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 ", " PTR_FORMAT ")",
2394             p2i(_hrm.reserved().start()),
2395             p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords),
2396             p2i(_hrm.reserved().end()));
2397   st->cr();
2398   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2399   uint young_regions = young_regions_count();
2400   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2401             (size_t) young_regions * HeapRegion::GrainBytes / K);
2402   uint survivor_regions = survivor_regions_count();
2403   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2404             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2405   st->cr();
2406   MetaspaceAux::print_on(st);
2407 }
2408 
2409 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2410   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2411                "HS=humongous(starts), HC=humongous(continues), "
2412                "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2413                "AC=allocation context, "
2414                "TAMS=top-at-mark-start (previous, next)");
2415   PrintRegionClosure blk(st);
2416   heap_region_iterate(&blk);
2417 }
2418 
2419 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2420   print_on(st);
2421 
2422   // Print the per-region information.
2423   print_regions_on(st);
2424 }
2425 
2426 void G1CollectedHeap::print_on_error(outputStream* st) const {
2427   this->CollectedHeap::print_on_error(st);
2428 
2429   if (_cm != NULL) {
2430     st->cr();
2431     _cm->print_on_error(st);
2432   }
2433 }
2434 
2435 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2436   workers()->print_worker_threads_on(st);
2437   _cmThread->print_on(st);
2438   st->cr();
2439   _cm->print_worker_threads_on(st);
2440   _cg1r->print_worker_threads_on(st); // also prints the sample thread
2441   if (G1StringDedup::is_enabled()) {
2442     G1StringDedup::print_worker_threads_on(st);
2443   }
2444 }
2445 
2446 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2447   workers()->threads_do(tc);
2448   tc->do_thread(_cmThread);
2449   _cm->threads_do(tc);
2450   _cg1r->threads_do(tc); // also iterates over the sample thread
2451   if (G1StringDedup::is_enabled()) {
2452     G1StringDedup::threads_do(tc);
2453   }
2454 }
2455 
2456 void G1CollectedHeap::print_tracing_info() const {
2457   g1_rem_set()->print_summary_info();
2458   concurrent_mark()->print_summary_info();
2459 }
2460 
2461 #ifndef PRODUCT
2462 // Helpful for debugging RSet issues.
2463 
2464 class PrintRSetsClosure : public HeapRegionClosure {
2465 private:
2466   const char* _msg;
2467   size_t _occupied_sum;
2468 
2469 public:
2470   bool doHeapRegion(HeapRegion* r) {
2471     HeapRegionRemSet* hrrs = r->rem_set();
2472     size_t occupied = hrrs->occupied();
2473     _occupied_sum += occupied;
2474 
2475     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2476     if (occupied == 0) {
2477       tty->print_cr("  RSet is empty");
2478     } else {
2479       hrrs->print();
2480     }
2481     tty->print_cr("----------");
2482     return false;
2483   }
2484 
2485   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2486     tty->cr();
2487     tty->print_cr("========================================");
2488     tty->print_cr("%s", msg);
2489     tty->cr();
2490   }
2491 
2492   ~PrintRSetsClosure() {
2493     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2494     tty->print_cr("========================================");
2495     tty->cr();
2496   }
2497 };
2498 
2499 void G1CollectedHeap::print_cset_rsets() {
2500   PrintRSetsClosure cl("Printing CSet RSets");
2501   collection_set_iterate(&cl);
2502 }
2503 
2504 void G1CollectedHeap::print_all_rsets() {
2505   PrintRSetsClosure cl("Printing All RSets");;
2506   heap_region_iterate(&cl);
2507 }
2508 #endif // PRODUCT
2509 
2510 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2511 
2512   size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2513   size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2514   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2515 
2516   size_t eden_capacity_bytes =
2517     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2518 
2519   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2520   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2521                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2522 }
2523 
2524 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2525   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2526                        stats->unused(), stats->used(), stats->region_end_waste(),
2527                        stats->regions_filled(), stats->direct_allocated(),
2528                        stats->failure_used(), stats->failure_waste());
2529 }
2530 
2531 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2532   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2533   gc_tracer->report_gc_heap_summary(when, heap_summary);
2534 
2535   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2536   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2537 }
2538 
2539 G1CollectedHeap* G1CollectedHeap::heap() {
2540   CollectedHeap* heap = Universe::heap();
2541   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2542   assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2543   return (G1CollectedHeap*)heap;
2544 }
2545 
2546 void G1CollectedHeap::gc_prologue(bool full) {
2547   // always_do_update_barrier = false;
2548   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2549 
2550   // This summary needs to be printed before incrementing total collections.
2551   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2552 
2553   // Update common counters.
2554   increment_total_collections(full /* full gc */);
2555   if (full) {
2556     increment_old_marking_cycles_started();
2557     reset_gc_time_stamp();
2558   } else {
2559     increment_gc_time_stamp();
2560   }
2561 
2562   // Fill TLAB's and such
2563   double start = os::elapsedTime();
2564   accumulate_statistics_all_tlabs();
2565   ensure_parsability(true);
2566   g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2567 }
2568 
2569 void G1CollectedHeap::gc_epilogue(bool full) {
2570   // Update common counters.
2571   if (full) {
2572     // Update the number of full collections that have been completed.
2573     increment_old_marking_cycles_completed(false /* concurrent */);
2574   }
2575 
2576   // We are at the end of the GC. Total collections has already been increased.
2577   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2578 
2579   // FIXME: what is this about?
2580   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2581   // is set.
2582 #if COMPILER2_OR_JVMCI
2583   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2584 #endif
2585   // always_do_update_barrier = true;
2586 
2587   double start = os::elapsedTime();
2588   resize_all_tlabs();
2589   g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2590 
2591   allocation_context_stats().update(full);
2592 
2593   MemoryService::track_memory_usage();
2594   // We have just completed a GC. Update the soft reference
2595   // policy with the new heap occupancy
2596   Universe::update_heap_info_at_gc();
2597 }
2598 
2599 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2600                                                uint gc_count_before,
2601                                                bool* succeeded,
2602                                                GCCause::Cause gc_cause) {
2603   assert_heap_not_locked_and_not_at_safepoint();
2604   VM_G1IncCollectionPause op(gc_count_before,
2605                              word_size,
2606                              false, /* should_initiate_conc_mark */
2607                              g1_policy()->max_pause_time_ms(),
2608                              gc_cause);
2609 
2610   op.set_allocation_context(AllocationContext::current());
2611   VMThread::execute(&op);
2612 
2613   HeapWord* result = op.result();
2614   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2615   assert(result == NULL || ret_succeeded,
2616          "the result should be NULL if the VM did not succeed");
2617   *succeeded = ret_succeeded;
2618 
2619   assert_heap_not_locked();
2620   return result;
2621 }
2622 
2623 void
2624 G1CollectedHeap::doConcurrentMark() {
2625   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2626   if (!_cmThread->in_progress()) {
2627     _cmThread->set_started();
2628     CGC_lock->notify();
2629   }
2630 }
2631 
2632 size_t G1CollectedHeap::pending_card_num() {
2633   size_t extra_cards = 0;
2634   JavaThread *curr = Threads::first();
2635   while (curr != NULL) {
2636     DirtyCardQueue& dcq = curr->dirty_card_queue();
2637     extra_cards += dcq.size();
2638     curr = curr->next();
2639   }
2640   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2641   size_t buffer_size = dcqs.buffer_size();
2642   size_t buffer_num = dcqs.completed_buffers_num();
2643 
2644   return buffer_size * buffer_num + extra_cards;
2645 }
2646 
2647 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2648  private:
2649   size_t _total_humongous;
2650   size_t _candidate_humongous;
2651 
2652   DirtyCardQueue _dcq;
2653 
2654   // We don't nominate objects with many remembered set entries, on
2655   // the assumption that such objects are likely still live.
2656   bool is_remset_small(HeapRegion* region) const {
2657     HeapRegionRemSet* const rset = region->rem_set();
2658     return G1EagerReclaimHumongousObjectsWithStaleRefs
2659       ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2660       : rset->is_empty();
2661   }
2662 
2663   bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2664     assert(region->is_starts_humongous(), "Must start a humongous object");
2665 
2666     oop obj = oop(region->bottom());
2667 
2668     // Dead objects cannot be eager reclaim candidates. Due to class
2669     // unloading it is unsafe to query their classes so we return early.
2670     if (heap->is_obj_dead(obj, region)) {
2671       return false;
2672     }
2673 
2674     // Candidate selection must satisfy the following constraints
2675     // while concurrent marking is in progress:
2676     //
2677     // * In order to maintain SATB invariants, an object must not be
2678     // reclaimed if it was allocated before the start of marking and
2679     // has not had its references scanned.  Such an object must have
2680     // its references (including type metadata) scanned to ensure no
2681     // live objects are missed by the marking process.  Objects
2682     // allocated after the start of concurrent marking don't need to
2683     // be scanned.
2684     //
2685     // * An object must not be reclaimed if it is on the concurrent
2686     // mark stack.  Objects allocated after the start of concurrent
2687     // marking are never pushed on the mark stack.
2688     //
2689     // Nominating only objects allocated after the start of concurrent
2690     // marking is sufficient to meet both constraints.  This may miss
2691     // some objects that satisfy the constraints, but the marking data
2692     // structures don't support efficiently performing the needed
2693     // additional tests or scrubbing of the mark stack.
2694     //
2695     // However, we presently only nominate is_typeArray() objects.
