1 /*
   2  * Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/metadataOnStackMark.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "classfile/symbolTable.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc/g1/bufferingOopClosure.hpp"
  32 #include "gc/g1/concurrentMarkThread.inline.hpp"
  33 #include "gc/g1/g1Allocator.inline.hpp"
  34 #include "gc/g1/g1CollectedHeap.inline.hpp"
  35 #include "gc/g1/g1CollectionSet.hpp"
  36 #include "gc/g1/g1CollectorPolicy.hpp"
  37 #include "gc/g1/g1CollectorState.hpp"
  38 #include "gc/g1/g1ConcurrentRefine.hpp"
  39 #include "gc/g1/g1ConcurrentRefineThread.hpp"
  40 #include "gc/g1/g1EvacStats.inline.hpp"
  41 #include "gc/g1/g1FullCollector.hpp"
  42 #include "gc/g1/g1GCPhaseTimes.hpp"
  43 #include "gc/g1/g1HeapSizingPolicy.hpp"
  44 #include "gc/g1/g1HeapTransition.hpp"
  45 #include "gc/g1/g1HeapVerifier.hpp"
  46 #include "gc/g1/g1HotCardCache.hpp"
  47 #include "gc/g1/g1OopClosures.inline.hpp"
  48 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  49 #include "gc/g1/g1Policy.hpp"
  50 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  51 #include "gc/g1/g1RemSet.hpp"
  52 #include "gc/g1/g1RootClosures.hpp"
  53 #include "gc/g1/g1RootProcessor.hpp"
  54 #include "gc/g1/g1StringDedup.hpp"
  55 #include "gc/g1/g1YCTypes.hpp"
  56 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
  57 #include "gc/g1/heapRegion.inline.hpp"
  58 #include "gc/g1/heapRegionRemSet.hpp"
  59 #include "gc/g1/heapRegionSet.inline.hpp"
  60 #include "gc/g1/vm_operations_g1.hpp"
  61 #include "gc/shared/gcHeapSummary.hpp"
  62 #include "gc/shared/gcId.hpp"
  63 #include "gc/shared/gcLocker.inline.hpp"
  64 #include "gc/shared/gcTimer.hpp"
  65 #include "gc/shared/gcTrace.hpp"
  66 #include "gc/shared/gcTraceTime.inline.hpp"
  67 #include "gc/shared/generationSpec.hpp"
  68 #include "gc/shared/isGCActiveMark.hpp"
  69 #include "gc/shared/preservedMarks.inline.hpp"
  70 #include "gc/shared/suspendibleThreadSet.hpp"
  71 #include "gc/shared/referenceProcessor.inline.hpp"
  72 #include "gc/shared/taskqueue.inline.hpp"
  73 #include "gc/shared/weakProcessor.hpp"
  74 #include "logging/log.hpp"
  75 #include "memory/allocation.hpp"
  76 #include "memory/iterator.hpp"
  77 #include "memory/resourceArea.hpp"
  78 #include "oops/oop.inline.hpp"
  79 #include "prims/resolvedMethodTable.hpp"
  80 #include "runtime/atomic.hpp"
  81 #include "runtime/init.hpp"
  82 #include "runtime/orderAccess.inline.hpp"
  83 #include "runtime/threadSMR.hpp"
  84 #include "runtime/vmThread.hpp"
  85 #include "utilities/align.hpp"
  86 #include "utilities/globalDefinitions.hpp"
  87 #include "utilities/stack.inline.hpp"
  88 
  89 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  90 
  91 // INVARIANTS/NOTES
  92 //
  93 // All allocation activity covered by the G1CollectedHeap interface is
  94 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  95 // and allocate_new_tlab, which are the "entry" points to the
  96 // allocation code from the rest of the JVM.  (Note that this does not
  97 // apply to TLAB allocation, which is not part of this interface: it
  98 // is done by clients of this interface.)
  99 
 100 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 101  private:
 102   size_t _num_dirtied;
 103   G1CollectedHeap* _g1h;
 104   G1SATBCardTableLoggingModRefBS* _g1_bs;
 105 
 106   HeapRegion* region_for_card(jbyte* card_ptr) const {
 107     return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
 108   }
 109 
 110   bool will_become_free(HeapRegion* hr) const {
 111     // A region will be freed by free_collection_set if the region is in the
 112     // collection set and has not had an evacuation failure.
 113     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 114   }
 115 
 116  public:
 117   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
 118     _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
 119 
 120   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 121     HeapRegion* hr = region_for_card(card_ptr);
 122 
 123     // Should only dirty cards in regions that won't be freed.
 124     if (!will_become_free(hr)) {
 125       *card_ptr = CardTableModRefBS::dirty_card_val();
 126       _num_dirtied++;
 127     }
 128 
 129     return true;
 130   }
 131 
 132   size_t num_dirtied()   const { return _num_dirtied; }
 133 };
 134 
 135 
 136 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 137   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 138 }
 139 
 140 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 141   // The from card cache is not the memory that is actually committed. So we cannot
 142   // take advantage of the zero_filled parameter.
 143   reset_from_card_cache(start_idx, num_regions);
 144 }
 145 
 146 
 147 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
 148                                              MemRegion mr) {
 149   return new HeapRegion(hrs_index, bot(), mr);
 150 }
 151 
 152 // Private methods.
 153 
 154 HeapRegion*
 155 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 156   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 157   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 158     if (!_secondary_free_list.is_empty()) {
 159       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 160                                       "secondary_free_list has %u entries",
 161                                       _secondary_free_list.length());
 162       // It looks as if there are free regions available on the
 163       // secondary_free_list. Let's move them to the free_list and try
 164       // again to allocate from it.
 165       append_secondary_free_list();
 166 
 167       assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
 168              "empty we should have moved at least one entry to the free_list");
 169       HeapRegion* res = _hrm.allocate_free_region(is_old);
 170       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 171                                       "allocated " HR_FORMAT " from secondary_free_list",
 172                                       HR_FORMAT_PARAMS(res));
 173       return res;
 174     }
 175 
 176     // Wait here until we get notified either when (a) there are no
 177     // more free regions coming or (b) some regions have been moved on
 178     // the secondary_free_list.
 179     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 180   }
 181 
 182   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 183                                   "could not allocate from secondary_free_list");
 184   return NULL;
 185 }
 186 
 187 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 188   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 189          "the only time we use this to allocate a humongous region is "
 190          "when we are allocating a single humongous region");
 191 
 192   HeapRegion* res;
 193   if (G1StressConcRegionFreeing) {
 194     if (!_secondary_free_list.is_empty()) {
 195       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 196                                       "forced to look at the secondary_free_list");
 197       res = new_region_try_secondary_free_list(is_old);
 198       if (res != NULL) {
 199         return res;
 200       }
 201     }
 202   }
 203 
 204   res = _hrm.allocate_free_region(is_old);
 205 
 206   if (res == NULL) {
 207     log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 208                                     "res == NULL, trying the secondary_free_list");
 209     res = new_region_try_secondary_free_list(is_old);
 210   }
 211   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 212     // Currently, only attempts to allocate GC alloc regions set
 213     // do_expand to true. So, we should only reach here during a
 214     // safepoint. If this assumption changes we might have to
 215     // reconsider the use of _expand_heap_after_alloc_failure.
 216     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 217 
 218     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 219                               word_size * HeapWordSize);
 220 
 221     if (expand(word_size * HeapWordSize)) {
 222       // Given that expand() succeeded in expanding the heap, and we
 223       // always expand the heap by an amount aligned to the heap
 224       // region size, the free list should in theory not be empty.
 225       // In either case allocate_free_region() will check for NULL.
 226       res = _hrm.allocate_free_region(is_old);
 227     } else {
 228       _expand_heap_after_alloc_failure = false;
 229     }
 230   }
 231   return res;
 232 }
 233 
 234 HeapWord*
 235 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 236                                                            uint num_regions,
 237                                                            size_t word_size,
 238                                                            AllocationContext_t context) {
 239   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 240   assert(is_humongous(word_size), "word_size should be humongous");
 241   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 242 
 243   // Index of last region in the series.
 244   uint last = first + num_regions - 1;
 245 
 246   // We need to initialize the region(s) we just discovered. This is
 247   // a bit tricky given that it can happen concurrently with
 248   // refinement threads refining cards on these regions and
 249   // potentially wanting to refine the BOT as they are scanning
 250   // those cards (this can happen shortly after a cleanup; see CR
 251   // 6991377). So we have to set up the region(s) carefully and in
 252   // a specific order.
 253 
 254   // The word size sum of all the regions we will allocate.
 255   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 256   assert(word_size <= word_size_sum, "sanity");
 257 
 258   // This will be the "starts humongous" region.
 259   HeapRegion* first_hr = region_at(first);
 260   // The header of the new object will be placed at the bottom of
 261   // the first region.
 262   HeapWord* new_obj = first_hr->bottom();
 263   // This will be the new top of the new object.
 264   HeapWord* obj_top = new_obj + word_size;
 265 
 266   // First, we need to zero the header of the space that we will be
 267   // allocating. When we update top further down, some refinement
 268   // threads might try to scan the region. By zeroing the header we
 269   // ensure that any thread that will try to scan the region will
 270   // come across the zero klass word and bail out.
 271   //
 272   // NOTE: It would not have been correct to have used
 273   // CollectedHeap::fill_with_object() and make the space look like
 274   // an int array. The thread that is doing the allocation will
 275   // later update the object header to a potentially different array
 276   // type and, for a very short period of time, the klass and length
 277   // fields will be inconsistent. This could cause a refinement
 278   // thread to calculate the object size incorrectly.
 279   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 280 
 281   // Next, pad out the unused tail of the last region with filler
 282   // objects, for improved usage accounting.
 283   // How many words we use for filler objects.
 284   size_t word_fill_size = word_size_sum - word_size;
 285 
 286   // How many words memory we "waste" which cannot hold a filler object.
 287   size_t words_not_fillable = 0;
 288 
 289   if (word_fill_size >= min_fill_size()) {
 290     fill_with_objects(obj_top, word_fill_size);
 291   } else if (word_fill_size > 0) {
 292     // We have space to fill, but we cannot fit an object there.
 293     words_not_fillable = word_fill_size;
 294     word_fill_size = 0;
 295   }
 296 
 297   // We will set up the first region as "starts humongous". This
 298   // will also update the BOT covering all the regions to reflect
 299   // that there is a single object that starts at the bottom of the
 300   // first region.
 301   first_hr->set_starts_humongous(obj_top, word_fill_size);
 302   first_hr->set_allocation_context(context);
 303   // Then, if there are any, we will set up the "continues
 304   // humongous" regions.
 305   HeapRegion* hr = NULL;
 306   for (uint i = first + 1; i <= last; ++i) {
 307     hr = region_at(i);
 308     hr->set_continues_humongous(first_hr);
 309     hr->set_allocation_context(context);
 310   }
 311 
 312   // Up to this point no concurrent thread would have been able to
 313   // do any scanning on any region in this series. All the top
 314   // fields still point to bottom, so the intersection between
 315   // [bottom,top] and [card_start,card_end] will be empty. Before we
 316   // update the top fields, we'll do a storestore to make sure that
 317   // no thread sees the update to top before the zeroing of the
 318   // object header and the BOT initialization.
 319   OrderAccess::storestore();
 320 
 321   // Now, we will update the top fields of the "continues humongous"
 322   // regions except the last one.
 323   for (uint i = first; i < last; ++i) {
 324     hr = region_at(i);
 325     hr->set_top(hr->end());
 326   }
 327 
 328   hr = region_at(last);
 329   // If we cannot fit a filler object, we must set top to the end
 330   // of the humongous object, otherwise we cannot iterate the heap
 331   // and the BOT will not be complete.
 332   hr->set_top(hr->end() - words_not_fillable);
 333 
 334   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 335          "obj_top should be in last region");
 336 
 337   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 338 
 339   assert(words_not_fillable == 0 ||
 340          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 341          "Miscalculation in humongous allocation");
 342 
 343   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 344 
 345   for (uint i = first; i <= last; ++i) {
 346     hr = region_at(i);
 347     _humongous_set.add(hr);
 348     _hr_printer.alloc(hr);
 349   }
 350 
 351   return new_obj;
 352 }
 353 
 354 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 355   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 356   return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 357 }
 358 
 359 // If could fit into free regions w/o expansion, try.
 360 // Otherwise, if can expand, do so.
 361 // Otherwise, if using ex regions might help, try with ex given back.
 362 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
 363   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 364 
 365   _verifier->verify_region_sets_optional();
 366 
 367   uint first = G1_NO_HRM_INDEX;
 368   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 369 
 370   if (obj_regions == 1) {
 371     // Only one region to allocate, try to use a fast path by directly allocating
 372     // from the free lists. Do not try to expand here, we will potentially do that
 373     // later.
 374     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 375     if (hr != NULL) {
 376       first = hr->hrm_index();
 377     }
 378   } else {
 379     // We can't allocate humongous regions spanning more than one region while
 380     // cleanupComplete() is running, since some of the regions we find to be
 381     // empty might not yet be added to the free list. It is not straightforward
 382     // to know in which list they are on so that we can remove them. We only
 383     // need to do this if we need to allocate more than one region to satisfy the
 384     // current humongous allocation request. If we are only allocating one region
 385     // we use the one-region region allocation code (see above), that already
 386     // potentially waits for regions from the secondary free list.
 387     wait_while_free_regions_coming();
 388     append_secondary_free_list_if_not_empty_with_lock();
 389 
 390     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 391     // are lucky enough to find some.
 392     first = _hrm.find_contiguous_only_empty(obj_regions);
 393     if (first != G1_NO_HRM_INDEX) {
 394       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 395     }
 396   }
 397 
 398   if (first == G1_NO_HRM_INDEX) {
 399     // Policy: We could not find enough regions for the humongous object in the
 400     // free list. Look through the heap to find a mix of free and uncommitted regions.
 401     // If so, try expansion.
 402     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 403     if (first != G1_NO_HRM_INDEX) {
 404       // We found something. Make sure these regions are committed, i.e. expand
 405       // the heap. Alternatively we could do a defragmentation GC.
 406       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 407                                     word_size * HeapWordSize);
 408 
 409       _hrm.expand_at(first, obj_regions, workers());
 410       g1_policy()->record_new_heap_size(num_regions());
 411 
 412 #ifdef ASSERT
 413       for (uint i = first; i < first + obj_regions; ++i) {
 414         HeapRegion* hr = region_at(i);
 415         assert(hr->is_free(), "sanity");
 416         assert(hr->is_empty(), "sanity");
 417         assert(is_on_master_free_list(hr), "sanity");
 418       }
 419 #endif
 420       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 421     } else {
 422       // Policy: Potentially trigger a defragmentation GC.
 423     }
 424   }
 425 
 426   HeapWord* result = NULL;
 427   if (first != G1_NO_HRM_INDEX) {
 428     result = humongous_obj_allocate_initialize_regions(first, obj_regions,
 429                                                        word_size, context);
 430     assert(result != NULL, "it should always return a valid result");
 431 
 432     // A successful humongous object allocation changes the used space
 433     // information of the old generation so we need to recalculate the
 434     // sizes and update the jstat counters here.
 435     g1mm()->update_sizes();
 436   }
 437 
 438   _verifier->verify_region_sets_optional();
 439 
 440   return result;
 441 }
 442 
 443 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 444   assert_heap_not_locked_and_not_at_safepoint();
 445   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 446 
 447   uint dummy_gc_count_before;
 448   uint dummy_gclocker_retry_count = 0;
 449   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 450 }
 451 
 452 HeapWord*
 453 G1CollectedHeap::mem_allocate(size_t word_size,
 454                               bool*  gc_overhead_limit_was_exceeded) {
 455   assert_heap_not_locked_and_not_at_safepoint();
 456 
 457   // Loop until the allocation is satisfied, or unsatisfied after GC.
 458   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 459     uint gc_count_before;
 460 
 461     HeapWord* result = NULL;
 462     if (!is_humongous(word_size)) {
 463       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 464     } else {
 465       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 466     }
 467     if (result != NULL) {
 468       return result;
 469     }
 470 
 471     // Create the garbage collection operation...
 472     VM_G1CollectForAllocation op(gc_count_before, word_size);
 473     op.set_allocation_context(AllocationContext::current());
 474 
 475     // ...and get the VM thread to execute it.
 476     VMThread::execute(&op);
 477 
 478     if (op.prologue_succeeded() && op.pause_succeeded()) {
 479       // If the operation was successful we'll return the result even
 480       // if it is NULL. If the allocation attempt failed immediately
 481       // after a Full GC, it's unlikely we'll be able to allocate now.
 482       HeapWord* result = op.result();
 483       if (result != NULL && !is_humongous(word_size)) {
 484         // Allocations that take place on VM operations do not do any
 485         // card dirtying and we have to do it here. We only have to do
 486         // this for non-humongous allocations, though.
 487         dirty_young_block(result, word_size);
 488       }
 489       return result;
 490     } else {
 491       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 492         return NULL;
 493       }
 494       assert(op.result() == NULL,
 495              "the result should be NULL if the VM op did not succeed");
 496     }
 497 
 498     // Give a warning if we seem to be looping forever.
 499     if ((QueuedAllocationWarningCount > 0) &&
 500         (try_count % QueuedAllocationWarningCount == 0)) {
 501       log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
 502     }
 503   }
 504 
 505   ShouldNotReachHere();
 506   return NULL;
 507 }
 508 
 509 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 510                                                    AllocationContext_t context,
 511                                                    uint* gc_count_before_ret,
 512                                                    uint* gclocker_retry_count_ret) {
 513   // Make sure you read the note in attempt_allocation_humongous().
 514 
 515   assert_heap_not_locked_and_not_at_safepoint();
 516   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 517          "be called for humongous allocation requests");
 518 
 519   // We should only get here after the first-level allocation attempt
 520   // (attempt_allocation()) failed to allocate.
 521 
 522   // We will loop until a) we manage to successfully perform the
 523   // allocation or b) we successfully schedule a collection which
 524   // fails to perform the allocation. b) is the only case when we'll
 525   // return NULL.
 526   HeapWord* result = NULL;
 527   for (int try_count = 1; /* we'll return */; try_count += 1) {
 528     bool should_try_gc;
 529     uint gc_count_before;
 530 
 531     {
 532       MutexLockerEx x(Heap_lock);
 533       result = _allocator->attempt_allocation_locked(word_size, context);
 534       if (result != NULL) {
 535         return result;
 536       }
 537 
 538       if (GCLocker::is_active_and_needs_gc()) {
 539         if (g1_policy()->can_expand_young_list()) {
 540           // No need for an ergo verbose message here,
 541           // can_expand_young_list() does this when it returns true.
 542           result = _allocator->attempt_allocation_force(word_size, context);
 543           if (result != NULL) {
 544             return result;
 545           }
 546         }
 547         should_try_gc = false;
 548       } else {
 549         // The GCLocker may not be active but the GCLocker initiated
 550         // GC may not yet have been performed (GCLocker::needs_gc()
 551         // returns true). In this case we do not try this GC and
 552         // wait until the GCLocker initiated GC is performed, and
 553         // then retry the allocation.
 554         if (GCLocker::needs_gc()) {
 555           should_try_gc = false;
 556         } else {
 557           // Read the GC count while still holding the Heap_lock.
 558           gc_count_before = total_collections();
 559           should_try_gc = true;
 560         }
 561       }
 562     }
 563 
 564     if (should_try_gc) {
 565       bool succeeded;
 566       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 567                                    GCCause::_g1_inc_collection_pause);
 568       if (result != NULL) {
 569         assert(succeeded, "only way to get back a non-NULL result");
 570         return result;
 571       }
 572 
 573       if (succeeded) {
 574         // If we get here we successfully scheduled a collection which
 575         // failed to allocate. No point in trying to allocate
 576         // further. We'll just return NULL.
 577         MutexLockerEx x(Heap_lock);
 578         *gc_count_before_ret = total_collections();
 579         return NULL;
 580       }
 581     } else {
 582       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 583         MutexLockerEx x(Heap_lock);
 584         *gc_count_before_ret = total_collections();
 585         return NULL;
 586       }
 587       // The GCLocker is either active or the GCLocker initiated
 588       // GC has not yet been performed. Stall until it is and
 589       // then retry the allocation.
 590       GCLocker::stall_until_clear();
 591       (*gclocker_retry_count_ret) += 1;
 592     }
 593 
 594     // We can reach here if we were unsuccessful in scheduling a
 595     // collection (because another thread beat us to it) or if we were
 596     // stalled due to the GC locker. In either can we should retry the
 597     // allocation attempt in case another thread successfully
 598     // performed a collection and reclaimed enough space. We do the
 599     // first attempt (without holding the Heap_lock) here and the
 600     // follow-on attempt will be at the start of the next loop
 601     // iteration (after taking the Heap_lock).
 602     result = _allocator->attempt_allocation(word_size, context);
 603     if (result != NULL) {
 604       return result;
 605     }
 606 
 607     // Give a warning if we seem to be looping forever.
 608     if ((QueuedAllocationWarningCount > 0) &&
 609         (try_count % QueuedAllocationWarningCount == 0)) {
 610       log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
 611                       "retries %d times", try_count);
 612     }
 613   }
 614 
 615   ShouldNotReachHere();
 616   return NULL;
 617 }
 618 
 619 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
 620   assert_at_safepoint(true /* should_be_vm_thread */);
 621   if (_archive_allocator == NULL) {
 622     _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
 623   }
 624 }
 625 
 626 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 627   // Allocations in archive regions cannot be of a size that would be considered
 628   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 629   // may be different at archive-restore time.
