addr);
2388   return hr->block_start(addr);
2389 }
2390 
2391 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2392   HeapRegion* hr = heap_region_containing(addr);
2393   return hr->block_size(addr);
2394 }
2395 
2396 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2397   HeapRegion* hr = heap_region_containing(addr);
2398   return hr->block_is_obj(addr);
2399 }
2400 
2401 bool G1CollectedHeap::supports_tlab_allocation() const {
2402   return true;
2403 }
2404 
2405 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2406   return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2407 }
2408 
2409 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2410   return _eden.length() * HeapRegion::GrainBytes;
2411 }
2412 
2413 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2414 // must be equal to the humongous object limit.
2415 size_t G1CollectedHeap::max_tlab_size() const {
2416   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2417 }
2418 
2419 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2420   AllocationContext_t context = AllocationContext::current();
2421   return _allocator->unsafe_max_tlab_alloc(context);
2422 }
2423 
2424 size_t G1CollectedHeap::max_capacity() const {
2425   return _hrm.reserved().byte_size();
2426 }
2427 
2428 jlong G1CollectedHeap::millis_since_last_gc() {
2429   // See the notes in GenCollectedHeap::millis_since_last_gc()
2430   // for more information about the implementation.
2431   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2432     _g1_policy->collection_pause_end_millis();
2433   if (ret_val < 0) {
2434     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2435       ". returning zero instead.", ret_val);
2436     return 0;
2437   }
2438   return ret_val;
2439 }
2440 
2441 void G1CollectedHeap::prepare_for_verify() {
2442   _verifier->prepare_for_verify();
2443 }
2444 
2445 void G1CollectedHeap::verify(VerifyOption vo) {
2446   _verifier->verify(vo);
2447 }
2448 
2449 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2450   return true;
2451 }
2452 
2453 const char* const* G1CollectedHeap::concurrent_phases() const {
2454   return _cmThread->concurrent_phases();
2455 }
2456 
2457 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2458   return _cmThread->request_concurrent_phase(phase);
2459 }
2460 
2461 class PrintRegionClosure: public HeapRegionClosure {
2462   outputStream* _st;
2463 public:
2464   PrintRegionClosure(outputStream* st) : _st(st) {}
2465   bool doHeapRegion(HeapRegion* r) {
2466     r->print_on(_st);
2467     return false;
2468   }
2469 };
2470 
2471 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2472                                        const HeapRegion* hr,
2473                                        const VerifyOption vo) const {
2474   switch (vo) {
2475   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2476   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2477   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked() && !hr->is_archive();
2478   default:                            ShouldNotReachHere();
2479   }
2480   return false; // keep some compilers happy
2481 }
2482 
2483 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2484                                        const VerifyOption vo) const {
2485   switch (vo) {
2486   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2487   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2488   case VerifyOption_G1UseMarkWord: {
2489     HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj);
2490     return !obj->is_gc_marked() && !hr->is_archive();
2491   }
2492   default:                            ShouldNotReachHere();
2493   }
2494   return false; // keep some compilers happy
2495 }
2496 
2497 void G1CollectedHeap::print_heap_regions() const {
2498   Log(gc, heap, region) log;
2499   if (log.is_trace()) {
2500     ResourceMark rm;
2501     print_regions_on(log.trace_stream());
2502   }
2503 }
2504 
2505 void G1CollectedHeap::print_on(outputStream* st) const {
2506   st->print(" %-20s", "garbage-first heap");
2507   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2508             capacity()/K, used_unlocked()/K);
2509   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
2510             p2i(_hrm.reserved().start()),
2511             p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords),
2512             p2i(_hrm.reserved().end()));
2513   st->cr();
2514   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2515   uint young_regions = young_regions_count();
2516   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2517             (size_t) young_regions * HeapRegion::GrainBytes / K);
2518   uint survivor_regions = survivor_regions_count();
2519   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2520             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2521   st->cr();
2522   MetaspaceAux::print_on(st);
2523 }
2524 
2525 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2526   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2527                "HS=humongous(starts), HC=humongous(continues), "
2528                "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2529                "AC=allocation context, "
2530                "TAMS=top-at-mark-start (previous, next)");
2531   PrintRegionClosure blk(st);
2532   heap_region_iterate(&blk);
2533 }
2534 
2535 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2536   print_on(st);
2537 
2538   // Print the per-region information.
2539   print_regions_on(st);
2540 }
2541 
2542 void G1CollectedHeap::print_on_error(outputStream* st) const {
2543   this->CollectedHeap::print_on_error(st);
2544 
2545   if (_cm != NULL) {
2546     st->cr();
2547     _cm->print_on_error(st);
2548   }
2549 }
2550 
2551 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2552   workers()->print_worker_threads_on(st);
2553   _cmThread->print_on(st);
2554   st->cr();
2555   _cm->print_worker_threads_on(st);
2556   _cg1r->print_worker_threads_on(st); // also prints the sample thread
2557   if (G1StringDedup::is_enabled()) {
2558     G1StringDedup::print_worker_threads_on(st);
2559   }
2560 }
2561 
2562 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2563   workers()->threads_do(tc);
2564   tc->do_thread(_cmThread);
2565   _cm->threads_do(tc);
2566   _cg1r->threads_do(tc); // also iterates over the sample thread
2567   if (G1StringDedup::is_enabled()) {
2568     G1StringDedup::threads_do(tc);
2569   }
2570 }
2571 
2572 void G1CollectedHeap::print_tracing_info() const {
2573   g1_rem_set()->print_summary_info();
2574   concurrent_mark()->print_summary_info();
2575 }
2576 
2577 #ifndef PRODUCT
2578 // Helpful for debugging RSet issues.
2579 
2580 class PrintRSetsClosure : public HeapRegionClosure {
2581 private:
2582   const char* _msg;
2583   size_t _occupied_sum;
2584 
2585 public:
2586   bool doHeapRegion(HeapRegion* r) {
2587     HeapRegionRemSet* hrrs = r->rem_set();
2588     size_t occupied = hrrs->occupied();
2589     _occupied_sum += occupied;
2590 
2591     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2592     if (occupied == 0) {
2593       tty->print_cr("  RSet is empty");
2594     } else {
2595       hrrs->print();
2596     }
2597     tty->print_cr("----------");
2598     return false;
2599   }
2600 
2601   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2602     tty->cr();
2603     tty->print_cr("========================================");
2604     tty->print_cr("%s", msg);
2605     tty->cr();
2606   }
2607 
2608   ~PrintRSetsClosure() {
2609     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2610     tty->print_cr("========================================");
2611     tty->cr();
2612   }
2613 };
2614 
2615 void G1CollectedHeap::print_cset_rsets() {
2616   PrintRSetsClosure cl("Printing CSet RSets");
2617   collection_set_iterate(&cl);
2618 }
2619 
2620 void G1CollectedHeap::print_all_rsets() {
2621   PrintRSetsClosure cl("Printing All RSets");;
2622   heap_region_iterate(&cl);
2623 }
2624 #endif // PRODUCT
2625 
2626 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2627 
2628   size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2629   size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2630   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2631 
2632   size_t eden_capacity_bytes =
2633     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2634 
2635   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2636   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2637                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2638 }
2639 
2640 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2641   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2642                        stats->unused(), stats->used(), stats->region_end_waste(),
2643                        stats->regions_filled(), stats->direct_allocated(),
2644                        stats->failure_used(), stats->failure_waste());
2645 }
2646 
2647 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2648   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2649   gc_tracer->report_gc_heap_summary(when, heap_summary);
2650 
2651   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2652   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2653 }
2654 
2655 G1CollectedHeap* G1CollectedHeap::heap() {
2656   CollectedHeap* heap = Universe::heap();
2657   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2658   assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2659   return (G1CollectedHeap*)heap;
2660 }
2661 
2662 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
2663   // always_do_update_barrier = false;
2664   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2665 
2666   double start = os::elapsedTime();
2667   // Fill TLAB's and such
2668   accumulate_statistics_all_tlabs();
2669   ensure_parsability(true);
2670   g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2671 
2672   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2673 }
2674 
2675 void G1CollectedHeap::gc_epilogue(bool full) {
2676   // we are at the end of the GC. Total collections has already been increased.
2677   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2678 
2679   // FIXME: what is this about?
2680   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2681   // is set.
2682 #if defined(COMPILER2) || INCLUDE_JVMCI
2683   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2684 #endif
2685   // always_do_update_barrier = true;
2686 
2687   double start = os::elapsedTime();
2688   resize_all_tlabs();
2689   g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2690 
2691   allocation_context_stats().update(full);
2692 
2693   // We have just completed a GC. Update the soft reference
2694   // policy with the new heap occupancy
2695   Universe::update_heap_info_at_gc();
2696 }
2697 
2698 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2699                                                uint gc_count_before,
2700                                                bool* succeeded,
2701                                                GCCause::Cause gc_cause) {
2702   assert_heap_not_locked_and_not_at_safepoint();
2703   VM_G1IncCollectionPause op(gc_count_before,
2704                              word_size,
2705                              false, /* should_initiate_conc_mark */
2706                              g1_policy()->max_pause_time_ms(),
2707                              gc_cause);
2708 
2709   op.set_allocation_context(AllocationContext::current());
2710   VMThread::execute(&op);
2711 
2712   HeapWord* result = op.result();
2713   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2714   assert(result == NULL || ret_succeeded,
2715          "the result should be NULL if the VM did not succeed");
2716   *succeeded = ret_succeeded;
2717 
2718   assert_heap_not_locked();
2719   return result;
2720 }
2721 
2722 void
2723 G1CollectedHeap::doConcurrentMark() {
2724   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2725   if (!_cmThread->in_progress()) {
2726     _cmThread->set_started();
2727     CGC_lock->notify();
2728   }
2729 }
2730 
2731 size_t G1CollectedHeap::pending_card_num() {
2732   size_t extra_cards = 0;
2733   JavaThread *curr = Threads::first();
2734   while (curr != NULL) {
2735     DirtyCardQueue& dcq = curr->dirty_card_queue();
2736     extra_cards += dcq.size();
2737     curr = curr->next();
2738   }
2739   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2740   size_t buffer_size = dcqs.buffer_size();
2741   size_t buffer_num = dcqs.completed_buffers_num();
2742 
2743   return buffer_size * buffer_num + extra_cards;
2744 }
2745 
2746 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2747  private:
2748   size_t _total_humongous;
2749   size_t _candidate_humongous;
2750 
2751   DirtyCardQueue _dcq;
2752 
2753   // We don't nominate objects with many remembered set entries, on
2754   // the assumption that such objects are likely still live.
2755   bool is_remset_small(HeapRegion* region) const {
2756     HeapRegionRemSet* const rset = region->rem_set();
2757     return G1EagerReclaimHumongousObjectsWithStaleRefs
2758       ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2759       : rset->is_empty();
2760   }
2761 
2762   bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2763     assert(region->is_starts_humongous(), "Must start a humongous object");
2764 
2765     oop obj = oop(region->bottom());
2766 
2767     // Dead objects cannot be eager reclaim candidates. Due to class
2768     // unloading it is unsafe to query their classes so we return early.
2769     if (heap->is_obj_dead(obj, region)) {
2770       return false;
2771     }
2772 
2773     // Candidate selection must satisfy the following constraints
2774     // while concurrent marking is in progress:
2775     //
2776     // * In order to maintain SATB invariants, an object must not be
2777     // reclaimed if it was allocated before the start of marking and
2778     // has not had its references scanned.  Such an object must have
2779     // its references (including type metadata) scanned to ensure no
2780     // live objects are missed by the marking process.  Objects
2781     // allocated after the start of concurrent marking don't need to
2782     // be scanned.
2783     //
2784     // * An object must not be reclaimed if it is on the concurrent
2785     // mark stack.  Objects allocated after the start of concurrent
2786     // marking are never pushed on the mark stack.
2787     //
2788     // Nominating only objects allocated after the start of concurrent
2789     // marking is sufficient to meet both constraints.  This may miss
2790     // some objects that satisfy the constraints, but the marking data
2791     // structures don't support efficiently performing the needed
2792     // additional tests or scrubbing of the mark stack.
2793     //
2794     // However, we presently only nominate is_typeArray() objects.