2696     // A humongous object containing references induces remembered
2697     // set entries on other regions.  In order to reclaim such an
2698     // object, those remembered sets would need to be cleaned up.
2699     //
2700     // We also treat is_typeArray() objects specially, allowing them
2701     // to be reclaimed even if allocated before the start of
2702     // concurrent mark.  For this we rely on mark stack insertion to
2703     // exclude is_typeArray() objects, preventing reclaiming an object
2704     // that is in the mark stack.  We also rely on the metadata for
2705     // such objects to be built-in and so ensured to be kept live.
2706     // Frequent allocation and drop of large binary blobs is an
2707     // important use case for eager reclaim, and this special handling
2708     // may reduce needed headroom.
2709 
2710     return obj->is_typeArray() && is_remset_small(region);
2711   }
2712 
2713  public:
2714   RegisterHumongousWithInCSetFastTestClosure()
2715   : _total_humongous(0),
2716     _candidate_humongous(0),
2717     _dcq(&JavaThread::dirty_card_queue_set()) {
2718   }
2719 
2720   virtual bool doHeapRegion(HeapRegion* r) {
2721     if (!r->is_starts_humongous()) {
2722       return false;
2723     }
2724     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2725 
2726     bool is_candidate = humongous_region_is_candidate(g1h, r);
2727     uint rindex = r->hrm_index();
2728     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2729     if (is_candidate) {
2730       _candidate_humongous++;
2731       g1h->register_humongous_region_with_cset(rindex);
2732       // Is_candidate already filters out humongous object with large remembered sets.
2733       // If we have a humongous object with a few remembered sets, we simply flush these
2734       // remembered set entries into the DCQS. That will result in automatic
2735       // re-evaluation of their remembered set entries during the following evacuation
2736       // phase.
2737       if (!r->rem_set()->is_empty()) {
2738         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2739                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2740         G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
2741         HeapRegionRemSetIterator hrrs(r->rem_set());
2742         size_t card_index;
2743         while (hrrs.has_next(card_index)) {
2744           jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
2745           // The remembered set might contain references to already freed
2746           // regions. Filter out such entries to avoid failing card table
2747           // verification.
2748           if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
2749             if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
2750               *card_ptr = CardTableModRefBS::dirty_card_val();
2751               _dcq.enqueue(card_ptr);
2752             }
2753           }
2754         }
2755         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2756                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2757                hrrs.n_yielded(), r->rem_set()->occupied());
2758         r->rem_set()->clear_locked();
2759       }
2760       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2761     }
2762     _total_humongous++;
2763 
2764     return false;
2765   }
2766 
2767   size_t total_humongous() const { return _total_humongous; }
2768   size_t candidate_humongous() const { return _candidate_humongous; }
2769 
2770   void flush_rem_set_entries() { _dcq.flush(); }
2771 };
2772 
2773 void G1CollectedHeap::register_humongous_regions_with_cset() {
2774   if (!G1EagerReclaimHumongousObjects) {
2775     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2776     return;
2777   }
2778   double time = os::elapsed_counter();
2779 
2780   // Collect reclaim candidate information and register candidates with cset.
2781   RegisterHumongousWithInCSetFastTestClosure cl;
2782   heap_region_iterate(&cl);
2783 
2784   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2785   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2786                                                                   cl.total_humongous(),
2787                                                                   cl.candidate_humongous());
2788   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2789 
2790   // Finally flush all remembered set entries to re-check into the global DCQS.
2791   cl.flush_rem_set_entries();
2792 }
2793 
2794 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2795   public:
2796     bool doHeapRegion(HeapRegion* hr) {
2797       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2798         hr->verify_rem_set();
2799       }
2800       return false;
2801     }
2802 };
2803 
2804 uint G1CollectedHeap::num_task_queues() const {
2805   return _task_queues->size();
2806 }
2807 
2808 #if TASKQUEUE_STATS
2809 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2810   st->print_raw_cr("GC Task Stats");
2811   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2812   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2813 }
2814 
2815 void G1CollectedHeap::print_taskqueue_stats() const {
2816   if (!log_is_enabled(Trace, gc, task, stats)) {
2817     return;
2818   }
2819   Log(gc, task, stats) log;
2820   ResourceMark rm;
2821   LogStream ls(log.trace());
2822   outputStream* st = &ls;
2823 
2824   print_taskqueue_stats_hdr(st);
2825 
2826   TaskQueueStats totals;
2827   const uint n = num_task_queues();
2828   for (uint i = 0; i < n; ++i) {
2829     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2830     totals += task_queue(i)->stats;
2831   }
2832   st->print_raw("tot "); totals.print(st); st->cr();
2833 
2834   DEBUG_ONLY(totals.verify());
2835 }
2836 
2837 void G1CollectedHeap::reset_taskqueue_stats() {
2838   const uint n = num_task_queues();
2839   for (uint i = 0; i < n; ++i) {
2840     task_queue(i)->stats.reset();
2841   }
2842 }
2843 #endif // TASKQUEUE_STATS
2844 
2845 void G1CollectedHeap::wait_for_root_region_scanning() {
2846   double scan_wait_start = os::elapsedTime();
2847   // We have to wait until the CM threads finish scanning the
2848   // root regions as it's the only way to ensure that all the
2849   // objects on them have been correctly scanned before we start
2850   // moving them during the GC.
2851   bool waited = _cm->root_regions()->wait_until_scan_finished();
2852   double wait_time_ms = 0.0;
2853   if (waited) {
2854     double scan_wait_end = os::elapsedTime();
2855     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2856   }
2857   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2858 }
2859 
2860 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2861 private:
2862   G1HRPrinter* _hr_printer;
2863 public:
2864   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2865 
2866   virtual bool doHeapRegion(HeapRegion* r) {
2867     _hr_printer->cset(r);
2868     return false;
2869   }
2870 };
2871 
2872 void G1CollectedHeap::start_new_collection_set() {
2873   collection_set()->start_incremental_building();
2874 
2875   clear_cset_fast_test();
2876 
2877   guarantee(_eden.length() == 0, "eden should have been cleared");
2878   g1_policy()->transfer_survivors_to_cset(survivor());
2879 }
2880 
2881 bool
2882 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2883   assert_at_safepoint(true /* should_be_vm_thread */);
2884   guarantee(!is_gc_active(), "collection is not reentrant");
2885 
2886   if (GCLocker::check_active_before_gc()) {
2887     return false;
2888   }
2889 
2890   _gc_timer_stw->register_gc_start();
2891 
2892   GCIdMark gc_id_mark;
2893   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2894 
2895   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2896   ResourceMark rm;
2897 
2898   g1_policy()->note_gc_start();
2899 
2900   wait_for_root_region_scanning();
2901 
2902   print_heap_before_gc();
2903   print_heap_regions();
2904   trace_heap_before_gc(_gc_tracer_stw);
2905 
2906   _verifier->verify_region_sets_optional();
2907   _verifier->verify_dirty_young_regions();
2908 
2909   // We should not be doing initial mark unless the conc mark thread is running
2910   if (!_cmThread->should_terminate()) {
2911     // This call will decide whether this pause is an initial-mark
2912     // pause. If it is, during_initial_mark_pause() will return true
2913     // for the duration of this pause.
2914     g1_policy()->decide_on_conc_mark_initiation();
2915   }
2916 
2917   // We do not allow initial-mark to be piggy-backed on a mixed GC.
2918   assert(!collector_state()->during_initial_mark_pause() ||
2919           collector_state()->gcs_are_young(), "sanity");
2920 
2921   // We also do not allow mixed GCs during marking.
2922   assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
2923 
2924   // Record whether this pause is an initial mark. When the current
2925   // thread has completed its logging output and it's safe to signal
2926   // the CM thread, the flag's value in the policy has been reset.
2927   bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
2928 
2929   // Inner scope for scope based logging, timers, and stats collection
2930   {
2931     EvacuationInfo evacuation_info;
2932 
2933     if (collector_state()->during_initial_mark_pause()) {
2934       // We are about to start a marking cycle, so we increment the
2935       // full collection counter.
2936       increment_old_marking_cycles_started();
2937       _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2938     }
2939 
2940     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2941 
2942     GCTraceCPUTime tcpu;
2943 
2944     FormatBuffer<> gc_string("Pause ");
2945     if (collector_state()->during_initial_mark_pause()) {
2946       gc_string.append("Initial Mark");
2947     } else if (collector_state()->gcs_are_young()) {
2948       gc_string.append("Young");
2949     } else {
2950       gc_string.append("Mixed");
2951     }
2952     GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2953 
2954     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2955                                                                   workers()->active_workers(),
2956                                                                   Threads::number_of_non_daemon_threads());
2957     workers()->update_active_workers(active_workers);
2958     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2959 
2960     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2961     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
2962 
2963     // If the secondary_free_list is not empty, append it to the
2964     // free_list. No need to wait for the cleanup operation to finish;
2965     // the region allocation code will check the secondary_free_list
2966     // and wait if necessary. If the G1StressConcRegionFreeing flag is
2967     // set, skip this step so that the region allocation code has to
2968     // get entries from the secondary_free_list.
2969     if (!G1StressConcRegionFreeing) {
2970       append_secondary_free_list_if_not_empty_with_lock();
2971     }
2972 
2973     G1HeapTransition heap_transition(this);
2974     size_t heap_used_bytes_before_gc = used();
2975 
2976     // Don't dynamically change the number of GC threads this early.  A value of
2977     // 0 is used to indicate serial work.  When parallel work is done,
2978     // it will be set.
