rev 47590 : [mq]: heap8
rev 47591 : [mq]: heap10a

   1 /*
   2  * Copyright (c) 2001, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/metadataOnStackMark.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "classfile/symbolTable.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc/g1/bufferingOopClosure.hpp"
  32 #include "gc/g1/concurrentG1Refine.hpp"
  33 #include "gc/g1/concurrentG1RefineThread.hpp"
  34 #include "gc/g1/concurrentMarkThread.inline.hpp"
  35 #include "gc/g1/g1Allocator.inline.hpp"
  36 #include "gc/g1/g1CollectedHeap.inline.hpp"
  37 #include "gc/g1/g1CollectionSet.hpp"
  38 #include "gc/g1/g1CollectorPolicy.hpp"
  39 #include "gc/g1/g1CollectorState.hpp"
  40 #include "gc/g1/g1EvacStats.inline.hpp"
  41 #include "gc/g1/g1FullGCScope.hpp"
  42 #include "gc/g1/g1GCPhaseTimes.hpp"
  43 #include "gc/g1/g1HeapSizingPolicy.hpp"
  44 #include "gc/g1/g1HeapTransition.hpp"
  45 #include "gc/g1/g1HeapVerifier.hpp"
  46 #include "gc/g1/g1HotCardCache.hpp"
  47 #include "gc/g1/g1OopClosures.inline.hpp"
  48 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  49 #include "gc/g1/g1Policy.hpp"
  50 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  51 #include "gc/g1/g1RemSet.inline.hpp"
  52 #include "gc/g1/g1RootClosures.hpp"
  53 #include "gc/g1/g1RootProcessor.hpp"
  54 #include "gc/g1/g1SerialFullCollector.hpp"
  55 #include "gc/g1/g1StringDedup.hpp"
  56 #include "gc/g1/g1YCTypes.hpp"
  57 #include "gc/g1/heapRegion.inline.hpp"
  58 #include "gc/g1/heapRegionRemSet.hpp"
  59 #include "gc/g1/heapRegionSet.inline.hpp"
  60 #include "gc/g1/vm_operations_g1.hpp"
  61 #include "gc/shared/gcHeapSummary.hpp"
  62 #include "gc/shared/gcId.hpp"
  63 #include "gc/shared/gcLocker.inline.hpp"
  64 #include "gc/shared/gcTimer.hpp"
  65 #include "gc/shared/gcTrace.hpp"
  66 #include "gc/shared/gcTraceTime.inline.hpp"
  67 #include "gc/shared/generationSpec.hpp"
  68 #include "gc/shared/isGCActiveMark.hpp"
  69 #include "gc/shared/preservedMarks.inline.hpp"
  70 #include "gc/shared/suspendibleThreadSet.hpp"
  71 #include "gc/shared/referenceProcessor.inline.hpp"
  72 #include "gc/shared/taskqueue.inline.hpp"
  73 #include "gc/shared/weakProcessor.hpp"
  74 #include "logging/log.hpp"
  75 #include "memory/allocation.hpp"
  76 #include "memory/iterator.hpp"
  77 #include "memory/resourceArea.hpp"
  78 #include "oops/oop.inline.hpp"
  79 #include "prims/resolvedMethodTable.hpp"
  80 #include "runtime/atomic.hpp"
  81 #include "runtime/init.hpp"
  82 #include "runtime/orderAccess.inline.hpp"
  83 #include "runtime/vmThread.hpp"
  84 #include "utilities/align.hpp"
  85 #include "utilities/globalDefinitions.hpp"
  86 #include "utilities/stack.inline.hpp"
  87 
  88 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  89 
  90 // INVARIANTS/NOTES
  91 //
  92 // All allocation activity covered by the G1CollectedHeap interface is
  93 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  94 // and allocate_new_tlab, which are the "entry" points to the
  95 // allocation code from the rest of the JVM.  (Note that this does not
  96 // apply to TLAB allocation, which is not part of this interface: it
  97 // is done by clients of this interface.)
  98 
  99 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 100  private:
 101   size_t _num_dirtied;
 102   G1CollectedHeap* _g1h;
 103   G1SATBCardTableLoggingModRefBS* _g1_bs;
 104 
 105   HeapRegion* region_for_card(jbyte* card_ptr) const {
 106     return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
 107   }
 108 
 109   bool will_become_free(HeapRegion* hr) const {
 110     // A region will be freed by free_collection_set if the region is in the
 111     // collection set and has not had an evacuation failure.
 112     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 113   }
 114 
 115  public:
 116   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
 117     _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
 118 
 119   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 120     HeapRegion* hr = region_for_card(card_ptr);
 121 
 122     // Should only dirty cards in regions that won't be freed.
 123     if (!will_become_free(hr)) {
 124       *card_ptr = CardTableModRefBS::dirty_card_val();
 125       _num_dirtied++;
 126     }
 127 
 128     return true;
 129   }
 130 
 131   size_t num_dirtied()   const { return _num_dirtied; }
 132 };
 133 
 134 
 135 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 136   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 137 }
 138 
 139 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 140   // The from card cache is not the memory that is actually committed. So we cannot
 141   // take advantage of the zero_filled parameter.
 142   reset_from_card_cache(start_idx, num_regions);
 143 }
 144 
 145 // Private methods.
 146 
 147 HeapRegion*
 148 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 149   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 150   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 151     if (!_secondary_free_list.is_empty()) {
 152       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 153                                       "secondary_free_list has %u entries",
 154                                       _secondary_free_list.length());
 155       // It looks as if there are free regions available on the
 156       // secondary_free_list. Let's move them to the free_list and try
 157       // again to allocate from it.
 158       append_secondary_free_list();
 159 
 160       assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
 161              "empty we should have moved at least one entry to the free_list");
 162       HeapRegion* res = _hrm.allocate_free_region(is_old);
 163       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 164                                       "allocated " HR_FORMAT " from secondary_free_list",
 165                                       HR_FORMAT_PARAMS(res));
 166       return res;
 167     }
 168 
 169     // Wait here until we get notified either when (a) there are no
 170     // more free regions coming or (b) some regions have been moved on
 171     // the secondary_free_list.
 172     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 173   }
 174 
 175   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 176                                   "could not allocate from secondary_free_list");
 177   return NULL;
 178 }
 179 
 180 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 181   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 182          "the only time we use this to allocate a humongous region is "
 183          "when we are allocating a single humongous region");
 184 
 185   HeapRegion* res;
 186   if (G1StressConcRegionFreeing) {
 187     if (!_secondary_free_list.is_empty()) {
 188       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 189                                       "forced to look at the secondary_free_list");
 190       res = new_region_try_secondary_free_list(is_old);
 191       if (res != NULL) {
 192         return res;
 193       }
 194     }
 195   }
 196 
 197   res = _hrm.allocate_free_region(is_old);
 198 
 199   if (res == NULL) {
 200     log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 201                                     "res == NULL, trying the secondary_free_list");
 202     res = new_region_try_secondary_free_list(is_old);
 203   }
 204   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 205     // Currently, only attempts to allocate GC alloc regions set
 206     // do_expand to true. So, we should only reach here during a
 207     // safepoint. If this assumption changes we might have to
 208     // reconsider the use of _expand_heap_after_alloc_failure.
 209     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 210 
 211     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 212                               word_size * HeapWordSize);
 213 
 214     if (expand(word_size * HeapWordSize)) {
 215       // Given that expand() succeeded in expanding the heap, and we
 216       // always expand the heap by an amount aligned to the heap
 217       // region size, the free list should in theory not be empty.
 218       // In either case allocate_free_region() will check for NULL.
 219       res = _hrm.allocate_free_region(is_old);
 220     } else {
 221       _expand_heap_after_alloc_failure = false;
 222     }
 223   }
 224   return res;
 225 }
 226 
 227 HeapWord*
 228 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 229                                                            uint num_regions,
 230                                                            size_t word_size,
 231                                                            AllocationContext_t context) {
 232   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 233   assert(is_humongous(word_size), "word_size should be humongous");
 234   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 235 
 236   // Index of last region in the series.
 237   uint last = first + num_regions - 1;
 238 
 239   // We need to initialize the region(s) we just discovered. This is
 240   // a bit tricky given that it can happen concurrently with
 241   // refinement threads refining cards on these regions and
 242   // potentially wanting to refine the BOT as they are scanning
 243   // those cards (this can happen shortly after a cleanup; see CR
 244   // 6991377). So we have to set up the region(s) carefully and in
 245   // a specific order.
 246 
 247   // The word size sum of all the regions we will allocate.
 248   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 249   assert(word_size <= word_size_sum, "sanity");
 250 
 251   // This will be the "starts humongous" region.
 252   HeapRegion* first_hr = region_at(first);
 253   // The header of the new object will be placed at the bottom of
 254   // the first region.
 255   HeapWord* new_obj = first_hr->bottom();
 256   // This will be the new top of the new object.
 257   HeapWord* obj_top = new_obj + word_size;
 258 
 259   // First, we need to zero the header of the space that we will be
 260   // allocating. When we update top further down, some refinement
 261   // threads might try to scan the region. By zeroing the header we
 262   // ensure that any thread that will try to scan the region will
 263   // come across the zero klass word and bail out.
 264   //
 265   // NOTE: It would not have been correct to have used
 266   // CollectedHeap::fill_with_object() and make the space look like
 267   // an int array. The thread that is doing the allocation will
 268   // later update the object header to a potentially different array
 269   // type and, for a very short period of time, the klass and length
 270   // fields will be inconsistent. This could cause a refinement
 271   // thread to calculate the object size incorrectly.
 272   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 273 
 274   // Next, pad out the unused tail of the last region with filler
 275   // objects, for improved usage accounting.
 276   // How many words we use for filler objects.
 277   size_t word_fill_size = word_size_sum - word_size;
 278 
 279   // How many words memory we "waste" which cannot hold a filler object.
 280   size_t words_not_fillable = 0;
 281 
 282   if (word_fill_size >= min_fill_size()) {
 283     fill_with_objects(obj_top, word_fill_size);
 284   } else if (word_fill_size > 0) {
 285     // We have space to fill, but we cannot fit an object there.
 286     words_not_fillable = word_fill_size;
 287     word_fill_size = 0;
 288   }
 289 
 290   // We will set up the first region as "starts humongous". This
 291   // will also update the BOT covering all the regions to reflect
 292   // that there is a single object that starts at the bottom of the
 293   // first region.
 294   first_hr->set_starts_humongous(obj_top, word_fill_size);
 295   first_hr->set_allocation_context(context);
 296   // Then, if there are any, we will set up the "continues
 297   // humongous" regions.
 298   HeapRegion* hr = NULL;
 299   for (uint i = first + 1; i <= last; ++i) {
 300     hr = region_at(i);
 301     hr->set_continues_humongous(first_hr);
 302     hr->set_allocation_context(context);
 303   }
 304 
 305   // Up to this point no concurrent thread would have been able to
 306   // do any scanning on any region in this series. All the top
 307   // fields still point to bottom, so the intersection between
 308   // [bottom,top] and [card_start,card_end] will be empty. Before we
 309   // update the top fields, we'll do a storestore to make sure that
 310   // no thread sees the update to top before the zeroing of the
 311   // object header and the BOT initialization.
 312   OrderAccess::storestore();
 313 
 314   // Now, we will update the top fields of the "continues humongous"
 315   // regions except the last one.
 316   for (uint i = first; i < last; ++i) {
 317     hr = region_at(i);
 318     hr->set_top(hr->end());
 319   }
 320 
 321   hr = region_at(last);
 322   // If we cannot fit a filler object, we must set top to the end
 323   // of the humongous object, otherwise we cannot iterate the heap
 324   // and the BOT will not be complete.
 325   hr->set_top(hr->end() - words_not_fillable);
 326 
 327   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 328          "obj_top should be in last region");
 329 
 330   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 331 
 332   assert(words_not_fillable == 0 ||
 333          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 334          "Miscalculation in humongous allocation");
 335 
 336   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 337 
 338   for (uint i = first; i <= last; ++i) {
 339     hr = region_at(i);
 340     _humongous_set.add(hr);
 341     _hr_printer.alloc(hr);
 342   }
 343 
 344   return new_obj;
 345 }
 346 
 347 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 348   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 349   return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 350 }
 351 
 352 // If could fit into free regions w/o expansion, try.
 353 // Otherwise, if can expand, do so.
 354 // Otherwise, if using ex regions might help, try with ex given back.