2795     // A humongous object containing references induces remembered
2796     // set entries on other regions.  In order to reclaim such an
2797     // object, those remembered sets would need to be cleaned up.
2798     //
2799     // We also treat is_typeArray() objects specially, allowing them
2800     // to be reclaimed even if allocated before the start of
2801     // concurrent mark.  For this we rely on mark stack insertion to
2802     // exclude is_typeArray() objects, preventing reclaiming an object
2803     // that is in the mark stack.  We also rely on the metadata for
2804     // such objects to be built-in and so ensured to be kept live.
2805     // Frequent allocation and drop of large binary blobs is an
2806     // important use case for eager reclaim, and this special handling
2807     // may reduce needed headroom.
2808 
2809     return obj->is_typeArray() && is_remset_small(region);
2810   }
2811 
2812  public:
2813   RegisterHumongousWithInCSetFastTestClosure()
2814   : _total_humongous(0),
2815     _candidate_humongous(0),
2816     _dcq(&JavaThread::dirty_card_queue_set()) {
2817   }
2818 
2819   virtual bool doHeapRegion(HeapRegion* r) {
2820     if (!r->is_starts_humongous()) {
2821       return false;
2822     }
2823     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2824 
2825     bool is_candidate = humongous_region_is_candidate(g1h, r);
2826     uint rindex = r->hrm_index();
2827     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2828     if (is_candidate) {
2829       _candidate_humongous++;
2830       g1h->register_humongous_region_with_cset(rindex);
2831       // Is_candidate already filters out humongous object with large remembered sets.
2832       // If we have a humongous object with a few remembered sets, we simply flush these
2833       // remembered set entries into the DCQS. That will result in automatic
2834       // re-evaluation of their remembered set entries during the following evacuation
2835       // phase.
2836       if (!r->rem_set()->is_empty()) {
2837         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2838                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2839         G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
2840         HeapRegionRemSetIterator hrrs(r->rem_set());
2841         size_t card_index;
2842         while (hrrs.has_next(card_index)) {
2843           jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
2844           // The remembered set might contain references to already freed
2845           // regions. Filter out such entries to avoid failing card table
2846           // verification.
2847           if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
2848             if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
2849               *card_ptr = CardTableModRefBS::dirty_card_val();
2850               _dcq.enqueue(card_ptr);
2851             }
2852           }
2853         }
2854         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2855                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2856                hrrs.n_yielded(), r->rem_set()->occupied());
2857         r->rem_set()->clear_locked();
2858       }
2859       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2860     }
2861     _total_humongous++;
2862 
2863     return false;
2864   }
2865 
2866   size_t total_humongous() const { return _total_humongous; }
2867   size_t candidate_humongous() const { return _candidate_humongous; }
2868 
2869   void flush_rem_set_entries() { _dcq.flush(); }
2870 };
2871 
2872 void G1CollectedHeap::register_humongous_regions_with_cset() {
2873   if (!G1EagerReclaimHumongousObjects) {
2874     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2875     return;
2876   }
2877   double time = os::elapsed_counter();
2878 
2879   // Collect reclaim candidate information and register candidates with cset.
2880   RegisterHumongousWithInCSetFastTestClosure cl;
2881   heap_region_iterate(&cl);
2882 
2883   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2884   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2885                                                                   cl.total_humongous(),
2886                                                                   cl.candidate_humongous());
2887   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2888 
2889   // Finally flush all remembered set entries to re-check into the global DCQS.
2890   cl.flush_rem_set_entries();
2891 }
2892 
2893 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2894   public:
2895     bool doHeapRegion(HeapRegion* hr) {
2896       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2897         hr->verify_rem_set();
2898       }
2899       return false;
2900     }
2901 };
2902 
2903 uint G1CollectedHeap::num_task_queues() const {
2904   return _task_queues->size();
2905 }
2906 
2907 #if TASKQUEUE_STATS
2908 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2909   st->print_raw_cr("GC Task Stats");
2910   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2911   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2912 }
2913 
2914 void G1CollectedHeap::print_taskqueue_stats() const {
2915   if (!log_is_enabled(Trace, gc, task, stats)) {
2916     return;
2917   }
2918   Log(gc, task, stats) log;
2919   ResourceMark rm;
2920   outputStream* st = log.trace_stream();
2921 
2922   print_taskqueue_stats_hdr(st);
2923 
2924   TaskQueueStats totals;
2925   const uint n = num_task_queues();
2926   for (uint i = 0; i < n; ++i) {
2927     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2928     totals += task_queue(i)->stats;
2929   }
2930   st->print_raw("tot "); totals.print(st); st->cr();
2931 
2932   DEBUG_ONLY(totals.verify());
2933 }
2934 
2935 void G1CollectedHeap::reset_taskqueue_stats() {
2936   const uint n = num_task_queues();
2937   for (uint i = 0; i < n; ++i) {
2938     task_queue(i)->stats.reset();
2939   }
2940 }
2941 #endif // TASKQUEUE_STATS
2942 
2943 void G1CollectedHeap::wait_for_root_region_scanning() {
2944   double scan_wait_start = os::elapsedTime();
2945   // We have to wait until the CM threads finish scanning the
2946   // root regions as it's the only way to ensure that all the
2947   // objects on them have been correctly scanned before we start
2948   // moving them during the GC.
2949   bool waited = _cm->root_regions()->wait_until_scan_finished();
2950   double wait_time_ms = 0.0;
2951   if (waited) {
2952     double scan_wait_end = os::elapsedTime();
2953     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2954   }
2955   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2956 }
2957 
2958 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2959 private:
2960   G1HRPrinter* _hr_printer;
2961 public:
2962   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2963 
2964   virtual bool doHeapRegion(HeapRegion* r) {
2965     _hr_printer->cset(r);
2966     return false;
2967   }
2968 };
2969 
2970 void G1CollectedHeap::start_new_collection_set() {
2971   collection_set()->start_incremental_building();
2972 
2973   clear_cset_fast_test();
2974 
2975   guarantee(_eden.length() == 0, "eden should have been cleared");
2976   g1_policy()->transfer_survivors_to_cset(survivor());
2977 }
2978 
2979 bool
2980 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2981   assert_at_safepoint(true /* should_be_vm_thread */);
2982   guarantee(!is_gc_active(), "collection is not reentrant");
2983 
2984   if (GCLocker::check_active_before_gc()) {
2985     return false;
2986   }
2987 
2988   _gc_timer_stw->register_gc_start();
2989 
2990   GCIdMark gc_id_mark;
2991   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2992 
2993   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2994   ResourceMark rm;
2995 
2996   g1_policy()->note_gc_start();
2997 
2998   wait_for_root_region_scanning();
2999 
3000   print_heap_before_gc();
3001   print_heap_regions();
3002   trace_heap_before_gc(_gc_tracer_stw);
3003 
3004   _verifier->verify_region_sets_optional();
3005   _verifier->verify_dirty_young_regions();
3006 
3007   // We should not be doing initial mark unless the conc mark thread is running
3008   if (!_cmThread->should_terminate()) {
3009     // This call will decide whether this pause is an initial-mark
3010     // pause. If it is, during_initial_mark_pause() will return true
3011     // for the duration of this pause.
3012     g1_policy()->decide_on_conc_mark_initiation();
3013   }
3014 
3015   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3016   assert(!collector_state()->during_initial_mark_pause() ||
3017           collector_state()->gcs_are_young(), "sanity");
3018 
3019   // We also do not allow mixed GCs during marking.
3020   assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
3021 
3022   // Record whether this pause is an initial mark. When the current
3023   // thread has completed its logging output and it's safe to signal
3024   // the CM thread, the flag's value in the policy has been reset.
3025   bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
3026 
3027   // Inner scope for scope based logging, timers, and stats collection
3028   {
3029     EvacuationInfo evacuation_info;
3030 
3031     if (collector_state()->during_initial_mark_pause()) {
3032       // We are about to start a marking cycle, so we increment the
3033       // full collection counter.
3034       increment_old_marking_cycles_started();
3035       _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
3036     }
3037 
3038     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
3039 
3040     GCTraceCPUTime tcpu;
3041 
3042     FormatBuffer<> gc_string("Pause ");
3043     if (collector_state()->during_initial_mark_pause()) {
3044       gc_string.append("Initial Mark");
3045     } else if (collector_state()->gcs_are_young()) {
3046       gc_string.append("Young");
3047     } else {
3048       gc_string.append("Mixed");
3049     }
3050     GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
3051 
3052     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
3053                                                                   workers()->active_workers(),
3054                                                                   Threads::number_of_non_daemon_threads());
3055     workers()->update_active_workers(active_workers);
3056     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
3057 
3058     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3059     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3060 
3061     // If the secondary_free_list is not empty, append it to the
3062     // free_list. No need to wait for the cleanup operation to finish;
3063     // the region allocation code will check the secondary_free_list
3064     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3065     // set, skip this step so that the region allocation code has to
3066     // get entries from the secondary_free_list.
3067     if (!G1StressConcRegionFreeing) {
3068       append_secondary_free_list_if_not_empty_with_lock();
3069     }
3070 
3071     G1HeapTransition heap_transition(this);
3072     size_t heap_used_bytes_before_gc = used();
3073 
3074     // Don't dynamically change the number of GC threads this early.  A value of
3075     // 0 is used to indicate serial work.  When parallel work is done,
3076     // it will be set.
3077 
3078     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3079       IsGCActiveMark x;
3080 
3081       gc_prologue(false);
3082       increment_total_collections(false /* full gc */);
3083       increment_gc_time_stamp();
3084 
3085       if (VerifyRememberedSets) {
3086         log_info(gc, verify)("[Verifying RemSets before GC]");
3087         VerifyRegionRemSetClosure v_cl;
3088         heap_region_iterate(&v_cl);
3089       }
3090 
3091       _verifier->verify_before_gc();
3092 
3093       _verifier->check_bitmaps("GC Start");
3094 
3095 #if defined(COMPILER2) || INCLUDE_JVMCI
3096       DerivedPointerTable::clear();
3097 #endif
3098 
3099       // Please see comment in g1CollectedHeap.hpp and
3100       // G1CollectedHeap::ref_processing_init() to see how
3101       // reference processing currently works in G1.
3102 
3103       // Enable discovery in the STW reference processor
3104       if (g1_policy()->should_process_references()) {
3105         ref_processor_stw()->enable_discovery();
3106       } else {
3107         ref_processor_stw()->disable_discovery();
3108       }
3109 
3110       {
3111         // We want to temporarily turn off discovery by the
3112         // CM ref processor, if necessary, and turn it back on
3113         // on again later if we do. Using a scoped
3114         // NoRefDiscovery object will do this.
3115         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3116 
3117         // Forget the current alloc region (we might even choose it to be part
3118         // of the collection set!).
3119         _allocator->release_mutator_alloc_region();
3120 
3121         // This timing is only used by the ergonomics to handle our pause target.
3122         // It is unclear why this should not include the full pause. We will
3123         // investigate this in CR 7178365.
3124         //
3125         // Preserving the old comment here if that helps the investigation:
3126         //
3127         // The elapsed time induced by the start time below deliberately elides
3128         // the possible verification above.
3129         double sample_start_time_sec = os::elapsedTime();
3130 
3131         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3132 
3133         if (collector_state()->during_initial_mark_pause()) {
3134           concurrent_mark()->checkpointRootsInitialPre();
3135         }
3136 
3137         g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
3138 
3139         evacuation_info.set_collectionset_regions(collection_set()->region_length());
3140 
3141         // Make sure the remembered sets are up to date. This needs to be
3142         // done before register_humongous_regions_with_cset(), because the
3143         // remembered sets are used there to choose eager reclaim candidates.
3144         // If the remembered sets are not up to date we might miss some
3145         // entries that need to be handled.
3146         g1_rem_set()->cleanupHRRS();
3147 
3148         register_humongous_regions_with_cset();
3149 
3150         assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3151 
3152         // We call this after finalize_cset() to
3153         // ensure that the CSet has been finalized.
3154         _cm->verify_no_cset_oops();
3155 
3156         if (_hr_printer.is_active()) {
3157           G1PrintCollectionSetClosure cl(&_hr_printer);
3158           _collection_set.iterate(&cl);
3159         }
3160 
3161         // Initialize the GC alloc regions.