2979 
2980     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2981       IsGCActiveMark x;
2982 
2983       gc_prologue(false);
2984 
2985       if (VerifyRememberedSets) {
2986         log_info(gc, verify)("[Verifying RemSets before GC]");
2987         VerifyRegionRemSetClosure v_cl;
2988         heap_region_iterate(&v_cl);
2989       }
2990 
2991       _verifier->verify_before_gc();
2992 
2993       _verifier->check_bitmaps("GC Start");
2994 
2995 #if COMPILER2_OR_JVMCI
2996       DerivedPointerTable::clear();
2997 #endif
2998 
2999       // Please see comment in g1CollectedHeap.hpp and
3000       // G1CollectedHeap::ref_processing_init() to see how
3001       // reference processing currently works in G1.
3002 
3003       // Enable discovery in the STW reference processor
3004       if (g1_policy()->should_process_references()) {
3005         ref_processor_stw()->enable_discovery();
3006       } else {
3007         ref_processor_stw()->disable_discovery();
3008       }
3009 
3010       {
3011         // We want to temporarily turn off discovery by the
3012         // CM ref processor, if necessary, and turn it back on
3013         // on again later if we do. Using a scoped
3014         // NoRefDiscovery object will do this.
3015         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3016 
3017         // Forget the current alloc region (we might even choose it to be part
3018         // of the collection set!).
3019         _allocator->release_mutator_alloc_region();
3020 
3021         // This timing is only used by the ergonomics to handle our pause target.
3022         // It is unclear why this should not include the full pause. We will
3023         // investigate this in CR 7178365.
3024         //
3025         // Preserving the old comment here if that helps the investigation:
3026         //
3027         // The elapsed time induced by the start time below deliberately elides
3028         // the possible verification above.
3029         double sample_start_time_sec = os::elapsedTime();
3030 
3031         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3032 
3033         if (collector_state()->during_initial_mark_pause()) {
3034           concurrent_mark()->checkpoint_roots_initial_pre();
3035         }
3036 
3037         g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
3038 
3039         evacuation_info.set_collectionset_regions(collection_set()->region_length());
3040 
3041         // Make sure the remembered sets are up to date. This needs to be
3042         // done before register_humongous_regions_with_cset(), because the
3043         // remembered sets are used there to choose eager reclaim candidates.
3044         // If the remembered sets are not up to date we might miss some
3045         // entries that need to be handled.
3046         g1_rem_set()->cleanupHRRS();
3047 
3048         register_humongous_regions_with_cset();
3049 
3050         assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3051 
3052         // We call this after finalize_cset() to
3053         // ensure that the CSet has been finalized.
3054         _cm->verify_no_cset_oops();
3055 
3056         if (_hr_printer.is_active()) {
3057           G1PrintCollectionSetClosure cl(&_hr_printer);
3058           _collection_set.iterate(&cl);
3059         }
3060 
3061         // Initialize the GC alloc regions.
3062         _allocator->init_gc_alloc_regions(evacuation_info);
3063 
3064         G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3065         pre_evacuate_collection_set();
3066 
3067         // Actually do the work...
3068         evacuate_collection_set(evacuation_info, &per_thread_states);
3069 
3070         post_evacuate_collection_set(evacuation_info, &per_thread_states);
3071 
3072         const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3073         free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
3074 
3075         eagerly_reclaim_humongous_regions();
3076 
3077         record_obj_copy_mem_stats();
3078         _survivor_evac_stats.adjust_desired_plab_sz();
3079         _old_evac_stats.adjust_desired_plab_sz();
3080 
3081         double start = os::elapsedTime();
3082         start_new_collection_set();
3083         g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
3084 
3085         if (evacuation_failed()) {
3086           set_used(recalculate_used());
3087           if (_archive_allocator != NULL) {
3088             _archive_allocator->clear_used();
3089           }
3090           for (uint i = 0; i < ParallelGCThreads; i++) {
3091             if (_evacuation_failed_info_array[i].has_failed()) {
3092               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3093             }
3094           }
3095         } else {
3096           // The "used" of the the collection set have already been subtracted
3097           // when they were freed.  Add in the bytes evacuated.
3098           increase_used(g1_policy()->bytes_copied_during_gc());
3099         }
3100 
3101         if (collector_state()->during_initial_mark_pause()) {
3102           // We have to do this before we notify the CM threads that
3103           // they can start working to make sure that all the
3104           // appropriate initialization is done on the CM object.
3105           concurrent_mark()->checkpoint_roots_initial_post();
3106           collector_state()->set_mark_in_progress(true);
3107           // Note that we don't actually trigger the CM thread at
3108           // this point. We do that later when we're sure that
3109           // the current thread has completed its logging output.
3110         }
3111 
3112         allocate_dummy_regions();
3113 
3114         _allocator->init_mutator_alloc_region();
3115 
3116         {
3117           size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3118           if (expand_bytes > 0) {
3119             size_t bytes_before = capacity();
3120             // No need for an ergo logging here,
3121             // expansion_amount() does this when it returns a value > 0.
3122             double expand_ms;
3123             if (!expand(expand_bytes, _workers, &expand_ms)) {
3124               // We failed to expand the heap. Cannot do anything about it.
3125             }
3126             g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3127           }
3128         }
3129 
3130         // We redo the verification but now wrt to the new CSet which
3131         // has just got initialized after the previous CSet was freed.
3132         _cm->verify_no_cset_oops();
3133 
3134         // This timing is only used by the ergonomics to handle our pause target.
3135         // It is unclear why this should not include the full pause. We will
3136         // investigate this in CR 7178365.
3137         double sample_end_time_sec = os::elapsedTime();
3138         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3139         size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
3140         g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3141 
3142         evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3143         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3144 
3145         if (VerifyRememberedSets) {
3146           log_info(gc, verify)("[Verifying RemSets after GC]");
3147           VerifyRegionRemSetClosure v_cl;
3148           heap_region_iterate(&v_cl);
3149         }
3150 
3151         _verifier->verify_after_gc();
3152         _verifier->check_bitmaps("GC End");
3153 
3154         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3155         ref_processor_stw()->verify_no_references_recorded();
3156 
3157         // CM reference discovery will be re-enabled if necessary.
3158       }
3159 
3160 #ifdef TRACESPINNING
3161       ParallelTaskTerminator::print_termination_counts();
3162 #endif
3163 
3164       gc_epilogue(false);
3165     }
3166 
3167     // Print the remainder of the GC log output.
3168     if (evacuation_failed()) {
3169       log_info(gc)("To-space exhausted");
3170     }
3171 
3172     g1_policy()->print_phases();
3173     heap_transition.print();
3174 
3175     // It is not yet to safe to tell the concurrent mark to
3176     // start as we have some optional output below. We don't want the
3177     // output from the concurrent mark thread interfering with this
3178     // logging output either.
3179 
3180     _hrm.verify_optional();
3181     _verifier->verify_region_sets_optional();
3182 
3183     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3184     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3185 
3186     print_heap_after_gc();
3187     print_heap_regions();
3188     trace_heap_after_gc(_gc_tracer_stw);
3189 
3190     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3191     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3192     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3193     // before any GC notifications are raised.
3194     g1mm()->update_sizes();
3195 
3196     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3197     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3198     _gc_timer_stw->register_gc_end();
3199     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3200   }
3201   // It should now be safe to tell the concurrent mark thread to start
3202   // without its logging output interfering with the logging output
3203   // that came from the pause.
3204 
3205   if (should_start_conc_mark) {
3206     // CAUTION: after the doConcurrentMark() call below,
3207     // the concurrent marking thread(s) could be running
3208     // concurrently with us. Make sure that anything after
3209     // this point does not assume that we are the only GC thread
3210     // running. Note: of course, the actual marking work will
3211     // not start until the safepoint itself is released in
3212     // SuspendibleThreadSet::desynchronize().
3213     doConcurrentMark();
3214   }
3215 
3216   return true;
3217 }
3218 
3219 void G1CollectedHeap::remove_self_forwarding_pointers() {
3220   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3221   workers()->run_task(&rsfp_task);
3222 }
3223 
3224 void G1CollectedHeap::restore_after_evac_failure() {
3225   double remove_self_forwards_start = os::elapsedTime();
3226 
3227   remove_self_forwarding_pointers();
3228   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3229   _preserved_marks_set.restore(&task_executor);
3230 
3231   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3232 }
3233 
3234 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3235   if (!_evacuation_failed) {
3236     _evacuation_failed = true;
3237   }
3238 
3239   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3240   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3241 }
3242 
3243 bool G1ParEvacuateFollowersClosure::offer_termination() {
3244   G1ParScanThreadState* const pss = par_scan_state();
3245   start_term_time();
3246   const bool res = terminator()->offer_termination();
3247   end_term_time();
3248   return res;
3249 }
3250 
3251 void G1ParEvacuateFollowersClosure::do_void() {
3252   G1ParScanThreadState* const pss = par_scan_state();
3253   pss->trim_queue();
3254   do {
3255     pss->steal_and_trim_queue(queues());
3256   } while (!offer_termination());
3257 }
3258 
3259 class G1ParTask : public AbstractGangTask {
3260 protected:
3261   G1CollectedHeap*         _g1h;
3262   G1ParScanThreadStateSet* _pss;
3263   RefToScanQueueSet*       _queues;
3264   G1RootProcessor*         _root_processor;
3265   ParallelTaskTerminator   _terminator;
3266   uint                     _n_workers;
3267 
3268 public:
3269   G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3270     : AbstractGangTask("G1 collection"),
3271       _g1h(g1h),
3272       _pss(per_thread_states),
3273       _queues(task_queues),
3274       _root_processor(root_processor),
3275       _terminator(n_workers, _queues),
3276       _n_workers(n_workers)
3277   {}
3278 
3279   void work(uint worker_id) {
3280     if (worker_id >= _n_workers) return;  // no work needed this round
3281 
3282     double start_sec = os::elapsedTime();
3283     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3284 
3285     {
3286       ResourceMark rm;
3287       HandleMark   hm;
3288 
3289       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
3290 
3291       G1ParScanThreadState*           pss = _pss->state_for_worker(worker_id);
3292       pss->set_ref_processor(rp);
3293 
3294       double start_strong_roots_sec = os::elapsedTime();
3295 
3296       _root_processor->evacuate_roots(pss->closures(), worker_id);
3297 
3298       // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3299       // treating the nmethods visited to act as roots for concurrent marking.