 355 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
 356   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 357 
 358   _verifier->verify_region_sets_optional();
 359 
 360   uint first = G1_NO_HRM_INDEX;
 361   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 362 
 363   if (obj_regions == 1) {
 364     // Only one region to allocate, try to use a fast path by directly allocating
 365     // from the free lists. Do not try to expand here, we will potentially do that
 366     // later.
 367     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 368     if (hr != NULL) {
 369       first = hr->hrm_index();
 370     }
 371   } else {
 372     // We can't allocate humongous regions spanning more than one region while
 373     // cleanupComplete() is running, since some of the regions we find to be
 374     // empty might not yet be added to the free list. It is not straightforward
 375     // to know in which list they are on so that we can remove them. We only
 376     // need to do this if we need to allocate more than one region to satisfy the
 377     // current humongous allocation request. If we are only allocating one region
 378     // we use the one-region region allocation code (see above), that already
 379     // potentially waits for regions from the secondary free list.
 380     wait_while_free_regions_coming();
 381     append_secondary_free_list_if_not_empty_with_lock();
 382 
 383     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 384     // are lucky enough to find some.
 385     first = _hrm.find_contiguous_only_empty(obj_regions);
 386     if (first != G1_NO_HRM_INDEX) {
 387       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 388     }
 389   }
 390 
 391   if (first == G1_NO_HRM_INDEX) {
 392     // Policy: We could not find enough regions for the humongous object in the
 393     // free list. Look through the heap to find a mix of free and uncommitted regions.
 394     // If so, try expansion.
 395     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 396     if (first != G1_NO_HRM_INDEX) {
 397       // We found something. Make sure these regions are committed, i.e. expand
 398       // the heap. Alternatively we could do a defragmentation GC.
 399       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 400                                     word_size * HeapWordSize);
 401 
 402       _hrm.expand_at(first, obj_regions, workers());
 403       g1_policy()->record_new_heap_size(num_regions());
 404 
 405 #ifdef ASSERT
 406       for (uint i = first; i < first + obj_regions; ++i) {
 407         HeapRegion* hr = region_at(i);
 408         assert(hr->is_free(), "sanity");
 409         assert(hr->is_empty(), "sanity");
 410         assert(is_on_master_free_list(hr), "sanity");
 411       }
 412 #endif
 413       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 414     } else {
 415       // Policy: Potentially trigger a defragmentation GC.
 416     }
 417   }
 418 
 419   HeapWord* result = NULL;
 420   if (first != G1_NO_HRM_INDEX) {
 421     result = humongous_obj_allocate_initialize_regions(first, obj_regions,
 422                                                        word_size, context);
 423     assert(result != NULL, "it should always return a valid result");
 424 
 425     // A successful humongous object allocation changes the used space
 426     // information of the old generation so we need to recalculate the
 427     // sizes and update the jstat counters here.
 428     g1mm()->update_sizes();
 429   }
 430 
 431   _verifier->verify_region_sets_optional();
 432 
 433   return result;
 434 }
 435 
 436 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 437   assert_heap_not_locked_and_not_at_safepoint();
 438   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 439 
 440   uint dummy_gc_count_before;
 441   uint dummy_gclocker_retry_count = 0;
 442   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 443 }
 444 
 445 HeapWord*
 446 G1CollectedHeap::mem_allocate(size_t word_size,
 447                               bool*  gc_overhead_limit_was_exceeded) {
 448   assert_heap_not_locked_and_not_at_safepoint();
 449 
 450   // Loop until the allocation is satisfied, or unsatisfied after GC.
 451   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 452     uint gc_count_before;
 453 
 454     HeapWord* result = NULL;
 455     if (!is_humongous(word_size)) {
 456       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 457     } else {
 458       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 459     }
 460     if (result != NULL) {
 461       return result;
 462     }
 463 
 464     // Create the garbage collection operation...
 465     VM_G1CollectForAllocation op(gc_count_before, word_size);
 466     op.set_allocation_context(AllocationContext::current());
 467 
 468     // ...and get the VM thread to execute it.
 469     VMThread::execute(&op);
 470 
 471     if (op.prologue_succeeded() && op.pause_succeeded()) {
 472       // If the operation was successful we'll return the result even
 473       // if it is NULL. If the allocation attempt failed immediately
 474       // after a Full GC, it's unlikely we'll be able to allocate now.
 475       HeapWord* result = op.result();
 476       if (result != NULL && !is_humongous(word_size)) {
 477         // Allocations that take place on VM operations do not do any
 478         // card dirtying and we have to do it here. We only have to do
 479         // this for non-humongous allocations, though.
 480         dirty_young_block(result, word_size);
 481       }
 482       return result;
 483     } else {
 484       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 485         return NULL;
 486       }
 487       assert(op.result() == NULL,
 488              "the result should be NULL if the VM op did not succeed");
 489     }
 490 
 491     // Give a warning if we seem to be looping forever.
 492     if ((QueuedAllocationWarningCount > 0) &&
 493         (try_count % QueuedAllocationWarningCount == 0)) {
 494       log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
 495     }
 496   }
 497 
 498   ShouldNotReachHere();
 499   return NULL;
 500 }
 501 
 502 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 503                                                    AllocationContext_t context,
 504                                                    uint* gc_count_before_ret,
 505                                                    uint* gclocker_retry_count_ret) {
 506   // Make sure you read the note in attempt_allocation_humongous().
 507 
 508   assert_heap_not_locked_and_not_at_safepoint();
 509   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 510          "be called for humongous allocation requests");
 511 
 512   // We should only get here after the first-level allocation attempt
 513   // (attempt_allocation()) failed to allocate.
 514 
 515   // We will loop until a) we manage to successfully perform the
 516   // allocation or b) we successfully schedule a collection which
 517   // fails to perform the allocation. b) is the only case when we'll
 518   // return NULL.
 519   HeapWord* result = NULL;
 520   for (int try_count = 1; /* we'll return */; try_count += 1) {
 521     bool should_try_gc;
 522     uint gc_count_before;
 523 
 524     {
 525       MutexLockerEx x(Heap_lock);
 526       result = _allocator->attempt_allocation_locked(word_size, context);
 527       if (result != NULL) {
 528         return result;
 529       }
 530 
 531       if (GCLocker::is_active_and_needs_gc()) {
 532         if (g1_policy()->can_expand_young_list()) {
 533           // No need for an ergo verbose message here,
 534           // can_expand_young_list() does this when it returns true.
 535           result = _allocator->attempt_allocation_force(word_size, context);
 536           if (result != NULL) {
 537             return result;
 538           }
 539         }
 540         should_try_gc = false;
 541       } else {
 542         // The GCLocker may not be active but the GCLocker initiated
 543         // GC may not yet have been performed (GCLocker::needs_gc()
 544         // returns true). In this case we do not try this GC and
 545         // wait until the GCLocker initiated GC is performed, and
 546         // then retry the allocation.
 547         if (GCLocker::needs_gc()) {
 548           should_try_gc = false;
 549         } else {
 550           // Read the GC count while still holding the Heap_lock.
 551           gc_count_before = total_collections();
 552           should_try_gc = true;
 553         }
 554       }
 555     }
 556 
 557     if (should_try_gc) {
 558       bool succeeded;
 559       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 560                                    GCCause::_g1_inc_collection_pause);
 561       if (result != NULL) {
 562         assert(succeeded, "only way to get back a non-NULL result");
 563         return result;
 564       }
 565 
 566       if (succeeded) {
 567         // If we get here we successfully scheduled a collection which
 568         // failed to allocate. No point in trying to allocate
 569         // further. We'll just return NULL.
 570         MutexLockerEx x(Heap_lock);
 571         *gc_count_before_ret = total_collections();
 572         return NULL;
 573       }
 574     } else {
 575       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 576         MutexLockerEx x(Heap_lock);
 577         *gc_count_before_ret = total_collections();
 578         return NULL;
 579       }
 580       // The GCLocker is either active or the GCLocker initiated
 581       // GC has not yet been performed. Stall until it is and
 582       // then retry the allocation.
 583       GCLocker::stall_until_clear();
 584       (*gclocker_retry_count_ret) += 1;
 585     }
 586 
 587     // We can reach here if we were unsuccessful in scheduling a
 588     // collection (because another thread beat us to it) or if we were
 589     // stalled due to the GC locker. In either can we should retry the
 590     // allocation attempt in case another thread successfully
 591     // performed a collection and reclaimed enough space. We do the
 592     // first attempt (without holding the Heap_lock) here and the
 593     // follow-on attempt will be at the start of the next loop
 594     // iteration (after taking the Heap_lock).
 595     result = _allocator->attempt_allocation(word_size, context);
 596     if (result != NULL) {
 597       return result;
 598     }
 599 
 600     // Give a warning if we seem to be looping forever.
 601     if ((QueuedAllocationWarningCount > 0) &&
 602         (try_count % QueuedAllocationWarningCount == 0)) {
 603       log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
 604                       "retries %d times", try_count);
 605     }
 606   }
 607 
 608   ShouldNotReachHere();
 609   return NULL;
 610 }
 611 
 612 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
 613   assert_at_safepoint(true /* should_be_vm_thread */);
 614   if (_archive_allocator == NULL) {
 615     _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
 616   }
 617 }
 618 
 619 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 620   // Allocations in archive regions cannot be of a size that would be considered
 621   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 622   // may be different at archive-restore time.
 623   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 624 }
 625 
 626 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 627   assert_at_safepoint(true /* should_be_vm_thread */);
 628   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 629   if (is_archive_alloc_too_large(word_size)) {
 630     return NULL;
 631   }
 632   return _archive_allocator->archive_mem_allocate(word_size);
 633 }
 634 
 635 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 636                                               size_t end_alignment_in_bytes) {
 637   assert_at_safepoint(true /* should_be_vm_thread */);
 638   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 639 
 640   // Call complete_archive to do the real work, filling in the MemRegion
 641   // array with the archive regions.
 642   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 643   delete _archive_allocator;
 644   _archive_allocator = NULL;
 645 }
 646 
 647 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 648   assert(ranges != NULL, "MemRegion array NULL");
 649   assert(count != 0, "No MemRegions provided");
 650   MemRegion reserved = _hrm.reserved();
 651   for (size_t i = 0; i < count; i++) {
 652     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 653       return false;
 654     }
 655   }
 656   return true;
 657 }
 658 
 659 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
 660                                             size_t count,
 661                                             bool open) {
 662   assert(!is_init_completed(), "Expect to be called at JVM init time");
 663   assert(ranges != NULL, "MemRegion array NULL");
 664   assert(count != 0, "No MemRegions provided");
 665   MutexLockerEx x(Heap_lock);
 666 
 667   MemRegion reserved = _hrm.reserved();
 668   HeapWord* prev_last_addr = NULL;
 669   HeapRegion* prev_last_region = NULL;
 670 
 671   // Temporarily disable pretouching of heap pages. This interface is used
 672   // when mmap'ing archived heap data in, so pre-touching is wasted.
 673   FlagSetting fs(AlwaysPreTouch, false);
 674 
 675   // Enable archive object checking used by G1MarkSweep. We have to let it know
 676   // about each archive range, so that objects in those ranges aren't marked.
 677   G1ArchiveAllocator::enable_archive_object_check();
 678 
 679   // For each specified MemRegion range, allocate the corresponding G1
 680   // regions and mark them as archive regions. We expect the ranges
 681   // in ascending starting address order, without overlap.
 682   for (size_t i = 0; i < count; i++) {
 683     MemRegion curr_range = ranges[i];
 684     HeapWord* start_address = curr_range.start();
 685     size_t word_size = curr_range.word_size();
 686     HeapWord* last_address = curr_range.last();
 687     size_t commits = 0;
 688 
 689     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 690               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 691               p2i(start_address), p2i(last_address));
 692     guarantee(start_address > prev_last_addr,
 693               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 694               p2i(start_address), p2i(prev_last_addr));
 695     prev_last_addr = last_address;
 696 
 697     // Check for ranges that start in the same G1 region in which the previous
 698     // range ended, and adjust the start address so we don't try to allocate
 699     // the same region again. If the current range is entirely within that
 700     // region, skip it, just adjusting the recorded top.
 701     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 702     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 703       start_address = start_region->end();
 704       if (start_address > last_address) {
 705         increase_used(word_size * HeapWordSize);
 706         start_region->set_top(last_address + 1);
 707         continue;
 708       }
 709       start_region->set_top(start_address);
 710       curr_range = MemRegion(start_address, last_address + 1);
 711       start_region = _hrm.addr_to_region(start_address);
 712     }
 713 
 714     // Perform the actual region allocation, exiting if it fails.