3162         _allocator->init_gc_alloc_regions(evacuation_info);
3163 
3164         G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3165         pre_evacuate_collection_set();
3166 
3167         // Actually do the work...
3168         evacuate_collection_set(evacuation_info, &per_thread_states);
3169 
3170         post_evacuate_collection_set(evacuation_info, &per_thread_states);
3171 
3172         const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3173         free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
3174 
3175         eagerly_reclaim_humongous_regions();
3176 
3177         record_obj_copy_mem_stats();
3178         _survivor_evac_stats.adjust_desired_plab_sz();
3179         _old_evac_stats.adjust_desired_plab_sz();
3180 
3181         double start = os::elapsedTime();
3182         start_new_collection_set();
3183         g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
3184 
3185         if (evacuation_failed()) {
3186           set_used(recalculate_used());
3187           if (_archive_allocator != NULL) {
3188             _archive_allocator->clear_used();
3189           }
3190           for (uint i = 0; i < ParallelGCThreads; i++) {
3191             if (_evacuation_failed_info_array[i].has_failed()) {
3192               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3193             }
3194           }
3195         } else {
3196           // The "used" of the the collection set have already been subtracted
3197           // when they were freed.  Add in the bytes evacuated.
3198           increase_used(g1_policy()->bytes_copied_during_gc());
3199         }
3200 
3201         if (collector_state()->during_initial_mark_pause()) {
3202           // We have to do this before we notify the CM threads that
3203           // they can start working to make sure that all the
3204           // appropriate initialization is done on the CM object.
3205           concurrent_mark()->checkpointRootsInitialPost();
3206           collector_state()->set_mark_in_progress(true);
3207           // Note that we don't actually trigger the CM thread at
3208           // this point. We do that later when we're sure that
3209           // the current thread has completed its logging output.
3210         }
3211 
3212         allocate_dummy_regions();
3213 
3214         _allocator->init_mutator_alloc_region();
3215 
3216         {
3217           size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3218           if (expand_bytes > 0) {
3219             size_t bytes_before = capacity();
3220             // No need for an ergo logging here,
3221             // expansion_amount() does this when it returns a value > 0.
3222             double expand_ms;
3223             if (!expand(expand_bytes, _workers, &expand_ms)) {
3224               // We failed to expand the heap. Cannot do anything about it.
3225             }
3226             g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3227           }
3228         }
3229 
3230         // We redo the verification but now wrt to the new CSet which
3231         // has just got initialized after the previous CSet was freed.
3232         _cm->verify_no_cset_oops();
3233 
3234         // This timing is only used by the ergonomics to handle our pause target.
3235         // It is unclear why this should not include the full pause. We will
3236         // investigate this in CR 7178365.
3237         double sample_end_time_sec = os::elapsedTime();
3238         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3239         size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
3240         g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3241 
3242         evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3243         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3244 
3245         MemoryService::track_memory_usage();
3246 
3247         if (VerifyRememberedSets) {
3248           log_info(gc, verify)("[Verifying RemSets after GC]");
3249           VerifyRegionRemSetClosure v_cl;
3250           heap_region_iterate(&v_cl);
3251         }
3252 
3253         _verifier->verify_after_gc();
3254         _verifier->check_bitmaps("GC End");
3255 
3256         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3257         ref_processor_stw()->verify_no_references_recorded();
3258 
3259         // CM reference discovery will be re-enabled if necessary.
3260       }
3261 
3262 #ifdef TRACESPINNING
3263       ParallelTaskTerminator::print_termination_counts();
3264 #endif
3265 
3266       gc_epilogue(false);
3267     }
3268 
3269     // Print the remainder of the GC log output.
3270     if (evacuation_failed()) {
3271       log_info(gc)("To-space exhausted");
3272     }
3273 
3274     g1_policy()->print_phases();
3275     heap_transition.print();
3276 
3277     // It is not yet to safe to tell the concurrent mark to
3278     // start as we have some optional output below. We don't want the
3279     // output from the concurrent mark thread interfering with this
3280     // logging output either.
3281 
3282     _hrm.verify_optional();
3283     _verifier->verify_region_sets_optional();
3284 
3285     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3286     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3287 
3288     print_heap_after_gc();
3289     print_heap_regions();
3290     trace_heap_after_gc(_gc_tracer_stw);
3291 
3292     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3293     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3294     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3295     // before any GC notifications are raised.
3296     g1mm()->update_sizes();
3297 
3298     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3299     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3300     _gc_timer_stw->register_gc_end();
3301     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3302   }
3303   // It should now be safe to tell the concurrent mark thread to start
3304   // without its logging output interfering with the logging output
3305   // that came from the pause.
3306 
3307   if (should_start_conc_mark) {
3308     // CAUTION: after the doConcurrentMark() call below,
3309     // the concurrent marking thread(s) could be running
3310     // concurrently with us. Make sure that anything after
3311     // this point does not assume that we are the only GC thread
3312     // running. Note: of course, the actual marking work will
3313     // not start until the safepoint itself is released in
3314     // SuspendibleThreadSet::desynchronize().
3315     doConcurrentMark();
3316   }
3317 
3318   return true;
3319 }
3320 
3321 void G1CollectedHeap::remove_self_forwarding_pointers() {
3322   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3323   workers()->run_task(&rsfp_task);
3324 }
3325 
3326 void G1CollectedHeap::restore_after_evac_failure() {
3327   double remove_self_forwards_start = os::elapsedTime();
3328 
3329   remove_self_forwarding_pointers();
3330   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3331   _preserved_marks_set.restore(&task_executor);
3332 
3333   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3334 }
3335 
3336 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3337   if (!_evacuation_failed) {
3338     _evacuation_failed = true;
3339   }
3340 
3341   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3342   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3343 }
3344 
3345 bool G1ParEvacuateFollowersClosure::offer_termination() {
3346   G1ParScanThreadState* const pss = par_scan_state();
3347   start_term_time();
3348   const bool res = terminator()->offer_termination();
3349   end_term_time();
3350   return res;
3351 }
3352 
3353 void G1ParEvacuateFollowersClosure::do_void() {
3354   G1ParScanThreadState* const pss = par_scan_state();
3355   pss->trim_queue();
3356   do {
3357     pss->steal_and_trim_queue(queues());
3358   } while (!offer_termination());
3359 }
3360 
3361 class G1ParTask : public AbstractGangTask {
3362 protected:
3363   G1CollectedHeap*         _g1h;
3364   G1ParScanThreadStateSet* _pss;
3365   RefToScanQueueSet*       _queues;
3366   G1RootProcessor*         _root_processor;
3367   ParallelTaskTerminator   _terminator;
3368   uint                     _n_workers;
3369 
3370 public:
3371   G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3372     : AbstractGangTask("G1 collection"),
3373       _g1h(g1h),
3374       _pss(per_thread_states),
3375       _queues(task_queues),
3376       _root_processor(root_processor),
3377       _terminator(n_workers, _queues),
3378       _n_workers(n_workers)
3379   {}
3380 
3381   void work(uint worker_id) {
3382     if (worker_id >= _n_workers) return;  // no work needed this round
3383 
3384     double start_sec = os::elapsedTime();
3385     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3386 
3387     {
3388       ResourceMark rm;
3389       HandleMark   hm;
3390 
3391       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
3392 
3393       G1ParScanThreadState*           pss = _pss->state_for_worker(worker_id);
3394       pss->set_ref_processor(rp);
3395 
3396       double start_strong_roots_sec = os::elapsedTime();
3397 
3398       _root_processor->evacuate_roots(pss->closures(), worker_id);
3399 
3400       // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3401       // treating the nmethods visited to act as roots for concurrent marking.
3402       // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3403       // objects copied by the current evacuation.
3404       _g1h->g1_rem_set()->oops_into_collection_set_do(pss,
3405                                                       pss->closures()->weak_codeblobs(),
3406                                                       worker_id);
3407 
3408       double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3409 
3410       double term_sec = 0.0;
3411       size_t evac_term_attempts = 0;
3412       {
3413         double start = os::elapsedTime();
3414         G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3415         evac.do_void();
3416 
3417         evac_term_attempts = evac.term_attempts();
3418         term_sec = evac.term_time();
3419         double elapsed_sec = os::elapsedTime() - start;
3420         _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3421         _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3422         _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3423       }
3424 
3425       assert(pss->queue_is_empty(), "should be empty");
3426 
3427       if (log_is_enabled(Debug, gc, task, stats)) {
3428         MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3429         size_t lab_waste;
3430         size_t lab_undo_waste;
3431         pss->waste(lab_waste, lab_undo_waste);
3432         _g1h->print_termination_stats(worker_id,
3433                                       (os::elapsedTime() - start_sec) * 1000.0,   /* elapsed time */
3434                                       strong_roots_sec * 1000.0,                  /* strong roots time */
3435                                       term_sec * 1000.0,                          /* evac term time */
3436                                       evac_term_attempts,                         /* evac term attempts */
3437                                       lab_waste,                                  /* alloc buffer waste */
3438                                       lab_undo_waste                              /* undo waste */
3439                                       );
3440       }
3441 
3442       // Close the inner scope so that the ResourceMark and HandleMark
3443       // destructors are executed here and are included as part of the
3444       // "GC Worker Time".
3445     }
3446     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3447   }
3448 };
3449 
3450 void G1CollectedHeap::print_termination_stats_hdr() {
3451   log_debug(gc, task, stats)("GC Termination Stats");
3452   log_debug(gc, task, stats)("     elapsed  --strong roots-- -------termination------- ------waste (KiB)------");
3453   log_debug(gc, task, stats)("thr     ms        ms      %%        ms      %%    attempts  total   alloc    undo");
3454   log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3455 }
3456 
3457 void G1CollectedHeap::print_termination_stats(uint worker_id,
3458                                               double elapsed_ms,
3459                                               double strong_roots_ms,
3460                                               double term_ms,
3461                                               size_t term_attempts,
3462                                               size_t alloc_buffer_waste,
3463                                               size_t undo_waste) const {
3464   log_debug(gc, task, stats)
3465               ("%3d %9.2f %9.2f %6.2f "
3466                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3467                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3468                worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3469                term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3470                (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3471                alloc_buffer_waste * HeapWordSize / K,
3472                undo_waste * HeapWordSize / K);
3473 }
3474 
3475 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3476 private:
3477   BoolObjectClosure* _is_alive;
3478   G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3479 
3480   int _initial_string_table_size;
3481   int _initial_symbol_table_size;
3482 
3483   bool  _process_strings;
3484   int _strings_processed;
3485   int _strings_removed;
3486 
3487   bool  _process_symbols;
3488   int _symbols_processed;
3489   int _symbols_removed;
3490 
3491   bool _process_string_dedup;
3492 
3493 public:
3494   G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3495     AbstractGangTask("String/Symbol Unlinking"),
3496     _is_alive(is_alive),
3497     _dedup_closure(is_alive, NULL, false),
3498     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3499     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3500     _process_string_dedup(process_string_dedup) {
3501 
3502     _initial_string_table_size = StringTable::the_table()->table_size();
3503     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3504     if (process_strings) {
3505       StringTable::clear_parallel_claimed_index();
3506     }
3507     if (process_symbols) {
3508       SymbolTable::clear_parallel_claimed_index();
3509     }
3510   }
3511 
3512   ~G1StringAndSymbolCleaningTask() {
3513     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3514               "claim value %d after unlink less than initial string table size %d",
3515               StringTable::parallel_claimed_index(), _initial_string_table_size);
3516     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3517               "claim value %d after unlink less than initial symbol table size %d",
3518               SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3519 
3520     log_info(gc, stringtable)(
3521         "Cleaned string and symbol table, "
3522         "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3523         "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3524         strings_processed(), strings_removed(),
3525         symbols_processed(), symbols_removed());
3526   }
3527 
3528   void work(uint worker_id) {
3529     int strings_processed = 0;
3530     int strings_removed = 0;
3531     int symbols_processed = 0;
3532     int symbols_removed = 0;
3533     if (_process_strings) {
3534       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3535       Atomic::add(strings_processed, &_strings_processed);
3536       Atomic::add(strings_removed, &_strings_removed);
3537     }
3538     if (_process_symbols) {
3539       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3540       Atomic::add(symbols_processed, &_symbols_processed);
3541       Atomic::add(symbols_removed, &_symbols_removed);
3542     }
3543     if (_process_string_dedup) {
3544       G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3545     }
3546   }
3547 
3548   size_t strings_processed() const { return (size_t)_strings_processed; }
3549   size_t strings_removed()   const { return (size_t)_strings_removed; }
3550 
3551   size_t symbols_processed() const { return (size_t)_symbols_processed; }
3552   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
3553 };
3554 
3555 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3556 private:
3557   static Monitor* _lock;
3558 
3559   BoolObjectClosure* const _is_alive;
3560   const bool               _unloading_occurred;
3561   const uint               _num_workers;
3562 
3563   // Variables used to claim nmethods.