3300       // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3301       // objects copied by the current evacuation.
3302       _g1h->g1_rem_set()->oops_into_collection_set_do(pss,
3303                                                       pss->closures()->weak_codeblobs(),
3304                                                       worker_id);
3305 
3306       double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3307 
3308       double term_sec = 0.0;
3309       size_t evac_term_attempts = 0;
3310       {
3311         double start = os::elapsedTime();
3312         G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3313         evac.do_void();
3314 
3315         evac_term_attempts = evac.term_attempts();
3316         term_sec = evac.term_time();
3317         double elapsed_sec = os::elapsedTime() - start;
3318         _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3319         _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3320         _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3321       }
3322 
3323       assert(pss->queue_is_empty(), "should be empty");
3324 
3325       if (log_is_enabled(Debug, gc, task, stats)) {
3326         MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3327         size_t lab_waste;
3328         size_t lab_undo_waste;
3329         pss->waste(lab_waste, lab_undo_waste);
3330         _g1h->print_termination_stats(worker_id,
3331                                       (os::elapsedTime() - start_sec) * 1000.0,   /* elapsed time */
3332                                       strong_roots_sec * 1000.0,                  /* strong roots time */
3333                                       term_sec * 1000.0,                          /* evac term time */
3334                                       evac_term_attempts,                         /* evac term attempts */
3335                                       lab_waste,                                  /* alloc buffer waste */
3336                                       lab_undo_waste                              /* undo waste */
3337                                       );
3338       }
3339 
3340       // Close the inner scope so that the ResourceMark and HandleMark
3341       // destructors are executed here and are included as part of the
3342       // "GC Worker Time".
3343     }
3344     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3345   }
3346 };
3347 
3348 void G1CollectedHeap::print_termination_stats_hdr() {
3349   log_debug(gc, task, stats)("GC Termination Stats");
3350   log_debug(gc, task, stats)("     elapsed  --strong roots-- -------termination------- ------waste (KiB)------");
3351   log_debug(gc, task, stats)("thr     ms        ms      %%        ms      %%    attempts  total   alloc    undo");
3352   log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3353 }
3354 
3355 void G1CollectedHeap::print_termination_stats(uint worker_id,
3356                                               double elapsed_ms,
3357                                               double strong_roots_ms,
3358                                               double term_ms,
3359                                               size_t term_attempts,
3360                                               size_t alloc_buffer_waste,
3361                                               size_t undo_waste) const {
3362   log_debug(gc, task, stats)
3363               ("%3d %9.2f %9.2f %6.2f "
3364                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3365                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3366                worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3367                term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3368                (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3369                alloc_buffer_waste * HeapWordSize / K,
3370                undo_waste * HeapWordSize / K);
3371 }
3372 
3373 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3374 private:
3375   BoolObjectClosure* _is_alive;
3376   G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3377 
3378   int _initial_string_table_size;
3379   int _initial_symbol_table_size;
3380 
3381   bool  _process_strings;
3382   int _strings_processed;
3383   int _strings_removed;
3384 
3385   bool  _process_symbols;
3386   int _symbols_processed;
3387   int _symbols_removed;
3388 
3389   bool _process_string_dedup;
3390 
3391 public:
3392   G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3393     AbstractGangTask("String/Symbol Unlinking"),
3394     _is_alive(is_alive),
3395     _dedup_closure(is_alive, NULL, false),
3396     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3397     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3398     _process_string_dedup(process_string_dedup) {
3399 
3400     _initial_string_table_size = StringTable::the_table()->table_size();
3401     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3402     if (process_strings) {
3403       StringTable::clear_parallel_claimed_index();
3404     }
3405     if (process_symbols) {
3406       SymbolTable::clear_parallel_claimed_index();
3407     }
3408   }
3409 
3410   ~G1StringAndSymbolCleaningTask() {
3411     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3412               "claim value %d after unlink less than initial string table size %d",
3413               StringTable::parallel_claimed_index(), _initial_string_table_size);
3414     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3415               "claim value %d after unlink less than initial symbol table size %d",
3416               SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3417 
3418     log_info(gc, stringtable)(
3419         "Cleaned string and symbol table, "
3420         "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3421         "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3422         strings_processed(), strings_removed(),
3423         symbols_processed(), symbols_removed());
3424   }
3425 
3426   void work(uint worker_id) {
3427     int strings_processed = 0;
3428     int strings_removed = 0;
3429     int symbols_processed = 0;
3430     int symbols_removed = 0;
3431     if (_process_strings) {
3432       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3433       Atomic::add(strings_processed, &_strings_processed);
3434       Atomic::add(strings_removed, &_strings_removed);
3435     }
3436     if (_process_symbols) {
3437       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3438       Atomic::add(symbols_processed, &_symbols_processed);
3439       Atomic::add(symbols_removed, &_symbols_removed);
3440     }
3441     if (_process_string_dedup) {
3442       G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3443     }
3444   }
3445 
3446   size_t strings_processed() const { return (size_t)_strings_processed; }
3447   size_t strings_removed()   const { return (size_t)_strings_removed; }
3448 
3449   size_t symbols_processed() const { return (size_t)_symbols_processed; }
3450   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
3451 };
3452 
3453 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3454 private:
3455   static Monitor* _lock;
3456 
3457   BoolObjectClosure* const _is_alive;
3458   const bool               _unloading_occurred;
3459   const uint               _num_workers;
3460 
3461   // Variables used to claim nmethods.
3462   CompiledMethod* _first_nmethod;
3463   CompiledMethod* volatile _claimed_nmethod;
3464 
3465   // The list of nmethods that need to be processed by the second pass.
3466   CompiledMethod* volatile _postponed_list;
3467   volatile uint            _num_entered_barrier;
3468 
3469  public:
3470   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3471       _is_alive(is_alive),
3472       _unloading_occurred(unloading_occurred),
3473       _num_workers(num_workers),
3474       _first_nmethod(NULL),
3475       _claimed_nmethod(NULL),
3476       _postponed_list(NULL),
3477       _num_entered_barrier(0)
3478   {
3479     CompiledMethod::increase_unloading_clock();
3480     // Get first alive nmethod
3481     CompiledMethodIterator iter = CompiledMethodIterator();
3482     if(iter.next_alive()) {
3483       _first_nmethod = iter.method();
3484     }
3485     _claimed_nmethod = _first_nmethod;
3486   }
3487 
3488   ~G1CodeCacheUnloadingTask() {
3489     CodeCache::verify_clean_inline_caches();
3490 
3491     CodeCache::set_needs_cache_clean(false);
3492     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3493 
3494     CodeCache::verify_icholder_relocations();
3495   }
3496 
3497  private:
3498   void add_to_postponed_list(CompiledMethod* nm) {
3499       CompiledMethod* old;
3500       do {
3501         old = _postponed_list;
3502         nm->set_unloading_next(old);
3503       } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
3504   }
3505 
3506   void clean_nmethod(CompiledMethod* nm) {
3507     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3508 
3509     if (postponed) {
3510       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3511       add_to_postponed_list(nm);
3512     }
3513 
3514     // Mark that this thread has been cleaned/unloaded.
3515     // After this call, it will be safe to ask if this nmethod was unloaded or not.
3516     nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3517   }
3518 
3519   void clean_nmethod_postponed(CompiledMethod* nm) {
3520     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3521   }
3522 
3523   static const int MaxClaimNmethods = 16;
3524 
3525   void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3526     CompiledMethod* first;
3527     CompiledMethodIterator last;
3528 
3529     do {
3530       *num_claimed_nmethods = 0;
3531 
3532       first = _claimed_nmethod;
3533       last = CompiledMethodIterator(first);
3534 
3535       if (first != NULL) {
3536 
3537         for (int i = 0; i < MaxClaimNmethods; i++) {
3538           if (!last.next_alive()) {
3539             break;
3540           }
3541           claimed_nmethods[i] = last.method();
3542           (*num_claimed_nmethods)++;
3543         }
3544       }
3545 
3546     } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
3547   }
3548 
3549   CompiledMethod* claim_postponed_nmethod() {
3550     CompiledMethod* claim;
3551     CompiledMethod* next;
3552 
3553     do {
3554       claim = _postponed_list;
3555       if (claim == NULL) {
3556         return NULL;
3557       }
3558 
3559       next = claim->unloading_next();
3560 
3561     } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
3562 
3563     return claim;
3564   }
3565 
3566  public:
3567   // Mark that we're done with the first pass of nmethod cleaning.