 715     // Then note how much new space we have allocated.
 716     if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
 717       return false;
 718     }
 719     increase_used(word_size * HeapWordSize);
 720     if (commits != 0) {
 721       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 722                                 HeapRegion::GrainWords * HeapWordSize * commits);
 723 
 724     }
 725 
 726     // Mark each G1 region touched by the range as archive, add it to
 727     // the old set, and set the allocation context and top.
 728     HeapRegion* curr_region = _hrm.addr_to_region(start_address);
 729     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 730     prev_last_region = last_region;
 731 
 732     while (curr_region != NULL) {
 733       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 734              "Region already in use (index %u)", curr_region->hrm_index());
 735       curr_region->set_allocation_context(AllocationContext::system());
 736       if (open) {
 737         curr_region->set_open_archive();
 738       } else {
 739         curr_region->set_closed_archive();
 740       }
 741       _hr_printer.alloc(curr_region);
 742       _old_set.add(curr_region);
 743       HeapWord* top;
 744       HeapRegion* next_region;
 745       if (curr_region != last_region) {
 746         top = curr_region->end();
 747         next_region = _hrm.next_region_in_heap(curr_region);
 748       } else {
 749         top = last_address + 1;
 750         next_region = NULL;
 751       }
 752       curr_region->set_top(top);
 753       curr_region->set_first_dead(top);
 754       curr_region->set_end_of_live(top);
 755       curr_region = next_region;
 756     }
 757 
 758     // Notify mark-sweep of the archive
 759     G1ArchiveAllocator::set_range_archive(curr_range, open);
 760   }
 761   return true;
 762 }
 763 
 764 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 765   assert(!is_init_completed(), "Expect to be called at JVM init time");
 766   assert(ranges != NULL, "MemRegion array NULL");
 767   assert(count != 0, "No MemRegions provided");
 768   MemRegion reserved = _hrm.reserved();
 769   HeapWord *prev_last_addr = NULL;
 770   HeapRegion* prev_last_region = NULL;
 771 
 772   // For each MemRegion, create filler objects, if needed, in the G1 regions
 773   // that contain the address range. The address range actually within the
 774   // MemRegion will not be modified. That is assumed to have been initialized
 775   // elsewhere, probably via an mmap of archived heap data.
 776   MutexLockerEx x(Heap_lock);
 777   for (size_t i = 0; i < count; i++) {
 778     HeapWord* start_address = ranges[i].start();
 779     HeapWord* last_address = ranges[i].last();
 780 
 781     assert(reserved.contains(start_address) && reserved.contains(last_address),
 782            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 783            p2i(start_address), p2i(last_address));
 784     assert(start_address > prev_last_addr,
 785            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 786            p2i(start_address), p2i(prev_last_addr));
 787 
 788     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 789     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 790     HeapWord* bottom_address = start_region->bottom();
 791 
 792     // Check for a range beginning in the same region in which the
 793     // previous one ended.
 794     if (start_region == prev_last_region) {
 795       bottom_address = prev_last_addr + 1;
 796     }
 797 
 798     // Verify that the regions were all marked as archive regions by
 799     // alloc_archive_regions.
 800     HeapRegion* curr_region = start_region;
 801     while (curr_region != NULL) {
 802       guarantee(curr_region->is_archive(),
 803                 "Expected archive region at index %u", curr_region->hrm_index());
 804       if (curr_region != last_region) {
 805         curr_region = _hrm.next_region_in_heap(curr_region);
 806       } else {
 807         curr_region = NULL;
 808       }
 809     }
 810 
 811     prev_last_addr = last_address;
 812     prev_last_region = last_region;
 813 
 814     // Fill the memory below the allocated range with dummy object(s),
 815     // if the region bottom does not match the range start, or if the previous
 816     // range ended within the same G1 region, and there is a gap.
 817     if (start_address != bottom_address) {
 818       size_t fill_size = pointer_delta(start_address, bottom_address);
 819       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 820       increase_used(fill_size * HeapWordSize);
 821     }
 822   }
 823 }
 824 
 825 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
 826                                                      uint* gc_count_before_ret,
 827                                                      uint* gclocker_retry_count_ret) {
 828   assert_heap_not_locked_and_not_at_safepoint();
 829   assert(!is_humongous(word_size), "attempt_allocation() should not "
 830          "be called for humongous allocation requests");
 831 
 832   AllocationContext_t context = AllocationContext::current();
 833   HeapWord* result = _allocator->attempt_allocation(word_size, context);
 834 
 835   if (result == NULL) {
 836     result = attempt_allocation_slow(word_size,
 837                                      context,
 838                                      gc_count_before_ret,
 839                                      gclocker_retry_count_ret);
 840   }
 841   assert_heap_not_locked();
 842   if (result != NULL) {
 843     dirty_young_block(result, word_size);
 844   }
 845   return result;
 846 }
 847 
 848 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
 849   assert(!is_init_completed(), "Expect to be called at JVM init time");
 850   assert(ranges != NULL, "MemRegion array NULL");
 851   assert(count != 0, "No MemRegions provided");
 852   MemRegion reserved = _hrm.reserved();
 853   HeapWord* prev_last_addr = NULL;
 854   HeapRegion* prev_last_region = NULL;
 855   size_t size_used = 0;
 856   size_t uncommitted_regions = 0;
 857 
 858   // For each Memregion, free the G1 regions that constitute it, and
 859   // notify mark-sweep that the range is no longer to be considered 'archive.'
 860   MutexLockerEx x(Heap_lock);
 861   for (size_t i = 0; i < count; i++) {
 862     HeapWord* start_address = ranges[i].start();
 863     HeapWord* last_address = ranges[i].last();
 864 
 865     assert(reserved.contains(start_address) && reserved.contains(last_address),
 866            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 867            p2i(start_address), p2i(last_address));
 868     assert(start_address > prev_last_addr,
 869            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 870            p2i(start_address), p2i(prev_last_addr));
 871     size_used += ranges[i].byte_size();
 872     prev_last_addr = last_address;
 873 
 874     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 875     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 876 
 877     // Check for ranges that start in the same G1 region in which the previous
 878     // range ended, and adjust the start address so we don't try to free
 879     // the same region again. If the current range is entirely within that
 880     // region, skip it.
 881     if (start_region == prev_last_region) {
 882       start_address = start_region->end();
 883       if (start_address > last_address) {
 884         continue;
 885       }
 886       start_region = _hrm.addr_to_region(start_address);
 887     }
 888     prev_last_region = last_region;
 889 
 890     // After verifying that each region was marked as an archive region by
 891     // alloc_archive_regions, set it free and empty and uncommit it.
 892     HeapRegion* curr_region = start_region;
 893     while (curr_region != NULL) {
 894       guarantee(curr_region->is_archive(),
 895                 "Expected archive region at index %u", curr_region->hrm_index());
 896       uint curr_index = curr_region->hrm_index();
 897       _old_set.remove(curr_region);
 898       curr_region->set_free();
 899       curr_region->set_top(curr_region->bottom());
 900       if (curr_region != last_region) {
 901         curr_region = _hrm.next_region_in_heap(curr_region);
 902       } else {
 903         curr_region = NULL;
 904       }
 905       _hrm.shrink_at(curr_index, 1);
 906       uncommitted_regions++;
 907     }
 908 
 909     // Notify mark-sweep that this is no longer an archive range.
 910     G1ArchiveAllocator::set_range_archive(ranges[i], false);
 911   }
 912 
 913   if (uncommitted_regions != 0) {
 914     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 915                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 916   }
 917   decrease_used(size_used);
 918 }
 919 
 920 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
 921                                                         uint* gc_count_before_ret,
 922                                                         uint* gclocker_retry_count_ret) {
 923   // The structure of this method has a lot of similarities to
 924   // attempt_allocation_slow(). The reason these two were not merged
 925   // into a single one is that such a method would require several "if
 926   // allocation is not humongous do this, otherwise do that"
 927   // conditional paths which would obscure its flow. In fact, an early
 928   // version of this code did use a unified method which was harder to
 929   // follow and, as a result, it had subtle bugs that were hard to
 930   // track down. So keeping these two methods separate allows each to
 931   // be more readable. It will be good to keep these two in sync as
 932   // much as possible.
 933 
 934   assert_heap_not_locked_and_not_at_safepoint();
 935   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 936          "should only be called for humongous allocations");
 937 
 938   // Humongous objects can exhaust the heap quickly, so we should check if we
 939   // need to start a marking cycle at each humongous object allocation. We do
 940   // the check before we do the actual allocation. The reason for doing it
 941   // before the allocation is that we avoid having to keep track of the newly
 942   // allocated memory while we do a GC.
 943   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
 944                                            word_size)) {
 945     collect(GCCause::_g1_humongous_allocation);
 946   }
 947 
 948   // We will loop until a) we manage to successfully perform the
 949   // allocation or b) we successfully schedule a collection which
 950   // fails to perform the allocation. b) is the only case when we'll
 951   // return NULL.
 952   HeapWord* result = NULL;
 953   for (int try_count = 1; /* we'll return */; try_count += 1) {
 954     bool should_try_gc;
 955     uint gc_count_before;
 956 
 957     {
 958       MutexLockerEx x(Heap_lock);
 959 
 960       // Given that humongous objects are not allocated in young
 961       // regions, we'll first try to do the allocation without doing a
 962       // collection hoping that there's enough space in the heap.
 963       result = humongous_obj_allocate(word_size, AllocationContext::current());
 964       if (result != NULL) {
 965         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 966         g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 967         return result;
 968       }
 969 
 970       if (GCLocker::is_active_and_needs_gc()) {
 971         should_try_gc = false;
 972       } else {
 973          // The GCLocker may not be active but the GCLocker initiated
 974         // GC may not yet have been performed (GCLocker::needs_gc()
 975         // returns true). In this case we do not try this GC and
 976         // wait until the GCLocker initiated GC is performed, and
 977         // then retry the allocation.
 978         if (GCLocker::needs_gc()) {
 979           should_try_gc = false;
 980         } else {
 981           // Read the GC count while still holding the Heap_lock.
 982           gc_count_before = total_collections();
 983           should_try_gc = true;
 984         }
 985       }
 986     }
 987 
 988     if (should_try_gc) {
 989       // If we failed to allocate the humongous object, we should try to
 990       // do a collection pause (if we're allowed) in case it reclaims
 991       // enough space for the allocation to succeed after the pause.
 992 
 993       bool succeeded;
 994       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 995                                    GCCause::_g1_humongous_allocation);
 996       if (result != NULL) {
 997         assert(succeeded, "only way to get back a non-NULL result");
 998         return result;
 999       }
1000 
1001       if (succeeded) {
1002         // If we get here we successfully scheduled a collection which
1003         // failed to allocate. No point in trying to allocate
1004         // further. We'll just return NULL.
1005         MutexLockerEx x(Heap_lock);
1006         *gc_count_before_ret = total_collections();
1007         return NULL;
1008       }
1009     } else {
1010       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1011         MutexLockerEx x(Heap_lock);
1012         *gc_count_before_ret = total_collections();
1013         return NULL;
1014       }
1015       // The GCLocker is either active or the GCLocker initiated
1016       // GC has not yet been performed. Stall until it is and
1017       // then retry the allocation.
1018       GCLocker::stall_until_clear();
1019       (*gclocker_retry_count_ret) += 1;
1020     }
1021 
1022     // We can reach here if we were unsuccessful in scheduling a
1023     // collection (because another thread beat us to it) or if we were
1024     // stalled due to the GC locker. In either can we should retry the
1025     // allocation attempt in case another thread successfully
1026     // performed a collection and reclaimed enough space.  Give a
1027     // warning if we seem to be looping forever.