3564   CompiledMethod* _first_nmethod;
3565   volatile CompiledMethod* _claimed_nmethod;
3566 
3567   // The list of nmethods that need to be processed by the second pass.
3568   volatile CompiledMethod* _postponed_list;
3569   volatile uint            _num_entered_barrier;
3570 
3571  public:
3572   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3573       _is_alive(is_alive),
3574       _unloading_occurred(unloading_occurred),
3575       _num_workers(num_workers),
3576       _first_nmethod(NULL),
3577       _claimed_nmethod(NULL),
3578       _postponed_list(NULL),
3579       _num_entered_barrier(0)
3580   {
3581     CompiledMethod::increase_unloading_clock();
3582     // Get first alive nmethod
3583     CompiledMethodIterator iter = CompiledMethodIterator();
3584     if(iter.next_alive()) {
3585       _first_nmethod = iter.method();
3586     }
3587     _claimed_nmethod = (volatile CompiledMethod*)_first_nmethod;
3588   }
3589 
3590   ~G1CodeCacheUnloadingTask() {
3591     CodeCache::verify_clean_inline_caches();
3592 
3593     CodeCache::set_needs_cache_clean(false);
3594     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3595 
3596     CodeCache::verify_icholder_relocations();
3597   }
3598 
3599  private:
3600   void add_to_postponed_list(CompiledMethod* nm) {
3601       CompiledMethod* old;
3602       do {
3603         old = (CompiledMethod*)_postponed_list;
3604         nm->set_unloading_next(old);
3605       } while ((CompiledMethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
3606   }
3607 
3608   void clean_nmethod(CompiledMethod* nm) {
3609     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3610 
3611     if (postponed) {
3612       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3613       add_to_postponed_list(nm);
3614     }
3615 
3616     // Mark that this thread has been cleaned/unloaded.
3617     // After this call, it will be safe to ask if this nmethod was unloaded or not.
3618     nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3619   }
3620 
3621   void clean_nmethod_postponed(CompiledMethod* nm) {
3622     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3623   }
3624 
3625   static const int MaxClaimNmethods = 16;
3626 
3627   void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3628     CompiledMethod* first;
3629     CompiledMethodIterator last;
3630 
3631     do {
3632       *num_claimed_nmethods = 0;
3633 
3634       first = (CompiledMethod*)_claimed_nmethod;
3635       last = CompiledMethodIterator(first);
3636 
3637       if (first != NULL) {
3638 
3639         for (int i = 0; i < MaxClaimNmethods; i++) {
3640           if (!last.next_alive()) {
3641             break;
3642           }
3643           claimed_nmethods[i] = last.method();
3644           (*num_claimed_nmethods)++;
3645         }
3646       }
3647 
3648     } while ((CompiledMethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
3649   }
3650 
3651   CompiledMethod* claim_postponed_nmethod() {
3652     CompiledMethod* claim;
3653     CompiledMethod* next;
3654 
3655     do {
3656       claim = (CompiledMethod*)_postponed_list;
3657       if (claim == NULL) {
3658         return NULL;
3659       }
3660 
3661       next = claim->unloading_next();
3662 
3663     } while ((CompiledMethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
3664 
3665     return claim;
3666   }
3667 
3668  public:
3669   // Mark that we're done with the first pass of nmethod cleaning.
3670   void barrier_mark(uint worker_id) {
3671     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3672     _num_entered_barrier++;
3673     if (_num_entered_barrier == _num_workers) {
3674       ml.notify_all();
3675     }
3676   }
3677 
3678   // See if we have to wait for the other workers to
3679   // finish their first-pass nmethod cleaning work.
3680   void barrier_wait(uint worker_id) {
3681     if (_num_entered_barrier < _num_workers) {
3682       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3683       while (_num_entered_barrier < _num_workers) {
3684           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3685       }
3686     }
3687   }
3688 
3689   // Cleaning and unloading of nmethods. Some work has to be postponed
3690   // to the second pass, when we know which nmethods survive.
3691   void work_first_pass(uint worker_id) {
3692     // The first nmethods is claimed by the first worker.
3693     if (worker_id == 0 && _first_nmethod != NULL) {
3694       clean_nmethod(_first_nmethod);
3695       _first_nmethod = NULL;
3696     }
3697 
3698     int num_claimed_nmethods;
3699     CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3700 
3701     while (true) {
3702       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3703 
3704       if (num_claimed_nmethods == 0) {
3705         break;
3706       }
3707 
3708       for (int i = 0; i < num_claimed_nmethods; i++) {
3709         clean_nmethod(claimed_nmethods[i]);
3710       }
3711     }
3712   }
3713 
3714   void work_second_pass(uint worker_id) {
3715     CompiledMethod* nm;
3716     // Take care of postponed nmethods.
3717     while ((nm = claim_postponed_nmethod()) != NULL) {
3718       clean_nmethod_postponed(nm);
3719     }
3720   }
3721 };
3722 
3723 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3724 
3725 class G1KlassCleaningTask : public StackObj {
3726   BoolObjectClosure*                      _is_alive;
3727   volatile jint                           _clean_klass_tree_claimed;
3728   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3729 
3730  public:
3731   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3732       _is_alive(is_alive),
3733       _clean_klass_tree_claimed(0),
3734       _klass_iterator() {
3735   }
3736 
3737  private:
3738   bool claim_clean_klass_tree_task() {
3739     if (_clean_klass_tree_claimed) {
3740       return false;
3741     }
3742 
3743     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
3744   }
3745 
3746   InstanceKlass* claim_next_klass() {
3747     Klass* klass;
3748     do {
3749       klass =_klass_iterator.next_klass();
3750     } while (klass != NULL && !klass->is_instance_klass());
3751 
3752     // this can be null so don't call InstanceKlass::cast
3753     return static_cast<InstanceKlass*>(klass);
3754   }
3755 
3756 public:
3757 
3758   void clean_klass(InstanceKlass* ik) {
3759     ik->clean_weak_instanceklass_links(_is_alive);
3760   }
3761 
3762   void work() {
3763     ResourceMark rm;
3764 
3765     // One worker will clean the subklass/sibling klass tree.
3766     if (claim_clean_klass_tree_task()) {
3767       Klass::clean_subklass_tree(_is_alive);
3768     }
3769 
3770     // All workers will help cleaning the classes,
3771     InstanceKlass* klass;
3772     while ((klass = claim_next_klass()) != NULL) {
3773       clean_klass(klass);
3774     }
3775   }
3776 };
3777 
3778 class G1ResolvedMethodCleaningTask : public StackObj {
3779   BoolObjectClosure* _is_alive;
3780   volatile jint      _resolved_method_task_claimed;
3781 public:
3782   G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) :
3783       _is_alive(is_alive), _resolved_method_task_claimed(0) {}
3784 
3785   bool claim_resolved_method_task() {
3786     if (_resolved_method_task_claimed) {
3787       return false;
3788     }
3789     return Atomic::cmpxchg(1, (jint*)&_resolved_method_task_claimed, 0) == 0;
3790   }
3791 
3792   // These aren't big, one thread can do it all.
3793   void work() {
3794     if (claim_resolved_method_task()) {
3795       ResolvedMethodTable::unlink(_is_alive);
3796     }
3797   }
3798 };
3799 
3800 
3801 // To minimize the remark pause times, the tasks below are done in parallel.
3802 class G1ParallelCleaningTask : public AbstractGangTask {
3803 private:
3804   G1StringAndSymbolCleaningTask _string_symbol_task;
3805   G1CodeCacheUnloadingTask      _code_cache_task;
3806   G1KlassCleaningTask           _klass_cleaning_task;
3807   G1ResolvedMethodCleaningTask  _resolved_method_cleaning_task;
3808 
3809 public:
3810   // The constructor is run in the VMThread.
3811   G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3812       AbstractGangTask("Parallel Cleaning"),
3813       _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3814       _code_cache_task(num_workers, is_alive, unloading_occurred),
3815       _klass_cleaning_task(is_alive),
3816       _resolved_method_cleaning_task(is_alive) {
3817   }
3818 
3819   // The parallel work done by all worker threads.
3820   void work(uint worker_id) {
3821     // Do first pass of code cache cleaning.
3822     _code_cache_task.work_first_pass(worker_id);
3823 
3824     // Let the threads mark that the first pass is done.
3825     _code_cache_task.barrier_mark(worker_id);
3826 
3827     // Clean the Strings and Symbols.
3828     _string_symbol_task.work(worker_id);
3829 
3830     // Clean unreferenced things in the ResolvedMethodTable
3831     _resolved_method_cleaning_task.work();
3832 
3833     // Wait for all workers to finish the first code cache cleaning pass.
3834     _code_cache_task.barrier_wait(worker_id);
3835 
3836     // Do the second code cache cleaning work, which realize on
3837     // the liveness information gathered during the first pass.
3838     _code_cache_task.work_second_pass(worker_id);
3839 
3840     // Clean all klasses that were not unloaded.
3841     _klass_cleaning_task.work();
3842   }
3843 };
3844 
3845 
3846 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3847                                         bool class_unloading_occurred) {
3848   uint n_workers = workers()->active_workers();
3849 
3850   G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3851   workers()->run_task(&g1_unlink_task);
3852 }
3853 
3854 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3855                                        bool process_strings,
3856                                        bool process_symbols,
3857                                        bool process_string_dedup) {
3858   if (!process_strings && !process_symbols && !process_string_dedup) {
3859     // Nothing to clean.
3860     return;
3861   }
3862 
3863   G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3864   workers()->run_task(&g1_unlink_task);
3865 
3866 }
3867 
3868 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3869  private:
3870   DirtyCardQueueSet* _queue;
3871   G1CollectedHeap* _g1h;
3872  public:
3873   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3874     _queue(queue), _g1h(g1h) { }
3875 
3876   virtual void work(uint worker_id) {
3877     G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3878     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3879 
3880     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3881     _queue->par_apply_closure_to_all_completed_buffers(&cl);
3882 
3883     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3884   }
3885 };
3886 
3887 void G1CollectedHeap::redirty_logged_cards() {
3888   double redirty_logged_cards_start = os::elapsedTime();
3889 
3890   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3891   dirty_card_queue_set().reset_for_par_iteration();
3892   workers()->run_task(&redirty_task);
3893 
3894   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
3895   dcq.merge_bufferlists(&dirty_card_queue_set());
3896   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3897 
3898   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3899 }
3900 
3901 // Weak Reference Processing support
3902 
3903 // An always "is_alive" closure that is used to preserve referents.
3904 // If the object is non-null then it's alive.  Used in the preservation
3905 // of referent objects that are pointed to by reference objects
3906 // discovered by the CM ref processor.
3907 class G1AlwaysAliveClosure: public BoolObjectClosure {
3908   G1CollectedHeap* _g1;
3909 public:
3910   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3911   bool do_object_b(oop p) {
3912     if (p != NULL) {
3913       return true;
3914     }
3915     return false;
3916   }
3917 };
3918 
3919 bool G1STWIsAliveClosure::do_object_b(oop p) {
3920   // An object is reachable if it is outside the collection set,
3921   // or is inside and copied.