 630   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 631 }
 632 
 633 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 634   assert_at_safepoint(true /* should_be_vm_thread */);
 635   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 636   if (is_archive_alloc_too_large(word_size)) {
 637     return NULL;
 638   }
 639   return _archive_allocator->archive_mem_allocate(word_size);
 640 }
 641 
 642 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 643                                               size_t end_alignment_in_bytes) {
 644   assert_at_safepoint(true /* should_be_vm_thread */);
 645   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 646 
 647   // Call complete_archive to do the real work, filling in the MemRegion
 648   // array with the archive regions.
 649   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 650   delete _archive_allocator;
 651   _archive_allocator = NULL;
 652 }
 653 
 654 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 655   assert(ranges != NULL, "MemRegion array NULL");
 656   assert(count != 0, "No MemRegions provided");
 657   MemRegion reserved = _hrm.reserved();
 658   for (size_t i = 0; i < count; i++) {
 659     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 660       return false;
 661     }
 662   }
 663   return true;
 664 }
 665 
 666 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
 667                                             size_t count,
 668                                             bool open) {
 669   assert(!is_init_completed(), "Expect to be called at JVM init time");
 670   assert(ranges != NULL, "MemRegion array NULL");
 671   assert(count != 0, "No MemRegions provided");
 672   MutexLockerEx x(Heap_lock);
 673 
 674   MemRegion reserved = _hrm.reserved();
 675   HeapWord* prev_last_addr = NULL;
 676   HeapRegion* prev_last_region = NULL;
 677 
 678   // Temporarily disable pretouching of heap pages. This interface is used
 679   // when mmap'ing archived heap data in, so pre-touching is wasted.
 680   FlagSetting fs(AlwaysPreTouch, false);
 681 
 682   // Enable archive object checking used by G1MarkSweep. We have to let it know
 683   // about each archive range, so that objects in those ranges aren't marked.
 684   G1ArchiveAllocator::enable_archive_object_check();
 685 
 686   // For each specified MemRegion range, allocate the corresponding G1
 687   // regions and mark them as archive regions. We expect the ranges
 688   // in ascending starting address order, without overlap.
 689   for (size_t i = 0; i < count; i++) {
 690     MemRegion curr_range = ranges[i];
 691     HeapWord* start_address = curr_range.start();
 692     size_t word_size = curr_range.word_size();
 693     HeapWord* last_address = curr_range.last();
 694     size_t commits = 0;
 695 
 696     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 697               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 698               p2i(start_address), p2i(last_address));
 699     guarantee(start_address > prev_last_addr,
 700               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 701               p2i(start_address), p2i(prev_last_addr));
 702     prev_last_addr = last_address;
 703 
 704     // Check for ranges that start in the same G1 region in which the previous
 705     // range ended, and adjust the start address so we don't try to allocate
 706     // the same region again. If the current range is entirely within that
 707     // region, skip it, just adjusting the recorded top.
 708     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 709     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 710       start_address = start_region->end();
 711       if (start_address > last_address) {
 712         increase_used(word_size * HeapWordSize);
 713         start_region->set_top(last_address + 1);
 714         continue;
 715       }
 716       start_region->set_top(start_address);
 717       curr_range = MemRegion(start_address, last_address + 1);
 718       start_region = _hrm.addr_to_region(start_address);
 719     }
 720 
 721     // Perform the actual region allocation, exiting if it fails.
 722     // Then note how much new space we have allocated.
 723     if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
 724       return false;
 725     }
 726     increase_used(word_size * HeapWordSize);
 727     if (commits != 0) {
 728       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 729                                 HeapRegion::GrainWords * HeapWordSize * commits);
 730 
 731     }
 732 
 733     // Mark each G1 region touched by the range as archive, add it to
 734     // the old set, and set the allocation context and top.
 735     HeapRegion* curr_region = _hrm.addr_to_region(start_address);
 736     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 737     prev_last_region = last_region;
 738 
 739     while (curr_region != NULL) {
 740       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 741              "Region already in use (index %u)", curr_region->hrm_index());
 742       curr_region->set_allocation_context(AllocationContext::system());
 743       if (open) {
 744         curr_region->set_open_archive();
 745       } else {
 746         curr_region->set_closed_archive();
 747       }
 748       _hr_printer.alloc(curr_region);
 749       _old_set.add(curr_region);
 750       HeapWord* top;
 751       HeapRegion* next_region;
 752       if (curr_region != last_region) {
 753         top = curr_region->end();
 754         next_region = _hrm.next_region_in_heap(curr_region);
 755       } else {
 756         top = last_address + 1;
 757         next_region = NULL;
 758       }
 759       curr_region->set_top(top);
 760       curr_region->set_first_dead(top);
 761       curr_region->set_end_of_live(top);
 762       curr_region = next_region;
 763     }
 764 
 765     // Notify mark-sweep of the archive
 766     G1ArchiveAllocator::set_range_archive(curr_range, open);
 767   }
 768   return true;
 769 }
 770 
 771 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 772   assert(!is_init_completed(), "Expect to be called at JVM init time");
 773   assert(ranges != NULL, "MemRegion array NULL");
 774   assert(count != 0, "No MemRegions provided");
 775   MemRegion reserved = _hrm.reserved();
 776   HeapWord *prev_last_addr = NULL;
 777   HeapRegion* prev_last_region = NULL;
 778 
 779   // For each MemRegion, create filler objects, if needed, in the G1 regions
 780   // that contain the address range. The address range actually within the
 781   // MemRegion will not be modified. That is assumed to have been initialized
 782   // elsewhere, probably via an mmap of archived heap data.
 783   MutexLockerEx x(Heap_lock);
 784   for (size_t i = 0; i < count; i++) {
 785     HeapWord* start_address = ranges[i].start();
 786     HeapWord* last_address = ranges[i].last();
 787 
 788     assert(reserved.contains(start_address) && reserved.contains(last_address),
 789            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 790            p2i(start_address), p2i(last_address));
 791     assert(start_address > prev_last_addr,
 792            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 793            p2i(start_address), p2i(prev_last_addr));
 794 
 795     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 796     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 797     HeapWord* bottom_address = start_region->bottom();
 798 
 799     // Check for a range beginning in the same region in which the
 800     // previous one ended.
 801     if (start_region == prev_last_region) {
 802       bottom_address = prev_last_addr + 1;
 803     }
 804 
 805     // Verify that the regions were all marked as archive regions by
 806     // alloc_archive_regions.
 807     HeapRegion* curr_region = start_region;
 808     while (curr_region != NULL) {
 809       guarantee(curr_region->is_archive(),
 810                 "Expected archive region at index %u", curr_region->hrm_index());
 811       if (curr_region != last_region) {
 812         curr_region = _hrm.next_region_in_heap(curr_region);
 813       } else {
 814         curr_region = NULL;
 815       }
 816     }
 817 
 818     prev_last_addr = last_address;
 819     prev_last_region = last_region;
 820 
 821     // Fill the memory below the allocated range with dummy object(s),
 822     // if the region bottom does not match the range start, or if the previous
 823     // range ended within the same G1 region, and there is a gap.
 824     if (start_address != bottom_address) {
 825       size_t fill_size = pointer_delta(start_address, bottom_address);
 826       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 827       increase_used(fill_size * HeapWordSize);
 828     }
 829   }
 830 }
 831 
 832 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
 833                                                      uint* gc_count_before_ret,
 834                                                      uint* gclocker_retry_count_ret) {
 835   assert_heap_not_locked_and_not_at_safepoint();
 836   assert(!is_humongous(word_size), "attempt_allocation() should not "
 837          "be called for humongous allocation requests");
 838 
 839   AllocationContext_t context = AllocationContext::current();
 840   HeapWord* result = _allocator->attempt_allocation(word_size, context);
 841 
 842   if (result == NULL) {
 843     result = attempt_allocation_slow(word_size,
 844                                      context,
 845                                      gc_count_before_ret,
 846                                      gclocker_retry_count_ret);
 847   }
 848   assert_heap_not_locked();
 849   if (result != NULL) {
 850     dirty_young_block(result, word_size);
 851   }
 852   return result;
 853 }
 854 
 855 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
 856   assert(!is_init_completed(), "Expect to be called at JVM init time");
 857   assert(ranges != NULL, "MemRegion array NULL");
 858   assert(count != 0, "No MemRegions provided");
 859   MemRegion reserved = _hrm.reserved();
 860   HeapWord* prev_last_addr = NULL;
 861   HeapRegion* prev_last_region = NULL;
 862   size_t size_used = 0;
 863   size_t uncommitted_regions = 0;
 864 
 865   // For each Memregion, free the G1 regions that constitute it, and
 866   // notify mark-sweep that the range is no longer to be considered 'archive.'
 867   MutexLockerEx x(Heap_lock);
 868   for (size_t i = 0; i < count; i++) {
 869     HeapWord* start_address = ranges[i].start();
 870     HeapWord* last_address = ranges[i].last();
 871 
 872     assert(reserved.contains(start_address) && reserved.contains(last_address),
 873            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 874            p2i(start_address), p2i(last_address));
 875     assert(start_address > prev_last_addr,
 876            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 877            p2i(start_address), p2i(prev_last_addr));
 878     size_used += ranges[i].byte_size();
 879     prev_last_addr = last_address;
 880 
 881     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 882     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 883 
 884     // Check for ranges that start in the same G1 region in which the previous
 885     // range ended, and adjust the start address so we don't try to free
 886     // the same region again. If the current range is entirely within that
 887     // region, skip it.
 888     if (start_region == prev_last_region) {
 889       start_address = start_region->end();
 890       if (start_address > last_address) {
 891         continue;
 892       }
 893       start_region = _hrm.addr_to_region(start_address);
 894     }
 895     prev_last_region = last_region;
 896 
 897     // After verifying that each region was marked as an archive region by
 898     // alloc_archive_regions, set it free and empty and uncommit it.
 899     HeapRegion* curr_region = start_region;
 900     while (curr_region != NULL) {
 901       guarantee(curr_region->is_archive(),
 902                 "Expected archive region at index %u", curr_region->hrm_index());
 903       uint curr_index = curr_region->hrm_index();
 904       _old_set.remove(curr_region);
 905       curr_region->set_free();
 906       curr_region->set_top(curr_region->bottom());
 907       if (curr_region != last_region) {
 908         curr_region = _hrm.next_region_in_heap(curr_region);
 909       } else {
 910         curr_region = NULL;
 911       }
 912       _hrm.shrink_at(curr_index, 1);
 913       uncommitted_regions++;
 914     }
 915 
 916     // Notify mark-sweep that this is no longer an archive range.
 917     G1ArchiveAllocator::set_range_archive(ranges[i], false);
 918   }
 919 
 920   if (uncommitted_regions != 0) {
 921     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 922                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 923   }
 924   decrease_used(size_used);
 925 }
 926 
 927 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
 928                                                         uint* gc_count_before_ret,
 929                                                         uint* gclocker_retry_count_ret) {
 930   // The structure of this method has a lot of similarities to
 931   // attempt_allocation_slow(). The reason these two were not merged
 932   // into a single one is that such a method would require several "if
 933   // allocation is not humongous do this, otherwise do that"
 934   // conditional paths which would obscure its flow. In fact, an early
 935   // version of this code did use a unified method which was harder to
 936   // follow and, as a result, it had subtle bugs that were hard to
 937   // track down. So keeping these two methods separate allows each to
 938   // be more readable. It will be good to keep these two in sync as
 939   // much as possible.
 940 
 941   assert_heap_not_locked_and_not_at_safepoint();
 942   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 943          "should only be called for humongous allocations");
 944 
 945   // Humongous objects can exhaust the heap quickly, so we should check if we
 946   // need to start a marking cycle at each humongous object allocation. We do
 947   // the check before we do the actual allocation. The reason for doing it
 948   // before the allocation is that we avoid having to keep track of the newly
 949   // allocated memory while we do a GC.
 950   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
 951                                            word_size)) {
 952     collect(GCCause::_g1_humongous_allocation);
 953   }
 954 
 955   // We will loop until a) we manage to successfully perform the
 956   // allocation or b) we successfully schedule a collection which
 957   // fails to perform the allocation. b) is the only case when we'll
 958   // return NULL.
 959   HeapWord* result = NULL;
 960   for (int try_count = 1; /* we'll return */; try_count += 1) {
 961     bool should_try_gc;
 962     uint gc_count_before;
 963 
 964     {
 965       MutexLockerEx x(Heap_lock);
 966 
 967       // Given that humongous objects are not allocated in young
 968       // regions, we'll first try to do the allocation without doing a
 969       // collection hoping that there's enough space in the heap.
 970       result = humongous_obj_allocate(word_size, AllocationContext::current());
 971       if (result != NULL) {
 972         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 973         g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 974         return result;
 975       }
 976 
 977       if (GCLocker::is_active_and_needs_gc()) {
 978         should_try_gc = false;
 979       } else {
 980          // The GCLocker may not be active but the GCLocker initiated
 981         // GC may not yet have been performed (GCLocker::needs_gc()
 982         // returns true). In this case we do not try this GC and
 983         // wait until the GCLocker initiated GC is performed, and
 984         // then retry the allocation.
 985         if (GCLocker::needs_gc()) {
 986           should_try_gc = false;
 987         } else {
 988           // Read the GC count while still holding the Heap_lock.
 989           gc_count_before = total_collections();
 990           should_try_gc = true;
 991         }
 992       }
 993     }
 994 
 995     if (should_try_gc) {
 996       // If we failed to allocate the humongous object, we should try to
 997       // do a collection pause (if we're allowed) in case it reclaims
 998       // enough space for the allocation to succeed after the pause.
 999 
1000       bool succeeded;
1001       result = do_collection_pause(word_size, gc_count_before, &succeeded,
1002                                    GCCause::_g1_humongous_allocation);
1003       if (result != NULL) {
1004         assert(succeeded, "only way to get back a non-NULL result");
1005         return result;
1006       }
1007 
1008       if (succeeded) {
1009         // If we get here we successfully scheduled a collection which
1010         // failed to allocate. No point in trying to allocate
1011         // further. We'll just return NULL.
1012         MutexLockerEx x(Heap_lock);
1013         *gc_count_before_ret = total_collections();
1014         return NULL;
1015       }
1016     } else {
1017       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1018         MutexLockerEx x(Heap_lock);
1019         *gc_count_before_ret = total_collections();
1020         return NULL;
1021       }
1022       // The GCLocker is either active or the GCLocker initiated
1023       // GC has not yet been performed. Stall until it is and
1024       // then retry the allocation.
1025       GCLocker::stall_until_clear();
1026       (*gclocker_retry_count_ret) += 1;
1027     }
1028 
1029     // We can reach here if we were unsuccessful in scheduling a
1030     // collection (because another thread beat us to it) or if we were
1031     // stalled due to the GC locker. In either can we should retry the
1032     // allocation attempt in case another thread successfully
1033     // performed a collection and reclaimed enough space.  Give a
1034     // warning if we seem to be looping forever.
1035 
1036     if ((QueuedAllocationWarningCount > 0) &&
1037         (try_count % QueuedAllocationWarningCount == 0)) {
1038       log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
1039                       "retries %d times", try_count);
1040     }
1041   }
1042 
1043   ShouldNotReachHere();
1044   return NULL;
1045 }
1046 
1047 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1048                                                            AllocationContext_t context,
1049                                                            bool expect_null_mutator_alloc_region) {
1050   assert_at_safepoint(true /* should_be_vm_thread */);
1051   assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1052          "the current alloc region was unexpectedly found to be non-NULL");
1053 
1054   if (!is_humongous(word_size)) {
1055     return _allocator->attempt_allocation_locked(word_size, context);
1056   } else {
1057     HeapWord* result = humongous_obj_allocate(word_size, context);
1058     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1059       collector_state()->set_initiate_conc_mark_if_possible(true);
1060     }
1061     return result;
1062   }
1063 
1064   ShouldNotReachHere();
1065 }
1066 
1067 class PostCompactionPrinterClosure: public HeapRegionClosure {
1068 private:
1069   G1HRPrinter* _hr_printer;
1070 public:
1071   bool doHeapRegion(HeapRegion* hr) {
1072     assert(!hr->is_young(), "not expecting to find young regions");
1073     _hr_printer->post_compaction(hr);
1074     return false;
1075   }
1076 
1077   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1078     : _hr_printer(hr_printer) { }
1079 };
1080 
1081 void G1CollectedHeap::print_hrm_post_compaction() {
1082   if (_hr_printer.is_active()) {
1083     PostCompactionPrinterClosure cl(hr_printer());
1084     heap_region_iterate(&cl);
1085   }
1086 }
1087 
1088 void G1CollectedHeap::abort_concurrent_cycle() {
1089   // Note: When we have a more flexible GC logging framework that
1090   // allows us to add optional attributes to a GC log record we
1091   // could consider timing and reporting how long we wait in the
1092   // following two methods.
1093   wait_while_free_regions_coming();
1094   // If we start the compaction before the CM threads finish
1095   // scanning the root regions we might trip them over as we'll
1096   // be moving objects / updating references. So let's wait until
1097   // they are done. By telling them to abort, they should complete
1098   // early.
1099   _cm->root_regions()->abort();
1100   _cm->root_regions()->wait_until_scan_finished();
1101   append_secondary_free_list_if_not_empty_with_lock();
1102 
1103   // Disable discovery and empty the discovered lists
1104   // for the CM ref processor.
1105   ref_processor_cm()->disable_discovery();
1106   ref_processor_cm()->abandon_partial_discovery();
1107   ref_processor_cm()->verify_no_references_recorded();
1108 
1109   // Abandon current iterations of concurrent marking and concurrent
1110   // refinement, if any are in progress.
1111   concurrent_mark()->abort();
1112 }
1113 
1114 void G1CollectedHeap::prepare_heap_for_full_collection() {
1115   // Make sure we'll choose a new allocation region afterwards.
1116   _allocator->release_mutator_alloc_region();
1117   _allocator->abandon_gc_alloc_regions();
1118   g1_rem_set()->cleanupHRRS();
1119 
1120   // We may have added regions to the current incremental collection
1121   // set between the last GC or pause and now. We need to clear the
1122   // incremental collection set and then start rebuilding it afresh
1123   // after this full GC.
1124   abandon_collection_set(collection_set());
1125 
1126   tear_down_region_sets(false /* free_list_only */);
1127   collector_state()->set_gcs_are_young(true);
1128 }
1129 
1130 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1131   assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1132   assert(used() == recalculate_used(), "Should be equal");
1133   _verifier->verify_region_sets_optional();
1134   _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
1135   _verifier->check_bitmaps("Full GC Start");
1136 }
1137 
1138 void G1CollectedHeap::prepare_heap_for_mutators() {
1139   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1140   ClassLoaderDataGraph::purge();
1141   MetaspaceAux::verify_metrics();
1142 
1143   // Prepare heap for normal collections.
1144   assert(num_free_regions() == 0, "we should not have added any free regions");
1145   rebuild_region_sets(false /* free_list_only */);
1146   abort_refinement();
1147   resize_if_necessary_after_full_collection();
1148 
1149   // Rebuild the strong code root lists for each region
1150   rebuild_strong_code_roots();
1151 
1152   // Start a new incremental collection set for the next pause
1153   start_new_collection_set();
1154 
1155   _allocator->init_mutator_alloc_region();
1156 
1157   // Post collection state updates.
1158   MetaspaceGC::compute_new_size();
1159 }
1160 
1161 void G1CollectedHeap::abort_refinement() {
1162   if (_hot_card_cache->use_cache()) {
1163     _hot_card_cache->reset_hot_cache();
1164   }
1165 
1166   // Discard all remembered set updates.
1167   JavaThread::dirty_card_queue_set().abandon_logs();
1168   assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1169 }
1170 
1171 void G1CollectedHeap::verify_after_full_collection() {
1172   check_gc_time_stamps();
1173   _hrm.verify_optional();
1174   _verifier->verify_region_sets_optional();
1175   _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);
1176   // Clear the previous marking bitmap, if needed for bitmap verification.
1177   // Note we cannot do this when we clear the next marking bitmap in
1178   // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1179   // objects marked during a full GC against the previous bitmap.
1180   // But we need to clear it before calling check_bitmaps below since
1181   // the full GC has compacted objects and updated TAMS but not updated
1182   // the prev bitmap.
1183   if (G1VerifyBitmaps) {
1184     GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1185     _cm->clear_prev_bitmap(workers());
1186   }
1187   _verifier->check_bitmaps("Full GC End");
1188 
1189   // At this point there should be no regions in the
1190   // entire heap tagged as young.
1191   assert(check_young_list_empty(), "young list should be empty at this point");
1192 
1193   // Note: since we've just done a full GC, concurrent
1194   // marking is no longer active. Therefore we need not
1195   // re-enable reference discovery for the CM ref processor.
1196   // That will be done at the start of the next marking cycle.
1197   // We also know that the STW processor should no longer
1198   // discover any new references.
1199   assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1200   assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1201   ref_processor_stw()->verify_no_references_recorded();
1202   ref_processor_cm()->verify_no_references_recorded();
1203 }
1204 
1205 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1206   // Post collection logging.
1207   // We should do this after we potentially resize the heap so
1208   // that all the COMMIT / UNCOMMIT events are generated before
1209   // the compaction events.
1210   print_hrm_post_compaction();
1211   heap_transition->print();
1212   print_heap_after_gc();
1213   print_heap_regions();
1214 #ifdef TRACESPINNING
1215   ParallelTaskTerminator::print_termination_counts();
1216 #endif
1217 }
1218 
1219 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1220                                          bool clear_all_soft_refs) {
1221   assert_at_safepoint(true /* should_be_vm_thread */);
1222 
1223   if (GCLocker::check_active_before_gc()) {
1224     // Full GC was not completed.
1225     return false;
1226   }
1227 
1228   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1229       collector_policy()->should_clear_all_soft_refs();
1230 
1231   G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs);
1232   GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1233 
1234   collector.prepare_collection();
1235   collector.collect();
1236   collector.complete_collection();
1237 
1238   // Full collection was successfully completed.