1028 
1029     if ((QueuedAllocationWarningCount > 0) &&
1030         (try_count % QueuedAllocationWarningCount == 0)) {
1031       log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
1032                       "retries %d times", try_count);
1033     }
1034   }
1035 
1036   ShouldNotReachHere();
1037   return NULL;
1038 }
1039 
1040 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1041                                                            AllocationContext_t context,
1042                                                            bool expect_null_mutator_alloc_region) {
1043   assert_at_safepoint(true /* should_be_vm_thread */);
1044   assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1045          "the current alloc region was unexpectedly found to be non-NULL");
1046 
1047   if (!is_humongous(word_size)) {
1048     return _allocator->attempt_allocation_locked(word_size, context);
1049   } else {
1050     HeapWord* result = humongous_obj_allocate(word_size, context);
1051     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1052       collector_state()->set_initiate_conc_mark_if_possible(true);
1053     }
1054     return result;
1055   }
1056 
1057   ShouldNotReachHere();
1058 }
1059 
1060 class PostCompactionPrinterClosure: public HeapRegionClosure {
1061 private:
1062   G1HRPrinter* _hr_printer;
1063 public:
1064   bool doHeapRegion(HeapRegion* hr) {
1065     assert(!hr->is_young(), "not expecting to find young regions");
1066     _hr_printer->post_compaction(hr);
1067     return false;
1068   }
1069 
1070   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1071     : _hr_printer(hr_printer) { }
1072 };
1073 
1074 void G1CollectedHeap::print_hrm_post_compaction() {
1075   if (_hr_printer.is_active()) {
1076     PostCompactionPrinterClosure cl(hr_printer());
1077     heap_region_iterate(&cl);
1078   }
1079 
1080 }
1081 
1082 void G1CollectedHeap::abort_concurrent_cycle() {
1083   // Note: When we have a more flexible GC logging framework that
1084   // allows us to add optional attributes to a GC log record we
1085   // could consider timing and reporting how long we wait in the
1086   // following two methods.
1087   wait_while_free_regions_coming();
1088   // If we start the compaction before the CM threads finish
1089   // scanning the root regions we might trip them over as we'll
1090   // be moving objects / updating references. So let's wait until
1091   // they are done. By telling them to abort, they should complete
1092   // early.
1093   _cm->root_regions()->abort();
1094   _cm->root_regions()->wait_until_scan_finished();
1095   append_secondary_free_list_if_not_empty_with_lock();
1096 
1097   // Disable discovery and empty the discovered lists
1098   // for the CM ref processor.
1099   ref_processor_cm()->disable_discovery();
1100   ref_processor_cm()->abandon_partial_discovery();
1101   ref_processor_cm()->verify_no_references_recorded();
1102 
1103   // Abandon current iterations of concurrent marking and concurrent
1104   // refinement, if any are in progress.
1105   concurrent_mark()->abort();
1106 }
1107 
1108 void G1CollectedHeap::prepare_heap_for_full_collection() {
1109   // Make sure we'll choose a new allocation region afterwards.
1110   _allocator->release_mutator_alloc_region();
1111   _allocator->abandon_gc_alloc_regions();
1112   g1_rem_set()->cleanupHRRS();
1113 
1114   // We may have added regions to the current incremental collection
1115   // set between the last GC or pause and now. We need to clear the
1116   // incremental collection set and then start rebuilding it afresh
1117   // after this full GC.
1118   abandon_collection_set(collection_set());
1119 
1120   tear_down_region_sets(false /* free_list_only */);
1121   collector_state()->set_gcs_are_young(true);
1122 }
1123 
1124 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1125   assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1126   assert(used() == recalculate_used(), "Should be equal");
1127   _verifier->verify_region_sets_optional();
1128   _verifier->verify_before_gc();
1129   _verifier->check_bitmaps("Full GC Start");
1130 }
1131 
1132 void G1CollectedHeap::prepare_heap_for_mutators() {
1133   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1134   ClassLoaderDataGraph::purge();
1135   MetaspaceAux::verify_metrics();
1136 
1137   // Prepare heap for normal collections.
1138   assert(num_free_regions() == 0, "we should not have added any free regions");
1139   rebuild_region_sets(false /* free_list_only */);
1140   abort_refinement();
1141   resize_if_necessary_after_full_collection();
1142 
1143   // Rebuild the strong code root lists for each region
1144   rebuild_strong_code_roots();
1145 
1146   // Start a new incremental collection set for the next pause
1147   start_new_collection_set();
1148 
1149   _allocator->init_mutator_alloc_region();
1150 
1151   // Post collection state updates.
1152   MetaspaceGC::compute_new_size();
1153 }
1154 
1155 void G1CollectedHeap::abort_refinement() {
1156   if (_hot_card_cache->use_cache()) {
1157     _hot_card_cache->reset_card_counts();
1158     _hot_card_cache->reset_hot_cache();
1159   }
1160 
1161   // Discard all remembered set updates.
1162   JavaThread::dirty_card_queue_set().abandon_logs();
1163   assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1164 }
1165 
1166 void G1CollectedHeap::verify_after_full_collection() {
1167   check_gc_time_stamps();
1168   _hrm.verify_optional();
1169   _verifier->verify_region_sets_optional();
1170   _verifier->verify_after_gc();
1171   // Clear the previous marking bitmap, if needed for bitmap verification.
1172   // Note we cannot do this when we clear the next marking bitmap in
1173   // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1174   // objects marked during a full GC against the previous bitmap.
1175   // But we need to clear it before calling check_bitmaps below since
1176   // the full GC has compacted objects and updated TAMS but not updated
1177   // the prev bitmap.
1178   if (G1VerifyBitmaps) {
1179     GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1180     _cm->clear_prev_bitmap(workers());
1181   }
1182   _verifier->check_bitmaps("Full GC End");
1183 
1184   // At this point there should be no regions in the
1185   // entire heap tagged as young.
1186   assert(check_young_list_empty(), "young list should be empty at this point");
1187 
1188   // Note: since we've just done a full GC, concurrent
1189   // marking is no longer active. Therefore we need not
1190   // re-enable reference discovery for the CM ref processor.
1191   // That will be done at the start of the next marking cycle.
1192   // We also know that the STW processor should no longer
1193   // discover any new references.
1194   assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1195   assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1196   ref_processor_stw()->verify_no_references_recorded();
1197   ref_processor_cm()->verify_no_references_recorded();
1198 }
1199 
1200 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1201   print_hrm_post_compaction();
1202   heap_transition->print();
1203   print_heap_after_gc();
1204   print_heap_regions();
1205 #ifdef TRACESPINNING
1206   ParallelTaskTerminator::print_termination_counts();
1207 #endif
1208 }
1209 
1210 void G1CollectedHeap::do_full_collection_inner(G1FullGCScope* scope) {
1211   GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1212   g1_policy()->record_full_collection_start();
1213 
1214   print_heap_before_gc();
1215   print_heap_regions();
1216 
1217   abort_concurrent_cycle();
1218   verify_before_full_collection(scope->is_explicit_gc());
1219 
1220   gc_prologue(true);
1221   prepare_heap_for_full_collection();
1222 
1223   G1SerialFullCollector serial(scope, ref_processor_stw());
1224   serial.prepare_collection();
1225   serial.collect();
1226   serial.complete_collection();
1227 
1228   prepare_heap_for_mutators();
1229 
1230   g1_policy()->record_full_collection_end();
1231   gc_epilogue(true);
1232 
1233   // Post collection verification.
1234   verify_after_full_collection();
1235 
1236   // Post collection logging.
1237   // We should do this after we potentially resize the heap so
1238   // that all the COMMIT / UNCOMMIT events are generated before
1239   // the compaction events.
1240   print_heap_after_full_collection(scope->heap_transition());
1241 }
1242 
1243 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1244                                          bool clear_all_soft_refs) {
1245   assert_at_safepoint(true /* should_be_vm_thread */);
1246 
1247   if (GCLocker::check_active_before_gc()) {
1248     // Full GC was not completed.
1249     return false;
1250   }
1251 
1252   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1253       collector_policy()->should_clear_all_soft_refs();
1254 
1255   G1FullGCScope scope(explicit_gc, do_clear_all_soft_refs);
1256   do_full_collection_inner(&scope);
1257 
1258   // Full collection was successfully completed.
1259   return true;
1260 }
1261 
1262 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1263   // Currently, there is no facility in the do_full_collection(bool) API to notify
1264   // the caller that the collection did not succeed (e.g., because it was locked
1265   // out by the GC locker). So, right now, we'll ignore the return value.
1266   bool dummy = do_full_collection(true,                /* explicit_gc */
1267                                   clear_all_soft_refs);
1268 }
1269 
1270 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1271   // Include bytes that will be pre-allocated to support collections, as "used".
1272   const size_t used_after_gc = used();
1273   const size_t capacity_after_gc = capacity();
1274   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1275 
1276   // This is enforced in arguments.cpp.
1277   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1278          "otherwise the code below doesn't make sense");
1279 
1280   // We don't have floating point command-line arguments
1281   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1282   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1283   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1284   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1285 
1286   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1287   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1288 
1289   // We have to be careful here as these two calculations can overflow
1290   // 32-bit size_t's.
1291   double used_after_gc_d = (double) used_after_gc;
1292   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1293   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1294 
1295   // Let's make sure that they are both under the max heap size, which
1296   // by default will make them fit into a size_t.
1297   double desired_capacity_upper_bound = (double) max_heap_size;
1298   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1299                                     desired_capacity_upper_bound);
1300   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1301                                     desired_capacity_upper_bound);
1302 
1303   // We can now safely turn them into size_t's.
1304   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1305   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1306 
1307   // This assert only makes sense here, before we adjust them
1308   // with respect to the min and max heap size.
1309   assert(minimum_desired_capacity <= maximum_desired_capacity,
1310          "minimum_desired_capacity = " SIZE_FORMAT ", "
1311          "maximum_desired_capacity = " SIZE_FORMAT,
1312          minimum_desired_capacity, maximum_desired_capacity);
1313 
1314   // Should not be greater than the heap max size. No need to adjust
1315   // it with respect to the heap min size as it's a lower bound (i.e.,
1316   // we'll try to make the capacity larger than it, not smaller).
1317   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1318   // Should not be less than the heap min size. No need to adjust it
1319   // with respect to the heap max size as it's an upper bound (i.e.,
1320   // we'll try to make the capacity smaller than it, not greater).
1321   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1322 
1323   if (capacity_after_gc < minimum_desired_capacity) {
1324     // Don't expand unless it's significant
1325     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1326 
1327     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1328                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1329                               capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1330 
1331     expand(expand_bytes, _workers);
1332 
1333     // No expansion, now see if we want to shrink
1334   } else if (capacity_after_gc > maximum_desired_capacity) {
1335     // Capacity too large, compute shrinking size
1336     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1337 
1338     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1339                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1340                               capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1341 
1342     shrink(shrink_bytes);
1343   }
1344 }
1345 
1346 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1347                                                             AllocationContext_t context,
1348                                                             bool do_gc,
1349                                                             bool clear_all_soft_refs,
1350                                                             bool expect_null_mutator_alloc_region,
1351                                                             bool* gc_succeeded) {
1352   *gc_succeeded = true;
1353   // Let's attempt the allocation first.
1354   HeapWord* result =
1355     attempt_allocation_at_safepoint(word_size,
1356                                     context,
1357                                     expect_null_mutator_alloc_region);
1358   if (result != NULL) {
1359     assert(*gc_succeeded, "sanity");
1360     return result;
1361   }
1362 
1363   // In a G1 heap, we're supposed to keep allocation from failing by
1364   // incremental pauses.  Therefore, at least for now, we'll favor
1365   // expansion over collection.  (This might change in the future if we can
1366   // do something smarter than full collection to satisfy a failed alloc.)
1367   result = expand_and_allocate(word_size, context);
1368   if (result != NULL) {
1369     assert(*gc_succeeded, "sanity");
1370     return result;
1371   }
1372 
1373   if (do_gc) {
1374     // Expansion didn't work, we'll try to do a Full GC.
1375     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1376                                        clear_all_soft_refs);
1377   }
1378 
1379   return NULL;
1380 }
1381 
1382 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1383                                                      AllocationContext_t context,
1384                                                      bool* succeeded) {
1385   assert_at_safepoint(true /* should_be_vm_thread */);
1386 
1387   // Attempts to allocate followed by Full GC.
1388   HeapWord* result =
1389     satisfy_failed_allocation_helper(word_size,
1390                                      context,
1391                                      true,  /* do_gc */
1392                                      false, /* clear_all_soft_refs */
1393                                      false, /* expect_null_mutator_alloc_region */
1394                                      succeeded);
1395 
1396   if (result != NULL || !*succeeded) {
1397     return result;
1398   }
1399 
1400   // Attempts to allocate followed by Full GC that will collect all soft references.