3922   return !_g1->is_in_cset(p) || p->is_forwarded();
3923 }
3924 
3925 // Non Copying Keep Alive closure
3926 class G1KeepAliveClosure: public OopClosure {
3927   G1CollectedHeap* _g1;
3928 public:
3929   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3930   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3931   void do_oop(oop* p) {
3932     oop obj = *p;
3933     assert(obj != NULL, "the caller should have filtered out NULL values");
3934 
3935     const InCSetState cset_state = _g1->in_cset_state(obj);
3936     if (!cset_state.is_in_cset_or_humongous()) {
3937       return;
3938     }
3939     if (cset_state.is_in_cset()) {
3940       assert( obj->is_forwarded(), "invariant" );
3941       *p = obj->forwardee();
3942     } else {
3943       assert(!obj->is_forwarded(), "invariant" );
3944       assert(cset_state.is_humongous(),
3945              "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3946       _g1->set_humongous_is_live(obj);
3947     }
3948   }
3949 };
3950 
3951 // Copying Keep Alive closure - can be called from both
3952 // serial and parallel code as long as different worker
3953 // threads utilize different G1ParScanThreadState instances
3954 // and different queues.
3955 
3956 class G1CopyingKeepAliveClosure: public OopClosure {
3957   G1CollectedHeap*         _g1h;
3958   OopClosure*              _copy_non_heap_obj_cl;
3959   G1ParScanThreadState*    _par_scan_state;
3960 
3961 public:
3962   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3963                             OopClosure* non_heap_obj_cl,
3964                             G1ParScanThreadState* pss):
3965     _g1h(g1h),
3966     _copy_non_heap_obj_cl(non_heap_obj_cl),
3967     _par_scan_state(pss)
3968   {}
3969 
3970   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3971   virtual void do_oop(      oop* p) { do_oop_work(p); }
3972 
3973   template <class T> void do_oop_work(T* p) {
3974     oop obj = oopDesc::load_decode_heap_oop(p);
3975 
3976     if (_g1h->is_in_cset_or_humongous(obj)) {
3977       // If the referent object has been forwarded (either copied
3978       // to a new location or to itself in the event of an
3979       // evacuation failure) then we need to update the reference
3980       // field and, if both reference and referent are in the G1
3981       // heap, update the RSet for the referent.
3982       //
3983       // If the referent has not been forwarded then we have to keep
3984       // it alive by policy. Therefore we have copy the referent.
3985       //
3986       // If the reference field is in the G1 heap then we can push
3987       // on the PSS queue. When the queue is drained (after each
3988       // phase of reference processing) the object and it's followers
3989       // will be copied, the reference field set to point to the
3990       // new location, and the RSet updated. Otherwise we need to
3991       // use the the non-heap or metadata closures directly to copy
3992       // the referent object and update the pointer, while avoiding
3993       // updating the RSet.
3994 
3995       if (_g1h->is_in_g1_reserved(p)) {
3996         _par_scan_state->push_on_queue(p);
3997       } else {
3998         assert(!Metaspace::contains((const void*)p),
3999                "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
4000         _copy_non_heap_obj_cl->do_oop(p);
4001       }
4002     }
4003   }
4004 };
4005 
4006 // Serial drain queue closure. Called as the 'complete_gc'
4007 // closure for each discovered list in some of the
4008 // reference processing phases.
4009 
4010 class G1STWDrainQueueClosure: public VoidClosure {
4011 protected:
4012   G1CollectedHeap* _g1h;
4013   G1ParScanThreadState* _par_scan_state;
4014 
4015   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4016 
4017 public:
4018   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
4019     _g1h(g1h),
4020     _par_scan_state(pss)
4021   { }
4022 
4023   void do_void() {
4024     G1ParScanThreadState* const pss = par_scan_state();
4025     pss->trim_queue();
4026   }
4027 };
4028 
4029 // Parallel Reference Processing closures
4030 
4031 // Implementation of AbstractRefProcTaskExecutor for parallel reference
4032 // processing during G1 evacuation pauses.
4033 
4034 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
4035 private:
4036   G1CollectedHeap*          _g1h;
4037   G1ParScanThreadStateSet*  _pss;
4038   RefToScanQueueSet*        _queues;
4039   WorkGang*                 _workers;
4040   uint                      _active_workers;
4041 
4042 public:
4043   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
4044                            G1ParScanThreadStateSet* per_thread_states,
4045                            WorkGang* workers,
4046                            RefToScanQueueSet *task_queues,
4047                            uint n_workers) :
4048     _g1h(g1h),
4049     _pss(per_thread_states),
4050     _queues(task_queues),
4051     _workers(workers),
4052     _active_workers(n_workers)
4053   {
4054     g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
4055   }
4056 
4057   // Executes the given task using concurrent marking worker threads.
4058   virtual void execute(ProcessTask& task);
4059   virtual void execute(EnqueueTask& task);
4060 };
4061 
4062 // Gang task for possibly parallel reference processing
4063 
4064 class G1STWRefProcTaskProxy: public AbstractGangTask {
4065   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
4066   ProcessTask&     _proc_task;
4067   G1CollectedHeap* _g1h;
4068   G1ParScanThreadStateSet* _pss;
4069   RefToScanQueueSet* _task_queues;
4070   ParallelTaskTerminator* _terminator;
4071 
4072 public:
4073   G1STWRefProcTaskProxy(ProcessTask& proc_task,
4074                         G1CollectedHeap* g1h,
4075                         G1ParScanThreadStateSet* per_thread_states,
4076                         RefToScanQueueSet *task_queues,
4077                         ParallelTaskTerminator* terminator) :
4078     AbstractGangTask("Process reference objects in parallel"),
4079     _proc_task(proc_task),
4080     _g1h(g1h),
4081     _pss(per_thread_states),
4082     _task_queues(task_queues),
4083     _terminator(terminator)
4084   {}
4085 
4086   virtual void work(uint worker_id) {
4087     // The reference processing task executed by a single worker.
4088     ResourceMark rm;
4089     HandleMark   hm;
4090 
4091     G1STWIsAliveClosure is_alive(_g1h);
4092 
4093     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4094     pss->set_ref_processor(NULL);
4095 
4096     // Keep alive closure.
4097     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4098 
4099     // Complete GC closure
4100     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
4101 
4102     // Call the reference processing task's work routine.
4103     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
4104 
4105     // Note we cannot assert that the refs array is empty here as not all
4106     // of the processing tasks (specifically phase2 - pp2_work) execute
4107     // the complete_gc closure (which ordinarily would drain the queue) so
4108     // the queue may not be empty.
4109   }
4110 };
4111 
4112 // Driver routine for parallel reference processing.
4113 // Creates an instance of the ref processing gang
4114 // task and has the worker threads execute it.
4115 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4116   assert(_workers != NULL, "Need parallel worker threads.");
4117 
4118   ParallelTaskTerminator terminator(_active_workers, _queues);
4119   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4120 
4121   _workers->run_task(&proc_task_proxy);
4122 }
4123 
4124 // Gang task for parallel reference enqueueing.
4125 
4126 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4127   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4128   EnqueueTask& _enq_task;
4129 
4130 public:
4131   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4132     AbstractGangTask("Enqueue reference objects in parallel"),
4133     _enq_task(enq_task)
4134   { }
4135 
4136   virtual void work(uint worker_id) {
4137     _enq_task.work(worker_id);
4138   }
4139 };
4140 
4141 // Driver routine for parallel reference enqueueing.
4142 // Creates an instance of the ref enqueueing gang
4143 // task and has the worker threads execute it.
4144 
4145 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4146   assert(_workers != NULL, "Need parallel worker threads.");
4147 
4148   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4149 
4150   _workers->run_task(&enq_task_proxy);
4151 }
4152 
4153 // End of weak reference support closures
4154 
4155 // Abstract task used to preserve (i.e. copy) any referent objects
4156 // that are in the collection set and are pointed to by reference
4157 // objects discovered by the CM ref processor.
4158 
4159 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4160 protected:
4161   G1CollectedHeap*         _g1h;
4162   G1ParScanThreadStateSet* _pss;
4163   RefToScanQueueSet*       _queues;
4164   ParallelTaskTerminator   _terminator;
4165   uint                     _n_workers;
4166 
4167 public:
4168   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4169     AbstractGangTask("ParPreserveCMReferents"),
4170     _g1h(g1h),
4171     _pss(per_thread_states),
4172     _queues(task_queues),
4173     _terminator(workers, _queues),
4174     _n_workers(workers)
4175   {
4176     g1h->ref_processor_cm()->set_active_mt_degree(workers);
4177   }
4178 
4179   void work(uint worker_id) {
4180     G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4181 
4182     ResourceMark rm;
4183     HandleMark   hm;
4184 
4185     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4186     pss->set_ref_processor(NULL);
4187     assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4188 
4189     // Is alive closure
4190     G1AlwaysAliveClosure always_alive(_g1h);
4191 
4192     // Copying keep alive closure. Applied to referent objects that need
4193     // to be copied.
4194     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4195 
4196     ReferenceProcessor* rp = _g1h->ref_processor_cm();
4197 
4198     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4199     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4200 
4201     // limit is set using max_num_q() - which was set using ParallelGCThreads.
4202     // So this must be true - but assert just in case someone decides to
4203     // change the worker ids.
4204     assert(worker_id < limit, "sanity");
4205     assert(!rp->discovery_is_atomic(), "check this code");
4206 
4207     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4208     for (uint idx = worker_id; idx < limit; idx += stride) {
4209       DiscoveredList& ref_list = rp->discovered_refs()[idx];
4210 
4211       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4212       while (iter.has_next()) {
4213         // Since discovery is not atomic for the CM ref processor, we
4214         // can see some null referent objects.
4215         iter.load_ptrs(DEBUG_ONLY(true));
4216         oop ref = iter.obj();
4217 
4218         // This will filter nulls.
4219         if (iter.is_referent_alive()) {
4220           iter.make_referent_alive();
4221         }
4222         iter.move_to_next();
4223       }
4224     }
4225 
4226     // Drain the queue - which may cause stealing
4227     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4228     drain_queue.do_void();
4229     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4230     assert(pss->queue_is_empty(), "should be");
4231   }
4232 };
4233 
4234 void G1CollectedHeap::process_weak_jni_handles() {
4235   double ref_proc_start = os::elapsedTime();
4236 
4237   G1STWIsAliveClosure is_alive(this);
4238   G1KeepAliveClosure keep_alive(this);
4239   JNIHandles::weak_oops_do(&is_alive, &keep_alive);
4240 
4241   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4242   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4243 }
4244 
4245 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4246   // Any reference objects, in the collection set, that were 'discovered'
4247   // by the CM ref processor should have already been copied (either by
4248   // applying the external root copy closure to the discovered lists, or
4249   // by following an RSet entry).
4250   //
4251   // But some of the referents, that are in the collection set, that these
4252   // reference objects point to may not have been copied: the STW ref
4253   // processor would have seen that the reference object had already
4254   // been 'discovered' and would have skipped discovering the reference,
4255   // but would not have treated the reference object as a regular oop.
4256   // As a result the copy closure would not have been applied to the
4257   // referent object.
4258   //
4259   // We need to explicitly copy these referent objects - the references
4260   // will be processed at the end of remarking.
4261   //
4262   // We also need to do this copying before we process the reference
4263   // objects discovered by the STW ref processor in case one of these
4264   // referents points to another object which is also referenced by an
4265   // object discovered by the STW ref processor.
4266   double preserve_cm_referents_time = 0.0;
4267 
4268   // To avoid spawning task when there is no work to do, check that
4269   // a concurrent cycle is active and that some references have been
4270   // discovered.
4271   if (concurrent_mark()->cmThread()->during_cycle() &&
4272       ref_processor_cm()->has_discovered_references()) {
4273     double preserve_cm_referents_start = os::elapsedTime();
4274     uint no_of_gc_workers = workers()->active_workers();
4275     G1ParPreserveCMReferentsTask keep_cm_referents(this,
4276                                                    per_thread_states,
4277                                                    no_of_gc_workers,
4278                                                    _task_queues);
4279     workers()->run_task(&keep_cm_referents);
4280     preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4281   }
4282 
4283   g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4284 }
4285 
4286 // Weak Reference processing during an evacuation pause (part 1).