3568   void barrier_mark(uint worker_id) {
3569     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3570     _num_entered_barrier++;
3571     if (_num_entered_barrier == _num_workers) {
3572       ml.notify_all();
3573     }
3574   }
3575 
3576   // See if we have to wait for the other workers to
3577   // finish their first-pass nmethod cleaning work.
3578   void barrier_wait(uint worker_id) {
3579     if (_num_entered_barrier < _num_workers) {
3580       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3581       while (_num_entered_barrier < _num_workers) {
3582           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3583       }
3584     }
3585   }
3586 
3587   // Cleaning and unloading of nmethods. Some work has to be postponed
3588   // to the second pass, when we know which nmethods survive.
3589   void work_first_pass(uint worker_id) {
3590     // The first nmethods is claimed by the first worker.
3591     if (worker_id == 0 && _first_nmethod != NULL) {
3592       clean_nmethod(_first_nmethod);
3593       _first_nmethod = NULL;
3594     }
3595 
3596     int num_claimed_nmethods;
3597     CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3598 
3599     while (true) {
3600       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3601 
3602       if (num_claimed_nmethods == 0) {
3603         break;
3604       }
3605 
3606       for (int i = 0; i < num_claimed_nmethods; i++) {
3607         clean_nmethod(claimed_nmethods[i]);
3608       }
3609     }
3610   }
3611 
3612   void work_second_pass(uint worker_id) {
3613     CompiledMethod* nm;
3614     // Take care of postponed nmethods.
3615     while ((nm = claim_postponed_nmethod()) != NULL) {
3616       clean_nmethod_postponed(nm);
3617     }
3618   }
3619 };
3620 
3621 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3622 
3623 class G1KlassCleaningTask : public StackObj {
3624   BoolObjectClosure*                      _is_alive;
3625   volatile jint                           _clean_klass_tree_claimed;
3626   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3627 
3628  public:
3629   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3630       _is_alive(is_alive),
3631       _clean_klass_tree_claimed(0),
3632       _klass_iterator() {
3633   }
3634 
3635  private:
3636   bool claim_clean_klass_tree_task() {
3637     if (_clean_klass_tree_claimed) {
3638       return false;
3639     }
3640 
3641     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
3642   }
3643 
3644   InstanceKlass* claim_next_klass() {
3645     Klass* klass;
3646     do {
3647       klass =_klass_iterator.next_klass();
3648     } while (klass != NULL && !klass->is_instance_klass());
3649 
3650     // this can be null so don't call InstanceKlass::cast
3651     return static_cast<InstanceKlass*>(klass);
3652   }
3653 
3654 public:
3655 
3656   void clean_klass(InstanceKlass* ik) {
3657     ik->clean_weak_instanceklass_links(_is_alive);
3658   }
3659 
3660   void work() {
3661     ResourceMark rm;
3662 
3663     // One worker will clean the subklass/sibling klass tree.
3664     if (claim_clean_klass_tree_task()) {
3665       Klass::clean_subklass_tree(_is_alive);
3666     }
3667 
3668     // All workers will help cleaning the classes,
3669     InstanceKlass* klass;
3670     while ((klass = claim_next_klass()) != NULL) {
3671       clean_klass(klass);
3672     }
3673   }
3674 };
3675 
3676 class G1ResolvedMethodCleaningTask : public StackObj {
3677   BoolObjectClosure* _is_alive;
3678   volatile jint      _resolved_method_task_claimed;
3679 public:
3680   G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) :
3681       _is_alive(is_alive), _resolved_method_task_claimed(0) {}
3682 
3683   bool claim_resolved_method_task() {
3684     if (_resolved_method_task_claimed) {
3685       return false;
3686     }
3687     return Atomic::cmpxchg(1, (jint*)&_resolved_method_task_claimed, 0) == 0;
3688   }
3689 
3690   // These aren't big, one thread can do it all.
3691   void work() {
3692     if (claim_resolved_method_task()) {
3693       ResolvedMethodTable::unlink(_is_alive);
3694     }
3695   }
3696 };
3697 
3698 
3699 // To minimize the remark pause times, the tasks below are done in parallel.
3700 class G1ParallelCleaningTask : public AbstractGangTask {
3701 private:
3702   G1StringAndSymbolCleaningTask _string_symbol_task;
3703   G1CodeCacheUnloadingTask      _code_cache_task;
3704   G1KlassCleaningTask           _klass_cleaning_task;
3705   G1ResolvedMethodCleaningTask  _resolved_method_cleaning_task;
3706 
3707 public:
3708   // The constructor is run in the VMThread.
3709   G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3710       AbstractGangTask("Parallel Cleaning"),
3711       _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3712       _code_cache_task(num_workers, is_alive, unloading_occurred),
3713       _klass_cleaning_task(is_alive),
3714       _resolved_method_cleaning_task(is_alive) {
3715   }
3716 
3717   // The parallel work done by all worker threads.
3718   void work(uint worker_id) {
3719     // Do first pass of code cache cleaning.
3720     _code_cache_task.work_first_pass(worker_id);
3721 
3722     // Let the threads mark that the first pass is done.
3723     _code_cache_task.barrier_mark(worker_id);
3724 
3725     // Clean the Strings and Symbols.
3726     _string_symbol_task.work(worker_id);
3727 
3728     // Clean unreferenced things in the ResolvedMethodTable
3729     _resolved_method_cleaning_task.work();
3730 
3731     // Wait for all workers to finish the first code cache cleaning pass.
3732     _code_cache_task.barrier_wait(worker_id);
3733 
3734     // Do the second code cache cleaning work, which realize on
3735     // the liveness information gathered during the first pass.
3736     _code_cache_task.work_second_pass(worker_id);
3737 
3738     // Clean all klasses that were not unloaded.
3739     _klass_cleaning_task.work();
3740   }
3741 };
3742 
3743 
3744 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3745                                         bool class_unloading_occurred) {
3746   uint n_workers = workers()->active_workers();
3747 
3748   G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3749   workers()->run_task(&g1_unlink_task);
3750 }
3751 
3752 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3753                                        bool process_strings,
3754                                        bool process_symbols,
3755                                        bool process_string_dedup) {
3756   if (!process_strings && !process_symbols && !process_string_dedup) {
3757     // Nothing to clean.
3758     return;
3759   }
3760 
3761   G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3762   workers()->run_task(&g1_unlink_task);
3763 
3764 }
3765 
3766 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3767  private:
3768   DirtyCardQueueSet* _queue;
3769   G1CollectedHeap* _g1h;
3770  public:
3771   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3772     _queue(queue), _g1h(g1h) { }
3773 
3774   virtual void work(uint worker_id) {
3775     G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3776     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3777 
3778     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3779     _queue->par_apply_closure_to_all_completed_buffers(&cl);
3780 
3781     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3782   }
3783 };
3784 
3785 void G1CollectedHeap::redirty_logged_cards() {
3786   double redirty_logged_cards_start = os::elapsedTime();
3787 
3788   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3789   dirty_card_queue_set().reset_for_par_iteration();
3790   workers()->run_task(&redirty_task);
3791 
3792   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
3793   dcq.merge_bufferlists(&dirty_card_queue_set());
3794   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3795 
3796   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3797 }
3798 
3799 // Weak Reference Processing support
3800 
3801 // An always "is_alive" closure that is used to preserve referents.
3802 // If the object is non-null then it's alive.  Used in the preservation
3803 // of referent objects that are pointed to by reference objects
3804 // discovered by the CM ref processor.
3805 class G1AlwaysAliveClosure: public BoolObjectClosure {
3806   G1CollectedHeap* _g1;
3807 public:
3808   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3809   bool do_object_b(oop p) {
3810     if (p != NULL) {
3811       return true;
3812     }
3813     return false;
3814   }
3815 };
3816 
3817 bool G1STWIsAliveClosure::do_object_b(oop p) {
3818   // An object is reachable if it is outside the collection set,
3819   // or is inside and copied.
3820   return !_g1->is_in_cset(p) || p->is_forwarded();
3821 }
3822 
3823 // Non Copying Keep Alive closure
3824 class G1KeepAliveClosure: public OopClosure {
3825   G1CollectedHeap* _g1;
3826 public:
3827   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3828   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3829   void do_oop(oop* p) {
3830     oop obj = *p;
3831     assert(obj != NULL, "the caller should have filtered out NULL values");
3832 
3833     const InCSetState cset_state = _g1->in_cset_state(obj);
3834     if (!cset_state.is_in_cset_or_humongous()) {
3835       return;
3836     }
3837     if (cset_state.is_in_cset()) {
3838       assert( obj->is_forwarded(), "invariant" );
3839       *p = obj->forwardee();
3840     } else {
3841       assert(!obj->is_forwarded(), "invariant" );
3842       assert(cset_state.is_humongous(),
3843              "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3844       _g1->set_humongous_is_live(obj);
3845     }
3846   }
3847 };
3848 
3849 // Copying Keep Alive closure - can be called from both
3850 // serial and parallel code as long as different worker
3851 // threads utilize different G1ParScanThreadState instances
3852 // and different queues.
3853 
3854 class G1CopyingKeepAliveClosure: public OopClosure {
3855   G1CollectedHeap*         _g1h;
3856   OopClosure*              _copy_non_heap_obj_cl;
3857   G1ParScanThreadState*    _par_scan_state;
3858 
3859 public:
3860   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3861                             OopClosure* non_heap_obj_cl,
3862                             G1ParScanThreadState* pss):
3863     _g1h(g1h),
3864     _copy_non_heap_obj_cl(non_heap_obj_cl),
3865     _par_scan_state(pss)
3866   {}
3867 
3868   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3869   virtual void do_oop(      oop* p) { do_oop_work(p); }
3870 
3871   template <class T> void do_oop_work(T* p) {
3872     oop obj = oopDesc::load_decode_heap_oop(p);
3873 
3874     if (_g1h->is_in_cset_or_humongous(obj)) {
3875       // If the referent object has been forwarded (either copied
3876       // to a new location or to itself in the event of an
3877       // evacuation failure) then we need to update the reference
3878       // field and, if both reference and referent are in the G1
3879       // heap, update the RSet for the referent.