1401   result = satisfy_failed_allocation_helper(word_size,
1402                                             context,
1403                                             true, /* do_gc */
1404                                             true, /* clear_all_soft_refs */
1405                                             true, /* expect_null_mutator_alloc_region */
1406                                             succeeded);
1407 
1408   if (result != NULL || !*succeeded) {
1409     return result;
1410   }
1411 
1412   // Attempts to allocate, no GC
1413   result = satisfy_failed_allocation_helper(word_size,
1414                                             context,
1415                                             false, /* do_gc */
1416                                             false, /* clear_all_soft_refs */
1417                                             true,  /* expect_null_mutator_alloc_region */
1418                                             succeeded);
1419 
1420   if (result != NULL) {
1421     assert(*succeeded, "sanity");
1422     return result;
1423   }
1424 
1425   assert(!collector_policy()->should_clear_all_soft_refs(),
1426          "Flag should have been handled and cleared prior to this point");
1427 
1428   // What else?  We might try synchronous finalization later.  If the total
1429   // space available is large enough for the allocation, then a more
1430   // complete compaction phase than we've tried so far might be
1431   // appropriate.
1432   assert(*succeeded, "sanity");
1433   return NULL;
1434 }
1435 
1436 // Attempting to expand the heap sufficiently
1437 // to support an allocation of the given "word_size".  If
1438 // successful, perform the allocation and return the address of the
1439 // allocated block, or else "NULL".
1440 
1441 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1442   assert_at_safepoint(true /* should_be_vm_thread */);
1443 
1444   _verifier->verify_region_sets_optional();
1445 
1446   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1447   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1448                             word_size * HeapWordSize);
1449 
1450 
1451   if (expand(expand_bytes, _workers)) {
1452     _hrm.verify_optional();
1453     _verifier->verify_region_sets_optional();
1454     return attempt_allocation_at_safepoint(word_size,
1455                                            context,
1456                                            false /* expect_null_mutator_alloc_region */);
1457   }
1458   return NULL;
1459 }
1460 
1461 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1462   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1463   aligned_expand_bytes = align_up(aligned_expand_bytes,
1464                                        HeapRegion::GrainBytes);
1465 
1466   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1467                             expand_bytes, aligned_expand_bytes);
1468 
1469   if (is_maximal_no_gc()) {
1470     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1471     return false;
1472   }
1473 
1474   double expand_heap_start_time_sec = os::elapsedTime();
1475   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1476   assert(regions_to_expand > 0, "Must expand by at least one region");
1477 
1478   uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1479   if (expand_time_ms != NULL) {
1480     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1481   }
1482 
1483   if (expanded_by > 0) {
1484     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1485     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1486     g1_policy()->record_new_heap_size(num_regions());
1487   } else {
1488     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1489 
1490     // The expansion of the virtual storage space was unsuccessful.
1491     // Let's see if it was because we ran out of swap.
1492     if (G1ExitOnExpansionFailure &&
1493         _hrm.available() >= regions_to_expand) {
1494       // We had head room...
1495       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1496     }
1497   }
1498   return regions_to_expand > 0;
1499 }
1500 
1501 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1502   size_t aligned_shrink_bytes =
1503     ReservedSpace::page_align_size_down(shrink_bytes);
1504   aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1505                                          HeapRegion::GrainBytes);
1506   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1507 
1508   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1509   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1510 
1511 
1512   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",
1513                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1514   if (num_regions_removed > 0) {
1515     g1_policy()->record_new_heap_size(num_regions());
1516   } else {
1517     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1518   }
1519 }
1520 
1521 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1522   _verifier->verify_region_sets_optional();
1523 
1524   // We should only reach here at the end of a Full GC which means we
1525   // should not not be holding to any GC alloc regions. The method
1526   // below will make sure of that and do any remaining clean up.
1527   _allocator->abandon_gc_alloc_regions();
1528 
1529   // Instead of tearing down / rebuilding the free lists here, we
1530   // could instead use the remove_all_pending() method on free_list to
1531   // remove only the ones that we need to remove.
1532   tear_down_region_sets(true /* free_list_only */);
1533   shrink_helper(shrink_bytes);
1534   rebuild_region_sets(true /* free_list_only */);
1535 
1536   _hrm.verify_optional();
1537   _verifier->verify_region_sets_optional();
1538 }
1539 
1540 // Public methods.
1541 
1542 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1543   CollectedHeap(),
1544   _collector_policy(collector_policy),
1545   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1546   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1547   _g1_policy(create_g1_policy(_gc_timer_stw)),
1548   _collection_set(this, _g1_policy),
1549   _dirty_card_queue_set(false),
1550   _is_alive_closure_cm(this),
1551   _is_alive_closure_stw(this),
1552   _ref_processor_cm(NULL),
1553   _ref_processor_stw(NULL),
1554   _bot(NULL),
1555   _hot_card_cache(NULL),
1556   _g1_rem_set(NULL),
1557   _cg1r(NULL),
1558   _g1mm(NULL),
1559   _preserved_marks_set(true /* in_c_heap */),
1560   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1561   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1562   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1563   _humongous_reclaim_candidates(),
1564   _has_humongous_reclaim_candidates(false),
1565   _archive_allocator(NULL),
1566   _free_regions_coming(false),
1567   _gc_time_stamp(0),
1568   _summary_bytes_used(0),
1569   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1570   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1571   _expand_heap_after_alloc_failure(true),
1572   _old_marking_cycles_started(0),
1573   _old_marking_cycles_completed(0),
1574   _in_cset_fast_test() {
1575 
1576   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1577                           /* are_GC_task_threads */true,
1578                           /* are_ConcurrentGC_threads */false);
1579   _workers->initialize_workers();
1580   _verifier = new G1HeapVerifier(this);
1581 
1582   _allocator = G1Allocator::create_allocator(this);
1583 
1584   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1585 
1586   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1587 
1588   // Override the default _filler_array_max_size so that no humongous filler
1589   // objects are created.
1590   _filler_array_max_size = _humongous_object_threshold_in_words;
1591 
1592   uint n_queues = ParallelGCThreads;
1593   _task_queues = new RefToScanQueueSet(n_queues);
1594 
1595   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1596 
1597   for (uint i = 0; i < n_queues; i++) {
1598     RefToScanQueue* q = new RefToScanQueue();
1599     q->initialize();
1600     _task_queues->register_queue(i, q);
1601     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1602   }
1603 
1604   // Initialize the G1EvacuationFailureALot counters and flags.
1605   NOT_PRODUCT(reset_evacuation_should_fail();)
1606 
1607   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1608 }
1609 
1610 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1611                                                                  size_t size,
1612                                                                  size_t translation_factor) {
1613   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1614   // Allocate a new reserved space, preferring to use large pages.
1615   ReservedSpace rs(size, preferred_page_size);
1616   G1RegionToSpaceMapper* result  =
1617     G1RegionToSpaceMapper::create_mapper(rs,
1618                                          size,
1619                                          rs.alignment(),
1620                                          HeapRegion::GrainBytes,
1621                                          translation_factor,
1622                                          mtGC);
1623 
1624   os::trace_page_sizes_for_requested_size(description,
1625                                           size,
1626                                           preferred_page_size,
1627                                           rs.alignment(),
1628                                           rs.base(),
1629                                           rs.size());
1630 
1631   return result;
1632 }
1633 
1634 jint G1CollectedHeap::initialize_concurrent_refinement() {
1635   jint ecode = JNI_OK;
1636   _cg1r = ConcurrentG1Refine::create(&ecode);
1637   return ecode;
1638 }
1639 
1640 jint G1CollectedHeap::initialize() {
1641   CollectedHeap::pre_initialize();
1642   os::enable_vtime();
1643 
1644   // Necessary to satisfy locking discipline assertions.
1645 
1646   MutexLocker x(Heap_lock);
1647 
1648   // While there are no constraints in the GC code that HeapWordSize
1649   // be any particular value, there are multiple other areas in the
1650   // system which believe this to be true (e.g. oop->object_size in some
1651   // cases incorrectly returns the size in wordSize units rather than
1652   // HeapWordSize).
1653   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1654 
1655   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1656   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1657   size_t heap_alignment = collector_policy()->heap_alignment();
1658 
1659   // Ensure that the sizes are properly aligned.
1660   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1661   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1662   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1663 
1664   // Reserve the maximum.
1665 
1666   // When compressed oops are enabled, the preferred heap base
1667   // is calculated by subtracting the requested size from the
1668   // 32Gb boundary and using the result as the base address for
1669   // heap reservation. If the requested size is not aligned to
1670   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1671   // into the ReservedHeapSpace constructor) then the actual
1672   // base of the reserved heap may end up differing from the
1673   // address that was requested (i.e. the preferred heap base).
1674   // If this happens then we could end up using a non-optimal
1675   // compressed oops mode.
1676 
1677   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1678                                                  heap_alignment);
1679 
1680   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1681 
1682   // Create the barrier set for the entire reserved region.
1683   G1SATBCardTableLoggingModRefBS* bs
1684     = new G1SATBCardTableLoggingModRefBS(reserved_region());
1685   bs->initialize();
1686   assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1687   set_barrier_set(bs);
1688 
1689   // Create the hot card cache.
1690   _hot_card_cache = new G1HotCardCache(this);
1691 
1692   // Carve out the G1 part of the heap.
1693   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1694   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1695   G1RegionToSpaceMapper* heap_storage =
1696     G1RegionToSpaceMapper::create_mapper(g1_rs,
1697                                          g1_rs.size(),
1698                                          page_size,
1699                                          HeapRegion::GrainBytes,
1700                                          1,
1701                                          mtJavaHeap);
1702   os::trace_page_sizes("Heap",
1703                        collector_policy()->min_heap_byte_size(),
1704                        max_byte_size,
1705                        page_size,
1706                        heap_rs.base(),
1707                        heap_rs.size());
1708   heap_storage->set_mapping_changed_listener(&_listener);
1709 
1710   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1711   G1RegionToSpaceMapper* bot_storage =
1712     create_aux_memory_mapper("Block Offset Table",
1713                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1714                              G1BlockOffsetTable::heap_map_factor());
1715 
1716   G1RegionToSpaceMapper* cardtable_storage =
1717     create_aux_memory_mapper("Card Table",
1718                              G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1719                              G1SATBCardTableLoggingModRefBS::heap_map_factor());
1720 
1721   G1RegionToSpaceMapper* card_counts_storage =
1722     create_aux_memory_mapper("Card Counts Table",
1723                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1724                              G1CardCounts::heap_map_factor());
1725 
1726   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1727   G1RegionToSpaceMapper* prev_bitmap_storage =
1728     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1729   G1RegionToSpaceMapper* next_bitmap_storage =
1730     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1731 
1732   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1733   g1_barrier_set()->initialize(cardtable_storage);
1734   // Do later initialization work for concurrent refinement.
1735   _hot_card_cache->initialize(card_counts_storage);
1736 
1737   // 6843694 - ensure that the maximum region index can fit
1738   // in the remembered set structures.
1739   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1740   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1741 
1742   // Also create a G1 rem set.
1743   _g1_rem_set = new G1RemSet(this, g1_barrier_set(), _hot_card_cache);
1744   _g1_rem_set->initialize(max_capacity(), max_regions());
1745 
1746   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1747   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1748   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1749             "too many cards per region");
1750 
1751   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1752 
1753   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1754 
1755   {
1756     HeapWord* start = _hrm.reserved().start();
1757     HeapWord* end = _hrm.reserved().end();
1758     size_t granularity = HeapRegion::GrainBytes;
1759 
1760     _in_cset_fast_test.initialize(start, end, granularity);
1761     _humongous_reclaim_candidates.initialize(start, end, granularity);
1762   }
1763 
1764   // Create the G1ConcurrentMark data structure and thread.
1765   // (Must do this late, so that "max_regions" is defined.)
1766   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1767   if (_cm == NULL || !_cm->completed_initialization()) {
1768     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1769     return JNI_ENOMEM;
1770   }
1771   _cmThread = _cm->cm_thread();
1772 
1773   // Now expand into the initial heap size.
1774   if (!expand(init_byte_size, _workers)) {
1775     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1776     return JNI_ENOMEM;
1777   }
1778 
1779   // Perform any initialization actions delegated to the policy.