4287 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4288   double ref_proc_start = os::elapsedTime();
4289 
4290   ReferenceProcessor* rp = _ref_processor_stw;
4291   assert(rp->discovery_enabled(), "should have been enabled");
4292 
4293   // Closure to test whether a referent is alive.
4294   G1STWIsAliveClosure is_alive(this);
4295 
4296   // Even when parallel reference processing is enabled, the processing
4297   // of JNI refs is serial and performed serially by the current thread
4298   // rather than by a worker. The following PSS will be used for processing
4299   // JNI refs.
4300 
4301   // Use only a single queue for this PSS.
4302   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
4303   pss->set_ref_processor(NULL);
4304   assert(pss->queue_is_empty(), "pre-condition");
4305 
4306   // Keep alive closure.
4307   G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4308 
4309   // Serial Complete GC closure
4310   G1STWDrainQueueClosure drain_queue(this, pss);
4311 
4312   // Setup the soft refs policy...
4313   rp->setup_policy(false);
4314 
4315   ReferenceProcessorStats stats;
4316   if (!rp->processing_is_mt()) {
4317     // Serial reference processing...
4318     stats = rp->process_discovered_references(&is_alive,
4319                                               &keep_alive,
4320                                               &drain_queue,
4321                                               NULL,
4322                                               _gc_timer_stw);
4323   } else {
4324     uint no_of_gc_workers = workers()->active_workers();
4325 
4326     // Parallel reference processing
4327     assert(no_of_gc_workers <= rp->max_num_q(),
4328            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4329            no_of_gc_workers,  rp->max_num_q());
4330 
4331     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4332     stats = rp->process_discovered_references(&is_alive,
4333                                               &keep_alive,
4334                                               &drain_queue,
4335                                               &par_task_executor,
4336                                               _gc_timer_stw);
4337   }
4338 
4339   _gc_tracer_stw->report_gc_reference_stats(stats);
4340 
4341   // We have completed copying any necessary live referent objects.
4342   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4343 
4344   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4345   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4346 }
4347 
4348 // Weak Reference processing during an evacuation pause (part 2).
4349 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4350   double ref_enq_start = os::elapsedTime();
4351 
4352   ReferenceProcessor* rp = _ref_processor_stw;
4353   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4354 
4355   // Now enqueue any remaining on the discovered lists on to
4356   // the pending list.
4357   if (!rp->processing_is_mt()) {
4358     // Serial reference processing...
4359     rp->enqueue_discovered_references();
4360   } else {
4361     // Parallel reference enqueueing
4362 
4363     uint n_workers = workers()->active_workers();
4364 
4365     assert(n_workers <= rp->max_num_q(),
4366            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4367            n_workers,  rp->max_num_q());
4368 
4369     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4370     rp->enqueue_discovered_references(&par_task_executor);
4371   }
4372 
4373   rp->verify_no_references_recorded();
4374   assert(!rp->discovery_enabled(), "should have been disabled");
4375 
4376   // FIXME
4377   // CM's reference processing also cleans up the string and symbol tables.
4378   // Should we do that here also? We could, but it is a serial operation
4379   // and could significantly increase the pause time.
4380 
4381   double ref_enq_time = os::elapsedTime() - ref_enq_start;
4382   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4383 }
4384 
4385 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4386   double merge_pss_time_start = os::elapsedTime();
4387   per_thread_states->flush();
4388   g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4389 }
4390 
4391 void G1CollectedHeap::pre_evacuate_collection_set() {
4392   _expand_heap_after_alloc_failure = true;
4393   _evacuation_failed = false;
4394 
4395   // Disable the hot card cache.
4396   _hot_card_cache->reset_hot_cache_claimed_index();
4397   _hot_card_cache->set_use_cache(false);
4398 
4399   g1_rem_set()->prepare_for_oops_into_collection_set_do();
4400   _preserved_marks_set.assert_empty();
4401 
4402   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4403 
4404   // InitialMark needs claim bits to keep track of the marked-through CLDs.
4405   if (collector_state()->during_initial_mark_pause()) {
4406     double start_clear_claimed_marks = os::elapsedTime();
4407 
4408     ClassLoaderDataGraph::clear_claimed_marks();
4409 
4410     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
4411     phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
4412   }
4413 }
4414 
4415 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4416   // Should G1EvacuationFailureALot be in effect for this GC?
4417   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4418 
4419   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4420 
4421   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4422 
4423   double start_par_time_sec = os::elapsedTime();
4424   double end_par_time_sec;
4425 
4426   {
4427     const uint n_workers = workers()->active_workers();
4428     G1RootProcessor root_processor(this, n_workers);
4429     G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4430 
4431     print_termination_stats_hdr();
4432 
4433     workers()->run_task(&g1_par_task);
4434     end_par_time_sec = os::elapsedTime();
4435 
4436     // Closing the inner scope will execute the destructor
4437     // for the G1RootProcessor object. We record the current
4438     // elapsed time before closing the scope so that time
4439     // taken for the destructor is NOT included in the
4440     // reported parallel time.
4441   }
4442 
4443   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4444   phase_times->record_par_time(par_time_ms);
4445 
4446   double code_root_fixup_time_ms =
4447         (os::elapsedTime() - end_par_time_sec) * 1000.0;
4448   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4449 }
4450 
4451 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4452   // Process any discovered reference objects - we have
4453   // to do this _before_ we retire the GC alloc regions
4454   // as we may have to copy some 'reachable' referent
4455   // objects (and their reachable sub-graphs) that were
4456   // not copied during the pause.
4457   if (g1_policy()->should_process_references()) {
4458     preserve_cm_referents(per_thread_states);
4459     process_discovered_references(per_thread_states);
4460   } else {
4461     ref_processor_stw()->verify_no_references_recorded();
4462     process_weak_jni_handles();
4463   }
4464 
4465   if (G1StringDedup::is_enabled()) {
4466     double fixup_start = os::elapsedTime();
4467 
4468     G1STWIsAliveClosure is_alive(this);
4469     G1KeepAliveClosure keep_alive(this);
4470     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4471 
4472     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4473     g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4474   }
4475 
4476   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4477 
4478   if (evacuation_failed()) {
4479     restore_after_evac_failure();
4480 
4481     // Reset the G1EvacuationFailureALot counters and flags
4482     // Note: the values are reset only when an actual
4483     // evacuation failure occurs.
4484     NOT_PRODUCT(reset_evacuation_should_fail();)
4485   }
4486 
4487   _preserved_marks_set.assert_empty();
4488 
4489   // Enqueue any remaining references remaining on the STW
4490   // reference processor's discovered lists. We need to do
4491   // this after the card table is cleaned (and verified) as
4492   // the act of enqueueing entries on to the pending list
4493   // will log these updates (and dirty their associated
4494   // cards). We need these updates logged to update any
4495   // RSets.
4496   if (g1_policy()->should_process_references()) {
4497     enqueue_discovered_references(per_thread_states);
4498   } else {
4499     g1_policy()->phase_times()->record_ref_enq_time(0);
4500   }
4501 
4502   _allocator->release_gc_alloc_regions(evacuation_info);
4503 
4504   merge_per_thread_state_info(per_thread_states);
4505 
4506   // Reset and re-enable the hot card cache.
4507   // Note the counts for the cards in the regions in the
4508   // collection set are reset when the collection set is freed.
4509   _hot_card_cache->reset_hot_cache();
4510   _hot_card_cache->set_use_cache(true);
4511 
4512   purge_code_root_memory();
4513 
4514   redirty_logged_cards();
4515 #if defined(COMPILER2) || INCLUDE_JVMCI
4516   double start = os::elapsedTime();
4517   DerivedPointerTable::update_pointers();
4518   g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4519 #endif
4520   g1_policy()->print_age_table();
4521 }
4522 
4523 void G1CollectedHeap::record_obj_copy_mem_stats() {
4524   g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4525 
4526   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4527                                                create_g1_evac_summary(&_old_evac_stats));
4528 }
4529 
4530 void G1CollectedHeap::free_region(HeapRegion* hr,
4531                                   FreeRegionList* free_list,
4532                                   bool skip_remset,
4533                                   bool skip_hot_card_cache,
4534                                   bool locked) {
4535   assert(!hr->is_free(), "the region should not be free");
4536   assert(!hr->is_empty(), "the region should not be empty");
4537   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4538   assert(free_list != NULL, "pre-condition");
4539 
4540   if (G1VerifyBitmaps) {
4541     MemRegion mr(hr->bottom(), hr->end());
4542     concurrent_mark()->clearRangePrevBitmap(mr);
4543   }
4544 
4545   // Clear the card counts for this region.
4546   // Note: we only need to do this if the region is not young
4547   // (since we don't refine cards in young regions).
4548   if (!skip_hot_card_cache && !hr->is_young()) {
4549     _hot_card_cache->reset_card_counts(hr);
4550   }
4551   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4552   free_list->add_ordered(hr);
4553 }
4554 
4555 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4556                                             FreeRegionList* free_list,
4557                                             bool skip_remset) {
4558   assert(hr->is_humongous(), "this is only for humongous regions");
4559   assert(free_list != NULL, "pre-condition");
4560   hr->clear_humongous();
4561   free_region(hr, free_list, skip_remset);
4562 }
4563 
4564 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4565                                            const uint humongous_regions_removed) {
4566   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4567     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4568     _old_set.bulk_remove(old_regions_removed);
4569     _humongous_set.bulk_remove(humongous_regions_removed);
4570   }
4571 
4572 }
4573 
4574 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4575   assert(list != NULL, "list can't be null");
4576   if (!list->is_empty()) {
4577     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4578     _hrm.insert_list_into_free_list(list);
4579   }
4580 }
4581 
4582 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4583   decrease_used(bytes);
4584 }
4585 
4586 class G1ParScrubRemSetTask: public AbstractGangTask {
4587 protected:
4588   G1RemSet* _g1rs;
4589   HeapRegionClaimer _hrclaimer;
4590 
4591 public:
4592   G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
4593     AbstractGangTask("G1 ScrubRS"),
4594     _g1rs(g1_rs),
4595     _hrclaimer(num_workers) {
4596   }
4597 
4598   void work(uint worker_id) {
4599     _g1rs->scrub(worker_id, &_hrclaimer);
4600   }
4601 };
4602 
4603 void G1CollectedHeap::scrub_rem_set() {
4604   uint num_workers = workers()->active_workers();
4605   G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
4606   workers()->run_task(&g1_par_scrub_rs_task);
4607 }
4608 
4609 class G1FreeCollectionSetTask : public AbstractGangTask {
4610 private:
4611 
4612   // Closure applied to all regions in the collection set to do work that needs to
4613   // be done serially in a single thread.
4614   class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4615   private:
4616     EvacuationInfo* _evacuation_info;
4617     const size_t* _surviving_young_words;
4618 
4619     // Bytes used in successfully evacuated regions before the evacuation.
4620     size_t _before_used_bytes;
4621     // Bytes used in unsucessfully evacuated regions before the evacuation
4622     size_t _after_used_bytes;
4623 
4624     size_t _bytes_allocated_in_old_since_last_gc;
4625 
4626     size_t _failure_used_words;
4627     size_t _failure_waste_words;
4628 
4629     FreeRegionList _local_free_list;
4630   public:
4631     G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4632       HeapRegionClosure(),
4633       _evacuation_info(evacuation_info),
4634       _surviving_young_words(surviving_young_words),
4635       _before_used_bytes(0),
4636       _after_used_bytes(0),
4637       _bytes_allocated_in_old_since_last_gc(0),
4638       _failure_used_words(0),
4639       _failure_waste_words(0),
4640       _local_free_list("Local Region List for CSet Freeing") {
4641     }
4642 
4643     virtual bool doHeapRegion(HeapRegion* r) {
4644       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4645 
4646       assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4647       g1h->clear_in_cset(r);
4648 
4649       if (r->is_young()) {
4650         assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4651                "Young index %d is wrong for region %u of type %s with %u young regions",
4652                r->young_index_in_cset(),
4653                r->hrm_index(),
4654                r->get_type_str(),
4655                g1h->collection_set()->young_region_length());
4656         size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4657         r->record_surv_words_in_group(words_survived);
4658       }
4659 
4660       if (!r->evacuation_failed()) {
4661         assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4662         _before_used_bytes += r->used();
4663         g1h->free_region(r,
4664                          &_local_free_list,
4665                          true, /* skip_remset */
4666                          true, /* skip_hot_card_cache */
4667                          true  /* locked */);
4668       } else {
4669         r->uninstall_surv_rate_group();
4670         r->set_young_index_in_cset(-1);
4671         r->set_evacuation_failed(false);
4672         // When moving a young gen region to old gen, we "allocate" that whole region
4673         // there. This is in addition to any already evacuated objects. Notify the
4674         // policy about that.