1239   return true;
1240 }
1241 
1242 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1243   // Currently, there is no facility in the do_full_collection(bool) API to notify
1244   // the caller that the collection did not succeed (e.g., because it was locked
1245   // out by the GC locker). So, right now, we'll ignore the return value.
1246   bool dummy = do_full_collection(true,                /* explicit_gc */
1247                                   clear_all_soft_refs);
1248 }
1249 
1250 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1251   // Capacity, free and used after the GC counted as full regions to
1252   // include the waste in the following calculations.
1253   const size_t capacity_after_gc = capacity();
1254   const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1255 
1256   // This is enforced in arguments.cpp.
1257   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1258          "otherwise the code below doesn't make sense");
1259 
1260   // We don't have floating point command-line arguments
1261   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1262   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1263   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1264   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1265 
1266   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1267   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1268 
1269   // We have to be careful here as these two calculations can overflow
1270   // 32-bit size_t's.
1271   double used_after_gc_d = (double) used_after_gc;
1272   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1273   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1274 
1275   // Let's make sure that they are both under the max heap size, which
1276   // by default will make them fit into a size_t.
1277   double desired_capacity_upper_bound = (double) max_heap_size;
1278   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1279                                     desired_capacity_upper_bound);
1280   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1281                                     desired_capacity_upper_bound);
1282 
1283   // We can now safely turn them into size_t's.
1284   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1285   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1286 
1287   // This assert only makes sense here, before we adjust them
1288   // with respect to the min and max heap size.
1289   assert(minimum_desired_capacity <= maximum_desired_capacity,
1290          "minimum_desired_capacity = " SIZE_FORMAT ", "
1291          "maximum_desired_capacity = " SIZE_FORMAT,
1292          minimum_desired_capacity, maximum_desired_capacity);
1293 
1294   // Should not be greater than the heap max size. No need to adjust
1295   // it with respect to the heap min size as it's a lower bound (i.e.,
1296   // we'll try to make the capacity larger than it, not smaller).
1297   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1298   // Should not be less than the heap min size. No need to adjust it
1299   // with respect to the heap max size as it's an upper bound (i.e.,
1300   // we'll try to make the capacity smaller than it, not greater).
1301   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1302 
1303   if (capacity_after_gc < minimum_desired_capacity) {
1304     // Don't expand unless it's significant
1305     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1306 
1307     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1308                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1309                               "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1310                               capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1311 
1312     expand(expand_bytes, _workers);
1313 
1314     // No expansion, now see if we want to shrink
1315   } else if (capacity_after_gc > maximum_desired_capacity) {
1316     // Capacity too large, compute shrinking size
1317     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1318 
1319     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1320                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1321                               "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1322                               capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1323 
1324     shrink(shrink_bytes);
1325   }
1326 }
1327 
1328 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1329                                                             AllocationContext_t context,
1330                                                             bool do_gc,
1331                                                             bool clear_all_soft_refs,
1332                                                             bool expect_null_mutator_alloc_region,
1333                                                             bool* gc_succeeded) {
1334   *gc_succeeded = true;
1335   // Let's attempt the allocation first.
1336   HeapWord* result =
1337     attempt_allocation_at_safepoint(word_size,
1338                                     context,
1339                                     expect_null_mutator_alloc_region);
1340   if (result != NULL) {
1341     assert(*gc_succeeded, "sanity");
1342     return result;
1343   }
1344 
1345   // In a G1 heap, we're supposed to keep allocation from failing by
1346   // incremental pauses.  Therefore, at least for now, we'll favor
1347   // expansion over collection.  (This might change in the future if we can
1348   // do something smarter than full collection to satisfy a failed alloc.)
1349   result = expand_and_allocate(word_size, context);
1350   if (result != NULL) {
1351     assert(*gc_succeeded, "sanity");
1352     return result;
1353   }
1354 
1355   if (do_gc) {
1356     // Expansion didn't work, we'll try to do a Full GC.
1357     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1358                                        clear_all_soft_refs);
1359   }
1360 
1361   return NULL;
1362 }
1363 
1364 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1365                                                      AllocationContext_t context,
1366                                                      bool* succeeded) {
1367   assert_at_safepoint(true /* should_be_vm_thread */);
1368 
1369   // Attempts to allocate followed by Full GC.
1370   HeapWord* result =
1371     satisfy_failed_allocation_helper(word_size,
1372                                      context,
1373                                      true,  /* do_gc */
1374                                      false, /* clear_all_soft_refs */
1375                                      false, /* expect_null_mutator_alloc_region */
1376                                      succeeded);
1377 
1378   if (result != NULL || !*succeeded) {
1379     return result;
1380   }
1381 
1382   // Attempts to allocate followed by Full GC that will collect all soft references.
1383   result = satisfy_failed_allocation_helper(word_size,
1384                                             context,
1385                                             true, /* do_gc */
1386                                             true, /* clear_all_soft_refs */
1387                                             true, /* expect_null_mutator_alloc_region */
1388                                             succeeded);
1389 
1390   if (result != NULL || !*succeeded) {
1391     return result;
1392   }
1393 
1394   // Attempts to allocate, no GC
1395   result = satisfy_failed_allocation_helper(word_size,
1396                                             context,
1397                                             false, /* do_gc */
1398                                             false, /* clear_all_soft_refs */
1399                                             true,  /* expect_null_mutator_alloc_region */
1400                                             succeeded);
1401 
1402   if (result != NULL) {
1403     assert(*succeeded, "sanity");
1404     return result;
1405   }
1406 
1407   assert(!collector_policy()->should_clear_all_soft_refs(),
1408          "Flag should have been handled and cleared prior to this point");
1409 
1410   // What else?  We might try synchronous finalization later.  If the total
1411   // space available is large enough for the allocation, then a more
1412   // complete compaction phase than we've tried so far might be
1413   // appropriate.
1414   assert(*succeeded, "sanity");
1415   return NULL;
1416 }
1417 
1418 // Attempting to expand the heap sufficiently
1419 // to support an allocation of the given "word_size".  If
1420 // successful, perform the allocation and return the address of the
1421 // allocated block, or else "NULL".
1422 
1423 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1424   assert_at_safepoint(true /* should_be_vm_thread */);
1425 
1426   _verifier->verify_region_sets_optional();
1427 
1428   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1429   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1430                             word_size * HeapWordSize);
1431 
1432 
1433   if (expand(expand_bytes, _workers)) {
1434     _hrm.verify_optional();
1435     _verifier->verify_region_sets_optional();
1436     return attempt_allocation_at_safepoint(word_size,
1437                                            context,
1438                                            false /* expect_null_mutator_alloc_region */);
1439   }
1440   return NULL;
1441 }
1442 
1443 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1444   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1445   aligned_expand_bytes = align_up(aligned_expand_bytes,
1446                                        HeapRegion::GrainBytes);
1447 
1448   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1449                             expand_bytes, aligned_expand_bytes);
1450 
1451   if (is_maximal_no_gc()) {
1452     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1453     return false;
1454   }
1455 
1456   double expand_heap_start_time_sec = os::elapsedTime();
1457   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1458   assert(regions_to_expand > 0, "Must expand by at least one region");
1459 
1460   uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1461   if (expand_time_ms != NULL) {
1462     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1463   }
1464 
1465   if (expanded_by > 0) {
1466     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1467     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1468     g1_policy()->record_new_heap_size(num_regions());
1469   } else {
1470     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1471 
1472     // The expansion of the virtual storage space was unsuccessful.
1473     // Let's see if it was because we ran out of swap.
1474     if (G1ExitOnExpansionFailure &&
1475         _hrm.available() >= regions_to_expand) {
1476       // We had head room...
1477       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1478     }
1479   }
1480   return regions_to_expand > 0;
1481 }
1482 
1483 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1484   size_t aligned_shrink_bytes =
1485     ReservedSpace::page_align_size_down(shrink_bytes);
1486   aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1487                                          HeapRegion::GrainBytes);
1488   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1489 
1490   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1491   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1492 
1493 
1494   log_debug(gc, ergo, heap)("Shrink the heap. requested shrinking amount: " SIZE_FORMAT "B aligned shrinking amount: " SIZE_FORMAT "B attempted shrinking amount: " SIZE_FORMAT "B",
1495                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1496   if (num_regions_removed > 0) {
1497     g1_policy()->record_new_heap_size(num_regions());
1498   } else {
1499     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1500   }
1501 }
1502 
1503 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1504   _verifier->verify_region_sets_optional();
1505 
1506   // We should only reach here at the end of a Full GC which means we
1507   // should not not be holding to any GC alloc regions. The method
1508   // below will make sure of that and do any remaining clean up.
1509   _allocator->abandon_gc_alloc_regions();
1510 
1511   // Instead of tearing down / rebuilding the free lists here, we
1512   // could instead use the remove_all_pending() method on free_list to
1513   // remove only the ones that we need to remove.
1514   tear_down_region_sets(true /* free_list_only */);
1515   shrink_helper(shrink_bytes);
1516   rebuild_region_sets(true /* free_list_only */);
1517 
1518   _hrm.verify_optional();
1519   _verifier->verify_region_sets_optional();
1520 }
1521 
1522 // Public methods.
1523 
1524 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1525   CollectedHeap(),
1526   _young_gen_sampling_thread(NULL),
1527   _collector_policy(collector_policy),
1528   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1529   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1530   _g1_policy(create_g1_policy(_gc_timer_stw)),
1531   _collection_set(this, _g1_policy),
1532   _dirty_card_queue_set(false),
1533   _is_alive_closure_cm(this),
1534   _is_alive_closure_stw(this),
1535   _ref_processor_cm(NULL),
1536   _ref_processor_stw(NULL),
1537   _bot(NULL),
1538   _hot_card_cache(NULL),
1539   _g1_rem_set(NULL),
1540   _cr(NULL),
1541   _g1mm(NULL),
1542   _preserved_marks_set(true /* in_c_heap */),
1543   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1544   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1545   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1546   _humongous_reclaim_candidates(),
1547   _has_humongous_reclaim_candidates(false),
1548   _archive_allocator(NULL),
1549   _free_regions_coming(false),
1550   _gc_time_stamp(0),
1551   _summary_bytes_used(0),
1552   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1553   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1554   _expand_heap_after_alloc_failure(true),
1555   _old_marking_cycles_started(0),
1556   _old_marking_cycles_completed(0),
1557   _in_cset_fast_test() {
1558 
1559   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1560                           /* are_GC_task_threads */true,
1561                           /* are_ConcurrentGC_threads */false);
1562   _workers->initialize_workers();
1563   _verifier = new G1HeapVerifier(this);
1564 
1565   _allocator = G1Allocator::create_allocator(this);
1566 
1567   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1568 
1569   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1570 
1571   // Override the default _filler_array_max_size so that no humongous filler
1572   // objects are created.
1573   _filler_array_max_size = _humongous_object_threshold_in_words;
1574 
1575   uint n_queues = ParallelGCThreads;
1576   _task_queues = new RefToScanQueueSet(n_queues);
1577 
1578   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1579 
1580   for (uint i = 0; i < n_queues; i++) {
1581     RefToScanQueue* q = new RefToScanQueue();
1582     q->initialize();
1583     _task_queues->register_queue(i, q);
1584     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1585   }
1586 
1587   // Initialize the G1EvacuationFailureALot counters and flags.
1588   NOT_PRODUCT(reset_evacuation_should_fail();)
1589 
1590   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1591 }
1592 
1593 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1594                                                                  size_t size,
1595                                                                  size_t translation_factor) {
1596   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1597   // Allocate a new reserved space, preferring to use large pages.
1598   ReservedSpace rs(size, preferred_page_size);
1599   G1RegionToSpaceMapper* result  =
1600     G1RegionToSpaceMapper::create_mapper(rs,
1601                                          size,
1602                                          rs.alignment(),
1603                                          HeapRegion::GrainBytes,
1604                                          translation_factor,
1605                                          mtGC);
1606 
1607   os::trace_page_sizes_for_requested_size(description,
1608                                           size,
1609                                           preferred_page_size,
1610                                           rs.alignment(),
1611                                           rs.base(),
1612                                           rs.size());
1613 
1614   return result;
1615 }
1616 
1617 jint G1CollectedHeap::initialize_concurrent_refinement() {
1618   jint ecode = JNI_OK;
1619   _cr = G1ConcurrentRefine::create(&ecode);
1620   return ecode;
1621 }
1622 
1623 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1624   _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1625   if (_young_gen_sampling_thread->osthread() == NULL) {
1626     vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1627     return JNI_ENOMEM;
1628   }
1629   return JNI_OK;
1630 }
1631 
1632 jint G1CollectedHeap::initialize() {
1633   CollectedHeap::pre_initialize();
1634   os::enable_vtime();
1635 
1636   // Necessary to satisfy locking discipline assertions.
1637 
1638   MutexLocker x(Heap_lock);
1639 
1640   // While there are no constraints in the GC code that HeapWordSize
1641   // be any particular value, there are multiple other areas in the
1642   // system which believe this to be true (e.g. oop->object_size in some
1643   // cases incorrectly returns the size in wordSize units rather than
1644   // HeapWordSize).
1645   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1646 
1647   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1648   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1649   size_t heap_alignment = collector_policy()->heap_alignment();
1650 
1651   // Ensure that the sizes are properly aligned.
1652   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1653   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1654   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1655 
1656   // Reserve the maximum.
1657 
1658   // When compressed oops are enabled, the preferred heap base
1659   // is calculated by subtracting the requested size from the
1660   // 32Gb boundary and using the result as the base address for
1661   // heap reservation. If the requested size is not aligned to
1662   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1663   // into the ReservedHeapSpace constructor) then the actual
1664   // base of the reserved heap may end up differing from the
1665   // address that was requested (i.e. the preferred heap base).
1666   // If this happens then we could end up using a non-optimal
1667   // compressed oops mode.
1668 
1669   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1670                                                  heap_alignment);
1671 
1672   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1673 
1674   // Create the barrier set for the entire reserved region.
1675   G1SATBCardTableLoggingModRefBS* bs
1676     = new G1SATBCardTableLoggingModRefBS(reserved_region());
1677   bs->initialize();
1678   assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1679   set_barrier_set(bs);
1680 
1681   // Create the hot card cache.
1682   _hot_card_cache = new G1HotCardCache(this);
1683 
1684   // Carve out the G1 part of the heap.
1685   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1686   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1687   G1RegionToSpaceMapper* heap_storage =
1688     G1RegionToSpaceMapper::create_mapper(g1_rs,
1689                                          g1_rs.size(),
1690                                          page_size,
1691                                          HeapRegion::GrainBytes,
1692                                          1,
1693                                          mtJavaHeap);
1694   os::trace_page_sizes("Heap",
1695                        collector_policy()->min_heap_byte_size(),
1696                        max_byte_size,
1697                        page_size,
1698                        heap_rs.base(),
1699                        heap_rs.size());
1700   heap_storage->set_mapping_changed_listener(&_listener);
1701 
1702   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1703   G1RegionToSpaceMapper* bot_storage =
1704     create_aux_memory_mapper("Block Offset Table",
1705                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1706                              G1BlockOffsetTable::heap_map_factor());
1707 
1708   G1RegionToSpaceMapper* cardtable_storage =
1709     create_aux_memory_mapper("Card Table",
1710                              G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1711                              G1SATBCardTableLoggingModRefBS::heap_map_factor());
1712 
1713   G1RegionToSpaceMapper* card_counts_storage =
1714     create_aux_memory_mapper("Card Counts Table",
1715                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1716                              G1CardCounts::heap_map_factor());
1717 
1718   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1719   G1RegionToSpaceMapper* prev_bitmap_storage =
1720     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1721   G1RegionToSpaceMapper* next_bitmap_storage =
1722     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1723 
1724   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1725   g1_barrier_set()->initialize(cardtable_storage);
1726   // Do later initialization work for concurrent refinement.
1727   _hot_card_cache->initialize(card_counts_storage);
1728 
1729   // 6843694 - ensure that the maximum region index can fit
1730   // in the remembered set structures.
1731   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1732   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1733 
1734   // Also create a G1 rem set.
1735   _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache);
1736   _g1_rem_set->initialize(max_capacity(), max_regions());
1737 
1738   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1739   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1740   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1741             "too many cards per region");
1742 
1743   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1744 
1745   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1746 
1747   {
1748     HeapWord* start = _hrm.reserved().start();
1749     HeapWord* end = _hrm.reserved().end();
1750     size_t granularity = HeapRegion::GrainBytes;
1751 
1752     _in_cset_fast_test.initialize(start, end, granularity);
1753     _humongous_reclaim_candidates.initialize(start, end, granularity);
1754   }
1755 
1756   // Create the G1ConcurrentMark data structure and thread.
1757   // (Must do this late, so that "max_regions" is defined.)
1758   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1759   if (_cm == NULL || !_cm->completed_initialization()) {
1760     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1761     return JNI_ENOMEM;
1762   }
1763   _cmThread = _cm->cm_thread();
1764 
1765   // Now expand into the initial heap size.
1766   if (!expand(init_byte_size, _workers)) {
1767     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1768     return JNI_ENOMEM;
1769   }
1770 
1771   // Perform any initialization actions delegated to the policy.
1772   g1_policy()->init(this, &_collection_set);
1773 
1774   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1775                                                SATB_Q_FL_lock,
1776                                                G1SATBProcessCompletedThreshold,
1777                                                Shared_SATB_Q_lock);
1778 
1779   jint ecode = initialize_concurrent_refinement();
1780   if (ecode != JNI_OK) {
1781     return ecode;
1782   }
1783 
1784   ecode = initialize_young_gen_sampling_thread();
1785   if (ecode != JNI_OK) {
1786     return ecode;
1787   }
1788 
1789   JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1790                                                 DirtyCardQ_FL_lock,
1791                                                 (int)concurrent_refine()->yellow_zone(),
1792                                                 (int)concurrent_refine()->red_zone(),
1793                                                 Shared_DirtyCardQ_lock,
1794                                                 NULL,  // fl_owner
1795                                                 true); // init_free_ids
1796 
1797   dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1798                                     DirtyCardQ_FL_lock,
1799                                     -1, // never trigger processing
1800                                     -1, // no limit on length
1801                                     Shared_DirtyCardQ_lock,
1802                                     &JavaThread::dirty_card_queue_set());
1803 
1804   // Here we allocate the dummy HeapRegion that is required by the
1805   // G1AllocRegion class.
1806   HeapRegion* dummy_region = _hrm.get_dummy_region();
1807 
1808   // We'll re-use the same region whether the alloc region will
1809   // require BOT updates or not and, if it doesn't, then a non-young
1810   // region will complain that it cannot support allocations without
1811   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1812   dummy_region->set_eden();
1813   // Make sure it's full.
1814   dummy_region->set_top(dummy_region->end());
1815   G1AllocRegion::setup(this, dummy_region);
1816 
1817   _allocator->init_mutator_alloc_region();
1818 
1819   // Do create of the monitoring and management support so that
1820   // values in the heap have been properly initialized.
1821   _g1mm = new G1MonitoringSupport(this);
1822 
1823   G1StringDedup::initialize();
1824 
1825   _preserved_marks_set.init(ParallelGCThreads);
1826 
1827   _collection_set.initialize(max_regions());
1828 
1829   return JNI_OK;
1830 }
1831 
1832 void G1CollectedHeap::stop() {
1833   // Stop all concurrent threads. We do this to make sure these threads
1834   // do not continue to execute and access resources (e.g. logging)
1835   // that are destroyed during shutdown.
1836   _cr->stop();
1837   _young_gen_sampling_thread->stop();
1838   _cmThread->stop();
1839   if (G1StringDedup::is_enabled()) {
1840     G1StringDedup::stop();
1841   }
1842 }
1843 
1844 void G1CollectedHeap::safepoint_synchronize_begin() {
1845   SuspendibleThreadSet::synchronize();
1846 }
1847 
1848 void G1CollectedHeap::safepoint_synchronize_end() {
1849   SuspendibleThreadSet::desynchronize();
1850 }
1851 
1852 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1853   return HeapRegion::max_region_size();
1854 }
1855 
1856 void G1CollectedHeap::post_initialize() {
1857   ref_processing_init();
1858 }
1859 
1860 void G1CollectedHeap::ref_processing_init() {
1861   // Reference processing in G1 currently works as follows:
1862   //
1863   // * There are two reference processor instances. One is
1864   //   used to record and process discovered references
1865   //   during concurrent marking; the other is used to
1866   //   record and process references during STW pauses
1867   //   (both full and incremental).
1868   // * Both ref processors need to 'span' the entire heap as
1869   //   the regions in the collection set may be dotted around.
1870   //
1871   // * For the concurrent marking ref processor:
1872   //   * Reference discovery is enabled at initial marking.
1873   //   * Reference discovery is disabled and the discovered
1874   //     references processed etc during remarking.
1875   //   * Reference discovery is MT (see below).
1876   //   * Reference discovery requires a barrier (see below).
1877   //   * Reference processing may or may not be MT
1878   //     (depending on the value of ParallelRefProcEnabled
1879   //     and ParallelGCThreads).
1880   //   * A full GC disables reference discovery by the CM
1881   //     ref processor and abandons any entries on it's
1882   //     discovered lists.
1883   //
1884   // * For the STW processor:
1885   //   * Non MT discovery is enabled at the start of a full GC.
1886   //   * Processing and enqueueing during a full GC is non-MT.
1887   //   * During a full GC, references are processed after marking.
1888   //
1889   //   * Discovery (may or may not be MT) is enabled at the start
1890   //     of an incremental evacuation pause.
1891   //   * References are processed near the end of a STW evacuation pause.