1780   g1_policy()->init(this, &_collection_set);
1781 
1782   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1783                                                SATB_Q_FL_lock,
1784                                                G1SATBProcessCompletedThreshold,
1785                                                Shared_SATB_Q_lock);
1786 
1787   jint ecode = initialize_concurrent_refinement();
1788   if (ecode != JNI_OK) {
1789     return ecode;
1790   }
1791 
1792   JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1793                                                 DirtyCardQ_FL_lock,
1794                                                 (int)concurrent_g1_refine()->yellow_zone(),
1795                                                 (int)concurrent_g1_refine()->red_zone(),
1796                                                 Shared_DirtyCardQ_lock,
1797                                                 NULL,  // fl_owner
1798                                                 true); // init_free_ids
1799 
1800   dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1801                                     DirtyCardQ_FL_lock,
1802                                     -1, // never trigger processing
1803                                     -1, // no limit on length
1804                                     Shared_DirtyCardQ_lock,
1805                                     &JavaThread::dirty_card_queue_set());
1806 
1807   // Here we allocate the dummy HeapRegion that is required by the
1808   // G1AllocRegion class.
1809   HeapRegion* dummy_region = _hrm.get_dummy_region();
1810 
1811   // We'll re-use the same region whether the alloc region will
1812   // require BOT updates or not and, if it doesn't, then a non-young
1813   // region will complain that it cannot support allocations without
1814   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1815   dummy_region->set_eden();
1816   // Make sure it's full.
1817   dummy_region->set_top(dummy_region->end());
1818   G1AllocRegion::setup(this, dummy_region);
1819 
1820   _allocator->init_mutator_alloc_region();
1821 
1822   // Do create of the monitoring and management support so that
1823   // values in the heap have been properly initialized.
1824   _g1mm = new G1MonitoringSupport(this);
1825 
1826   G1StringDedup::initialize();
1827 
1828   _preserved_marks_set.init(ParallelGCThreads);
1829 
1830   _collection_set.initialize(max_regions());
1831 
1832   return JNI_OK;
1833 }
1834 
1835 void G1CollectedHeap::stop() {
1836   // Stop all concurrent threads. We do this to make sure these threads
1837   // do not continue to execute and access resources (e.g. logging)
1838   // that are destroyed during shutdown.
1839   _cg1r->stop();
1840   _cmThread->stop();
1841   if (G1StringDedup::is_enabled()) {
1842     G1StringDedup::stop();
1843   }
1844 }
1845 
1846 void G1CollectedHeap::safepoint_synchronize_begin() {
1847   SuspendibleThreadSet::synchronize();
1848 }
1849 
1850 void G1CollectedHeap::safepoint_synchronize_end() {
1851   SuspendibleThreadSet::desynchronize();
1852 }
1853 
1854 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1855   return HeapRegion::max_region_size();
1856 }
1857 
1858 void G1CollectedHeap::post_initialize() {
1859   ref_processing_init();
1860 }
1861 
1862 void G1CollectedHeap::ref_processing_init() {
1863   // Reference processing in G1 currently works as follows:
1864   //
1865   // * There are two reference processor instances. One is
1866   //   used to record and process discovered references
1867   //   during concurrent marking; the other is used to
1868   //   record and process references during STW pauses
1869   //   (both full and incremental).
1870   // * Both ref processors need to 'span' the entire heap as
1871   //   the regions in the collection set may be dotted around.
1872   //
1873   // * For the concurrent marking ref processor:
1874   //   * Reference discovery is enabled at initial marking.
1875   //   * Reference discovery is disabled and the discovered
1876   //     references processed etc during remarking.
1877   //   * Reference discovery is MT (see below).
1878   //   * Reference discovery requires a barrier (see below).
1879   //   * Reference processing may or may not be MT
1880   //     (depending on the value of ParallelRefProcEnabled
1881   //     and ParallelGCThreads).
1882   //   * A full GC disables reference discovery by the CM
1883   //     ref processor and abandons any entries on it's
1884   //     discovered lists.
1885   //
1886   // * For the STW processor:
1887   //   * Non MT discovery is enabled at the start of a full GC.
1888   //   * Processing and enqueueing during a full GC is non-MT.
1889   //   * During a full GC, references are processed after marking.
1890   //
1891   //   * Discovery (may or may not be MT) is enabled at the start
1892   //     of an incremental evacuation pause.
1893   //   * References are processed near the end of a STW evacuation pause.
1894   //   * For both types of GC:
1895   //     * Discovery is atomic - i.e. not concurrent.
1896   //     * Reference discovery will not need a barrier.
1897 
1898   MemRegion mr = reserved_region();
1899 
1900   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1901 
1902   // Concurrent Mark ref processor
1903   _ref_processor_cm =
1904     new ReferenceProcessor(mr,    // span
1905                            mt_processing,
1906                                 // mt processing
1907                            ParallelGCThreads,
1908                                 // degree of mt processing
1909                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
1910                                 // mt discovery
1911                            MAX2(ParallelGCThreads, ConcGCThreads),
1912                                 // degree of mt discovery
1913                            false,
1914                                 // Reference discovery is not atomic
1915                            &_is_alive_closure_cm);
1916                                 // is alive closure
1917                                 // (for efficiency/performance)
1918 
1919   // STW ref processor
1920   _ref_processor_stw =
1921     new ReferenceProcessor(mr,    // span
1922                            mt_processing,
1923                                 // mt processing
1924                            ParallelGCThreads,
1925                                 // degree of mt processing
1926                            (ParallelGCThreads > 1),
1927                                 // mt discovery
1928                            ParallelGCThreads,
1929                                 // degree of mt discovery
1930                            true,
1931                                 // Reference discovery is atomic
1932                            &_is_alive_closure_stw);
1933                                 // is alive closure
1934                                 // (for efficiency/performance)
1935 }
1936 
1937 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1938   return _collector_policy;
1939 }
1940 
1941 size_t G1CollectedHeap::capacity() const {
1942   return _hrm.length() * HeapRegion::GrainBytes;
1943 }
1944 
1945 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
1946   hr->reset_gc_time_stamp();
1947 }
1948 
1949 #ifndef PRODUCT
1950 
1951 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
1952 private:
1953   unsigned _gc_time_stamp;
1954   bool _failures;
1955 
1956 public:
1957   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
1958     _gc_time_stamp(gc_time_stamp), _failures(false) { }
1959 
1960   virtual bool doHeapRegion(HeapRegion* hr) {
1961     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
1962     if (_gc_time_stamp != region_gc_time_stamp) {
1963       log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
1964                             region_gc_time_stamp, _gc_time_stamp);
1965       _failures = true;
1966     }
1967     return false;
1968   }
1969 
1970   bool failures() { return _failures; }
1971 };
1972 
1973 void G1CollectedHeap::check_gc_time_stamps() {
1974   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
1975   heap_region_iterate(&cl);
1976   guarantee(!cl.failures(), "all GC time stamps should have been reset");
1977 }
1978 #endif // PRODUCT
1979 
1980 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
1981   _hot_card_cache->drain(cl, worker_i);
1982 }
1983 
1984 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
1985   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1986   size_t n_completed_buffers = 0;
1987   while (dcqs.apply_closure_during_gc(cl, worker_i)) {
1988     n_completed_buffers++;
1989   }
1990   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
1991   dcqs.clear_n_completed_buffers();
1992   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
1993 }
1994 
1995 // Computes the sum of the storage used by the various regions.
1996 size_t G1CollectedHeap::used() const {
1997   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1998   if (_archive_allocator != NULL) {
1999     result += _archive_allocator->used();
2000   }
2001   return result;
2002 }
2003 
2004 size_t G1CollectedHeap::used_unlocked() const {
2005   return _summary_bytes_used;
2006 }
2007 
2008 class SumUsedClosure: public HeapRegionClosure {
2009   size_t _used;
2010 public:
2011   SumUsedClosure() : _used(0) {}
2012   bool doHeapRegion(HeapRegion* r) {
2013     _used += r->used();
2014     return false;
2015   }
2016   size_t result() { return _used; }
2017 };
2018 
2019 size_t G1CollectedHeap::recalculate_used() const {
2020   double recalculate_used_start = os::elapsedTime();
2021 
2022   SumUsedClosure blk;
2023   heap_region_iterate(&blk);
2024 
2025   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2026   return blk.result();
2027 }
2028 
2029 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2030   switch (cause) {
2031     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
2032     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
2033     case GCCause::_update_allocation_context_stats_inc: return true;
2034     case GCCause::_wb_conc_mark:                        return true;
2035     default :                                           return false;
2036   }
2037 }
2038 
2039 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2040   switch (cause) {
2041     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2042     case GCCause::_g1_humongous_allocation: return true;
2043     default:                                return is_user_requested_concurrent_full_gc(cause);
2044   }
2045 }
2046 
2047 #ifndef PRODUCT
2048 void G1CollectedHeap::allocate_dummy_regions() {
2049   // Let's fill up most of the region
2050   size_t word_size = HeapRegion::GrainWords - 1024;
2051   // And as a result the region we'll allocate will be humongous.
2052   guarantee(is_humongous(word_size), "sanity");
2053 
2054   // _filler_array_max_size is set to humongous object threshold
2055   // but temporarily change it to use CollectedHeap::fill_with_object().
2056   SizeTFlagSetting fs(_filler_array_max_size, word_size);
2057 
2058   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2059     // Let's use the existing mechanism for the allocation
2060     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2061                                                  AllocationContext::system());
2062     if (dummy_obj != NULL) {
2063       MemRegion mr(dummy_obj, word_size);
2064       CollectedHeap::fill_with_object(mr);
2065     } else {
2066       // If we can't allocate once, we probably cannot allocate
2067       // again. Let's get out of the loop.
2068       break;
2069     }
2070   }
2071 }
2072 #endif // !PRODUCT
2073 
2074 void G1CollectedHeap::increment_old_marking_cycles_started() {
2075   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2076          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2077          "Wrong marking cycle count (started: %d, completed: %d)",
2078          _old_marking_cycles_started, _old_marking_cycles_completed);
2079 
2080   _old_marking_cycles_started++;
2081 }
2082 
2083 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2084   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2085 
2086   // We assume that if concurrent == true, then the caller is a
2087   // concurrent thread that was joined the Suspendible Thread
2088   // Set. If there's ever a cheap way to check this, we should add an
2089   // assert here.
2090 
2091   // Given that this method is called at the end of a Full GC or of a
2092   // concurrent cycle, and those can be nested (i.e., a Full GC can
2093   // interrupt a concurrent cycle), the number of full collections
2094   // completed should be either one (in the case where there was no
2095   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2096   // behind the number of full collections started.
2097 
2098   // This is the case for the inner caller, i.e. a Full GC.
2099   assert(concurrent ||
2100          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2101          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2102          "for inner caller (Full GC): _old_marking_cycles_started = %u "
2103          "is inconsistent with _old_marking_cycles_completed = %u",
2104          _old_marking_cycles_started, _old_marking_cycles_completed);
2105 
2106   // This is the case for the outer caller, i.e. the concurrent cycle.
2107   assert(!concurrent ||
2108          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2109          "for outer caller (concurrent cycle): "
2110          "_old_marking_cycles_started = %u "
2111          "is inconsistent with _old_marking_cycles_completed = %u",
2112          _old_marking_cycles_started, _old_marking_cycles_completed);
2113 
2114   _old_marking_cycles_completed += 1;
2115 
2116   // We need to clear the "in_progress" flag in the CM thread before
2117   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2118   // is set) so that if a waiter requests another System.gc() it doesn't
2119   // incorrectly see that a marking cycle is still in progress.
2120   if (concurrent) {
2121     _cmThread->set_idle();
2122   }
2123 
2124   // This notify_all() will ensure that a thread that called
2125   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2126   // and it's waiting for a full GC to finish will be woken up. It is
2127   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2128   FullGCCount_lock->notify_all();
2129 }
2130 
2131 void G1CollectedHeap::collect(GCCause::Cause cause) {
2132   assert_heap_not_locked();
2133 
2134   uint gc_count_before;
2135   uint old_marking_count_before;
2136   uint full_gc_count_before;
2137   bool retry_gc;
2138 
2139   do {
2140     retry_gc = false;
2141 
2142     {
2143       MutexLocker ml(Heap_lock);
2144 
2145       // Read the GC count while holding the Heap_lock
2146       gc_count_before = total_collections();
2147       full_gc_count_before = total_full_collections();
2148       old_marking_count_before = _old_marking_cycles_started;
2149     }
2150 
2151     if (should_do_concurrent_full_gc(cause)) {
2152       // Schedule an initial-mark evacuation pause that will start a
2153       // concurrent cycle. We're setting word_size to 0 which means that
2154       // we are not requesting a post-GC allocation.