4675         // Old gen regions do not cause an additional allocation: both the objects
4676         // still in the region and the ones already moved are accounted for elsewhere.
4677         if (r->is_young()) {
4678           _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4679         }
4680         // The region is now considered to be old.
4681         r->set_old();
4682         // Do some allocation statistics accounting. Regions that failed evacuation
4683         // are always made old, so there is no need to update anything in the young
4684         // gen statistics, but we need to update old gen statistics.
4685         size_t used_words = r->marked_bytes() / HeapWordSize;
4686 
4687         _failure_used_words += used_words;
4688         _failure_waste_words += HeapRegion::GrainWords - used_words;
4689 
4690         g1h->old_set_add(r);
4691         _after_used_bytes += r->used();
4692       }
4693       return false;
4694     }
4695 
4696     void complete_work() {
4697       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4698 
4699       _evacuation_info->set_regions_freed(_local_free_list.length());
4700       _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4701 
4702       g1h->prepend_to_freelist(&_local_free_list);
4703       g1h->decrement_summary_bytes(_before_used_bytes);
4704 
4705       G1Policy* policy = g1h->g1_policy();
4706       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4707 
4708       g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4709     }
4710   };
4711 
4712   G1CollectionSet* _collection_set;
4713   G1SerialFreeCollectionSetClosure _cl;
4714   const size_t* _surviving_young_words;
4715 
4716   size_t _rs_lengths;
4717 
4718   volatile jint _serial_work_claim;
4719 
4720   struct WorkItem {
4721     uint region_idx;
4722     bool is_young;
4723     bool evacuation_failed;
4724 
4725     WorkItem(HeapRegion* r) {
4726       region_idx = r->hrm_index();
4727       is_young = r->is_young();
4728       evacuation_failed = r->evacuation_failed();
4729     }
4730   };
4731 
4732   volatile size_t _parallel_work_claim;
4733   size_t _num_work_items;
4734   WorkItem* _work_items;
4735 
4736   void do_serial_work() {
4737     // Need to grab the lock to be allowed to modify the old region list.
4738     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4739     _collection_set->iterate(&_cl);
4740   }
4741 
4742   void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4743     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4744 
4745     HeapRegion* r = g1h->region_at(region_idx);
4746     assert(!g1h->is_on_master_free_list(r), "sanity");
4747 
4748     Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4749 
4750     if (!is_young) {
4751       g1h->_hot_card_cache->reset_card_counts(r);
4752     }
4753 
4754     if (!evacuation_failed) {
4755       r->rem_set()->clear_locked();
4756     }
4757   }
4758 
4759   class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4760   private:
4761     size_t _cur_idx;
4762     WorkItem* _work_items;
4763   public:
4764     G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4765 
4766     virtual bool doHeapRegion(HeapRegion* r) {
4767       _work_items[_cur_idx++] = WorkItem(r);
4768       return false;
4769     }
4770   };
4771 
4772   void prepare_work() {
4773     G1PrepareFreeCollectionSetClosure cl(_work_items);
4774     _collection_set->iterate(&cl);
4775   }
4776 
4777   void complete_work() {
4778     _cl.complete_work();
4779 
4780     G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4781     policy->record_max_rs_lengths(_rs_lengths);
4782     policy->cset_regions_freed();
4783   }
4784 public:
4785   G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4786     AbstractGangTask("G1 Free Collection Set"),
4787     _cl(evacuation_info, surviving_young_words),
4788     _collection_set(collection_set),
4789     _surviving_young_words(surviving_young_words),
4790     _serial_work_claim(0),
4791     _rs_lengths(0),
4792     _parallel_work_claim(0),
4793     _num_work_items(collection_set->region_length()),
4794     _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4795     prepare_work();
4796   }
4797 
4798   ~G1FreeCollectionSetTask() {
4799     complete_work();
4800     FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4801   }
4802 
4803   // Chunk size for work distribution. The chosen value has been determined experimentally
4804   // to be a good tradeoff between overhead and achievable parallelism.
4805   static uint chunk_size() { return 32; }
4806 
4807   virtual void work(uint worker_id) {
4808     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4809 
4810     // Claim serial work.
4811     if (_serial_work_claim == 0) {
4812       jint value = Atomic::add(1, &_serial_work_claim) - 1;
4813       if (value == 0) {
4814         double serial_time = os::elapsedTime();
4815         do_serial_work();
4816         timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4817       }
4818     }
4819 
4820     // Start parallel work.
4821     double young_time = 0.0;
4822     bool has_young_time = false;
4823     double non_young_time = 0.0;
4824     bool has_non_young_time = false;
4825 
4826     while (true) {
4827       size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4828       size_t cur = end - chunk_size();
4829 
4830       if (cur >= _num_work_items) {
4831         break;
4832       }
4833 
4834       double start_time = os::elapsedTime();
4835 
4836       end = MIN2(end, _num_work_items);
4837 
4838       for (; cur < end; cur++) {
4839         bool is_young = _work_items[cur].is_young;
4840 
4841         do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4842 
4843         double end_time = os::elapsedTime();
4844         double time_taken = end_time - start_time;
4845         if (is_young) {
4846           young_time += time_taken;
4847           has_young_time = true;
4848         } else {
4849           non_young_time += time_taken;
4850           has_non_young_time = true;
4851         }
4852         start_time = end_time;
4853       }
4854     }
4855 
4856     if (has_young_time) {
4857       timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4858     }
4859     if (has_non_young_time) {
4860       timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time);
4861     }
4862   }
4863 };
4864 
4865 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4866   _eden.clear();
4867 
4868   double free_cset_start_time = os::elapsedTime();
4869 
4870   {
4871     uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4872     uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4873 
4874     G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4875 
4876     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4877                         cl.name(),
4878                         num_workers,
4879                         _collection_set.region_length());
4880     workers()->run_task(&cl, num_workers);
4881   }
4882   g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4883 
4884   collection_set->clear();
4885 }
4886 
4887 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4888  private:
4889   FreeRegionList* _free_region_list;
4890   HeapRegionSet* _proxy_set;
4891   uint _humongous_objects_reclaimed;
4892   uint _humongous_regions_reclaimed;
4893   size_t _freed_bytes;
4894  public:
4895 
4896   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4897     _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4898   }
4899 
4900   virtual bool doHeapRegion(HeapRegion* r) {
4901     if (!r->is_starts_humongous()) {
4902       return false;
4903     }
4904 
4905     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4906 
4907     oop obj = (oop)r->bottom();
4908     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
4909 
4910     // The following checks whether the humongous object is live are sufficient.
4911     // The main additional check (in addition to having a reference from the roots
4912     // or the young gen) is whether the humongous object has a remembered set entry.
4913     //
4914     // A humongous object cannot be live if there is no remembered set for it
4915     // because:
4916     // - there can be no references from within humongous starts regions referencing
4917     // the object because we never allocate other objects into them.
4918     // (I.e. there are no intra-region references that may be missed by the
4919     // remembered set)
4920     // - as soon there is a remembered set entry to the humongous starts region
4921     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4922     // until the end of a concurrent mark.
4923     //
4924     // It is not required to check whether the object has been found dead by marking
4925     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4926     // all objects allocated during that time are considered live.
4927     // SATB marking is even more conservative than the remembered set.
4928     // So if at this point in the collection there is no remembered set entry,
4929     // nobody has a reference to it.
4930     // At the start of collection we flush all refinement logs, and remembered sets
4931     // are completely up-to-date wrt to references to the humongous object.
4932     //
4933     // Other implementation considerations:
4934     // - never consider object arrays at this time because they would pose
4935     // considerable effort for cleaning up the the remembered sets. This is
4936     // required because stale remembered sets might reference locations that
4937     // are currently allocated into.
4938     uint region_idx = r->hrm_index();
4939     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4940         !r->rem_set()->is_empty()) {
4941       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",
4942                                region_idx,
4943                                (size_t)obj->size() * HeapWordSize,
4944                                p2i(r->bottom()),
4945                                r->rem_set()->occupied(),
4946                                r->rem_set()->strong_code_roots_list_length(),
4947                                next_bitmap->is_marked(r->bottom()),
4948                                g1h->is_humongous_reclaim_candidate(region_idx),
4949                                obj->is_typeArray()
4950                               );
4951       return false;
4952     }
4953 
4954     guarantee(obj->is_typeArray(),
4955               "Only eagerly reclaiming type arrays is supported, but the object "
4956               PTR_FORMAT " is not.", p2i(r->bottom()));
4957 
4958     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",
4959                              region_idx,
4960                              (size_t)obj->size() * HeapWordSize,
4961                              p2i(r->bottom()),
4962                              r->rem_set()->occupied(),
4963                              r->rem_set()->strong_code_roots_list_length(),
4964                              next_bitmap->is_marked(r->bottom()),
4965                              g1h->is_humongous_reclaim_candidate(region_idx),
4966                              obj->is_typeArray()
4967                             );
4968 
4969     // Need to clear mark bit of the humongous object if already set.
4970     if (next_bitmap->is_marked(r->bottom())) {
4971       next_bitmap->clear(r->bottom());
4972     }
4973     _humongous_objects_reclaimed++;
4974     do {
4975       HeapRegion* next = g1h->next_region_in_humongous(r);
4976       _freed_bytes += r->used();
4977       r->set_containing_set(NULL);
4978       _humongous_regions_reclaimed++;
4979       g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ );
4980       r = next;
4981     } while (r != NULL);
4982 
4983     return false;
4984   }
4985 
4986   uint humongous_objects_reclaimed() {
4987     return _humongous_objects_reclaimed;
4988   }
4989 
4990   uint humongous_regions_reclaimed() {
4991     return _humongous_regions_reclaimed;
4992   }
4993 
4994   size_t bytes_freed() const {
4995     return _freed_bytes;
4996   }
4997 };
4998 
4999 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
5000   assert_at_safepoint(true);
5001 
5002   if (!G1EagerReclaimHumongousObjects ||
5003       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
5004     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
5005     return;
5006   }
5007 
5008   double start_time = os::elapsedTime();
5009 
5010   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
5011 
5012   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
5013   heap_region_iterate(&cl);
5014 
5015   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
5016 
5017   G1HRPrinter* hrp = hr_printer();
5018   if (hrp->is_active()) {
5019     FreeRegionListIterator iter(&local_cleanup_list);
5020     while (iter.more_available()) {
5021       HeapRegion* hr = iter.get_next();
5022       hrp->cleanup(hr);
5023     }
5024   }
5025 
5026   prepend_to_freelist(&local_cleanup_list);
5027   decrement_summary_bytes(cl.bytes_freed());
5028 
5029   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
5030                                                                     cl.humongous_objects_reclaimed());
5031 }
5032 
5033 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
5034 public:
5035   virtual bool doHeapRegion(HeapRegion* r) {
5036     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
5037     G1CollectedHeap::heap()->clear_in_cset(r);
5038     r->set_young_index_in_cset(-1);
5039     return false;
5040   }
5041 };
5042 
5043 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
5044   G1AbandonCollectionSetClosure cl;
5045   collection_set->iterate(&cl);
5046 
5047   collection_set->clear();
5048   collection_set->stop_incremental_building();
5049 }
5050 
5051 void G1CollectedHeap::set_free_regions_coming() {
5052   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
5053 
5054   assert(!free_regions_coming(), "pre-condition");
5055   _free_regions_coming = true;
5056 }
5057 
5058 void G1CollectedHeap::reset_free_regions_coming() {
5059   assert(free_regions_coming(), "pre-condition");
5060 
5061   {
5062     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5063     _free_regions_coming = false;
5064     SecondaryFreeList_lock->notify_all();
5065   }
5066 
5067   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
5068 }
5069 
5070 void G1CollectedHeap::wait_while_free_regions_coming() {
5071   // Most of the time we won't have to wait, so let's do a quick test
5072   // first before we take the lock.