3880       //
3881       // If the referent has not been forwarded then we have to keep
3882       // it alive by policy. Therefore we have copy the referent.
3883       //
3884       // If the reference field is in the G1 heap then we can push
3885       // on the PSS queue. When the queue is drained (after each
3886       // phase of reference processing) the object and it's followers
3887       // will be copied, the reference field set to point to the
3888       // new location, and the RSet updated. Otherwise we need to
3889       // use the the non-heap or metadata closures directly to copy
3890       // the referent object and update the pointer, while avoiding
3891       // updating the RSet.
3892 
3893       if (_g1h->is_in_g1_reserved(p)) {
3894         _par_scan_state->push_on_queue(p);
3895       } else {
3896         assert(!Metaspace::contains((const void*)p),
3897                "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3898         _copy_non_heap_obj_cl->do_oop(p);
3899       }
3900     }
3901   }
3902 };
3903 
3904 // Serial drain queue closure. Called as the 'complete_gc'
3905 // closure for each discovered list in some of the
3906 // reference processing phases.
3907 
3908 class G1STWDrainQueueClosure: public VoidClosure {
3909 protected:
3910   G1CollectedHeap* _g1h;
3911   G1ParScanThreadState* _par_scan_state;
3912 
3913   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3914 
3915 public:
3916   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3917     _g1h(g1h),
3918     _par_scan_state(pss)
3919   { }
3920 
3921   void do_void() {
3922     G1ParScanThreadState* const pss = par_scan_state();
3923     pss->trim_queue();
3924   }
3925 };
3926 
3927 // Parallel Reference Processing closures
3928 
3929 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3930 // processing during G1 evacuation pauses.
3931 
3932 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3933 private:
3934   G1CollectedHeap*          _g1h;
3935   G1ParScanThreadStateSet*  _pss;
3936   RefToScanQueueSet*        _queues;
3937   WorkGang*                 _workers;
3938   uint                      _active_workers;
3939 
3940 public:
3941   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3942                            G1ParScanThreadStateSet* per_thread_states,
3943                            WorkGang* workers,
3944                            RefToScanQueueSet *task_queues,
3945                            uint n_workers) :
3946     _g1h(g1h),
3947     _pss(per_thread_states),
3948     _queues(task_queues),
3949     _workers(workers),
3950     _active_workers(n_workers)
3951   {
3952     g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
3953   }
3954 
3955   // Executes the given task using concurrent marking worker threads.
3956   virtual void execute(ProcessTask& task);
3957   virtual void execute(EnqueueTask& task);
3958 };
3959 
3960 // Gang task for possibly parallel reference processing
3961 
3962 class G1STWRefProcTaskProxy: public AbstractGangTask {
3963   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3964   ProcessTask&     _proc_task;
3965   G1CollectedHeap* _g1h;
3966   G1ParScanThreadStateSet* _pss;
3967   RefToScanQueueSet* _task_queues;
3968   ParallelTaskTerminator* _terminator;
3969 
3970 public:
3971   G1STWRefProcTaskProxy(ProcessTask& proc_task,
3972                         G1CollectedHeap* g1h,
3973                         G1ParScanThreadStateSet* per_thread_states,
3974                         RefToScanQueueSet *task_queues,
3975                         ParallelTaskTerminator* terminator) :
3976     AbstractGangTask("Process reference objects in parallel"),
3977     _proc_task(proc_task),
3978     _g1h(g1h),
3979     _pss(per_thread_states),
3980     _task_queues(task_queues),
3981     _terminator(terminator)
3982   {}
3983 
3984   virtual void work(uint worker_id) {
3985     // The reference processing task executed by a single worker.
3986     ResourceMark rm;
3987     HandleMark   hm;
3988 
3989     G1STWIsAliveClosure is_alive(_g1h);
3990 
3991     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
3992     pss->set_ref_processor(NULL);
3993 
3994     // Keep alive closure.
3995     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
3996 
3997     // Complete GC closure
3998     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
3999 
4000     // Call the reference processing task's work routine.
4001     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
4002 
4003     // Note we cannot assert that the refs array is empty here as not all
4004     // of the processing tasks (specifically phase2 - pp2_work) execute
4005     // the complete_gc closure (which ordinarily would drain the queue) so
4006     // the queue may not be empty.
4007   }
4008 };
4009 
4010 // Driver routine for parallel reference processing.
4011 // Creates an instance of the ref processing gang
4012 // task and has the worker threads execute it.
4013 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4014   assert(_workers != NULL, "Need parallel worker threads.");
4015 
4016   ParallelTaskTerminator terminator(_active_workers, _queues);
4017   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4018 
4019   _workers->run_task(&proc_task_proxy);
4020 }
4021 
4022 // Gang task for parallel reference enqueueing.
4023 
4024 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4025   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4026   EnqueueTask& _enq_task;
4027 
4028 public:
4029   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4030     AbstractGangTask("Enqueue reference objects in parallel"),
4031     _enq_task(enq_task)
4032   { }
4033 
4034   virtual void work(uint worker_id) {
4035     _enq_task.work(worker_id);
4036   }
4037 };
4038 
4039 // Driver routine for parallel reference enqueueing.
4040 // Creates an instance of the ref enqueueing gang
4041 // task and has the worker threads execute it.
4042 
4043 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4044   assert(_workers != NULL, "Need parallel worker threads.");
4045 
4046   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4047 
4048   _workers->run_task(&enq_task_proxy);
4049 }
4050 
4051 // End of weak reference support closures
4052 
4053 // Abstract task used to preserve (i.e. copy) any referent objects
4054 // that are in the collection set and are pointed to by reference
4055 // objects discovered by the CM ref processor.
4056 
4057 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4058 protected:
4059   G1CollectedHeap*         _g1h;
4060   G1ParScanThreadStateSet* _pss;
4061   RefToScanQueueSet*       _queues;
4062   ParallelTaskTerminator   _terminator;
4063   uint                     _n_workers;
4064 
4065 public:
4066   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4067     AbstractGangTask("ParPreserveCMReferents"),
4068     _g1h(g1h),
4069     _pss(per_thread_states),
4070     _queues(task_queues),
4071     _terminator(workers, _queues),
4072     _n_workers(workers)
4073   {
4074     g1h->ref_processor_cm()->set_active_mt_degree(workers);
4075   }
4076 
4077   void work(uint worker_id) {
4078     G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4079 
4080     ResourceMark rm;
4081     HandleMark   hm;
4082 
4083     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4084     pss->set_ref_processor(NULL);
4085     assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4086 
4087     // Is alive closure
4088     G1AlwaysAliveClosure always_alive(_g1h);
4089 
4090     // Copying keep alive closure. Applied to referent objects that need
4091     // to be copied.
4092     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4093 
4094     ReferenceProcessor* rp = _g1h->ref_processor_cm();
4095 
4096     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4097     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4098 
4099     // limit is set using max_num_q() - which was set using ParallelGCThreads.
4100     // So this must be true - but assert just in case someone decides to
4101     // change the worker ids.
4102     assert(worker_id < limit, "sanity");
4103     assert(!rp->discovery_is_atomic(), "check this code");
4104 
4105     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4106     for (uint idx = worker_id; idx < limit; idx += stride) {
4107       DiscoveredList& ref_list = rp->discovered_refs()[idx];
4108 
4109       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4110       while (iter.has_next()) {
4111         // Since discovery is not atomic for the CM ref processor, we
4112         // can see some null referent objects.
4113         iter.load_ptrs(DEBUG_ONLY(true));
4114         oop ref = iter.obj();
4115 
4116         // This will filter nulls.
4117         if (iter.is_referent_alive()) {
4118           iter.make_referent_alive();
4119         }
4120         iter.move_to_next();
4121       }
4122     }
4123 
4124     // Drain the queue - which may cause stealing
4125     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4126     drain_queue.do_void();
4127     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4128     assert(pss->queue_is_empty(), "should be");
4129   }
4130 };
4131 
4132 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4133   // Any reference objects, in the collection set, that were 'discovered'
4134   // by the CM ref processor should have already been copied (either by
4135   // applying the external root copy closure to the discovered lists, or
4136   // by following an RSet entry).
4137   //
4138   // But some of the referents, that are in the collection set, that these
4139   // reference objects point to may not have been copied: the STW ref
4140   // processor would have seen that the reference object had already
4141   // been 'discovered' and would have skipped discovering the reference,
4142   // but would not have treated the reference object as a regular oop.
4143   // As a result the copy closure would not have been applied to the
4144   // referent object.
4145   //
4146   // We need to explicitly copy these referent objects - the references
4147   // will be processed at the end of remarking.
4148   //
4149   // We also need to do this copying before we process the reference
4150   // objects discovered by the STW ref processor in case one of these
4151   // referents points to another object which is also referenced by an
4152   // object discovered by the STW ref processor.
4153   double preserve_cm_referents_time = 0.0;
4154 
4155   // To avoid spawning task when there is no work to do, check that
4156   // a concurrent cycle is active and that some references have been
4157   // discovered.