2155       VM_G1IncCollectionPause op(gc_count_before,
2156                                  0,     /* word_size */
2157                                  true,  /* should_initiate_conc_mark */
2158                                  g1_policy()->max_pause_time_ms(),
2159                                  cause);
2160       op.set_allocation_context(AllocationContext::current());
2161 
2162       VMThread::execute(&op);
2163       if (!op.pause_succeeded()) {
2164         if (old_marking_count_before == _old_marking_cycles_started) {
2165           retry_gc = op.should_retry_gc();
2166         } else {
2167           // A Full GC happened while we were trying to schedule the
2168           // initial-mark GC. No point in starting a new cycle given
2169           // that the whole heap was collected anyway.
2170         }
2171 
2172         if (retry_gc) {
2173           if (GCLocker::is_active_and_needs_gc()) {
2174             GCLocker::stall_until_clear();
2175           }
2176         }
2177       }
2178     } else {
2179       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2180           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2181 
2182         // Schedule a standard evacuation pause. We're setting word_size
2183         // to 0 which means that we are not requesting a post-GC allocation.
2184         VM_G1IncCollectionPause op(gc_count_before,
2185                                    0,     /* word_size */
2186                                    false, /* should_initiate_conc_mark */
2187                                    g1_policy()->max_pause_time_ms(),
2188                                    cause);
2189         VMThread::execute(&op);
2190       } else {
2191         // Schedule a Full GC.
2192         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2193         VMThread::execute(&op);
2194       }
2195     }
2196   } while (retry_gc);
2197 }
2198 
2199 bool G1CollectedHeap::is_in(const void* p) const {
2200   if (_hrm.reserved().contains(p)) {
2201     // Given that we know that p is in the reserved space,
2202     // heap_region_containing() should successfully
2203     // return the containing region.
2204     HeapRegion* hr = heap_region_containing(p);
2205     return hr->is_in(p);
2206   } else {
2207     return false;
2208   }
2209 }
2210 
2211 #ifdef ASSERT
2212 bool G1CollectedHeap::is_in_exact(const void* p) const {
2213   bool contains = reserved_region().contains(p);
2214   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2215   if (contains && available) {
2216     return true;
2217   } else {
2218     return false;
2219   }
2220 }
2221 #endif
2222 
2223 // Iteration functions.
2224 
2225 // Iterates an ObjectClosure over all objects within a HeapRegion.
2226 
2227 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2228   ObjectClosure* _cl;
2229 public:
2230   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2231   bool doHeapRegion(HeapRegion* r) {
2232     if (!r->is_continues_humongous()) {
2233       r->object_iterate(_cl);
2234     }
2235     return false;
2236   }
2237 };
2238 
2239 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2240   IterateObjectClosureRegionClosure blk(cl);
2241   heap_region_iterate(&blk);
2242 }
2243 
2244 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2245   _hrm.iterate(cl);
2246 }
2247 
2248 void G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2249                                               uint worker_id,
2250                                               HeapRegionClaimer *hrclaimer) const {
2251   _hrm.par_iterate(cl, worker_id, hrclaimer);
2252 }
2253 
2254 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2255   _collection_set.iterate(cl);
2256 }
2257 
2258 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2259   _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2260 }
2261 
2262 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2263   HeapRegion* result = _hrm.next_region_in_heap(from);
2264   while (result != NULL && result->is_pinned()) {
2265     result = _hrm.next_region_in_heap(result);
2266   }
2267   return result;
2268 }
2269 
2270 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2271   HeapRegion* hr = heap_region_containing(addr);
2272   return hr->block_start(addr);
2273 }
2274 
2275 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2276   HeapRegion* hr = heap_region_containing(addr);
2277   return hr->block_size(addr);
2278 }
2279 
2280 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2281   HeapRegion* hr = heap_region_containing(addr);
2282   return hr->block_is_obj(addr);
2283 }
2284 
2285 bool G1CollectedHeap::supports_tlab_allocation() const {
2286   return true;
2287 }
2288 
2289 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2290   return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2291 }
2292 
2293 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2294   return _eden.length() * HeapRegion::GrainBytes;
2295 }
2296 
2297 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2298 // must be equal to the humongous object limit.
2299 size_t G1CollectedHeap::max_tlab_size() const {
2300   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2301 }
2302 
2303 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2304   AllocationContext_t context = AllocationContext::current();
2305   return _allocator->unsafe_max_tlab_alloc(context);
2306 }
2307 
2308 size_t G1CollectedHeap::max_capacity() const {
2309   return _hrm.reserved().byte_size();
2310 }
2311 
2312 jlong G1CollectedHeap::millis_since_last_gc() {
2313   // See the notes in GenCollectedHeap::millis_since_last_gc()
2314   // for more information about the implementation.
2315   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2316     _g1_policy->collection_pause_end_millis();
2317   if (ret_val < 0) {
2318     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2319       ". returning zero instead.", ret_val);
2320     return 0;
2321   }
2322   return ret_val;
2323 }
2324 
2325 void G1CollectedHeap::prepare_for_verify() {
2326   _verifier->prepare_for_verify();
2327 }
2328 
2329 void G1CollectedHeap::verify(VerifyOption vo) {
2330   _verifier->verify(vo);
2331 }
2332 
2333 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2334   return true;
2335 }
2336 
2337 const char* const* G1CollectedHeap::concurrent_phases() const {
2338   return _cmThread->concurrent_phases();
2339 }
2340 
2341 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2342   return _cmThread->request_concurrent_phase(phase);
2343 }
2344 
2345 class PrintRegionClosure: public HeapRegionClosure {
2346   outputStream* _st;
2347 public:
2348   PrintRegionClosure(outputStream* st) : _st(st) {}
2349   bool doHeapRegion(HeapRegion* r) {
2350     r->print_on(_st);
2351     return false;
2352   }
2353 };
2354 
2355 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2356                                        const HeapRegion* hr,
2357                                        const VerifyOption vo) const {
2358   switch (vo) {
2359   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2360   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2361   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked() && !hr->is_archive();
2362   default:                            ShouldNotReachHere();
2363   }
2364   return false; // keep some compilers happy
2365 }
2366 
2367 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2368                                        const VerifyOption vo) const {
2369   switch (vo) {
2370   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2371   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2372   case VerifyOption_G1UseMarkWord: {
2373     HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj);
2374     return !obj->is_gc_marked() && !hr->is_archive();
2375   }
2376   default:                            ShouldNotReachHere();
2377   }
2378   return false; // keep some compilers happy
2379 }
2380 
2381 void G1CollectedHeap::print_heap_regions() const {
2382   LogTarget(Trace, gc, heap, region) lt;
2383   if (lt.is_enabled()) {
2384     LogStream ls(lt);
2385     print_regions_on(&ls);
2386   }
2387 }
2388 
2389 void G1CollectedHeap::print_on(outputStream* st) const {
2390   st->print(" %-20s", "garbage-first heap");
2391   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2392             capacity()/K, used_unlocked()/K);
2393   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2394             p2i(_hrm.reserved().start()),
2395             p2i(_hrm.reserved().end()));
2396   st->cr();
2397   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2398   uint young_regions = young_regions_count();
2399   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2400             (size_t) young_regions * HeapRegion::GrainBytes / K);
2401   uint survivor_regions = survivor_regions_count();
2402   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2403             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2404   st->cr();
2405   MetaspaceAux::print_on(st);
2406 }
2407 
2408 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2409   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2410                "HS=humongous(starts), HC=humongous(continues), "
2411                "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2412                "AC=allocation context, "
2413                "TAMS=top-at-mark-start (previous, next)");
2414   PrintRegionClosure blk(st);
2415   heap_region_iterate(&blk);
2416 }
2417 
2418 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2419   print_on(st);
2420 
2421   // Print the per-region information.
2422   print_regions_on(st);
2423 }
2424 
2425 void G1CollectedHeap::print_on_error(outputStream* st) const {
2426   this->CollectedHeap::print_on_error(st);
2427 
2428   if (_cm != NULL) {
2429     st->cr();
2430     _cm->print_on_error(st);
2431   }
2432 }
2433 
2434 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2435   workers()->print_worker_threads_on(st);
2436   _cmThread->print_on(st);
2437   st->cr();
2438   _cm->print_worker_threads_on(st);
2439   _cg1r->print_worker_threads_on(st); // also prints the sample thread
2440   if (G1StringDedup::is_enabled()) {
2441     G1StringDedup::print_worker_threads_on(st);
2442   }
2443 }
2444 
2445 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2446   workers()->threads_do(tc);
2447   tc->do_thread(_cmThread);
2448   _cm->threads_do(tc);
2449   _cg1r->threads_do(tc); // also iterates over the sample thread
2450   if (G1StringDedup::is_enabled()) {
2451     G1StringDedup::threads_do(tc);
2452   }
2453 }
2454 
2455 void G1CollectedHeap::print_tracing_info() const {
2456   g1_rem_set()->print_summary_info();
2457   concurrent_mark()->print_summary_info();
2458 }
2459 
2460 #ifndef PRODUCT
2461 // Helpful for debugging RSet issues.
2462 
2463 class PrintRSetsClosure : public HeapRegionClosure {
2464 private:
2465   const char* _msg;
2466   size_t _occupied_sum;
2467 
2468 public:
2469   bool doHeapRegion(HeapRegion* r) {
2470     HeapRegionRemSet* hrrs = r->rem_set();
2471     size_t occupied = hrrs->occupied();
2472     _occupied_sum += occupied;
2473 
2474     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2475     if (occupied == 0) {
2476       tty->print_cr("  RSet is empty");
2477     } else {
2478       hrrs->print();
2479     }
2480     tty->print_cr("----------");
2481     return false;
2482   }
2483 
2484   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2485     tty->cr();
2486     tty->print_cr("========================================");
2487     tty->print_cr("%s", msg);
2488     tty->cr();
2489   }
2490 
2491   ~PrintRSetsClosure() {
2492     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2493     tty->print_cr("========================================");
2494     tty->cr();
2495   }
2496 };
2497 
2498 void G1CollectedHeap::print_cset_rsets() {
2499   PrintRSetsClosure cl("Printing CSet RSets");
2500   collection_set_iterate(&cl);
2501 }
2502 
2503 void G1CollectedHeap::print_all_rsets() {
2504   PrintRSetsClosure cl("Printing All RSets");;
2505   heap_region_iterate(&cl);
2506 }
2507 #endif // PRODUCT
2508 
2509 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2510 
2511   size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2512   size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2513   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2514 
2515   size_t eden_capacity_bytes =
2516     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2517 
2518   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2519   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2520                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2521 }
2522 
2523 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2524   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2525                        stats->unused(), stats->used(), stats->region_end_waste(),
2526                        stats->regions_filled(), stats->direct_allocated(),
2527                        stats->failure_used(), stats->failure_waste());
2528 }
2529 
2530 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2531   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2532   gc_tracer->report_gc_heap_summary(when, heap_summary);
2533 
2534   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2535   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2536 }
2537 
2538 G1CollectedHeap* G1CollectedHeap::heap() {
2539   CollectedHeap* heap = Universe::heap();
2540   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2541   assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2542   return (G1CollectedHeap*)heap;
2543 }
2544 
2545 void G1CollectedHeap::gc_prologue(bool full) {
2546   // always_do_update_barrier = false;
2547   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2548 
2549   // This summary needs to be printed before incrementing total collections.
2550   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2551 
2552   // Update common counters.
2553   increment_total_collections(full /* full gc */);
2554   if (full) {
2555     increment_old_marking_cycles_started();
2556     reset_gc_time_stamp();
2557   } else {
2558     increment_gc_time_stamp();
2559   }
2560 
2561   // Fill TLAB's and such
2562   double start = os::elapsedTime();
2563   accumulate_statistics_all_tlabs();
2564   ensure_parsability(true);
2565   g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2566 }
2567 
2568 void G1CollectedHeap::gc_epilogue(bool full) {
2569   // Update common counters.
2570   if (full) {
2571     // Update the number of full collections that have been completed.
2572     increment_old_marking_cycles_completed(false /* concurrent */);
2573   }
2574 
2575   // We are at the end of the GC. Total collections has already been increased.
2576   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2577 
2578   // FIXME: what is this about?
2579   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2580   // is set.