1892   //   * For both types of GC:
1893   //     * Discovery is atomic - i.e. not concurrent.
1894   //     * Reference discovery will not need a barrier.
1895 
1896   MemRegion mr = reserved_region();
1897 
1898   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1899 
1900   // Concurrent Mark ref processor
1901   _ref_processor_cm =
1902     new ReferenceProcessor(mr,    // span
1903                            mt_processing,
1904                                 // mt processing
1905                            ParallelGCThreads,
1906                                 // degree of mt processing
1907                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
1908                                 // mt discovery
1909                            MAX2(ParallelGCThreads, ConcGCThreads),
1910                                 // degree of mt discovery
1911                            false,
1912                                 // Reference discovery is not atomic
1913                            &_is_alive_closure_cm);
1914                                 // is alive closure
1915                                 // (for efficiency/performance)
1916 
1917   // STW ref processor
1918   _ref_processor_stw =
1919     new ReferenceProcessor(mr,    // span
1920                            mt_processing,
1921                                 // mt processing
1922                            ParallelGCThreads,
1923                                 // degree of mt processing
1924                            (ParallelGCThreads > 1),
1925                                 // mt discovery
1926                            ParallelGCThreads,
1927                                 // degree of mt discovery
1928                            true,
1929                                 // Reference discovery is atomic
1930                            &_is_alive_closure_stw);
1931                                 // is alive closure
1932                                 // (for efficiency/performance)
1933 }
1934 
1935 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1936   return _collector_policy;
1937 }
1938 
1939 size_t G1CollectedHeap::capacity() const {
1940   return _hrm.length() * HeapRegion::GrainBytes;
1941 }
1942 
1943 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1944   return _hrm.total_free_bytes();
1945 }
1946 
1947 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
1948   hr->reset_gc_time_stamp();
1949 }
1950 
1951 #ifndef PRODUCT
1952 
1953 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
1954 private:
1955   unsigned _gc_time_stamp;
1956   bool _failures;
1957 
1958 public:
1959   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
1960     _gc_time_stamp(gc_time_stamp), _failures(false) { }
1961 
1962   virtual bool doHeapRegion(HeapRegion* hr) {
1963     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
1964     if (_gc_time_stamp != region_gc_time_stamp) {
1965       log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
1966                             region_gc_time_stamp, _gc_time_stamp);
1967       _failures = true;
1968     }
1969     return false;
1970   }
1971 
1972   bool failures() { return _failures; }
1973 };
1974 
1975 void G1CollectedHeap::check_gc_time_stamps() {
1976   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
1977   heap_region_iterate(&cl);
1978   guarantee(!cl.failures(), "all GC time stamps should have been reset");
1979 }
1980 #endif // PRODUCT
1981 
1982 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
1983   _hot_card_cache->drain(cl, worker_i);
1984 }
1985 
1986 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
1987   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1988   size_t n_completed_buffers = 0;
1989   while (dcqs.apply_closure_during_gc(cl, worker_i)) {
1990     n_completed_buffers++;
1991   }
1992   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
1993   dcqs.clear_n_completed_buffers();
1994   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
1995 }
1996 
1997 // Computes the sum of the storage used by the various regions.
1998 size_t G1CollectedHeap::used() const {
1999   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
2000   if (_archive_allocator != NULL) {
2001     result += _archive_allocator->used();
2002   }
2003   return result;
2004 }
2005 
2006 size_t G1CollectedHeap::used_unlocked() const {
2007   return _summary_bytes_used;
2008 }
2009 
2010 class SumUsedClosure: public HeapRegionClosure {
2011   size_t _used;
2012 public:
2013   SumUsedClosure() : _used(0) {}
2014   bool doHeapRegion(HeapRegion* r) {
2015     _used += r->used();
2016     return false;
2017   }
2018   size_t result() { return _used; }
2019 };
2020 
2021 size_t G1CollectedHeap::recalculate_used() const {
2022   double recalculate_used_start = os::elapsedTime();
2023 
2024   SumUsedClosure blk;
2025   heap_region_iterate(&blk);
2026 
2027   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2028   return blk.result();
2029 }
2030 
2031 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2032   switch (cause) {
2033     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
2034     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
2035     case GCCause::_update_allocation_context_stats_inc: return true;
2036     case GCCause::_wb_conc_mark:                        return true;
2037     default :                                           return false;
2038   }
2039 }
2040 
2041 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2042   switch (cause) {
2043     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2044     case GCCause::_g1_humongous_allocation: return true;
2045     default:                                return is_user_requested_concurrent_full_gc(cause);
2046   }
2047 }
2048 
2049 #ifndef PRODUCT
2050 void G1CollectedHeap::allocate_dummy_regions() {
2051   // Let's fill up most of the region
2052   size_t word_size = HeapRegion::GrainWords - 1024;
2053   // And as a result the region we'll allocate will be humongous.
2054   guarantee(is_humongous(word_size), "sanity");
2055 
2056   // _filler_array_max_size is set to humongous object threshold
2057   // but temporarily change it to use CollectedHeap::fill_with_object().
2058   SizeTFlagSetting fs(_filler_array_max_size, word_size);
2059 
2060   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2061     // Let's use the existing mechanism for the allocation
2062     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2063                                                  AllocationContext::system());
2064     if (dummy_obj != NULL) {
2065       MemRegion mr(dummy_obj, word_size);
2066       CollectedHeap::fill_with_object(mr);
2067     } else {
2068       // If we can't allocate once, we probably cannot allocate
2069       // again. Let's get out of the loop.
2070       break;
2071     }
2072   }
2073 }
2074 #endif // !PRODUCT
2075 
2076 void G1CollectedHeap::increment_old_marking_cycles_started() {
2077   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2078          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2079          "Wrong marking cycle count (started: %d, completed: %d)",
2080          _old_marking_cycles_started, _old_marking_cycles_completed);
2081 
2082   _old_marking_cycles_started++;
2083 }
2084 
2085 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2086   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2087 
2088   // We assume that if concurrent == true, then the caller is a
2089   // concurrent thread that was joined the Suspendible Thread
2090   // Set. If there's ever a cheap way to check this, we should add an
2091   // assert here.
2092 
2093   // Given that this method is called at the end of a Full GC or of a
2094   // concurrent cycle, and those can be nested (i.e., a Full GC can
2095   // interrupt a concurrent cycle), the number of full collections
2096   // completed should be either one (in the case where there was no
2097   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2098   // behind the number of full collections started.
2099 
2100   // This is the case for the inner caller, i.e. a Full GC.
2101   assert(concurrent ||
2102          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2103          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2104          "for inner caller (Full GC): _old_marking_cycles_started = %u "
2105          "is inconsistent with _old_marking_cycles_completed = %u",
2106          _old_marking_cycles_started, _old_marking_cycles_completed);
2107 
2108   // This is the case for the outer caller, i.e. the concurrent cycle.
2109   assert(!concurrent ||
2110          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2111          "for outer caller (concurrent cycle): "
2112          "_old_marking_cycles_started = %u "
2113          "is inconsistent with _old_marking_cycles_completed = %u",
2114          _old_marking_cycles_started, _old_marking_cycles_completed);
2115 
2116   _old_marking_cycles_completed += 1;
2117 
2118   // We need to clear the "in_progress" flag in the CM thread before
2119   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2120   // is set) so that if a waiter requests another System.gc() it doesn't
2121   // incorrectly see that a marking cycle is still in progress.
2122   if (concurrent) {
2123     _cmThread->set_idle();
2124   }
2125 
2126   // This notify_all() will ensure that a thread that called
2127   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2128   // and it's waiting for a full GC to finish will be woken up. It is
2129   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2130   FullGCCount_lock->notify_all();
2131 }
2132 
2133 void G1CollectedHeap::collect(GCCause::Cause cause) {
2134   assert_heap_not_locked();
2135 
2136   uint gc_count_before;
2137   uint old_marking_count_before;
2138   uint full_gc_count_before;
2139   bool retry_gc;
2140 
2141   do {
2142     retry_gc = false;
2143 
2144     {
2145       MutexLocker ml(Heap_lock);
2146 
2147       // Read the GC count while holding the Heap_lock
2148       gc_count_before = total_collections();
2149       full_gc_count_before = total_full_collections();
2150       old_marking_count_before = _old_marking_cycles_started;
2151     }
2152 
2153     if (should_do_concurrent_full_gc(cause)) {
2154       // Schedule an initial-mark evacuation pause that will start a
2155       // concurrent cycle. We're setting word_size to 0 which means that
2156       // we are not requesting a post-GC allocation.
2157       VM_G1IncCollectionPause op(gc_count_before,
2158                                  0,     /* word_size */
2159                                  true,  /* should_initiate_conc_mark */
2160                                  g1_policy()->max_pause_time_ms(),
2161                                  cause);
2162       op.set_allocation_context(AllocationContext::current());
2163 
2164       VMThread::execute(&op);
2165       if (!op.pause_succeeded()) {
2166         if (old_marking_count_before == _old_marking_cycles_started) {
2167           retry_gc = op.should_retry_gc();
2168         } else {
2169           // A Full GC happened while we were trying to schedule the
2170           // initial-mark GC. No point in starting a new cycle given
2171           // that the whole heap was collected anyway.
2172         }
2173 
2174         if (retry_gc) {
2175           if (GCLocker::is_active_and_needs_gc()) {
2176             GCLocker::stall_until_clear();
2177           }
2178         }
2179       }
2180     } else {
2181       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2182           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2183 
2184         // Schedule a standard evacuation pause. We're setting word_size
2185         // to 0 which means that we are not requesting a post-GC allocation.
2186         VM_G1IncCollectionPause op(gc_count_before,
2187                                    0,     /* word_size */
2188                                    false, /* should_initiate_conc_mark */
2189                                    g1_policy()->max_pause_time_ms(),
2190                                    cause);
2191         VMThread::execute(&op);
2192       } else {
2193         // Schedule a Full GC.
2194         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2195         VMThread::execute(&op);
2196       }
2197     }
2198   } while (retry_gc);
2199 }
2200 
2201 bool G1CollectedHeap::is_in(const void* p) const {
2202   if (_hrm.reserved().contains(p)) {
2203     // Given that we know that p is in the reserved space,
2204     // heap_region_containing() should successfully
2205     // return the containing region.
2206     HeapRegion* hr = heap_region_containing(p);
2207     return hr->is_in(p);
2208   } else {
2209     return false;
2210   }
2211 }
2212 
2213 #ifdef ASSERT
2214 bool G1CollectedHeap::is_in_exact(const void* p) const {
2215   bool contains = reserved_region().contains(p);
2216   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2217   if (contains && available) {
2218     return true;
2219   } else {
2220     return false;
2221   }
2222 }
2223 #endif
2224 
2225 // Iteration functions.
2226 
2227 // Iterates an ObjectClosure over all objects within a HeapRegion.
2228 
2229 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2230   ObjectClosure* _cl;
2231 public:
2232   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2233   bool doHeapRegion(HeapRegion* r) {
2234     if (!r->is_continues_humongous()) {
2235       r->object_iterate(_cl);
2236     }
2237     return false;
2238   }
2239 };
2240 
2241 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2242   IterateObjectClosureRegionClosure blk(cl);
2243   heap_region_iterate(&blk);
2244 }
2245 
2246 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2247   _hrm.iterate(cl);
2248 }
2249 
2250 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2251                                                                  HeapRegionClaimer *hrclaimer,
2252                                                                  uint worker_id) const {
2253   _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2254 }
2255 
2256 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2257                                                          HeapRegionClaimer *hrclaimer) const {
2258   _hrm.par_iterate(cl, hrclaimer, 0);
2259 }
2260 
2261 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2262   _collection_set.iterate(cl);
2263 }
2264 
2265 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2266   _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2267 }
2268 
2269 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2270   HeapRegion* hr = heap_region_containing(addr);
2271   return hr->block_start(addr);
2272 }
2273 
2274 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2275   HeapRegion* hr = heap_region_containing(addr);
2276   return hr->block_size(addr);
2277 }
2278 
2279 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2280   HeapRegion* hr = heap_region_containing(addr);
2281   return hr->block_is_obj(addr);
2282 }
2283 
2284 bool G1CollectedHeap::supports_tlab_allocation() const {
2285   return true;
2286 }
2287 
2288 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2289   return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2290 }
2291 
2292 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2293   return _eden.length() * HeapRegion::GrainBytes;
2294 }
2295 
2296 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2297 // must be equal to the humongous object limit.
2298 size_t G1CollectedHeap::max_tlab_size() const {
2299   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2300 }
2301 
2302 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2303   AllocationContext_t context = AllocationContext::current();
2304   return _allocator->unsafe_max_tlab_alloc(context);
2305 }
2306 
2307 size_t G1CollectedHeap::max_capacity() const {
2308   return _hrm.reserved().byte_size();
2309 }
2310 
2311 jlong G1CollectedHeap::millis_since_last_gc() {
2312   // See the notes in GenCollectedHeap::millis_since_last_gc()
2313   // for more information about the implementation.
2314   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2315     _g1_policy->collection_pause_end_millis();
2316   if (ret_val < 0) {
2317     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2318       ". returning zero instead.", ret_val);
2319     return 0;
2320   }
2321   return ret_val;
2322 }
2323 
2324 void G1CollectedHeap::prepare_for_verify() {
2325   _verifier->prepare_for_verify();
2326 }
2327 
2328 void G1CollectedHeap::verify(VerifyOption vo) {
2329   _verifier->verify(vo);
2330 }
2331 
2332 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2333   return true;
2334 }
2335 
2336 const char* const* G1CollectedHeap::concurrent_phases() const {
2337   return _cmThread->concurrent_phases();
2338 }
2339 
2340 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2341   return _cmThread->request_concurrent_phase(phase);
2342 }
2343 
2344 class PrintRegionClosure: public HeapRegionClosure {
2345   outputStream* _st;
2346 public:
2347   PrintRegionClosure(outputStream* st) : _st(st) {}
2348   bool doHeapRegion(HeapRegion* r) {
2349     r->print_on(_st);
2350     return false;
2351   }
2352 };
2353 
2354 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2355                                        const HeapRegion* hr,
2356                                        const VerifyOption vo) const {
2357   switch (vo) {
2358   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2359   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2360   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2361   default:                            ShouldNotReachHere();
2362   }
2363   return false; // keep some compilers happy
2364 }
2365 
2366 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2367                                        const VerifyOption vo) const {
2368   switch (vo) {
2369   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2370   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2371   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2372   default:                            ShouldNotReachHere();
2373   }
2374   return false; // keep some compilers happy
2375 }
2376 
2377 void G1CollectedHeap::print_heap_regions() const {
2378   LogTarget(Trace, gc, heap, region) lt;
2379   if (lt.is_enabled()) {
2380     LogStream ls(lt);
2381     print_regions_on(&ls);
2382   }
2383 }
2384 
2385 void G1CollectedHeap::print_on(outputStream* st) const {
2386   st->print(" %-20s", "garbage-first heap");
2387   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2388             capacity()/K, used_unlocked()/K);
2389   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2390             p2i(_hrm.reserved().start()),
2391             p2i(_hrm.reserved().end()));
2392   st->cr();
2393   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2394   uint young_regions = young_regions_count();
2395   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2396             (size_t) young_regions * HeapRegion::GrainBytes / K);
2397   uint survivor_regions = survivor_regions_count();
2398   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2399             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2400   st->cr();
2401   MetaspaceAux::print_on(st);
2402 }
2403 
2404 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2405   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2406                "HS=humongous(starts), HC=humongous(continues), "
2407                "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2408                "AC=allocation context, "
2409                "TAMS=top-at-mark-start (previous, next)");
2410   PrintRegionClosure blk(st);
2411   heap_region_iterate(&blk);
2412 }
2413 
2414 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2415   print_on(st);
2416 
2417   // Print the per-region information.
2418   print_regions_on(st);
2419 }
2420 
2421 void G1CollectedHeap::print_on_error(outputStream* st) const {
2422   this->CollectedHeap::print_on_error(st);
2423 
2424   if (_cm != NULL) {
2425     st->cr();
2426     _cm->print_on_error(st);
2427   }
2428 }
2429 
2430 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2431   workers()->print_worker_threads_on(st);
2432   _cmThread->print_on(st);
2433   st->cr();
2434   _cm->print_worker_threads_on(st);
2435   _cr->print_threads_on(st);
2436   _young_gen_sampling_thread->print_on(st);
2437   if (G1StringDedup::is_enabled()) {
2438     G1StringDedup::print_worker_threads_on(st);
2439   }
2440 }
2441 
2442 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2443   workers()->threads_do(tc);
2444   tc->do_thread(_cmThread);
2445   _cm->threads_do(tc);
2446   _cr->threads_do(tc);
2447   tc->do_thread(_young_gen_sampling_thread);
2448   if (G1StringDedup::is_enabled()) {
2449     G1StringDedup::threads_do(tc);
2450   }
2451 }
2452 
2453 void G1CollectedHeap::print_tracing_info() const {
2454   g1_rem_set()->print_summary_info();
2455   concurrent_mark()->print_summary_info();
2456 }
2457 
2458 #ifndef PRODUCT
2459 // Helpful for debugging RSet issues.
2460 
2461 class PrintRSetsClosure : public HeapRegionClosure {
2462 private:
2463   const char* _msg;
2464   size_t _occupied_sum;
2465 
2466 public:
2467   bool doHeapRegion(HeapRegion* r) {
2468     HeapRegionRemSet* hrrs = r->rem_set();
2469     size_t occupied = hrrs->occupied();
2470     _occupied_sum += occupied;
2471 
2472     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2473     if (occupied == 0) {
2474       tty->print_cr("  RSet is empty");
2475     } else {
2476       hrrs->print();
2477     }
2478     tty->print_cr("----------");
2479     return false;
2480   }
2481 
2482   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2483     tty->cr();
2484     tty->print_cr("========================================");
2485     tty->print_cr("%s", msg);
2486     tty->cr();
2487   }
2488 
2489   ~PrintRSetsClosure() {
2490     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2491     tty->print_cr("========================================");
2492     tty->cr();
2493   }
2494 };
2495 
2496 void G1CollectedHeap::print_cset_rsets() {
2497   PrintRSetsClosure cl("Printing CSet RSets");
2498   collection_set_iterate(&cl);
2499 }
2500 
2501 void G1CollectedHeap::print_all_rsets() {
2502   PrintRSetsClosure cl("Printing All RSets");;
2503   heap_region_iterate(&cl);
2504 }
2505 #endif // PRODUCT
2506 
2507 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2508 
2509   size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2510   size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2511   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2512 
2513   size_t eden_capacity_bytes =
2514     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2515 
2516   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2517   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2518                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2519 }
2520 
2521 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2522   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2523                        stats->unused(), stats->used(), stats->region_end_waste(),
2524                        stats->regions_filled(), stats->direct_allocated(),
2525                        stats->failure_used(), stats->failure_waste());
2526 }
2527 
2528 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2529   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2530   gc_tracer->report_gc_heap_summary(when, heap_summary);
2531 
2532   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2533   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2534 }
2535 
2536 G1CollectedHeap* G1CollectedHeap::heap() {
2537   CollectedHeap* heap = Universe::heap();
2538   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2539   assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2540   return (G1CollectedHeap*)heap;
2541 }
2542 
2543 void G1CollectedHeap::gc_prologue(bool full) {
2544   // always_do_update_barrier = false;
2545   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2546 
2547   // This summary needs to be printed before incrementing total collections.
2548   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2549 
2550   // Update common counters.
2551   increment_total_collections(full /* full gc */);
2552   if (full) {
2553     increment_old_marking_cycles_started();
2554     reset_gc_time_stamp();
2555   } else {
2556     increment_gc_time_stamp();
2557   }
2558 
2559   // Fill TLAB's and such
2560   double start = os::elapsedTime();
2561   accumulate_statistics_all_tlabs();
2562   ensure_parsability(true);
2563   g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2564 }
2565 
2566 void G1CollectedHeap::gc_epilogue(bool full) {
2567   // Update common counters.
2568   if (full) {
2569     // Update the number of full collections that have been completed.
2570     increment_old_marking_cycles_completed(false /* concurrent */);
2571   }
2572 
2573   // We are at the end of the GC. Total collections has already been increased.
2574   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2575 
2576   // FIXME: what is this about?
2577   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2578   // is set.
2579 #if COMPILER2_OR_JVMCI
2580   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2581 #endif
2582   // always_do_update_barrier = true;
2583 
2584   double start = os::elapsedTime();
2585   resize_all_tlabs();
2586   g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2587 
2588   allocation_context_stats().update(full);
2589 
2590   MemoryService::track_memory_usage();
2591   // We have just completed a GC. Update the soft reference
2592   // policy with the new heap occupancy
2593   Universe::update_heap_info_at_gc();
2594 }
2595 
2596 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2597                                                uint gc_count_before,
2598                                                bool* succeeded,
2599                                                GCCause::Cause gc_cause) {
2600   assert_heap_not_locked_and_not_at_safepoint();
2601   VM_G1IncCollectionPause op(gc_count_before,
2602                              word_size,
2603                              false, /* should_initiate_conc_mark */
2604                              g1_policy()->max_pause_time_ms(),
2605                              gc_cause);
2606 
2607   op.set_allocation_context(AllocationContext::current());
2608   VMThread::execute(&op);
2609 
2610   HeapWord* result = op.result();
2611   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2612   assert(result == NULL || ret_succeeded,
2613          "the result should be NULL if the VM did not succeed");
2614   *succeeded = ret_succeeded;
2615 
2616   assert_heap_not_locked();
2617   return result;
2618 }
2619 
2620 void
2621 G1CollectedHeap::doConcurrentMark() {
2622   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2623   if (!_cmThread->in_progress()) {
2624     _cmThread->set_started();
2625     CGC_lock->notify();
2626   }
2627 }
2628 
2629 size_t G1CollectedHeap::pending_card_num() {
2630   size_t extra_cards = 0;
2631   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) {
2632     DirtyCardQueue& dcq = curr->dirty_card_queue();
2633     extra_cards += dcq.size();
2634   }
2635   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2636   size_t buffer_size = dcqs.buffer_size();
2637   size_t buffer_num = dcqs.completed_buffers_num();
2638 
2639   return buffer_size * buffer_num + extra_cards;
2640 }
2641 
2642 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2643  private:
2644   size_t _total_humongous;
2645   size_t _candidate_humongous;
2646 
2647   DirtyCardQueue _dcq;
2648 
2649   // We don't nominate objects with many remembered set entries, on
2650   // the assumption that such objects are likely still live.