4158   if (concurrent_mark()->cm_thread()->during_cycle() &&
4159       ref_processor_cm()->has_discovered_references()) {
4160     double preserve_cm_referents_start = os::elapsedTime();
4161     uint no_of_gc_workers = workers()->active_workers();
4162     G1ParPreserveCMReferentsTask keep_cm_referents(this,
4163                                                    per_thread_states,
4164                                                    no_of_gc_workers,
4165                                                    _task_queues);
4166     workers()->run_task(&keep_cm_referents);
4167     preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4168   }
4169 
4170   g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4171 }
4172 
4173 // Weak Reference processing during an evacuation pause (part 1).
4174 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4175   double ref_proc_start = os::elapsedTime();
4176 
4177   ReferenceProcessor* rp = _ref_processor_stw;
4178   assert(rp->discovery_enabled(), "should have been enabled");
4179 
4180   // Closure to test whether a referent is alive.
4181   G1STWIsAliveClosure is_alive(this);
4182 
4183   // Even when parallel reference processing is enabled, the processing
4184   // of JNI refs is serial and performed serially by the current thread
4185   // rather than by a worker. The following PSS will be used for processing
4186   // JNI refs.
4187 
4188   // Use only a single queue for this PSS.
4189   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
4190   pss->set_ref_processor(NULL);
4191   assert(pss->queue_is_empty(), "pre-condition");
4192 
4193   // Keep alive closure.
4194   G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4195 
4196   // Serial Complete GC closure
4197   G1STWDrainQueueClosure drain_queue(this, pss);
4198 
4199   // Setup the soft refs policy...
4200   rp->setup_policy(false);
4201 
4202   ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4203 
4204   ReferenceProcessorStats stats;
4205   if (!rp->processing_is_mt()) {
4206     // Serial reference processing...
4207     stats = rp->process_discovered_references(&is_alive,
4208                                               &keep_alive,
4209                                               &drain_queue,
4210                                               NULL,
4211                                               pt);
4212   } else {
4213     uint no_of_gc_workers = workers()->active_workers();
4214 
4215     // Parallel reference processing
4216     assert(no_of_gc_workers <= rp->max_num_q(),
4217            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4218            no_of_gc_workers,  rp->max_num_q());
4219 
4220     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4221     stats = rp->process_discovered_references(&is_alive,
4222                                               &keep_alive,
4223                                               &drain_queue,
4224                                               &par_task_executor,
4225                                               pt);
4226   }
4227 
4228   _gc_tracer_stw->report_gc_reference_stats(stats);
4229 
4230   // We have completed copying any necessary live referent objects.
4231   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4232 
4233   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4234   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4235 }
4236 
4237 // Weak Reference processing during an evacuation pause (part 2).
4238 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4239   double ref_enq_start = os::elapsedTime();
4240 
4241   ReferenceProcessor* rp = _ref_processor_stw;
4242   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4243 
4244   ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4245 
4246   // Now enqueue any remaining on the discovered lists on to
4247   // the pending list.
4248   if (!rp->processing_is_mt()) {
4249     // Serial reference processing...
4250     rp->enqueue_discovered_references(NULL, pt);
4251   } else {
4252     // Parallel reference enqueueing
4253 
4254     uint n_workers = workers()->active_workers();
4255 
4256     assert(n_workers <= rp->max_num_q(),
4257            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4258            n_workers,  rp->max_num_q());
4259 
4260     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4261     rp->enqueue_discovered_references(&par_task_executor, pt);
4262   }
4263 
4264   rp->verify_no_references_recorded();
4265   assert(!rp->discovery_enabled(), "should have been disabled");
4266 
4267   // If during an initial mark pause we install a pending list head which is not otherwise reachable
4268   // ensure that it is marked in the bitmap for concurrent marking to discover.
4269   if (collector_state()->during_initial_mark_pause()) {
4270     oop pll_head = Universe::reference_pending_list();
4271     if (pll_head != NULL) {
4272       _cm->mark_in_next_bitmap(pll_head);
4273     }
4274   }
4275 
4276   // FIXME
4277   // CM's reference processing also cleans up the string and symbol tables.
4278   // Should we do that here also? We could, but it is a serial operation
4279   // and could significantly increase the pause time.
4280 
4281   double ref_enq_time = os::elapsedTime() - ref_enq_start;
4282   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4283 }
4284 
4285 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4286   double merge_pss_time_start = os::elapsedTime();
4287   per_thread_states->flush();
4288   g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4289 }
4290 
4291 void G1CollectedHeap::pre_evacuate_collection_set() {
4292   _expand_heap_after_alloc_failure = true;
4293   _evacuation_failed = false;
4294 
4295   // Disable the hot card cache.
4296   _hot_card_cache->reset_hot_cache_claimed_index();
4297   _hot_card_cache->set_use_cache(false);
4298 
4299   g1_rem_set()->prepare_for_oops_into_collection_set_do();
4300   _preserved_marks_set.assert_empty();
4301 
4302   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4303 
4304   // InitialMark needs claim bits to keep track of the marked-through CLDs.
4305   if (collector_state()->during_initial_mark_pause()) {
4306     double start_clear_claimed_marks = os::elapsedTime();
4307 
4308     ClassLoaderDataGraph::clear_claimed_marks();
4309 
4310     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
4311     phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
4312   }
4313 }
4314 
4315 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4316   // Should G1EvacuationFailureALot be in effect for this GC?
4317   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4318 
4319   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4320 
4321   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4322 
4323   double start_par_time_sec = os::elapsedTime();
4324   double end_par_time_sec;
4325 
4326   {
4327     const uint n_workers = workers()->active_workers();
4328     G1RootProcessor root_processor(this, n_workers);
4329     G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4330 
4331     print_termination_stats_hdr();
4332 
4333     workers()->run_task(&g1_par_task);
4334     end_par_time_sec = os::elapsedTime();
4335 
4336     // Closing the inner scope will execute the destructor
4337     // for the G1RootProcessor object. We record the current
4338     // elapsed time before closing the scope so that time
4339     // taken for the destructor is NOT included in the
4340     // reported parallel time.
4341   }
4342 
4343   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4344   phase_times->record_par_time(par_time_ms);
4345 
4346   double code_root_fixup_time_ms =
4347         (os::elapsedTime() - end_par_time_sec) * 1000.0;
4348   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4349 }
4350 
4351 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4352   // Process any discovered reference objects - we have
4353   // to do this _before_ we retire the GC alloc regions
4354   // as we may have to copy some 'reachable' referent
4355   // objects (and their reachable sub-graphs) that were
4356   // not copied during the pause.
4357   if (g1_policy()->should_process_references()) {
4358     preserve_cm_referents(per_thread_states);
4359     process_discovered_references(per_thread_states);
4360   } else {
4361     ref_processor_stw()->verify_no_references_recorded();
4362   }
4363 
4364   G1STWIsAliveClosure is_alive(this);
4365   G1KeepAliveClosure keep_alive(this);
4366 
4367   {
4368     double start = os::elapsedTime();
4369 
4370     WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
4371 
4372     double time_ms = (os::elapsedTime() - start) * 1000.0;
4373     g1_policy()->phase_times()->record_ref_proc_time(time_ms);
4374   }
4375 
4376   if (G1StringDedup::is_enabled()) {
4377     double fixup_start = os::elapsedTime();
4378 
4379     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4380 
4381     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4382     g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4383   }
4384 
4385   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4386 
4387   if (evacuation_failed()) {
4388     restore_after_evac_failure();
4389 
4390     // Reset the G1EvacuationFailureALot counters and flags
4391     // Note: the values are reset only when an actual
4392     // evacuation failure occurs.
4393     NOT_PRODUCT(reset_evacuation_should_fail();)
4394   }
4395 
4396   _preserved_marks_set.assert_empty();
4397 
4398   // Enqueue any remaining references remaining on the STW
4399   // reference processor's discovered lists. We need to do
4400   // this after the card table is cleaned (and verified) as
4401   // the act of enqueueing entries on to the pending list
4402   // will log these updates (and dirty their associated
4403   // cards). We need these updates logged to update any
4404   // RSets.
4405   if (g1_policy()->should_process_references()) {
4406     enqueue_discovered_references(per_thread_states);
4407   } else {
4408     g1_policy()->phase_times()->record_ref_enq_time(0);
4409   }
4410 
4411   _allocator->release_gc_alloc_regions(evacuation_info);
4412 
4413   merge_per_thread_state_info(per_thread_states);
4414 
4415   // Reset and re-enable the hot card cache.
4416   // Note the counts for the cards in the regions in the
4417   // collection set are reset when the collection set is freed.
4418   _hot_card_cache->reset_hot_cache();
4419   _hot_card_cache->set_use_cache(true);
4420 
4421   purge_code_root_memory();
4422 
4423   redirty_logged_cards();
4424 #if COMPILER2_OR_JVMCI
4425   double start = os::elapsedTime();
4426   DerivedPointerTable::update_pointers();
4427   g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4428 #endif
4429   g1_policy()->print_age_table();
4430 }
4431 
4432 void G1CollectedHeap::record_obj_copy_mem_stats() {
4433   g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4434 
4435   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4436                                                create_g1_evac_summary(&_old_evac_stats));
4437 }
4438 
4439 void G1CollectedHeap::free_region(HeapRegion* hr,
4440                                   FreeRegionList* free_list,
4441                                   bool skip_remset,
4442                                   bool skip_hot_card_cache,
4443                                   bool locked) {
4444   assert(!hr->is_free(), "the region should not be free");
4445   assert(!hr->is_empty(), "the region should not be empty");
4446   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4447   assert(free_list != NULL, "pre-condition");
4448 
4449   if (G1VerifyBitmaps) {
4450     MemRegion mr(hr->bottom(), hr->end());
4451     concurrent_mark()->clear_range_in_prev_bitmap(mr);
4452   }
4453 
4454   // Clear the card counts for this region.