2581 #if defined(COMPILER2) || INCLUDE_JVMCI
2582   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2583 #endif
2584   // always_do_update_barrier = true;
2585 
2586   double start = os::elapsedTime();
2587   resize_all_tlabs();
2588   g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2589 
2590   allocation_context_stats().update(full);
2591 
2592   MemoryService::track_memory_usage();
2593   // We have just completed a GC. Update the soft reference
2594   // policy with the new heap occupancy
2595   Universe::update_heap_info_at_gc();
2596 }
2597 
2598 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2599                                                uint gc_count_before,
2600                                                bool* succeeded,
2601                                                GCCause::Cause gc_cause) {
2602   assert_heap_not_locked_and_not_at_safepoint();
2603   VM_G1IncCollectionPause op(gc_count_before,
2604                              word_size,
2605                              false, /* should_initiate_conc_mark */
2606                              g1_policy()->max_pause_time_ms(),
2607                              gc_cause);
2608 
2609   op.set_allocation_context(AllocationContext::current());
2610   VMThread::execute(&op);
2611 
2612   HeapWord* result = op.result();
2613   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2614   assert(result == NULL || ret_succeeded,
2615          "the result should be NULL if the VM did not succeed");
2616   *succeeded = ret_succeeded;
2617 
2618   assert_heap_not_locked();
2619   return result;
2620 }
2621 
2622 void
2623 G1CollectedHeap::doConcurrentMark() {
2624   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2625   if (!_cmThread->in_progress()) {
2626     _cmThread->set_started();
2627     CGC_lock->notify();
2628   }
2629 }
2630 
2631 size_t G1CollectedHeap::pending_card_num() {
2632   size_t extra_cards = 0;
2633   JavaThread *curr = Threads::first();
2634   while (curr != NULL) {
2635     DirtyCardQueue& dcq = curr->dirty_card_queue();
2636     extra_cards += dcq.size();
2637     curr = curr->next();
2638   }
2639   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2640   size_t buffer_size = dcqs.buffer_size();
2641   size_t buffer_num = dcqs.completed_buffers_num();
2642 
2643   return buffer_size * buffer_num + extra_cards;
2644 }
2645 
2646 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2647  private:
2648   size_t _total_humongous;
2649   size_t _candidate_humongous;
2650 
2651   DirtyCardQueue _dcq;
2652 
2653   // We don't nominate objects with many remembered set entries, on
2654   // the assumption that such objects are likely still live.
2655   bool is_remset_small(HeapRegion* region) const {
2656     HeapRegionRemSet* const rset = region->rem_set();
2657     return G1EagerReclaimHumongousObjectsWithStaleRefs
2658       ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2659       : rset->is_empty();
2660   }
2661 
2662   bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2663     assert(region->is_starts_humongous(), "Must start a humongous object");
2664 
2665     oop obj = oop(region->bottom());
2666 
2667     // Dead objects cannot be eager reclaim candidates. Due to class
2668     // unloading it is unsafe to query their classes so we return early.
2669     if (heap->is_obj_dead(obj, region)) {
2670       return false;
2671     }
2672 
2673     // Candidate selection must satisfy the following constraints
2674     // while concurrent marking is in progress:
2675     //
2676     // * In order to maintain SATB invariants, an object must not be
2677     // reclaimed if it was allocated before the start of marking and
2678     // has not had its references scanned.  Such an object must have
2679     // its references (including type metadata) scanned to ensure no
2680     // live objects are missed by the marking process.  Objects
2681     // allocated after the start of concurrent marking don't need to
2682     // be scanned.
2683     //
2684     // * An object must not be reclaimed if it is on the concurrent
2685     // mark stack.  Objects allocated after the start of concurrent
2686     // marking are never pushed on the mark stack.
2687     //
2688     // Nominating only objects allocated after the start of concurrent
2689     // marking is sufficient to meet both constraints.  This may miss
2690     // some objects that satisfy the constraints, but the marking data
2691     // structures don't support efficiently performing the needed
2692     // additional tests or scrubbing of the mark stack.
2693     //
2694     // However, we presently only nominate is_typeArray() objects.
2695     // A humongous object containing references induces remembered
2696     // set entries on other regions.  In order to reclaim such an
2697     // object, those remembered sets would need to be cleaned up.
2698     //
2699     // We also treat is_typeArray() objects specially, allowing them
2700     // to be reclaimed even if allocated before the start of
2701     // concurrent mark.  For this we rely on mark stack insertion to
2702     // exclude is_typeArray() objects, preventing reclaiming an object
2703     // that is in the mark stack.  We also rely on the metadata for
2704     // such objects to be built-in and so ensured to be kept live.
2705     // Frequent allocation and drop of large binary blobs is an
2706     // important use case for eager reclaim, and this special handling
2707     // may reduce needed headroom.
2708 
2709     return obj->is_typeArray() && is_remset_small(region);
2710   }
2711 
2712  public:
2713   RegisterHumongousWithInCSetFastTestClosure()
2714   : _total_humongous(0),
2715     _candidate_humongous(0),
2716     _dcq(&JavaThread::dirty_card_queue_set()) {
2717   }
2718 
2719   virtual bool doHeapRegion(HeapRegion* r) {
2720     if (!r->is_starts_humongous()) {
2721       return false;
2722     }
2723     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2724 
2725     bool is_candidate = humongous_region_is_candidate(g1h, r);
2726     uint rindex = r->hrm_index();
2727     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2728     if (is_candidate) {
2729       _candidate_humongous++;
2730       g1h->register_humongous_region_with_cset(rindex);
2731       // Is_candidate already filters out humongous object with large remembered sets.
2732       // If we have a humongous object with a few remembered sets, we simply flush these
2733       // remembered set entries into the DCQS. That will result in automatic
2734       // re-evaluation of their remembered set entries during the following evacuation
2735       // phase.
2736       if (!r->rem_set()->is_empty()) {
2737         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2738                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2739         G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
2740         HeapRegionRemSetIterator hrrs(r->rem_set());
2741         size_t card_index;
2742         while (hrrs.has_next(card_index)) {
2743           jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
2744           // The remembered set might contain references to already freed
2745           // regions. Filter out such entries to avoid failing card table
2746           // verification.
2747           if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
2748             if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
2749               *card_ptr = CardTableModRefBS::dirty_card_val();
2750               _dcq.enqueue(card_ptr);
2751             }
2752           }
2753         }
2754         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2755                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2756                hrrs.n_yielded(), r->rem_set()->occupied());
2757         r->rem_set()->clear_locked();
2758       }
2759       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2760     }
2761     _total_humongous++;
2762 
2763     return false;
2764   }
2765 
2766   size_t total_humongous() const { return _total_humongous; }
2767   size_t candidate_humongous() const { return _candidate_humongous; }
2768 
2769   void flush_rem_set_entries() { _dcq.flush(); }
2770 };
2771 
2772 void G1CollectedHeap::register_humongous_regions_with_cset() {
2773   if (!G1EagerReclaimHumongousObjects) {
2774     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2775     return;
2776   }
2777   double time = os::elapsed_counter();
2778 
2779   // Collect reclaim candidate information and register candidates with cset.
2780   RegisterHumongousWithInCSetFastTestClosure cl;
2781   heap_region_iterate(&cl);
2782 
2783   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2784   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2785                                                                   cl.total_humongous(),
2786                                                                   cl.candidate_humongous());
2787   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2788 
2789   // Finally flush all remembered set entries to re-check into the global DCQS.
2790   cl.flush_rem_set_entries();
2791 }
2792 
2793 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2794   public:
2795     bool doHeapRegion(HeapRegion* hr) {
2796       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2797         hr->verify_rem_set();
2798       }
2799       return false;
2800     }
2801 };
2802 
2803 uint G1CollectedHeap::num_task_queues() const {
2804   return _task_queues->size();
2805 }
2806 
2807 #if TASKQUEUE_STATS
2808 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2809   st->print_raw_cr("GC Task Stats");
2810   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2811   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2812 }
2813 
2814 void G1CollectedHeap::print_taskqueue_stats() const {
2815   if (!log_is_enabled(Trace, gc, task, stats)) {
2816     return;
2817   }
2818   Log(gc, task, stats) log;
2819   ResourceMark rm;
2820   LogStream ls(log.trace());
2821   outputStream* st = &ls;
2822 
2823   print_taskqueue_stats_hdr(st);
2824 
2825   TaskQueueStats totals;
2826   const uint n = num_task_queues();
2827   for (uint i = 0; i < n; ++i) {
2828     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2829     totals += task_queue(i)->stats;
2830   }
2831   st->print_raw("tot "); totals.print(st); st->cr();
2832 
2833   DEBUG_ONLY(totals.verify());
2834 }
2835 
2836 void G1CollectedHeap::reset_taskqueue_stats() {
2837   const uint n = num_task_queues();
2838   for (uint i = 0; i < n; ++i) {
2839     task_queue(i)->stats.reset();
2840   }
2841 }
2842 #endif // TASKQUEUE_STATS
2843 
2844 void G1CollectedHeap::wait_for_root_region_scanning() {
2845   double scan_wait_start = os::elapsedTime();
2846   // We have to wait until the CM threads finish scanning the
2847   // root regions as it's the only way to ensure that all the
2848   // objects on them have been correctly scanned before we start
2849   // moving them during the GC.
2850   bool waited = _cm->root_regions()->wait_until_scan_finished();
2851   double wait_time_ms = 0.0;
2852   if (waited) {
2853     double scan_wait_end = os::elapsedTime();
2854     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2855   }
2856   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2857 }
2858 
2859 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2860 private:
2861   G1HRPrinter* _hr_printer;
2862 public:
2863   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2864 
2865   virtual bool doHeapRegion(HeapRegion* r) {
2866     _hr_printer->cset(r);
2867     return false;
2868   }
2869 };
2870 
2871 void G1CollectedHeap::start_new_collection_set() {
2872   collection_set()->start_incremental_building();
2873 
2874   clear_cset_fast_test();
2875 
2876   guarantee(_eden.length() == 0, "eden should have been cleared");
2877   g1_policy()->transfer_survivors_to_cset(survivor());
2878 }
2879 
2880 bool
2881 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2882   assert_at_safepoint(true /* should_be_vm_thread */);
2883   guarantee(!is_gc_active(), "collection is not reentrant");
2884 
2885   if (GCLocker::check_active_before_gc()) {
2886     return false;
2887   }
2888 
2889   _gc_timer_stw->register_gc_start();
2890 
2891   GCIdMark gc_id_mark;
2892   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2893 
2894   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2895   ResourceMark rm;
2896 
2897   g1_policy()->note_gc_start();
2898 
2899   wait_for_root_region_scanning();
2900 
2901   print_heap_before_gc();
2902   print_heap_regions();
2903   trace_heap_before_gc(_gc_tracer_stw);
2904 
2905   _verifier->verify_region_sets_optional();
2906   _verifier->verify_dirty_young_regions();
2907 
2908   // We should not be doing initial mark unless the conc mark thread is running
2909   if (!_cmThread->should_terminate()) {
2910     // This call will decide whether this pause is an initial-mark
2911     // pause. If it is, during_initial_mark_pause() will return true
2912     // for the duration of this pause.
2913     g1_policy()->decide_on_conc_mark_initiation();
2914   }
2915 
2916   // We do not allow initial-mark to be piggy-backed on a mixed GC.
2917   assert(!collector_state()->during_initial_mark_pause() ||
2918           collector_state()->gcs_are_young(), "sanity");
2919 
2920   // We also do not allow mixed GCs during marking.
2921   assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
2922 
2923   // Record whether this pause is an initial mark. When the current
2924   // thread has completed its logging output and it's safe to signal
2925   // the CM thread, the flag's value in the policy has been reset.
2926   bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
2927 
2928   // Inner scope for scope based logging, timers, and stats collection
2929   {
2930     EvacuationInfo evacuation_info;
2931 
2932     if (collector_state()->during_initial_mark_pause()) {
2933       // We are about to start a marking cycle, so we increment the
2934       // full collection counter.
2935       increment_old_marking_cycles_started();
2936       _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2937     }
2938 
2939     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2940 
2941     GCTraceCPUTime tcpu;
2942 
2943     FormatBuffer<> gc_string("Pause ");
2944     if (collector_state()->during_initial_mark_pause()) {
2945       gc_string.append("Initial Mark");
2946     } else if (collector_state()->gcs_are_young()) {
2947       gc_string.append("Young");
2948     } else {
2949       gc_string.append("Mixed");
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();
2991 
2992       _verifier->check_bitmaps("GC Start");
2993 
2994 #if defined(COMPILER2) || INCLUDE_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();
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 jint                           _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, (jint*)&_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 jint      _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, (jint*)&_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 defined(COMPILER2) || INCLUDE_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 }
--- EOF ---