2651   bool is_remset_small(HeapRegion* region) const {
2652     HeapRegionRemSet* const rset = region->rem_set();
2653     return G1EagerReclaimHumongousObjectsWithStaleRefs
2654       ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2655       : rset->is_empty();
2656   }
2657 
2658   bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2659     assert(region->is_starts_humongous(), "Must start a humongous object");
2660 
2661     oop obj = oop(region->bottom());
2662 
2663     // Dead objects cannot be eager reclaim candidates. Due to class
2664     // unloading it is unsafe to query their classes so we return early.
2665     if (heap->is_obj_dead(obj, region)) {
2666       return false;
2667     }
2668 
2669     // Candidate selection must satisfy the following constraints
2670     // while concurrent marking is in progress:
2671     //
2672     // * In order to maintain SATB invariants, an object must not be
2673     // reclaimed if it was allocated before the start of marking and
2674     // has not had its references scanned.  Such an object must have
2675     // its references (including type metadata) scanned to ensure no
2676     // live objects are missed by the marking process.  Objects
2677     // allocated after the start of concurrent marking don't need to
2678     // be scanned.
2679     //
2680     // * An object must not be reclaimed if it is on the concurrent
2681     // mark stack.  Objects allocated after the start of concurrent
2682     // marking are never pushed on the mark stack.
2683     //
2684     // Nominating only objects allocated after the start of concurrent
2685     // marking is sufficient to meet both constraints.  This may miss
2686     // some objects that satisfy the constraints, but the marking data
2687     // structures don't support efficiently performing the needed
2688     // additional tests or scrubbing of the mark stack.
2689     //
2690     // However, we presently only nominate is_typeArray() objects.
2691     // A humongous object containing references induces remembered
2692     // set entries on other regions.  In order to reclaim such an
2693     // object, those remembered sets would need to be cleaned up.
2694     //
2695     // We also treat is_typeArray() objects specially, allowing them
2696     // to be reclaimed even if allocated before the start of
2697     // concurrent mark.  For this we rely on mark stack insertion to
2698     // exclude is_typeArray() objects, preventing reclaiming an object
2699     // that is in the mark stack.  We also rely on the metadata for
2700     // such objects to be built-in and so ensured to be kept live.
2701     // Frequent allocation and drop of large binary blobs is an
2702     // important use case for eager reclaim, and this special handling
2703     // may reduce needed headroom.
2704 
2705     return obj->is_typeArray() && is_remset_small(region);
2706   }
2707 
2708  public:
2709   RegisterHumongousWithInCSetFastTestClosure()
2710   : _total_humongous(0),
2711     _candidate_humongous(0),
2712     _dcq(&JavaThread::dirty_card_queue_set()) {
2713   }
2714 
2715   virtual bool doHeapRegion(HeapRegion* r) {
2716     if (!r->is_starts_humongous()) {
2717       return false;
2718     }
2719     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2720 
2721     bool is_candidate = humongous_region_is_candidate(g1h, r);
2722     uint rindex = r->hrm_index();
2723     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2724     if (is_candidate) {
2725       _candidate_humongous++;
2726       g1h->register_humongous_region_with_cset(rindex);
2727       // Is_candidate already filters out humongous object with large remembered sets.
2728       // If we have a humongous object with a few remembered sets, we simply flush these
2729       // remembered set entries into the DCQS. That will result in automatic
2730       // re-evaluation of their remembered set entries during the following evacuation
2731       // phase.
2732       if (!r->rem_set()->is_empty()) {
2733         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2734                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2735         G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
2736         HeapRegionRemSetIterator hrrs(r->rem_set());
2737         size_t card_index;
2738         while (hrrs.has_next(card_index)) {
2739           jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
2740           // The remembered set might contain references to already freed
2741           // regions. Filter out such entries to avoid failing card table
2742           // verification.
2743           if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
2744             if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
2745               *card_ptr = CardTableModRefBS::dirty_card_val();
2746               _dcq.enqueue(card_ptr);
2747             }
2748           }
2749         }
2750         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2751                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2752                hrrs.n_yielded(), r->rem_set()->occupied());
2753         r->rem_set()->clear_locked();
2754       }
2755       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2756     }
2757     _total_humongous++;
2758 
2759     return false;
2760   }
2761 
2762   size_t total_humongous() const { return _total_humongous; }
2763   size_t candidate_humongous() const { return _candidate_humongous; }
2764 
2765   void flush_rem_set_entries() { _dcq.flush(); }
2766 };
2767 
2768 void G1CollectedHeap::register_humongous_regions_with_cset() {
2769   if (!G1EagerReclaimHumongousObjects) {
2770     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2771     return;
2772   }
2773   double time = os::elapsed_counter();
2774 
2775   // Collect reclaim candidate information and register candidates with cset.
2776   RegisterHumongousWithInCSetFastTestClosure cl;
2777   heap_region_iterate(&cl);
2778 
2779   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2780   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2781                                                                   cl.total_humongous(),
2782                                                                   cl.candidate_humongous());
2783   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2784 
2785   // Finally flush all remembered set entries to re-check into the global DCQS.
2786   cl.flush_rem_set_entries();
2787 }
2788 
2789 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2790   public:
2791     bool doHeapRegion(HeapRegion* hr) {
2792       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2793         hr->verify_rem_set();
2794       }
2795       return false;
2796     }
2797 };
2798 
2799 uint G1CollectedHeap::num_task_queues() const {
2800   return _task_queues->size();
2801 }
2802 
2803 #if TASKQUEUE_STATS
2804 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2805   st->print_raw_cr("GC Task Stats");
2806   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2807   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2808 }
2809 
2810 void G1CollectedHeap::print_taskqueue_stats() const {
2811   if (!log_is_enabled(Trace, gc, task, stats)) {
2812     return;
2813   }
2814   Log(gc, task, stats) log;
2815   ResourceMark rm;
2816   LogStream ls(log.trace());
2817   outputStream* st = &ls;
2818 
2819   print_taskqueue_stats_hdr(st);
2820 
2821   TaskQueueStats totals;
2822   const uint n = num_task_queues();
2823   for (uint i = 0; i < n; ++i) {
2824     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2825     totals += task_queue(i)->stats;
2826   }
2827   st->print_raw("tot "); totals.print(st); st->cr();
2828 
2829   DEBUG_ONLY(totals.verify());
2830 }
2831 
2832 void G1CollectedHeap::reset_taskqueue_stats() {
2833   const uint n = num_task_queues();
2834   for (uint i = 0; i < n; ++i) {
2835     task_queue(i)->stats.reset();
2836   }
2837 }
2838 #endif // TASKQUEUE_STATS
2839 
2840 void G1CollectedHeap::wait_for_root_region_scanning() {
2841   double scan_wait_start = os::elapsedTime();
2842   // We have to wait until the CM threads finish scanning the
2843   // root regions as it's the only way to ensure that all the
2844   // objects on them have been correctly scanned before we start
2845   // moving them during the GC.
2846   bool waited = _cm->root_regions()->wait_until_scan_finished();
2847   double wait_time_ms = 0.0;
2848   if (waited) {
2849     double scan_wait_end = os::elapsedTime();
2850     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2851   }
2852   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2853 }
2854 
2855 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2856 private:
2857   G1HRPrinter* _hr_printer;
2858 public:
2859   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2860 
2861   virtual bool doHeapRegion(HeapRegion* r) {
2862     _hr_printer->cset(r);
2863     return false;
2864   }
2865 };
2866 
2867 void G1CollectedHeap::start_new_collection_set() {
2868   collection_set()->start_incremental_building();
2869 
2870   clear_cset_fast_test();
2871 
2872   guarantee(_eden.length() == 0, "eden should have been cleared");
2873   g1_policy()->transfer_survivors_to_cset(survivor());
2874 }
2875 
2876 bool
2877 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2878   assert_at_safepoint(true /* should_be_vm_thread */);
2879   guarantee(!is_gc_active(), "collection is not reentrant");
2880 
2881   if (GCLocker::check_active_before_gc()) {
2882     return false;
2883   }
2884 
2885   _gc_timer_stw->register_gc_start();
2886 
2887   GCIdMark gc_id_mark;
2888   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2889 
2890   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2891   ResourceMark rm;
2892 
2893   g1_policy()->note_gc_start();
2894 
2895   wait_for_root_region_scanning();
2896 
2897   print_heap_before_gc();
2898   print_heap_regions();
2899   trace_heap_before_gc(_gc_tracer_stw);
2900 
2901   _verifier->verify_region_sets_optional();
2902   _verifier->verify_dirty_young_regions();
2903 
2904   // We should not be doing initial mark unless the conc mark thread is running
2905   if (!_cmThread->should_terminate()) {
2906     // This call will decide whether this pause is an initial-mark
2907     // pause. If it is, during_initial_mark_pause() will return true
2908     // for the duration of this pause.
2909     g1_policy()->decide_on_conc_mark_initiation();
2910   }
2911 
2912   // We do not allow initial-mark to be piggy-backed on a mixed GC.
2913   assert(!collector_state()->during_initial_mark_pause() ||
2914           collector_state()->gcs_are_young(), "sanity");
2915 
2916   // We also do not allow mixed GCs during marking.
2917   assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
2918 
2919   // Record whether this pause is an initial mark. When the current
2920   // thread has completed its logging output and it's safe to signal
2921   // the CM thread, the flag's value in the policy has been reset.
2922   bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
2923 
2924   // Inner scope for scope based logging, timers, and stats collection
2925   {
2926     EvacuationInfo evacuation_info;
2927 
2928     if (collector_state()->during_initial_mark_pause()) {
2929       // We are about to start a marking cycle, so we increment the
2930       // full collection counter.
2931       increment_old_marking_cycles_started();
2932       _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2933     }
2934 
2935     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2936 
2937     GCTraceCPUTime tcpu;
2938 
2939     G1HeapVerifier::G1VerifyType verify_type;
2940     FormatBuffer<> gc_string("Pause ");
2941     if (collector_state()->during_initial_mark_pause()) {
2942       gc_string.append("Initial Mark");
2943       verify_type = G1HeapVerifier::G1VerifyInitialMark;
2944     } else if (collector_state()->gcs_are_young()) {
2945       gc_string.append("Young");
2946       verify_type = G1HeapVerifier::G1VerifyYoungOnly;
2947     } else {
2948       gc_string.append("Mixed");
2949       verify_type = G1HeapVerifier::G1VerifyMixed;
2950     }
2951     GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2952 
2953     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2954                                                                   workers()->active_workers(),
2955                                                                   Threads::number_of_non_daemon_threads());
2956     workers()->update_active_workers(active_workers);
2957     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2958 
2959     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2960     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
2961 
2962     // If the secondary_free_list is not empty, append it to the
2963     // free_list. No need to wait for the cleanup operation to finish;
2964     // the region allocation code will check the secondary_free_list
2965     // and wait if necessary. If the G1StressConcRegionFreeing flag is
2966     // set, skip this step so that the region allocation code has to
2967     // get entries from the secondary_free_list.
2968     if (!G1StressConcRegionFreeing) {
2969       append_secondary_free_list_if_not_empty_with_lock();
2970     }
2971 
2972     G1HeapTransition heap_transition(this);
2973     size_t heap_used_bytes_before_gc = used();
2974 
2975     // Don't dynamically change the number of GC threads this early.  A value of
2976     // 0 is used to indicate serial work.  When parallel work is done,
2977     // it will be set.
2978 
2979     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2980       IsGCActiveMark x;
2981 
2982       gc_prologue(false);
2983 
2984       if (VerifyRememberedSets) {
2985         log_info(gc, verify)("[Verifying RemSets before GC]");
2986         VerifyRegionRemSetClosure v_cl;
2987         heap_region_iterate(&v_cl);
2988       }
2989 
2990       _verifier->verify_before_gc(verify_type);
2991 
2992       _verifier->check_bitmaps("GC Start");
2993 
2994 #if COMPILER2_OR_JVMCI
2995       DerivedPointerTable::clear();
2996 #endif
2997 
2998       // Please see comment in g1CollectedHeap.hpp and
2999       // G1CollectedHeap::ref_processing_init() to see how
3000       // reference processing currently works in G1.
3001 
3002       // Enable discovery in the STW reference processor
3003       if (g1_policy()->should_process_references()) {
3004         ref_processor_stw()->enable_discovery();
3005       } else {
3006         ref_processor_stw()->disable_discovery();
3007       }
3008 
3009       {
3010         // We want to temporarily turn off discovery by the
3011         // CM ref processor, if necessary, and turn it back on
3012         // on again later if we do. Using a scoped
3013         // NoRefDiscovery object will do this.
3014         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3015 
3016         // Forget the current alloc region (we might even choose it to be part
3017         // of the collection set!).
3018         _allocator->release_mutator_alloc_region();
3019 
3020         // This timing is only used by the ergonomics to handle our pause target.
3021         // It is unclear why this should not include the full pause. We will
3022         // investigate this in CR 7178365.
3023         //
3024         // Preserving the old comment here if that helps the investigation:
3025         //
3026         // The elapsed time induced by the start time below deliberately elides
3027         // the possible verification above.
3028         double sample_start_time_sec = os::elapsedTime();
3029 
3030         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3031 
3032         if (collector_state()->during_initial_mark_pause()) {
3033           concurrent_mark()->checkpoint_roots_initial_pre();
3034         }
3035 
3036         g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
3037 
3038         evacuation_info.set_collectionset_regions(collection_set()->region_length());
3039 
3040         // Make sure the remembered sets are up to date. This needs to be
3041         // done before register_humongous_regions_with_cset(), because the
3042         // remembered sets are used there to choose eager reclaim candidates.
3043         // If the remembered sets are not up to date we might miss some
3044         // entries that need to be handled.
3045         g1_rem_set()->cleanupHRRS();
3046 
3047         register_humongous_regions_with_cset();
3048 
3049         assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3050 
3051         // We call this after finalize_cset() to
3052         // ensure that the CSet has been finalized.
3053         _cm->verify_no_cset_oops();
3054 
3055         if (_hr_printer.is_active()) {
3056           G1PrintCollectionSetClosure cl(&_hr_printer);
3057           _collection_set.iterate(&cl);
3058         }
3059 
3060         // Initialize the GC alloc regions.
3061         _allocator->init_gc_alloc_regions(evacuation_info);
3062 
3063         G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3064         pre_evacuate_collection_set();
3065 
3066         // Actually do the work...
3067         evacuate_collection_set(evacuation_info, &per_thread_states);
3068 
3069         post_evacuate_collection_set(evacuation_info, &per_thread_states);
3070 
3071         const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3072         free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
3073 
3074         eagerly_reclaim_humongous_regions();
3075 
3076         record_obj_copy_mem_stats();
3077         _survivor_evac_stats.adjust_desired_plab_sz();
3078         _old_evac_stats.adjust_desired_plab_sz();
3079 
3080         double start = os::elapsedTime();
3081         start_new_collection_set();
3082         g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
3083 
3084         if (evacuation_failed()) {
3085           set_used(recalculate_used());
3086           if (_archive_allocator != NULL) {
3087             _archive_allocator->clear_used();
3088           }
3089           for (uint i = 0; i < ParallelGCThreads; i++) {
3090             if (_evacuation_failed_info_array[i].has_failed()) {
3091               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3092             }
3093           }
3094         } else {
3095           // The "used" of the the collection set have already been subtracted
3096           // when they were freed.  Add in the bytes evacuated.
3097           increase_used(g1_policy()->bytes_copied_during_gc());
3098         }
3099 
3100         if (collector_state()->during_initial_mark_pause()) {
3101           // We have to do this before we notify the CM threads that
3102           // they can start working to make sure that all the
3103           // appropriate initialization is done on the CM object.
3104           concurrent_mark()->checkpoint_roots_initial_post();
3105           collector_state()->set_mark_in_progress(true);
3106           // Note that we don't actually trigger the CM thread at
3107           // this point. We do that later when we're sure that
3108           // the current thread has completed its logging output.
3109         }
3110 
3111         allocate_dummy_regions();
3112 
3113         _allocator->init_mutator_alloc_region();
3114 
3115         {
3116           size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3117           if (expand_bytes > 0) {
3118             size_t bytes_before = capacity();
3119             // No need for an ergo logging here,
3120             // expansion_amount() does this when it returns a value > 0.
3121             double expand_ms;
3122             if (!expand(expand_bytes, _workers, &expand_ms)) {
3123               // We failed to expand the heap. Cannot do anything about it.
3124             }
3125             g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3126           }
3127         }
3128 
3129         // We redo the verification but now wrt to the new CSet which
3130         // has just got initialized after the previous CSet was freed.
3131         _cm->verify_no_cset_oops();
3132 
3133         // This timing is only used by the ergonomics to handle our pause target.
3134         // It is unclear why this should not include the full pause. We will
3135         // investigate this in CR 7178365.
3136         double sample_end_time_sec = os::elapsedTime();
3137         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3138         size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
3139         g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3140 
3141         evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3142         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3143 
3144         if (VerifyRememberedSets) {
3145           log_info(gc, verify)("[Verifying RemSets after GC]");
3146           VerifyRegionRemSetClosure v_cl;
3147           heap_region_iterate(&v_cl);
3148         }
3149 
3150         _verifier->verify_after_gc(verify_type);
3151         _verifier->check_bitmaps("GC End");
3152 
3153         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3154         ref_processor_stw()->verify_no_references_recorded();
3155 
3156         // CM reference discovery will be re-enabled if necessary.
3157       }
3158 
3159 #ifdef TRACESPINNING
3160       ParallelTaskTerminator::print_termination_counts();
3161 #endif
3162 
3163       gc_epilogue(false);
3164     }
3165 
3166     // Print the remainder of the GC log output.
3167     if (evacuation_failed()) {
3168       log_info(gc)("To-space exhausted");
3169     }
3170 
3171     g1_policy()->print_phases();
3172     heap_transition.print();
3173 
3174     // It is not yet to safe to tell the concurrent mark to
3175     // start as we have some optional output below. We don't want the
3176     // output from the concurrent mark thread interfering with this
3177     // logging output either.
3178 
3179     _hrm.verify_optional();
3180     _verifier->verify_region_sets_optional();
3181 
3182     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3183     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3184 
3185     print_heap_after_gc();
3186     print_heap_regions();
3187     trace_heap_after_gc(_gc_tracer_stw);
3188 
3189     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3190     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3191     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3192     // before any GC notifications are raised.
3193     g1mm()->update_sizes();
3194 
3195     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3196     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3197     _gc_timer_stw->register_gc_end();
3198     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3199   }
3200   // It should now be safe to tell the concurrent mark thread to start
3201   // without its logging output interfering with the logging output
3202   // that came from the pause.
3203 
3204   if (should_start_conc_mark) {
3205     // CAUTION: after the doConcurrentMark() call below,
3206     // the concurrent marking thread(s) could be running
3207     // concurrently with us. Make sure that anything after
3208     // this point does not assume that we are the only GC thread
3209     // running. Note: of course, the actual marking work will
3210     // not start until the safepoint itself is released in
3211     // SuspendibleThreadSet::desynchronize().
3212     doConcurrentMark();
3213   }
3214 
3215   return true;
3216 }
3217 
3218 void G1CollectedHeap::remove_self_forwarding_pointers() {
3219   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3220   workers()->run_task(&rsfp_task);
3221 }
3222 
3223 void G1CollectedHeap::restore_after_evac_failure() {
3224   double remove_self_forwards_start = os::elapsedTime();
3225 
3226   remove_self_forwarding_pointers();
3227   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3228   _preserved_marks_set.restore(&task_executor);
3229 
3230   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3231 }
3232 
3233 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3234   if (!_evacuation_failed) {
3235     _evacuation_failed = true;
3236   }
3237 
3238   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3239   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3240 }
3241 
3242 bool G1ParEvacuateFollowersClosure::offer_termination() {
3243   G1ParScanThreadState* const pss = par_scan_state();
3244   start_term_time();
3245   const bool res = terminator()->offer_termination();
3246   end_term_time();
3247   return res;
3248 }
3249 
3250 void G1ParEvacuateFollowersClosure::do_void() {
3251   G1ParScanThreadState* const pss = par_scan_state();
3252   pss->trim_queue();
3253   do {
3254     pss->steal_and_trim_queue(queues());
3255   } while (!offer_termination());
3256 }
3257 
3258 class G1ParTask : public AbstractGangTask {
3259 protected:
3260   G1CollectedHeap*         _g1h;
3261   G1ParScanThreadStateSet* _pss;
3262   RefToScanQueueSet*       _queues;
3263   G1RootProcessor*         _root_processor;
3264   ParallelTaskTerminator   _terminator;
3265   uint                     _n_workers;
3266 
3267 public:
3268   G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3269     : AbstractGangTask("G1 collection"),
3270       _g1h(g1h),
3271       _pss(per_thread_states),
3272       _queues(task_queues),
3273       _root_processor(root_processor),
3274       _terminator(n_workers, _queues),
3275       _n_workers(n_workers)
3276   {}
3277 
3278   void work(uint worker_id) {
3279     if (worker_id >= _n_workers) return;  // no work needed this round
3280 
3281     double start_sec = os::elapsedTime();
3282     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3283 
3284     {
3285       ResourceMark rm;
3286       HandleMark   hm;
3287 
3288       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
3289 
3290       G1ParScanThreadState*           pss = _pss->state_for_worker(worker_id);
3291       pss->set_ref_processor(rp);
3292 
3293       double start_strong_roots_sec = os::elapsedTime();
3294 
3295       _root_processor->evacuate_roots(pss->closures(), worker_id);
3296 
3297       // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3298       // treating the nmethods visited to act as roots for concurrent marking.