5073   if (!free_regions_coming()) {
5074     return;
5075   }
5076 
5077   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
5078 
5079   {
5080     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5081     while (free_regions_coming()) {
5082       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5083     }
5084   }
5085 
5086   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
5087 }
5088 
5089 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
5090   return _allocator->is_retained_old_region(hr);
5091 }
5092 
5093 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5094   _eden.add(hr);
5095   _g1_policy->set_region_eden(hr);
5096 }
5097 
5098 #ifdef ASSERT
5099 
5100 class NoYoungRegionsClosure: public HeapRegionClosure {
5101 private:
5102   bool _success;
5103 public:
5104   NoYoungRegionsClosure() : _success(true) { }
5105   bool doHeapRegion(HeapRegion* r) {
5106     if (r->is_young()) {
5107       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5108                             p2i(r->bottom()), p2i(r->end()));
5109       _success = false;
5110     }
5111     return false;
5112   }
5113   bool success() { return _success; }
5114 };
5115 
5116 bool G1CollectedHeap::check_young_list_empty() {
5117   bool ret = (young_regions_count() == 0);
5118 
5119   NoYoungRegionsClosure closure;
5120   heap_region_iterate(&closure);
5121   ret = ret && closure.success();
5122 
5123   return ret;
5124 }
5125 
5126 #endif // ASSERT
5127 
5128 class TearDownRegionSetsClosure : public HeapRegionClosure {
5129 private:
5130   HeapRegionSet *_old_set;
5131 
5132 public:
5133   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5134 
5135   bool doHeapRegion(HeapRegion* r) {
5136     if (r->is_old()) {
5137       _old_set->remove(r);
5138     } else if(r->is_young()) {
5139       r->uninstall_surv_rate_group();
5140     } else {
5141       // We ignore free regions, we'll empty the free list afterwards.
5142       // We ignore humongous regions, we're not tearing down the
5143       // humongous regions set.
5144       assert(r->is_free() || r->is_humongous(),
5145              "it cannot be another type");
5146     }
5147     return false;
5148   }
5149 
5150   ~TearDownRegionSetsClosure() {
5151     assert(_old_set->is_empty(), "post-condition");
5152   }
5153 };
5154 
5155 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5156   assert_at_safepoint(true /* should_be_vm_thread */);
5157 
5158   if (!free_list_only) {
5159     TearDownRegionSetsClosure cl(&_old_set);
5160     heap_region_iterate(&cl);
5161 
5162     // Note that emptying the _young_list is postponed and instead done as
5163     // the first step when rebuilding the regions sets again. The reason for
5164     // this is that during a full GC string deduplication needs to know if
5165     // a collected region was young or old when the full GC was initiated.
5166   }
5167   _hrm.remove_all_free_regions();
5168 }
5169 
5170 void G1CollectedHeap::increase_used(size_t bytes) {
5171   _summary_bytes_used += bytes;
5172 }
5173 
5174 void G1CollectedHeap::decrease_used(size_t bytes) {
5175   assert(_summary_bytes_used >= bytes,
5176          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5177          _summary_bytes_used, bytes);
5178   _summary_bytes_used -= bytes;
5179 }
5180 
5181 void G1CollectedHeap::set_used(size_t bytes) {
5182   _summary_bytes_used = bytes;
5183 }
5184 
5185 class RebuildRegionSetsClosure : public HeapRegionClosure {
5186 private:
5187   bool            _free_list_only;
5188   HeapRegionSet*   _old_set;
5189   HeapRegionManager*   _hrm;
5190   size_t          _total_used;
5191 
5192 public:
5193   RebuildRegionSetsClosure(bool free_list_only,
5194                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
5195     _free_list_only(free_list_only),
5196     _old_set(old_set), _hrm(hrm), _total_used(0) {
5197     assert(_hrm->num_free_regions() == 0, "pre-condition");
5198     if (!free_list_only) {
5199       assert(_old_set->is_empty(), "pre-condition");
5200     }
5201   }
5202 
5203   bool doHeapRegion(HeapRegion* r) {
5204     if (r->is_empty()) {
5205       // Add free regions to the free list
5206       r->set_free();
5207       r->set_allocation_context(AllocationContext::system());
5208       _hrm->insert_into_free_list(r);
5209     } else if (!_free_list_only) {
5210 
5211       if (r->is_humongous()) {
5212         // We ignore humongous regions. We left the humongous set unchanged.
5213       } else {
5214         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
5215         // We now consider all regions old, so register as such. Leave
5216         // archive regions set that way, however, while still adding
5217         // them to the old set.
5218         if (!r->is_archive()) {
5219           r->set_old();
5220         }
5221         _old_set->add(r);
5222       }
5223       _total_used += r->used();
5224     }
5225 
5226     return false;
5227   }
5228 
5229   size_t total_used() {
5230     return _total_used;
5231   }
5232 };
5233 
5234 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5235   assert_at_safepoint(true /* should_be_vm_thread */);
5236 
5237   if (!free_list_only) {
5238     _eden.clear();
5239     _survivor.clear();
5240   }
5241 
5242   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5243   heap_region_iterate(&cl);
5244 
5245   if (!free_list_only) {
5246     set_used(cl.total_used());
5247     if (_archive_allocator != NULL) {
5248       _archive_allocator->clear_used();
5249     }
5250   }
5251   assert(used_unlocked() == recalculate_used(),
5252          "inconsistent used_unlocked(), "
5253          "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5254          used_unlocked(), recalculate_used());
5255 }
5256 
5257 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5258   HeapRegion* hr = heap_region_containing(p);
5259   return hr->is_in(p);
5260 }
5261 
5262 // Methods for the mutator alloc region
5263 
5264 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5265                                                       bool force) {
5266   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5267   bool should_allocate = g1_policy()->should_allocate_mutator_region();
5268   if (force || should_allocate) {
5269     HeapRegion* new_alloc_region = new_region(word_size,
5270                                               false /* is_old */,
5271                                               false /* do_expand */);
5272     if (new_alloc_region != NULL) {
5273       set_region_short_lived_locked(new_alloc_region);
5274       _hr_printer.alloc(new_alloc_region, !should_allocate);
5275       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5276       return new_alloc_region;
5277     }
5278   }
5279   return NULL;
5280 }
5281 
5282 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5283                                                   size_t allocated_bytes) {
5284   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5285   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5286 
5287   collection_set()->add_eden_region(alloc_region);
5288   increase_used(allocated_bytes);
5289   _hr_printer.retire(alloc_region);
5290   // We update the eden sizes here, when the region is retired,
5291   // instead of when it's allocated, since this is the point that its
5292   // used space has been recored in _summary_bytes_used.
5293   g1mm()->update_eden_size();
5294 }
5295 
5296 // Methods for the GC alloc regions
5297 
5298 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
5299   if (dest.is_old()) {
5300     return true;
5301   } else {
5302     return survivor_regions_count() < g1_policy()->max_survivor_regions();
5303   }
5304 }
5305 
5306 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
5307   assert(FreeList_lock->owned_by_self(), "pre-condition");
5308 
5309   if (!has_more_regions(dest)) {
5310     return NULL;
5311   }
5312 
5313   const bool is_survivor = dest.is_young();
5314 
5315   HeapRegion* new_alloc_region = new_region(word_size,
5316                                             !is_survivor,
5317                                             true /* do_expand */);
5318   if (new_alloc_region != NULL) {
5319     // We really only need to do this for old regions given that we
5320     // should never scan survivors. But it doesn't hurt to do it
5321     // for survivors too.
5322     new_alloc_region->record_timestamp();
5323     if (is_survivor) {
5324       new_alloc_region->set_survivor();
5325       _survivor.add(new_alloc_region);
5326       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5327     } else {
5328       new_alloc_region->set_old();
5329       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5330     }
5331     _hr_printer.alloc(new_alloc_region);
5332     bool during_im = collector_state()->during_initial_mark_pause();
5333     new_alloc_region->note_start_of_copying(during_im);
5334     return new_alloc_region;
5335   }
5336   return NULL;
5337 }
5338 
5339 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5340                                              size_t allocated_bytes,
5341                                              InCSetState dest) {
5342   bool during_im = collector_state()->during_initial_mark_pause();
5343   alloc_region->note_end_of_copying(during_im);
5344   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5345   if (dest.is_old()) {
5346     _old_set.add(alloc_region);
5347   }
5348   _hr_printer.retire(alloc_region);
5349 }
5350 
5351 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5352   bool expanded = false;
5353   uint index = _hrm.find_highest_free(&expanded);
5354 
5355   if (index != G1_NO_HRM_INDEX) {
5356     if (expanded) {
5357       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5358                                 HeapRegion::GrainWords * HeapWordSize);
5359     }
5360     _hrm.allocate_free_regions_starting_at(index, 1);
5361     return region_at(index);
5362   }
5363   return NULL;
5364 }
5365 
5366 // Optimized nmethod scanning
5367 
5368 class RegisterNMethodOopClosure: public OopClosure {
5369   G1CollectedHeap* _g1h;
5370   nmethod* _nm;
5371 
5372   template <class T> void do_oop_work(T* p) {
5373     T heap_oop = oopDesc::load_heap_oop(p);
5374     if (!oopDesc::is_null(heap_oop)) {
5375       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5376       HeapRegion* hr = _g1h->heap_region_containing(obj);
5377       assert(!hr->is_continues_humongous(),
5378              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5379              " starting at " HR_FORMAT,
5380              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5381 
5382       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5383       hr->add_strong_code_root_locked(_nm);
5384     }
5385   }
5386 
5387 public:
5388   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5389     _g1h(g1h), _nm(nm) {}
5390 
5391   void do_oop(oop* p)       { do_oop_work(p); }
5392   void do_oop(narrowOop* p) { do_oop_work(p); }
5393 };
5394 
5395 class UnregisterNMethodOopClosure: public OopClosure {
5396   G1CollectedHeap* _g1h;
5397   nmethod* _nm;
5398 
5399   template <class T> void do_oop_work(T* p) {
5400     T heap_oop = oopDesc::load_heap_oop(p);
5401     if (!oopDesc::is_null(heap_oop)) {
5402       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5403       HeapRegion* hr = _g1h->heap_region_containing(obj);
5404       assert(!hr->is_continues_humongous(),
5405              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5406              " starting at " HR_FORMAT,
5407              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5408 
5409       hr->remove_strong_code_root(_nm);
5410     }
5411   }
5412 
5413 public:
5414   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5415     _g1h(g1h), _nm(nm) {}
5416 
5417   void do_oop(oop* p)       { do_oop_work(p); }
5418   void do_oop(narrowOop* p) { do_oop_work(p); }
5419 };
5420 
5421 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5422   CollectedHeap::register_nmethod(nm);
5423 
5424   guarantee(nm != NULL, "sanity");
5425   RegisterNMethodOopClosure reg_cl(this, nm);
5426   nm->oops_do(&reg_cl);
5427 }
5428 
5429 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5430   CollectedHeap::unregister_nmethod(nm);
5431 
5432   guarantee(nm != NULL, "sanity");
5433   UnregisterNMethodOopClosure reg_cl(this, nm);
5434   nm->oops_do(&reg_cl, true);
5435 }
5436 
5437 void G1CollectedHeap::purge_code_root_memory() {
5438   double purge_start = os::elapsedTime();
5439   G1CodeRootSet::purge();
5440   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5441   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5442 }
5443 
5444 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5445   G1CollectedHeap* _g1h;
5446 
5447 public:
5448   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5449     _g1h(g1h) {}
5450 
5451   void do_code_blob(CodeBlob* cb) {
5452     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5453     if (nm == NULL) {
5454       return;
5455     }
5456 
5457     if (ScavengeRootsInCode) {
5458       _g1h->register_nmethod(nm);
5459     }
5460   }
5461 };
5462 
5463 void G1CollectedHeap::rebuild_strong_code_roots() {
5464   RebuildStrongCodeRootClosure blob_cl(this);
5465   CodeCache::blobs_do(&blob_cl);
5466 }