3299       // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3300       // objects copied by the current evacuation.
3301       _g1h->g1_rem_set()->oops_into_collection_set_do(pss,
3302                                                       pss->closures()->weak_codeblobs(),
3303                                                       worker_id);
3304 
3305       double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3306 
3307       double term_sec = 0.0;
3308       size_t evac_term_attempts = 0;
3309       {
3310         double start = os::elapsedTime();
3311         G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3312         evac.do_void();
3313 
3314         evac_term_attempts = evac.term_attempts();
3315         term_sec = evac.term_time();
3316         double elapsed_sec = os::elapsedTime() - start;
3317         _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3318         _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3319         _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3320       }
3321 
3322       assert(pss->queue_is_empty(), "should be empty");
3323 
3324       if (log_is_enabled(Debug, gc, task, stats)) {
3325         MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3326         size_t lab_waste;
3327         size_t lab_undo_waste;
3328         pss->waste(lab_waste, lab_undo_waste);
3329         _g1h->print_termination_stats(worker_id,
3330                                       (os::elapsedTime() - start_sec) * 1000.0,   /* elapsed time */
3331                                       strong_roots_sec * 1000.0,                  /* strong roots time */
3332                                       term_sec * 1000.0,                          /* evac term time */
3333                                       evac_term_attempts,                         /* evac term attempts */
3334                                       lab_waste,                                  /* alloc buffer waste */
3335                                       lab_undo_waste                              /* undo waste */
3336                                       );
3337       }
3338 
3339       // Close the inner scope so that the ResourceMark and HandleMark
3340       // destructors are executed here and are included as part of the
3341       // "GC Worker Time".
3342     }
3343     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3344   }
3345 };
3346 
3347 void G1CollectedHeap::print_termination_stats_hdr() {
3348   log_debug(gc, task, stats)("GC Termination Stats");
3349   log_debug(gc, task, stats)("     elapsed  --strong roots-- -------termination------- ------waste (KiB)------");
3350   log_debug(gc, task, stats)("thr     ms        ms      %%        ms      %%    attempts  total   alloc    undo");
3351   log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3352 }
3353 
3354 void G1CollectedHeap::print_termination_stats(uint worker_id,
3355                                               double elapsed_ms,
3356                                               double strong_roots_ms,
3357                                               double term_ms,
3358                                               size_t term_attempts,
3359                                               size_t alloc_buffer_waste,
3360                                               size_t undo_waste) const {
3361   log_debug(gc, task, stats)
3362               ("%3d %9.2f %9.2f %6.2f "
3363                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3364                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3365                worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3366                term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3367                (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3368                alloc_buffer_waste * HeapWordSize / K,
3369                undo_waste * HeapWordSize / K);
3370 }
3371 
3372 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3373 private:
3374   BoolObjectClosure* _is_alive;
3375   G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3376 
3377   int _initial_string_table_size;
3378   int _initial_symbol_table_size;
3379 
3380   bool  _process_strings;
3381   int _strings_processed;
3382   int _strings_removed;
3383 
3384   bool  _process_symbols;
3385   int _symbols_processed;
3386   int _symbols_removed;
3387 
3388   bool _process_string_dedup;
3389 
3390 public:
3391   G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3392     AbstractGangTask("String/Symbol Unlinking"),
3393     _is_alive(is_alive),
3394     _dedup_closure(is_alive, NULL, false),
3395     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3396     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3397     _process_string_dedup(process_string_dedup) {
3398 
3399     _initial_string_table_size = StringTable::the_table()->table_size();
3400     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3401     if (process_strings) {
3402       StringTable::clear_parallel_claimed_index();
3403     }
3404     if (process_symbols) {
3405       SymbolTable::clear_parallel_claimed_index();
3406     }
3407   }
3408 
3409   ~G1StringAndSymbolCleaningTask() {
3410     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3411               "claim value %d after unlink less than initial string table size %d",
3412               StringTable::parallel_claimed_index(), _initial_string_table_size);
3413     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3414               "claim value %d after unlink less than initial symbol table size %d",
3415               SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3416 
3417     log_info(gc, stringtable)(
3418         "Cleaned string and symbol table, "
3419         "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3420         "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3421         strings_processed(), strings_removed(),
3422         symbols_processed(), symbols_removed());
3423   }
3424 
3425   void work(uint worker_id) {
3426     int strings_processed = 0;
3427     int strings_removed = 0;
3428     int symbols_processed = 0;
3429     int symbols_removed = 0;
3430     if (_process_strings) {
3431       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3432       Atomic::add(strings_processed, &_strings_processed);
3433       Atomic::add(strings_removed, &_strings_removed);
3434     }
3435     if (_process_symbols) {
3436       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3437       Atomic::add(symbols_processed, &_symbols_processed);
3438       Atomic::add(symbols_removed, &_symbols_removed);
3439     }
3440     if (_process_string_dedup) {
3441       G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3442     }
3443   }
3444 
3445   size_t strings_processed() const { return (size_t)_strings_processed; }
3446   size_t strings_removed()   const { return (size_t)_strings_removed; }
3447 
3448   size_t symbols_processed() const { return (size_t)_symbols_processed; }
3449   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
3450 };
3451 
3452 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3453 private:
3454   static Monitor* _lock;
3455 
3456   BoolObjectClosure* const _is_alive;
3457   const bool               _unloading_occurred;
3458   const uint               _num_workers;
3459 
3460   // Variables used to claim nmethods.
3461   CompiledMethod* _first_nmethod;
3462   CompiledMethod* volatile _claimed_nmethod;
3463 
3464   // The list of nmethods that need to be processed by the second pass.
3465   CompiledMethod* volatile _postponed_list;
3466   volatile uint            _num_entered_barrier;
3467 
3468  public:
3469   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3470       _is_alive(is_alive),
3471       _unloading_occurred(unloading_occurred),
3472       _num_workers(num_workers),
3473       _first_nmethod(NULL),
3474       _claimed_nmethod(NULL),
3475       _postponed_list(NULL),
3476       _num_entered_barrier(0)
3477   {
3478     CompiledMethod::increase_unloading_clock();
3479     // Get first alive nmethod
3480     CompiledMethodIterator iter = CompiledMethodIterator();
3481     if(iter.next_alive()) {
3482       _first_nmethod = iter.method();
3483     }
3484     _claimed_nmethod = _first_nmethod;
3485   }
3486 
3487   ~G1CodeCacheUnloadingTask() {
3488     CodeCache::verify_clean_inline_caches();
3489 
3490     CodeCache::set_needs_cache_clean(false);
3491     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3492 
3493     CodeCache::verify_icholder_relocations();
3494   }
3495 
3496  private:
3497   void add_to_postponed_list(CompiledMethod* nm) {
3498       CompiledMethod* old;
3499       do {
3500         old = _postponed_list;
3501         nm->set_unloading_next(old);
3502       } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
3503   }
3504 
3505   void clean_nmethod(CompiledMethod* nm) {
3506     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3507 
3508     if (postponed) {
3509       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3510       add_to_postponed_list(nm);
3511     }
3512 
3513     // Mark that this thread has been cleaned/unloaded.
3514     // After this call, it will be safe to ask if this nmethod was unloaded or not.
3515     nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3516   }
3517 
3518   void clean_nmethod_postponed(CompiledMethod* nm) {
3519     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3520   }
3521 
3522   static const int MaxClaimNmethods = 16;
3523 
3524   void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3525     CompiledMethod* first;
3526     CompiledMethodIterator last;
3527 
3528     do {
3529       *num_claimed_nmethods = 0;
3530 
3531       first = _claimed_nmethod;
3532       last = CompiledMethodIterator(first);
3533 
3534       if (first != NULL) {
3535 
3536         for (int i = 0; i < MaxClaimNmethods; i++) {
3537           if (!last.next_alive()) {
3538             break;
3539           }
3540           claimed_nmethods[i] = last.method();
3541           (*num_claimed_nmethods)++;
3542         }
3543       }
3544 
3545     } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
3546   }
3547 
3548   CompiledMethod* claim_postponed_nmethod() {
3549     CompiledMethod* claim;
3550     CompiledMethod* next;
3551 
3552     do {
3553       claim = _postponed_list;
3554       if (claim == NULL) {
3555         return NULL;
3556       }
3557 
3558       next = claim->unloading_next();
3559 
3560     } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
3561 
3562     return claim;
3563   }
3564 
3565  public:
3566   // Mark that we're done with the first pass of nmethod cleaning.
3567   void barrier_mark(uint worker_id) {
3568     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3569     _num_entered_barrier++;
3570     if (_num_entered_barrier == _num_workers) {
3571       ml.notify_all();
3572     }
3573   }
3574 
3575   // See if we have to wait for the other workers to
3576   // finish their first-pass nmethod cleaning work.
3577   void barrier_wait(uint worker_id) {
3578     if (_num_entered_barrier < _num_workers) {
3579       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3580       while (_num_entered_barrier < _num_workers) {
3581           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3582       }
3583     }
3584   }
3585 
3586   // Cleaning and unloading of nmethods. Some work has to be postponed
3587   // to the second pass, when we know which nmethods survive.
3588   void work_first_pass(uint worker_id) {
3589     // The first nmethods is claimed by the first worker.
3590     if (worker_id == 0 && _first_nmethod != NULL) {
3591       clean_nmethod(_first_nmethod);
3592       _first_nmethod = NULL;
3593     }
3594 
3595     int num_claimed_nmethods;
3596     CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3597 
3598     while (true) {
3599       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3600 
3601       if (num_claimed_nmethods == 0) {
3602         break;
3603       }
3604 
3605       for (int i = 0; i < num_claimed_nmethods; i++) {
3606         clean_nmethod(claimed_nmethods[i]);
3607       }
3608     }
3609   }
3610 
3611   void work_second_pass(uint worker_id) {
3612     CompiledMethod* nm;
3613     // Take care of postponed nmethods.
3614     while ((nm = claim_postponed_nmethod()) != NULL) {
3615       clean_nmethod_postponed(nm);
3616     }
3617   }
3618 };
3619 
3620 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3621 
3622 class G1KlassCleaningTask : public StackObj {
3623   BoolObjectClosure*                      _is_alive;
3624   volatile int                            _clean_klass_tree_claimed;
3625   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3626 
3627  public:
3628   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3629       _is_alive(is_alive),
3630       _clean_klass_tree_claimed(0),
3631       _klass_iterator() {
3632   }
3633 
3634  private:
3635   bool claim_clean_klass_tree_task() {
3636     if (_clean_klass_tree_claimed) {
3637       return false;
3638     }
3639 
3640     return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0;
3641   }
3642 
3643   InstanceKlass* claim_next_klass() {
3644     Klass* klass;
3645     do {
3646       klass =_klass_iterator.next_klass();
3647     } while (klass != NULL && !klass->is_instance_klass());
3648 
3649     // this can be null so don't call InstanceKlass::cast
3650     return static_cast<InstanceKlass*>(klass);
3651   }
3652 
3653 public:
3654 
3655   void clean_klass(InstanceKlass* ik) {
3656     ik->clean_weak_instanceklass_links(_is_alive);
3657   }
3658 
3659   void work() {
3660     ResourceMark rm;
3661 
3662     // One worker will clean the subklass/sibling klass tree.
3663     if (claim_clean_klass_tree_task()) {
3664       Klass::clean_subklass_tree(_is_alive);
3665     }
3666 
3667     // All workers will help cleaning the classes,
3668     InstanceKlass* klass;
3669     while ((klass = claim_next_klass()) != NULL) {
3670       clean_klass(klass);
3671     }
3672   }
3673 };
3674 
3675 class G1ResolvedMethodCleaningTask : public StackObj {
3676   BoolObjectClosure* _is_alive;
3677   volatile int       _resolved_method_task_claimed;
3678 public:
3679   G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) :
3680       _is_alive(is_alive), _resolved_method_task_claimed(0) {}
3681 
3682   bool claim_resolved_method_task() {
3683     if (_resolved_method_task_claimed) {
3684       return false;
3685     }
3686     return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0;
3687   }
3688 
3689   // These aren't big, one thread can do it all.
3690   void work() {
3691     if (claim_resolved_method_task()) {
3692       ResolvedMethodTable::unlink(_is_alive);
3693     }
3694   }
3695 };
3696 
3697 
3698 // To minimize the remark pause times, the tasks below are done in parallel.
3699 class G1ParallelCleaningTask : public AbstractGangTask {
3700 private:
3701   G1StringAndSymbolCleaningTask _string_symbol_task;
3702   G1CodeCacheUnloadingTask      _code_cache_task;
3703   G1KlassCleaningTask           _klass_cleaning_task;
3704   G1ResolvedMethodCleaningTask  _resolved_method_cleaning_task;
3705 
3706 public:
3707   // The constructor is run in the VMThread.
3708   G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3709       AbstractGangTask("Parallel Cleaning"),
3710       _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3711       _code_cache_task(num_workers, is_alive, unloading_occurred),
3712       _klass_cleaning_task(is_alive),
3713       _resolved_method_cleaning_task(is_alive) {
3714   }
3715 
3716   // The parallel work done by all worker threads.
3717   void work(uint worker_id) {
3718     // Do first pass of code cache cleaning.
3719     _code_cache_task.work_first_pass(worker_id);
3720 
3721     // Let the threads mark that the first pass is done.
3722     _code_cache_task.barrier_mark(worker_id);
3723 
3724     // Clean the Strings and Symbols.
3725     _string_symbol_task.work(worker_id);
3726 
3727     // Clean unreferenced things in the ResolvedMethodTable
3728     _resolved_method_cleaning_task.work();
3729 
3730     // Wait for all workers to finish the first code cache cleaning pass.
3731     _code_cache_task.barrier_wait(worker_id);
3732 
3733     // Do the second code cache cleaning work, which realize on
3734     // the liveness information gathered during the first pass.
3735     _code_cache_task.work_second_pass(worker_id);
3736 
3737     // Clean all klasses that were not unloaded.
3738     _klass_cleaning_task.work();
3739   }
3740 };
3741 
3742 
3743 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3744                                         bool class_unloading_occurred) {
3745   uint n_workers = workers()->active_workers();
3746 
3747   G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3748   workers()->run_task(&g1_unlink_task);
3749 }
3750 
3751 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3752                                        bool process_strings,
3753                                        bool process_symbols,
3754                                        bool process_string_dedup) {
3755   if (!process_strings && !process_symbols && !process_string_dedup) {
3756     // Nothing to clean.
3757     return;
3758   }
3759 
3760   G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3761   workers()->run_task(&g1_unlink_task);
3762 
3763 }
3764 
3765 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3766  private:
3767   DirtyCardQueueSet* _queue;
3768   G1CollectedHeap* _g1h;
3769  public:
3770   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3771     _queue(queue), _g1h(g1h) { }
3772 
3773   virtual void work(uint worker_id) {
3774     G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3775     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3776 
3777     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3778     _queue->par_apply_closure_to_all_completed_buffers(&cl);
3779 
3780     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3781   }
3782 };
3783 
3784 void G1CollectedHeap::redirty_logged_cards() {
3785   double redirty_logged_cards_start = os::elapsedTime();
3786 
3787   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3788   dirty_card_queue_set().reset_for_par_iteration();
3789   workers()->run_task(&redirty_task);
3790 
3791   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
3792   dcq.merge_bufferlists(&dirty_card_queue_set());
3793   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3794 
3795   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3796 }
3797 
3798 // Weak Reference Processing support
3799 
3800 // An always "is_alive" closure that is used to preserve referents.
3801 // If the object is non-null then it's alive.  Used in the preservation
3802 // of referent objects that are pointed to by reference objects
3803 // discovered by the CM ref processor.
3804 class G1AlwaysAliveClosure: public BoolObjectClosure {
3805   G1CollectedHeap* _g1;
3806 public:
3807   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3808   bool do_object_b(oop p) {
3809     if (p != NULL) {
3810       return true;
3811     }
3812     return false;
3813   }
3814 };
3815 
3816 bool G1STWIsAliveClosure::do_object_b(oop p) {
3817   // An object is reachable if it is outside the collection set,
3818   // or is inside and copied.
3819   return !_g1->is_in_cset(p) || p->is_forwarded();
3820 }
3821 
3822 // Non Copying Keep Alive closure
3823 class G1KeepAliveClosure: public OopClosure {
3824   G1CollectedHeap* _g1;
3825 public:
3826   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3827   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3828   void do_oop(oop* p) {
3829     oop obj = *p;
3830     assert(obj != NULL, "the caller should have filtered out NULL values");
3831 
3832     const InCSetState cset_state = _g1->in_cset_state(obj);
3833     if (!cset_state.is_in_cset_or_humongous()) {
3834       return;
3835     }
3836     if (cset_state.is_in_cset()) {
3837       assert( obj->is_forwarded(), "invariant" );
3838       *p = obj->forwardee();
3839     } else {
3840       assert(!obj->is_forwarded(), "invariant" );
3841       assert(cset_state.is_humongous(),
3842              "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3843       _g1->set_humongous_is_live(obj);
3844     }
3845   }
3846 };
3847 
3848 // Copying Keep Alive closure - can be called from both
3849 // serial and parallel code as long as different worker
3850 // threads utilize different G1ParScanThreadState instances
3851 // and different queues.
3852 
3853 class G1CopyingKeepAliveClosure: public OopClosure {
3854   G1CollectedHeap*         _g1h;
3855   OopClosure*              _copy_non_heap_obj_cl;
3856   G1ParScanThreadState*    _par_scan_state;
3857 
3858 public:
3859   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3860                             OopClosure* non_heap_obj_cl,
3861                             G1ParScanThreadState* pss):
3862     _g1h(g1h),
3863     _copy_non_heap_obj_cl(non_heap_obj_cl),
3864     _par_scan_state(pss)
3865   {}
3866 
3867   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3868   virtual void do_oop(      oop* p) { do_oop_work(p); }
3869 
3870   template <class T> void do_oop_work(T* p) {
3871     oop obj = oopDesc::load_decode_heap_oop(p);
3872 
3873     if (_g1h->is_in_cset_or_humongous(obj)) {
3874       // If the referent object has been forwarded (either copied
3875       // to a new location or to itself in the event of an
3876       // evacuation failure) then we need to update the reference
3877       // field and, if both reference and referent are in the G1
3878       // heap, update the RSet for the referent.
3879       //
3880       // If the referent has not been forwarded then we have to keep
3881       // it alive by policy. Therefore we have copy the referent.
3882       //
3883       // If the reference field is in the G1 heap then we can push
3884       // on the PSS queue. When the queue is drained (after each
3885       // phase of reference processing) the object and it's followers
3886       // will be copied, the reference field set to point to the
3887       // new location, and the RSet updated. Otherwise we need to
3888       // use the the non-heap or metadata closures directly to copy
3889       // the referent object and update the pointer, while avoiding
3890       // updating the RSet.
3891 
3892       if (_g1h->is_in_g1_reserved(p)) {
3893         _par_scan_state->push_on_queue(p);
3894       } else {
3895         assert(!Metaspace::contains((const void*)p),
3896                "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3897         _copy_non_heap_obj_cl->do_oop(p);
3898       }
3899     }
3900   }
3901 };
3902 
3903 // Serial drain queue closure. Called as the 'complete_gc'
3904 // closure for each discovered list in some of the
3905 // reference processing phases.
3906 
3907 class G1STWDrainQueueClosure: public VoidClosure {
3908 protected:
3909   G1CollectedHeap* _g1h;
3910   G1ParScanThreadState* _par_scan_state;
3911 
3912   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3913 
3914 public:
3915   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3916     _g1h(g1h),
3917     _par_scan_state(pss)
3918   { }
3919 
3920   void do_void() {
3921     G1ParScanThreadState* const pss = par_scan_state();
3922     pss->trim_queue();
3923   }
3924 };
3925 
3926 // Parallel Reference Processing closures
3927 
3928 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3929 // processing during G1 evacuation pauses.
3930 
3931 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3932 private:
3933   G1CollectedHeap*          _g1h;
3934   G1ParScanThreadStateSet*  _pss;
3935   RefToScanQueueSet*        _queues;
3936   WorkGang*                 _workers;
3937   uint                      _active_workers;
3938 
3939 public:
3940   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3941                            G1ParScanThreadStateSet* per_thread_states,
3942                            WorkGang* workers,
3943                            RefToScanQueueSet *task_queues,
3944                            uint n_workers) :
3945     _g1h(g1h),
3946     _pss(per_thread_states),
3947     _queues(task_queues),
3948     _workers(workers),
3949     _active_workers(n_workers)
3950   {
3951     g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
3952   }
3953 
3954   // Executes the given task using concurrent marking worker threads.
3955   virtual void execute(ProcessTask& task);
3956   virtual void execute(EnqueueTask& task);
3957 };
3958 
3959 // Gang task for possibly parallel reference processing
3960 
3961 class G1STWRefProcTaskProxy: public AbstractGangTask {
3962   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3963   ProcessTask&     _proc_task;
3964   G1CollectedHeap* _g1h;
3965   G1ParScanThreadStateSet* _pss;
3966   RefToScanQueueSet* _task_queues;
3967   ParallelTaskTerminator* _terminator;
3968 
3969 public:
3970   G1STWRefProcTaskProxy(ProcessTask& proc_task,
3971                         G1CollectedHeap* g1h,
3972                         G1ParScanThreadStateSet* per_thread_states,
3973                         RefToScanQueueSet *task_queues,
3974                         ParallelTaskTerminator* terminator) :
3975     AbstractGangTask("Process reference objects in parallel"),
3976     _proc_task(proc_task),
3977     _g1h(g1h),
3978     _pss(per_thread_states),
3979     _task_queues(task_queues),
3980     _terminator(terminator)
3981   {}
3982 
3983   virtual void work(uint worker_id) {
3984     // The reference processing task executed by a single worker.
3985     ResourceMark rm;
3986     HandleMark   hm;
3987 
3988     G1STWIsAliveClosure is_alive(_g1h);
3989 
3990     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
3991     pss->set_ref_processor(NULL);
3992 
3993     // Keep alive closure.
3994     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
3995 
3996     // Complete GC closure
3997     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
3998 
3999     // Call the reference processing task's work routine.
4000     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
4001 
4002     // Note we cannot assert that the refs array is empty here as not all
4003     // of the processing tasks (specifically phase2 - pp2_work) execute
4004     // the complete_gc closure (which ordinarily would drain the queue) so
4005     // the queue may not be empty.
4006   }
4007 };
4008 
4009 // Driver routine for parallel reference processing.
4010 // Creates an instance of the ref processing gang
4011 // task and has the worker threads execute it.
4012 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4013   assert(_workers != NULL, "Need parallel worker threads.");
4014 
4015   ParallelTaskTerminator terminator(_active_workers, _queues);
4016   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4017 
4018   _workers->run_task(&proc_task_proxy);
4019 }
4020 
4021 // Gang task for parallel reference enqueueing.
4022 
4023 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4024   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4025   EnqueueTask& _enq_task;
4026 
4027 public:
4028   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4029     AbstractGangTask("Enqueue reference objects in parallel"),
4030     _enq_task(enq_task)
4031   { }
4032 
4033   virtual void work(uint worker_id) {
4034     _enq_task.work(worker_id);
4035   }
4036 };
4037 
4038 // Driver routine for parallel reference enqueueing.
4039 // Creates an instance of the ref enqueueing gang
4040 // task and has the worker threads execute it.
4041 
4042 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4043   assert(_workers != NULL, "Need parallel worker threads.");
4044 
4045   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4046 
4047   _workers->run_task(&enq_task_proxy);
4048 }
4049 
4050 // End of weak reference support closures
4051 
4052 // Abstract task used to preserve (i.e. copy) any referent objects
4053 // that are in the collection set and are pointed to by reference
4054 // objects discovered by the CM ref processor.
4055 
4056 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4057 protected:
4058   G1CollectedHeap*         _g1h;
4059   G1ParScanThreadStateSet* _pss;
4060   RefToScanQueueSet*       _queues;
4061   ParallelTaskTerminator   _terminator;
4062   uint                     _n_workers;
4063 
4064 public:
4065   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4066     AbstractGangTask("ParPreserveCMReferents"),
4067     _g1h(g1h),
4068     _pss(per_thread_states),
4069     _queues(task_queues),
4070     _terminator(workers, _queues),
4071     _n_workers(workers)
4072   {
4073     g1h->ref_processor_cm()->set_active_mt_degree(workers);
4074   }
4075 
4076   void work(uint worker_id) {
4077     G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4078 
4079     ResourceMark rm;
4080     HandleMark   hm;
4081 
4082     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4083     pss->set_ref_processor(NULL);
4084     assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4085 
4086     // Is alive closure
4087     G1AlwaysAliveClosure always_alive(_g1h);
4088 
4089     // Copying keep alive closure. Applied to referent objects that need
4090     // to be copied.
4091     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4092 
4093     ReferenceProcessor* rp = _g1h->ref_processor_cm();
4094 
4095     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4096     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4097 
4098     // limit is set using max_num_q() - which was set using ParallelGCThreads.
4099     // So this must be true - but assert just in case someone decides to
4100     // change the worker ids.
4101     assert(worker_id < limit, "sanity");
4102     assert(!rp->discovery_is_atomic(), "check this code");
4103 
4104     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4105     for (uint idx = worker_id; idx < limit; idx += stride) {
4106       DiscoveredList& ref_list = rp->discovered_refs()[idx];
4107 
4108       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4109       while (iter.has_next()) {
4110         // Since discovery is not atomic for the CM ref processor, we
4111         // can see some null referent objects.
4112         iter.load_ptrs(DEBUG_ONLY(true));
4113         oop ref = iter.obj();
4114 
4115         // This will filter nulls.
4116         if (iter.is_referent_alive()) {
4117           iter.make_referent_alive();
4118         }
4119         iter.move_to_next();
4120       }
4121     }
4122 
4123     // Drain the queue - which may cause stealing
4124     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4125     drain_queue.do_void();
4126     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4127     assert(pss->queue_is_empty(), "should be");
4128   }
4129 };
4130 
4131 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4132   // Any reference objects, in the collection set, that were 'discovered'
4133   // by the CM ref processor should have already been copied (either by
4134   // applying the external root copy closure to the discovered lists, or
4135   // by following an RSet entry).
4136   //
4137   // But some of the referents, that are in the collection set, that these
4138   // reference objects point to may not have been copied: the STW ref
4139   // processor would have seen that the reference object had already
4140   // been 'discovered' and would have skipped discovering the reference,
4141   // but would not have treated the reference object as a regular oop.
4142   // As a result the copy closure would not have been applied to the
4143   // referent object.
4144   //
4145   // We need to explicitly copy these referent objects - the references
4146   // will be processed at the end of remarking.
4147   //
4148   // We also need to do this copying before we process the reference
4149   // objects discovered by the STW ref processor in case one of these
4150   // referents points to another object which is also referenced by an
4151   // object discovered by the STW ref processor.
4152   double preserve_cm_referents_time = 0.0;
4153 
4154   // To avoid spawning task when there is no work to do, check that
4155   // a concurrent cycle is active and that some references have been
4156   // discovered.
4157   if (concurrent_mark()->cm_thread()->during_cycle() &&
4158       ref_processor_cm()->has_discovered_references()) {
4159     double preserve_cm_referents_start = os::elapsedTime();
4160     uint no_of_gc_workers = workers()->active_workers();
4161     G1ParPreserveCMReferentsTask keep_cm_referents(this,
4162                                                    per_thread_states,
4163                                                    no_of_gc_workers,
4164                                                    _task_queues);
4165     workers()->run_task(&keep_cm_referents);
4166     preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4167   }
4168 
4169   g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4170 }
4171 
4172 // Weak Reference processing during an evacuation pause (part 1).
4173 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4174   double ref_proc_start = os::elapsedTime();
4175 
4176   ReferenceProcessor* rp = _ref_processor_stw;
4177   assert(rp->discovery_enabled(), "should have been enabled");
4178 
4179   // Closure to test whether a referent is alive.
4180   G1STWIsAliveClosure is_alive(this);
4181 
4182   // Even when parallel reference processing is enabled, the processing
4183   // of JNI refs is serial and performed serially by the current thread
4184   // rather than by a worker. The following PSS will be used for processing
4185   // JNI refs.
4186 
4187   // Use only a single queue for this PSS.
4188   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
4189   pss->set_ref_processor(NULL);
4190   assert(pss->queue_is_empty(), "pre-condition");
4191 
4192   // Keep alive closure.
4193   G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4194 
4195   // Serial Complete GC closure
4196   G1STWDrainQueueClosure drain_queue(this, pss);
4197 
4198   // Setup the soft refs policy...
4199   rp->setup_policy(false);
4200 
4201   ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4202 
4203   ReferenceProcessorStats stats;
4204   if (!rp->processing_is_mt()) {
4205     // Serial reference processing...
4206     stats = rp->process_discovered_references(&is_alive,
4207                                               &keep_alive,
4208                                               &drain_queue,
4209                                               NULL,
4210                                               pt);
4211   } else {
4212     uint no_of_gc_workers = workers()->active_workers();
4213 
4214     // Parallel reference processing
4215     assert(no_of_gc_workers <= rp->max_num_q(),
4216            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4217            no_of_gc_workers,  rp->max_num_q());
4218 
4219     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4220     stats = rp->process_discovered_references(&is_alive,
4221                                               &keep_alive,
4222                                               &drain_queue,
4223                                               &par_task_executor,
4224                                               pt);
4225   }
4226 
4227   _gc_tracer_stw->report_gc_reference_stats(stats);
4228 
4229   // We have completed copying any necessary live referent objects.
4230   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4231 
4232   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4233   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4234 }
4235 
4236 // Weak Reference processing during an evacuation pause (part 2).
4237 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4238   double ref_enq_start = os::elapsedTime();
4239 
4240   ReferenceProcessor* rp = _ref_processor_stw;
4241   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4242 
4243   ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4244 
4245   // Now enqueue any remaining on the discovered lists on to
4246   // the pending list.
4247   if (!rp->processing_is_mt()) {
4248     // Serial reference processing...
4249     rp->enqueue_discovered_references(NULL, pt);
4250   } else {
4251     // Parallel reference enqueueing
4252 
4253     uint n_workers = workers()->active_workers();
4254 
4255     assert(n_workers <= rp->max_num_q(),
4256            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4257            n_workers,  rp->max_num_q());
4258 
4259     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4260     rp->enqueue_discovered_references(&par_task_executor, pt);
4261   }
4262 
4263   rp->verify_no_references_recorded();
4264   assert(!rp->discovery_enabled(), "should have been disabled");
4265 
4266   // If during an initial mark pause we install a pending list head which is not otherwise reachable
4267   // ensure that it is marked in the bitmap for concurrent marking to discover.
4268   if (collector_state()->during_initial_mark_pause()) {
4269     oop pll_head = Universe::reference_pending_list();
4270     if (pll_head != NULL) {
4271       _cm->mark_in_next_bitmap(pll_head);
4272     }
4273   }
4274 
4275   // FIXME
4276   // CM's reference processing also cleans up the string and symbol tables.
4277   // Should we do that here also? We could, but it is a serial operation
4278   // and could significantly increase the pause time.
4279 
4280   double ref_enq_time = os::elapsedTime() - ref_enq_start;
4281   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4282 }
4283 
4284 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4285   double merge_pss_time_start = os::elapsedTime();
4286   per_thread_states->flush();
4287   g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4288 }
4289 
4290 void G1CollectedHeap::pre_evacuate_collection_set() {
4291   _expand_heap_after_alloc_failure = true;
4292   _evacuation_failed = false;
4293 
4294   // Disable the hot card cache.
4295   _hot_card_cache->reset_hot_cache_claimed_index();
4296   _hot_card_cache->set_use_cache(false);
4297 
4298   g1_rem_set()->prepare_for_oops_into_collection_set_do();
4299   _preserved_marks_set.assert_empty();
4300 
4301   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4302 
4303   // InitialMark needs claim bits to keep track of the marked-through CLDs.
4304   if (collector_state()->during_initial_mark_pause()) {
4305     double start_clear_claimed_marks = os::elapsedTime();
4306 
4307     ClassLoaderDataGraph::clear_claimed_marks();
4308 
4309     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
4310     phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
4311   }
4312 }
4313 
4314 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4315   // Should G1EvacuationFailureALot be in effect for this GC?
4316   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4317 
4318   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4319 
4320   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4321 
4322   double start_par_time_sec = os::elapsedTime();
4323   double end_par_time_sec;
4324 
4325   {
4326     const uint n_workers = workers()->active_workers();
4327     G1RootProcessor root_processor(this, n_workers);
4328     G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4329 
4330     print_termination_stats_hdr();
4331 
4332     workers()->run_task(&g1_par_task);
4333     end_par_time_sec = os::elapsedTime();
4334 
4335     // Closing the inner scope will execute the destructor
4336     // for the G1RootProcessor object. We record the current
4337     // elapsed time before closing the scope so that time
4338     // taken for the destructor is NOT included in the
4339     // reported parallel time.
4340   }
4341 
4342   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4343   phase_times->record_par_time(par_time_ms);
4344 
4345   double code_root_fixup_time_ms =
4346         (os::elapsedTime() - end_par_time_sec) * 1000.0;
4347   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4348 }
4349 
4350 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4351   // Process any discovered reference objects - we have
4352   // to do this _before_ we retire the GC alloc regions
4353   // as we may have to copy some 'reachable' referent
4354   // objects (and their reachable sub-graphs) that were
4355   // not copied during the pause.
4356   if (g1_policy()->should_process_references()) {
4357     preserve_cm_referents(per_thread_states);
4358     process_discovered_references(per_thread_states);
4359   } else {
4360     ref_processor_stw()->verify_no_references_recorded();
4361   }
4362 
4363   G1STWIsAliveClosure is_alive(this);
4364   G1KeepAliveClosure keep_alive(this);
4365 
4366   {
4367     double start = os::elapsedTime();
4368 
4369     WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
4370 
4371     double time_ms = (os::elapsedTime() - start) * 1000.0;
4372     g1_policy()->phase_times()->record_ref_proc_time(time_ms);
4373   }
4374 
4375   if (G1StringDedup::is_enabled()) {
4376     double fixup_start = os::elapsedTime();
4377 
4378     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4379 
4380     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4381     g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4382   }
4383 
4384   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4385 
4386   if (evacuation_failed()) {
4387     restore_after_evac_failure();
4388 
4389     // Reset the G1EvacuationFailureALot counters and flags
4390     // Note: the values are reset only when an actual
4391     // evacuation failure occurs.
4392     NOT_PRODUCT(reset_evacuation_should_fail();)
4393   }
4394 
4395   _preserved_marks_set.assert_empty();
4396 
4397   // Enqueue any remaining references remaining on the STW
4398   // reference processor's discovered lists. We need to do
4399   // this after the card table is cleaned (and verified) as
4400   // the act of enqueueing entries on to the pending list
4401   // will log these updates (and dirty their associated
4402   // cards). We need these updates logged to update any
4403   // RSets.
4404   if (g1_policy()->should_process_references()) {
4405     enqueue_discovered_references(per_thread_states);
4406   } else {
4407     g1_policy()->phase_times()->record_ref_enq_time(0);
4408   }
4409 
4410   _allocator->release_gc_alloc_regions(evacuation_info);
4411 
4412   merge_per_thread_state_info(per_thread_states);
4413 
4414   // Reset and re-enable the hot card cache.
4415   // Note the counts for the cards in the regions in the
4416   // collection set are reset when the collection set is freed.
4417   _hot_card_cache->reset_hot_cache();
4418   _hot_card_cache->set_use_cache(true);
4419 
4420   purge_code_root_memory();
4421 
4422   redirty_logged_cards();
4423 #if COMPILER2_OR_JVMCI
4424   double start = os::elapsedTime();
4425   DerivedPointerTable::update_pointers();
4426   g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4427 #endif
4428   g1_policy()->print_age_table();
4429 }
4430 
4431 void G1CollectedHeap::record_obj_copy_mem_stats() {
4432   g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4433 
4434   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4435                                                create_g1_evac_summary(&_old_evac_stats));
4436 }
4437 
4438 void G1CollectedHeap::free_region(HeapRegion* hr,
4439                                   FreeRegionList* free_list,
4440                                   bool skip_remset,
4441                                   bool skip_hot_card_cache,
4442                                   bool locked) {
4443   assert(!hr->is_free(), "the region should not be free");
4444   assert(!hr->is_empty(), "the region should not be empty");
4445   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4446   assert(free_list != NULL, "pre-condition");
4447 
4448   if (G1VerifyBitmaps) {
4449     MemRegion mr(hr->bottom(), hr->end());
4450     concurrent_mark()->clear_range_in_prev_bitmap(mr);
4451   }
4452 
4453   // Clear the card counts for this region.
4454   // Note: we only need to do this if the region is not young
4455   // (since we don't refine cards in young regions).
4456   if (!skip_hot_card_cache && !hr->is_young()) {
4457     _hot_card_cache->reset_card_counts(hr);
4458   }
4459   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4460   free_list->add_ordered(hr);
4461 }
4462 
4463 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4464                                             FreeRegionList* free_list,
4465                                             bool skip_remset) {
4466   assert(hr->is_humongous(), "this is only for humongous regions");
4467   assert(free_list != NULL, "pre-condition");
4468   hr->clear_humongous();
4469   free_region(hr, free_list, skip_remset);
4470 }
4471 
4472 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4473                                            const uint humongous_regions_removed) {
4474   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4475     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4476     _old_set.bulk_remove(old_regions_removed);
4477     _humongous_set.bulk_remove(humongous_regions_removed);
4478   }
4479 
4480 }
4481 
4482 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4483   assert(list != NULL, "list can't be null");
4484   if (!list->is_empty()) {
4485     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4486     _hrm.insert_list_into_free_list(list);
4487   }
4488 }
4489 
4490 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4491   decrease_used(bytes);
4492 }
4493 
4494 class G1ParScrubRemSetTask: public AbstractGangTask {
4495 protected:
4496   G1RemSet* _g1rs;
4497   HeapRegionClaimer _hrclaimer;
4498 
4499 public:
4500   G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
4501     AbstractGangTask("G1 ScrubRS"),
4502     _g1rs(g1_rs),
4503     _hrclaimer(num_workers) {
4504   }
4505 
4506   void work(uint worker_id) {
4507     _g1rs->scrub(worker_id, &_hrclaimer);
4508   }
4509 };
4510 
4511 void G1CollectedHeap::scrub_rem_set() {
4512   uint num_workers = workers()->active_workers();
4513   G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
4514   workers()->run_task(&g1_par_scrub_rs_task);
4515 }
4516 
4517 class G1FreeCollectionSetTask : public AbstractGangTask {
4518 private:
4519 
4520   // Closure applied to all regions in the collection set to do work that needs to
4521   // be done serially in a single thread.
4522   class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4523   private:
4524     EvacuationInfo* _evacuation_info;
4525     const size_t* _surviving_young_words;
4526 
4527     // Bytes used in successfully evacuated regions before the evacuation.
4528     size_t _before_used_bytes;
4529     // Bytes used in unsucessfully evacuated regions before the evacuation
4530     size_t _after_used_bytes;
4531 
4532     size_t _bytes_allocated_in_old_since_last_gc;
4533 
4534     size_t _failure_used_words;
4535     size_t _failure_waste_words;
4536 
4537     FreeRegionList _local_free_list;
4538   public:
4539     G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4540       HeapRegionClosure(),
4541       _evacuation_info(evacuation_info),
4542       _surviving_young_words(surviving_young_words),
4543       _before_used_bytes(0),
4544       _after_used_bytes(0),
4545       _bytes_allocated_in_old_since_last_gc(0),
4546       _failure_used_words(0),
4547       _failure_waste_words(0),
4548       _local_free_list("Local Region List for CSet Freeing") {
4549     }
4550 
4551     virtual bool doHeapRegion(HeapRegion* r) {
4552       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4553 
4554       assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4555       g1h->clear_in_cset(r);
4556 
4557       if (r->is_young()) {
4558         assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4559                "Young index %d is wrong for region %u of type %s with %u young regions",
4560                r->young_index_in_cset(),
4561                r->hrm_index(),
4562                r->get_type_str(),
4563                g1h->collection_set()->young_region_length());
4564         size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4565         r->record_surv_words_in_group(words_survived);
4566       }
4567 
4568       if (!r->evacuation_failed()) {
4569         assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4570         _before_used_bytes += r->used();
4571         g1h->free_region(r,
4572                          &_local_free_list,
4573                          true, /* skip_remset */
4574                          true, /* skip_hot_card_cache */
4575                          true  /* locked */);
4576       } else {
4577         r->uninstall_surv_rate_group();
4578         r->set_young_index_in_cset(-1);
4579         r->set_evacuation_failed(false);
4580         // When moving a young gen region to old gen, we "allocate" that whole region
4581         // there. This is in addition to any already evacuated objects. Notify the
4582         // policy about that.
4583         // Old gen regions do not cause an additional allocation: both the objects
4584         // still in the region and the ones already moved are accounted for elsewhere.
4585         if (r->is_young()) {
4586           _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4587         }
4588         // The region is now considered to be old.
4589         r->set_old();
4590         // Do some allocation statistics accounting. Regions that failed evacuation
4591         // are always made old, so there is no need to update anything in the young
4592         // gen statistics, but we need to update old gen statistics.
4593         size_t used_words = r->marked_bytes() / HeapWordSize;
4594 
4595         _failure_used_words += used_words;
4596         _failure_waste_words += HeapRegion::GrainWords - used_words;
4597 
4598         g1h->old_set_add(r);
4599         _after_used_bytes += r->used();
4600       }
4601       return false;
4602     }
4603 
4604     void complete_work() {
4605       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4606 
4607       _evacuation_info->set_regions_freed(_local_free_list.length());
4608       _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4609 
4610       g1h->prepend_to_freelist(&_local_free_list);
4611       g1h->decrement_summary_bytes(_before_used_bytes);
4612 
4613       G1Policy* policy = g1h->g1_policy();
4614       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4615 
4616       g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4617     }
4618   };
4619 
4620   G1CollectionSet* _collection_set;
4621   G1SerialFreeCollectionSetClosure _cl;
4622   const size_t* _surviving_young_words;
4623 
4624   size_t _rs_lengths;
4625 
4626   volatile jint _serial_work_claim;
4627 
4628   struct WorkItem {
4629     uint region_idx;
4630     bool is_young;
4631     bool evacuation_failed;
4632 
4633     WorkItem(HeapRegion* r) {
4634       region_idx = r->hrm_index();
4635       is_young = r->is_young();
4636       evacuation_failed = r->evacuation_failed();
4637     }
4638   };
4639 
4640   volatile size_t _parallel_work_claim;
4641   size_t _num_work_items;
4642   WorkItem* _work_items;
4643 
4644   void do_serial_work() {
4645     // Need to grab the lock to be allowed to modify the old region list.
4646     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4647     _collection_set->iterate(&_cl);
4648   }
4649 
4650   void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4651     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4652 
4653     HeapRegion* r = g1h->region_at(region_idx);
4654     assert(!g1h->is_on_master_free_list(r), "sanity");
4655 
4656     Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4657 
4658     if (!is_young) {
4659       g1h->_hot_card_cache->reset_card_counts(r);
4660     }
4661 
4662     if (!evacuation_failed) {
4663       r->rem_set()->clear_locked();
4664     }
4665   }
4666 
4667   class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4668   private:
4669     size_t _cur_idx;
4670     WorkItem* _work_items;
4671   public:
4672     G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4673 
4674     virtual bool doHeapRegion(HeapRegion* r) {
4675       _work_items[_cur_idx++] = WorkItem(r);
4676       return false;
4677     }
4678   };
4679 
4680   void prepare_work() {
4681     G1PrepareFreeCollectionSetClosure cl(_work_items);
4682     _collection_set->iterate(&cl);
4683   }
4684 
4685   void complete_work() {
4686     _cl.complete_work();
4687 
4688     G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4689     policy->record_max_rs_lengths(_rs_lengths);
4690     policy->cset_regions_freed();
4691   }
4692 public:
4693   G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4694     AbstractGangTask("G1 Free Collection Set"),
4695     _cl(evacuation_info, surviving_young_words),
4696     _collection_set(collection_set),
4697     _surviving_young_words(surviving_young_words),
4698     _serial_work_claim(0),
4699     _rs_lengths(0),
4700     _parallel_work_claim(0),
4701     _num_work_items(collection_set->region_length()),
4702     _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4703     prepare_work();
4704   }
4705 
4706   ~G1FreeCollectionSetTask() {
4707     complete_work();
4708     FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4709   }
4710 
4711   // Chunk size for work distribution. The chosen value has been determined experimentally
4712   // to be a good tradeoff between overhead and achievable parallelism.
4713   static uint chunk_size() { return 32; }
4714 
4715   virtual void work(uint worker_id) {
4716     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4717 
4718     // Claim serial work.
4719     if (_serial_work_claim == 0) {
4720       jint value = Atomic::add(1, &_serial_work_claim) - 1;
4721       if (value == 0) {
4722         double serial_time = os::elapsedTime();
4723         do_serial_work();
4724         timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4725       }
4726     }
4727 
4728     // Start parallel work.
4729     double young_time = 0.0;
4730     bool has_young_time = false;
4731     double non_young_time = 0.0;
4732     bool has_non_young_time = false;
4733 
4734     while (true) {
4735       size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4736       size_t cur = end - chunk_size();
4737 
4738       if (cur >= _num_work_items) {
4739         break;
4740       }
4741 
4742       double start_time = os::elapsedTime();
4743 
4744       end = MIN2(end, _num_work_items);
4745 
4746       for (; cur < end; cur++) {
4747         bool is_young = _work_items[cur].is_young;
4748 
4749         do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4750 
4751         double end_time = os::elapsedTime();
4752         double time_taken = end_time - start_time;
4753         if (is_young) {
4754           young_time += time_taken;
4755           has_young_time = true;
4756         } else {
4757           non_young_time += time_taken;
4758           has_non_young_time = true;
4759         }
4760         start_time = end_time;
4761       }
4762     }
4763 
4764     if (has_young_time) {
4765       timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4766     }
4767     if (has_non_young_time) {
4768       timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time);
4769     }
4770   }
4771 };
4772 
4773 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4774   _eden.clear();
4775 
4776   double free_cset_start_time = os::elapsedTime();
4777 
4778   {
4779     uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4780     uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4781 
4782     G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4783 
4784     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4785                         cl.name(),
4786                         num_workers,
4787                         _collection_set.region_length());
4788     workers()->run_task(&cl, num_workers);
4789   }
4790   g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4791 
4792   collection_set->clear();
4793 }
4794 
4795 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4796  private:
4797   FreeRegionList* _free_region_list;
4798   HeapRegionSet* _proxy_set;
4799   uint _humongous_objects_reclaimed;
4800   uint _humongous_regions_reclaimed;
4801   size_t _freed_bytes;
4802  public:
4803 
4804   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4805     _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4806   }
4807 
4808   virtual bool doHeapRegion(HeapRegion* r) {
4809     if (!r->is_starts_humongous()) {
4810       return false;
4811     }
4812 
4813     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4814 
4815     oop obj = (oop)r->bottom();
4816     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4817 
4818     // The following checks whether the humongous object is live are sufficient.
4819     // The main additional check (in addition to having a reference from the roots
4820     // or the young gen) is whether the humongous object has a remembered set entry.
4821     //
4822     // A humongous object cannot be live if there is no remembered set for it
4823     // because:
4824     // - there can be no references from within humongous starts regions referencing
4825     // the object because we never allocate other objects into them.
4826     // (I.e. there are no intra-region references that may be missed by the
4827     // remembered set)
4828     // - as soon there is a remembered set entry to the humongous starts region
4829     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4830     // until the end of a concurrent mark.
4831     //
4832     // It is not required to check whether the object has been found dead by marking
4833     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4834     // all objects allocated during that time are considered live.
4835     // SATB marking is even more conservative than the remembered set.
4836     // So if at this point in the collection there is no remembered set entry,
4837     // nobody has a reference to it.
4838     // At the start of collection we flush all refinement logs, and remembered sets
4839     // are completely up-to-date wrt to references to the humongous object.
4840     //
4841     // Other implementation considerations:
4842     // - never consider object arrays at this time because they would pose
4843     // considerable effort for cleaning up the the remembered sets. This is
4844     // required because stale remembered sets might reference locations that
4845     // are currently allocated into.
4846     uint region_idx = r->hrm_index();
4847     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4848         !r->rem_set()->is_empty()) {
4849       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",
4850                                region_idx,
4851                                (size_t)obj->size() * HeapWordSize,
4852                                p2i(r->bottom()),
4853                                r->rem_set()->occupied(),
4854                                r->rem_set()->strong_code_roots_list_length(),
4855                                next_bitmap->is_marked(r->bottom()),
4856                                g1h->is_humongous_reclaim_candidate(region_idx),
4857                                obj->is_typeArray()
4858                               );
4859       return false;
4860     }
4861 
4862     guarantee(obj->is_typeArray(),
4863               "Only eagerly reclaiming type arrays is supported, but the object "
4864               PTR_FORMAT " is not.", p2i(r->bottom()));
4865 
4866     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",
4867                              region_idx,
4868                              (size_t)obj->size() * HeapWordSize,
4869                              p2i(r->bottom()),
4870                              r->rem_set()->occupied(),
4871                              r->rem_set()->strong_code_roots_list_length(),
4872                              next_bitmap->is_marked(r->bottom()),
4873                              g1h->is_humongous_reclaim_candidate(region_idx),
4874                              obj->is_typeArray()
4875                             );
4876 
4877     // Need to clear mark bit of the humongous object if already set.
4878     if (next_bitmap->is_marked(r->bottom())) {
4879       next_bitmap->clear(r->bottom());
4880     }
4881     _humongous_objects_reclaimed++;
4882     do {
4883       HeapRegion* next = g1h->next_region_in_humongous(r);
4884       _freed_bytes += r->used();
4885       r->set_containing_set(NULL);
4886       _humongous_regions_reclaimed++;
4887       g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ );
4888       r = next;
4889     } while (r != NULL);
4890 
4891     return false;
4892   }
4893 
4894   uint humongous_objects_reclaimed() {
4895     return _humongous_objects_reclaimed;
4896   }
4897 
4898   uint humongous_regions_reclaimed() {
4899     return _humongous_regions_reclaimed;
4900   }
4901 
4902   size_t bytes_freed() const {
4903     return _freed_bytes;
4904   }
4905 };
4906 
4907 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4908   assert_at_safepoint(true);
4909 
4910   if (!G1EagerReclaimHumongousObjects ||
4911       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4912     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4913     return;
4914   }
4915 
4916   double start_time = os::elapsedTime();
4917 
4918   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4919 
4920   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4921   heap_region_iterate(&cl);
4922 
4923   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4924 
4925   G1HRPrinter* hrp = hr_printer();
4926   if (hrp->is_active()) {
4927     FreeRegionListIterator iter(&local_cleanup_list);
4928     while (iter.more_available()) {
4929       HeapRegion* hr = iter.get_next();
4930       hrp->cleanup(hr);
4931     }
4932   }
4933 
4934   prepend_to_freelist(&local_cleanup_list);
4935   decrement_summary_bytes(cl.bytes_freed());
4936 
4937   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4938                                                                     cl.humongous_objects_reclaimed());
4939 }
4940 
4941 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4942 public:
4943   virtual bool doHeapRegion(HeapRegion* r) {
4944     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4945     G1CollectedHeap::heap()->clear_in_cset(r);
4946     r->set_young_index_in_cset(-1);
4947     return false;
4948   }
4949 };
4950 
4951 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4952   G1AbandonCollectionSetClosure cl;
4953   collection_set->iterate(&cl);
4954 
4955   collection_set->clear();
4956   collection_set->stop_incremental_building();
4957 }
4958 
4959 void G1CollectedHeap::set_free_regions_coming() {
4960   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
4961 
4962   assert(!free_regions_coming(), "pre-condition");
4963   _free_regions_coming = true;
4964 }
4965 
4966 void G1CollectedHeap::reset_free_regions_coming() {
4967   assert(free_regions_coming(), "pre-condition");
4968 
4969   {
4970     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4971     _free_regions_coming = false;
4972     SecondaryFreeList_lock->notify_all();
4973   }
4974 
4975   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
4976 }
4977 
4978 void G1CollectedHeap::wait_while_free_regions_coming() {
4979   // Most of the time we won't have to wait, so let's do a quick test
4980   // first before we take the lock.
4981   if (!free_regions_coming()) {
4982     return;
4983   }
4984 
4985   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
4986 
4987   {
4988     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4989     while (free_regions_coming()) {
4990       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
4991     }
4992   }
4993 
4994   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
4995 }
4996 
4997 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4998   return _allocator->is_retained_old_region(hr);
4999 }
5000 
5001 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5002   _eden.add(hr);
5003   _g1_policy->set_region_eden(hr);
5004 }
5005 
5006 #ifdef ASSERT
5007 
5008 class NoYoungRegionsClosure: public HeapRegionClosure {
5009 private:
5010   bool _success;
5011 public:
5012   NoYoungRegionsClosure() : _success(true) { }
5013   bool doHeapRegion(HeapRegion* r) {
5014     if (r->is_young()) {
5015       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5016                             p2i(r->bottom()), p2i(r->end()));
5017       _success = false;
5018     }
5019     return false;
5020   }
5021   bool success() { return _success; }
5022 };
5023 
5024 bool G1CollectedHeap::check_young_list_empty() {
5025   bool ret = (young_regions_count() == 0);
5026 
5027   NoYoungRegionsClosure closure;
5028   heap_region_iterate(&closure);
5029   ret = ret && closure.success();
5030 
5031   return ret;
5032 }
5033 
5034 #endif // ASSERT
5035 
5036 class TearDownRegionSetsClosure : public HeapRegionClosure {
5037 private:
5038   HeapRegionSet *_old_set;
5039 
5040 public:
5041   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5042 
5043   bool doHeapRegion(HeapRegion* r) {
5044     if (r->is_old()) {
5045       _old_set->remove(r);
5046     } else if(r->is_young()) {
5047       r->uninstall_surv_rate_group();
5048     } else {
5049       // We ignore free regions, we'll empty the free list afterwards.
5050       // We ignore humongous regions, we're not tearing down the
5051       // humongous regions set.
5052       assert(r->is_free() || r->is_humongous(),
5053              "it cannot be another type");
5054     }
5055     return false;
5056   }
5057 
5058   ~TearDownRegionSetsClosure() {
5059     assert(_old_set->is_empty(), "post-condition");
5060   }
5061 };
5062 
5063 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5064   assert_at_safepoint(true /* should_be_vm_thread */);
5065 
5066   if (!free_list_only) {
5067     TearDownRegionSetsClosure cl(&_old_set);
5068     heap_region_iterate(&cl);
5069 
5070     // Note that emptying the _young_list is postponed and instead done as
5071     // the first step when rebuilding the regions sets again. The reason for
5072     // this is that during a full GC string deduplication needs to know if
5073     // a collected region was young or old when the full GC was initiated.
5074   }
5075   _hrm.remove_all_free_regions();
5076 }
5077 
5078 void G1CollectedHeap::increase_used(size_t bytes) {
5079   _summary_bytes_used += bytes;
5080 }
5081 
5082 void G1CollectedHeap::decrease_used(size_t bytes) {
5083   assert(_summary_bytes_used >= bytes,
5084          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5085          _summary_bytes_used, bytes);
5086   _summary_bytes_used -= bytes;
5087 }
5088 
5089 void G1CollectedHeap::set_used(size_t bytes) {
5090   _summary_bytes_used = bytes;
5091 }
5092 
5093 class RebuildRegionSetsClosure : public HeapRegionClosure {
5094 private:
5095   bool            _free_list_only;
5096   HeapRegionSet*   _old_set;
5097   HeapRegionManager*   _hrm;
5098   size_t          _total_used;
5099 
5100 public:
5101   RebuildRegionSetsClosure(bool free_list_only,
5102                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
5103     _free_list_only(free_list_only),
5104     _old_set(old_set), _hrm(hrm), _total_used(0) {
5105     assert(_hrm->num_free_regions() == 0, "pre-condition");
5106     if (!free_list_only) {
5107       assert(_old_set->is_empty(), "pre-condition");
5108     }
5109   }
5110 
5111   bool doHeapRegion(HeapRegion* r) {
5112     if (r->is_empty()) {
5113       // Add free regions to the free list
5114       r->set_free();
5115       r->set_allocation_context(AllocationContext::system());
5116       _hrm->insert_into_free_list(r);
5117     } else if (!_free_list_only) {
5118 
5119       if (r->is_humongous()) {
5120         // We ignore humongous regions. We left the humongous set unchanged.
5121       } else {
5122         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
5123         // We now move all (non-humongous, non-old) regions to old gen, and register them as such.
5124         r->move_to_old();
5125         _old_set->add(r);
5126       }
5127       _total_used += r->used();
5128     }
5129 
5130     return false;
5131   }
5132 
5133   size_t total_used() {
5134     return _total_used;
5135   }
5136 };
5137 
5138 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5139   assert_at_safepoint(true /* should_be_vm_thread */);
5140 
5141   if (!free_list_only) {
5142     _eden.clear();
5143     _survivor.clear();
5144   }
5145 
5146   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5147   heap_region_iterate(&cl);
5148 
5149   if (!free_list_only) {
5150     set_used(cl.total_used());
5151     if (_archive_allocator != NULL) {
5152       _archive_allocator->clear_used();
5153     }
5154   }
5155   assert(used_unlocked() == recalculate_used(),
5156          "inconsistent used_unlocked(), "
5157          "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5158          used_unlocked(), recalculate_used());
5159 }
5160 
5161 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5162   HeapRegion* hr = heap_region_containing(p);
5163   return hr->is_in(p);
5164 }
5165 
5166 // Methods for the mutator alloc region
5167 
5168 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5169                                                       bool force) {
5170   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5171   bool should_allocate = g1_policy()->should_allocate_mutator_region();
5172   if (force || should_allocate) {
5173     HeapRegion* new_alloc_region = new_region(word_size,
5174                                               false /* is_old */,
5175                                               false /* do_expand */);
5176     if (new_alloc_region != NULL) {
5177       set_region_short_lived_locked(new_alloc_region);
5178       _hr_printer.alloc(new_alloc_region, !should_allocate);
5179       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5180       return new_alloc_region;
5181     }
5182   }
5183   return NULL;
5184 }
5185 
5186 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5187                                                   size_t allocated_bytes) {
5188   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5189   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5190 
5191   collection_set()->add_eden_region(alloc_region);
5192   increase_used(allocated_bytes);
5193   _hr_printer.retire(alloc_region);
5194   // We update the eden sizes here, when the region is retired,
5195   // instead of when it's allocated, since this is the point that its
5196   // used space has been recored in _summary_bytes_used.
5197   g1mm()->update_eden_size();
5198 }
5199 
5200 // Methods for the GC alloc regions
5201 
5202 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
5203   if (dest.is_old()) {
5204     return true;
5205   } else {
5206     return survivor_regions_count() < g1_policy()->max_survivor_regions();
5207   }
5208 }
5209 
5210 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
5211   assert(FreeList_lock->owned_by_self(), "pre-condition");
5212 
5213   if (!has_more_regions(dest)) {
5214     return NULL;
5215   }
5216 
5217   const bool is_survivor = dest.is_young();
5218 
5219   HeapRegion* new_alloc_region = new_region(word_size,
5220                                             !is_survivor,
5221                                             true /* do_expand */);
5222   if (new_alloc_region != NULL) {
5223     // We really only need to do this for old regions given that we
5224     // should never scan survivors. But it doesn't hurt to do it
5225     // for survivors too.
5226     new_alloc_region->record_timestamp();
5227     if (is_survivor) {
5228       new_alloc_region->set_survivor();
5229       _survivor.add(new_alloc_region);
5230       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5231     } else {
5232       new_alloc_region->set_old();
5233       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5234     }
5235     _hr_printer.alloc(new_alloc_region);
5236     bool during_im = collector_state()->during_initial_mark_pause();
5237     new_alloc_region->note_start_of_copying(during_im);
5238     return new_alloc_region;
5239   }
5240   return NULL;
5241 }
5242 
5243 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5244                                              size_t allocated_bytes,
5245                                              InCSetState dest) {
5246   bool during_im = collector_state()->during_initial_mark_pause();
5247   alloc_region->note_end_of_copying(during_im);
5248   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5249   if (dest.is_old()) {
5250     _old_set.add(alloc_region);
5251   }
5252   _hr_printer.retire(alloc_region);
5253 }
5254 
5255 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5256   bool expanded = false;
5257   uint index = _hrm.find_highest_free(&expanded);
5258 
5259   if (index != G1_NO_HRM_INDEX) {
5260     if (expanded) {
5261       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5262                                 HeapRegion::GrainWords * HeapWordSize);
5263     }
5264     _hrm.allocate_free_regions_starting_at(index, 1);
5265     return region_at(index);
5266   }
5267   return NULL;
5268 }
5269 
5270 // Optimized nmethod scanning
5271 
5272 class RegisterNMethodOopClosure: public OopClosure {
5273   G1CollectedHeap* _g1h;
5274   nmethod* _nm;
5275 
5276   template <class T> void do_oop_work(T* p) {
5277     T heap_oop = oopDesc::load_heap_oop(p);
5278     if (!oopDesc::is_null(heap_oop)) {
5279       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5280       HeapRegion* hr = _g1h->heap_region_containing(obj);
5281       assert(!hr->is_continues_humongous(),
5282              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5283              " starting at " HR_FORMAT,
5284              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5285 
5286       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5287       hr->add_strong_code_root_locked(_nm);
5288     }
5289   }
5290 
5291 public:
5292   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5293     _g1h(g1h), _nm(nm) {}
5294 
5295   void do_oop(oop* p)       { do_oop_work(p); }
5296   void do_oop(narrowOop* p) { do_oop_work(p); }
5297 };
5298 
5299 class UnregisterNMethodOopClosure: public OopClosure {
5300   G1CollectedHeap* _g1h;
5301   nmethod* _nm;
5302 
5303   template <class T> void do_oop_work(T* p) {
5304     T heap_oop = oopDesc::load_heap_oop(p);
5305     if (!oopDesc::is_null(heap_oop)) {
5306       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5307       HeapRegion* hr = _g1h->heap_region_containing(obj);
5308       assert(!hr->is_continues_humongous(),
5309              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5310              " starting at " HR_FORMAT,
5311              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5312 
5313       hr->remove_strong_code_root(_nm);
5314     }
5315   }
5316 
5317 public:
5318   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5319     _g1h(g1h), _nm(nm) {}
5320 
5321   void do_oop(oop* p)       { do_oop_work(p); }
5322   void do_oop(narrowOop* p) { do_oop_work(p); }
5323 };
5324 
5325 // Returns true if the reference points to an object that
5326 // can move in an incremental collection.
5327 bool G1CollectedHeap::is_scavengable(oop obj) {
5328   HeapRegion* hr = heap_region_containing(obj);
5329   return !hr->is_pinned();
5330 }
5331 
5332 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5333   guarantee(nm != NULL, "sanity");
5334   RegisterNMethodOopClosure reg_cl(this, nm);
5335   nm->oops_do(&reg_cl);
5336 }
5337 
5338 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5339   guarantee(nm != NULL, "sanity");
5340   UnregisterNMethodOopClosure reg_cl(this, nm);
5341   nm->oops_do(&reg_cl, true);
5342 }
5343 
5344 void G1CollectedHeap::purge_code_root_memory() {
5345   double purge_start = os::elapsedTime();
5346   G1CodeRootSet::purge();
5347   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5348   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5349 }
5350 
5351 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5352   G1CollectedHeap* _g1h;
5353 
5354 public:
5355   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5356     _g1h(g1h) {}
5357 
5358   void do_code_blob(CodeBlob* cb) {
5359     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5360     if (nm == NULL) {
5361       return;
5362     }
5363 
5364     if (ScavengeRootsInCode) {
5365       _g1h->register_nmethod(nm);
5366     }
5367   }
5368 };
5369 
5370 void G1CollectedHeap::rebuild_strong_code_roots() {
5371   RebuildStrongCodeRootClosure blob_cl(this);
5372   CodeCache::blobs_do(&blob_cl);
5373 }