4455   // Note: we only need to do this if the region is not young
4456   // (since we don't refine cards in young regions).
4457   if (!skip_hot_card_cache && !hr->is_young()) {
4458     _hot_card_cache->reset_card_counts(hr);
4459   }
4460   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4461   free_list->add_ordered(hr);
4462 }
4463 
4464 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4465                                             FreeRegionList* free_list,
4466                                             bool skip_remset) {
4467   assert(hr->is_humongous(), "this is only for humongous regions");
4468   assert(free_list != NULL, "pre-condition");
4469   hr->clear_humongous();
4470   free_region(hr, free_list, skip_remset);
4471 }
4472 
4473 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4474                                            const uint humongous_regions_removed) {
4475   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4476     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4477     _old_set.bulk_remove(old_regions_removed);
4478     _humongous_set.bulk_remove(humongous_regions_removed);
4479   }
4480 
4481 }
4482 
4483 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4484   assert(list != NULL, "list can't be null");
4485   if (!list->is_empty()) {
4486     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4487     _hrm.insert_list_into_free_list(list);
4488   }
4489 }
4490 
4491 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4492   decrease_used(bytes);
4493 }
4494 
4495 class G1ParScrubRemSetTask: public AbstractGangTask {
4496 protected:
4497   G1RemSet* _g1rs;
4498   HeapRegionClaimer _hrclaimer;
4499 
4500 public:
4501   G1ParScrubRemSetTask(G1RemSet* g1_rs, uint num_workers) :
4502     AbstractGangTask("G1 ScrubRS"),
4503     _g1rs(g1_rs),
4504     _hrclaimer(num_workers) {
4505   }
4506 
4507   void work(uint worker_id) {
4508     _g1rs->scrub(worker_id, &_hrclaimer);
4509   }
4510 };
4511 
4512 void G1CollectedHeap::scrub_rem_set() {
4513   uint num_workers = workers()->active_workers();
4514   G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), num_workers);
4515   workers()->run_task(&g1_par_scrub_rs_task);
4516 }
4517 
4518 class G1FreeCollectionSetTask : public AbstractGangTask {
4519 private:
4520 
4521   // Closure applied to all regions in the collection set to do work that needs to
4522   // be done serially in a single thread.
4523   class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4524   private:
4525     EvacuationInfo* _evacuation_info;
4526     const size_t* _surviving_young_words;
4527 
4528     // Bytes used in successfully evacuated regions before the evacuation.
4529     size_t _before_used_bytes;
4530     // Bytes used in unsucessfully evacuated regions before the evacuation
4531     size_t _after_used_bytes;
4532 
4533     size_t _bytes_allocated_in_old_since_last_gc;
4534 
4535     size_t _failure_used_words;
4536     size_t _failure_waste_words;
4537 
4538     FreeRegionList _local_free_list;
4539   public:
4540     G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4541       HeapRegionClosure(),
4542       _evacuation_info(evacuation_info),
4543       _surviving_young_words(surviving_young_words),
4544       _before_used_bytes(0),
4545       _after_used_bytes(0),
4546       _bytes_allocated_in_old_since_last_gc(0),
4547       _failure_used_words(0),
4548       _failure_waste_words(0),
4549       _local_free_list("Local Region List for CSet Freeing") {
4550     }
4551 
4552     virtual bool doHeapRegion(HeapRegion* r) {
4553       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4554 
4555       assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4556       g1h->clear_in_cset(r);
4557 
4558       if (r->is_young()) {
4559         assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4560                "Young index %d is wrong for region %u of type %s with %u young regions",
4561                r->young_index_in_cset(),
4562                r->hrm_index(),
4563                r->get_type_str(),
4564                g1h->collection_set()->young_region_length());
4565         size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4566         r->record_surv_words_in_group(words_survived);
4567       }
4568 
4569       if (!r->evacuation_failed()) {
4570         assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4571         _before_used_bytes += r->used();
4572         g1h->free_region(r,
4573                          &_local_free_list,
4574                          true, /* skip_remset */
4575                          true, /* skip_hot_card_cache */
4576                          true  /* locked */);
4577       } else {
4578         r->uninstall_surv_rate_group();
4579         r->set_young_index_in_cset(-1);
4580         r->set_evacuation_failed(false);
4581         // When moving a young gen region to old gen, we "allocate" that whole region
4582         // there. This is in addition to any already evacuated objects. Notify the
4583         // policy about that.
4584         // Old gen regions do not cause an additional allocation: both the objects
4585         // still in the region and the ones already moved are accounted for elsewhere.
4586         if (r->is_young()) {
4587           _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4588         }
4589         // The region is now considered to be old.
4590         r->set_old();
4591         // Do some allocation statistics accounting. Regions that failed evacuation
4592         // are always made old, so there is no need to update anything in the young
4593         // gen statistics, but we need to update old gen statistics.
4594         size_t used_words = r->marked_bytes() / HeapWordSize;
4595 
4596         _failure_used_words += used_words;
4597         _failure_waste_words += HeapRegion::GrainWords - used_words;
4598 
4599         g1h->old_set_add(r);
4600         _after_used_bytes += r->used();
4601       }
4602       return false;
4603     }
4604 
4605     void complete_work() {
4606       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4607 
4608       _evacuation_info->set_regions_freed(_local_free_list.length());
4609       _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4610 
4611       g1h->prepend_to_freelist(&_local_free_list);
4612       g1h->decrement_summary_bytes(_before_used_bytes);
4613 
4614       G1Policy* policy = g1h->g1_policy();
4615       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4616 
4617       g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4618     }
4619   };
4620 
4621   G1CollectionSet* _collection_set;
4622   G1SerialFreeCollectionSetClosure _cl;
4623   const size_t* _surviving_young_words;
4624 
4625   size_t _rs_lengths;
4626 
4627   volatile jint _serial_work_claim;
4628 
4629   struct WorkItem {
4630     uint region_idx;
4631     bool is_young;
4632     bool evacuation_failed;
4633 
4634     WorkItem(HeapRegion* r) {
4635       region_idx = r->hrm_index();
4636       is_young = r->is_young();
4637       evacuation_failed = r->evacuation_failed();
4638     }
4639   };
4640 
4641   volatile size_t _parallel_work_claim;
4642   size_t _num_work_items;
4643   WorkItem* _work_items;
4644 
4645   void do_serial_work() {
4646     // Need to grab the lock to be allowed to modify the old region list.
4647     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4648     _collection_set->iterate(&_cl);
4649   }
4650 
4651   void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4652     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4653 
4654     HeapRegion* r = g1h->region_at(region_idx);
4655     assert(!g1h->is_on_master_free_list(r), "sanity");
4656 
4657     Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4658 
4659     if (!is_young) {
4660       g1h->_hot_card_cache->reset_card_counts(r);
4661     }
4662 
4663     if (!evacuation_failed) {
4664       r->rem_set()->clear_locked();
4665     }
4666   }
4667 
4668   class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4669   private:
4670     size_t _cur_idx;
4671     WorkItem* _work_items;
4672   public:
4673     G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4674 
4675     virtual bool doHeapRegion(HeapRegion* r) {
4676       _work_items[_cur_idx++] = WorkItem(r);
4677       return false;
4678     }
4679   };
4680 
4681   void prepare_work() {
4682     G1PrepareFreeCollectionSetClosure cl(_work_items);
4683     _collection_set->iterate(&cl);
4684   }
4685 
4686   void complete_work() {
4687     _cl.complete_work();
4688 
4689     G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4690     policy->record_max_rs_lengths(_rs_lengths);
4691     policy->cset_regions_freed();
4692   }
4693 public:
4694   G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4695     AbstractGangTask("G1 Free Collection Set"),
4696     _cl(evacuation_info, surviving_young_words),
4697     _collection_set(collection_set),
4698     _surviving_young_words(surviving_young_words),
4699     _serial_work_claim(0),
4700     _rs_lengths(0),
4701     _parallel_work_claim(0),
4702     _num_work_items(collection_set->region_length()),
4703     _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4704     prepare_work();
4705   }
4706 
4707   ~G1FreeCollectionSetTask() {
4708     complete_work();
4709     FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4710   }
4711 
4712   // Chunk size for work distribution. The chosen value has been determined experimentally
4713   // to be a good tradeoff between overhead and achievable parallelism.
4714   static uint chunk_size() { return 32; }
4715 
4716   virtual void work(uint worker_id) {
4717     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4718 
4719     // Claim serial work.
4720     if (_serial_work_claim == 0) {
4721       jint value = Atomic::add(1, &_serial_work_claim) - 1;
4722       if (value == 0) {
4723         double serial_time = os::elapsedTime();
4724         do_serial_work();
4725         timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4726       }
4727     }
4728 
4729     // Start parallel work.
4730     double young_time = 0.0;
4731     bool has_young_time = false;
4732     double non_young_time = 0.0;
4733     bool has_non_young_time = false;
4734 
4735     while (true) {
4736       size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4737       size_t cur = end - chunk_size();
4738 
4739       if (cur >= _num_work_items) {
4740         break;
4741       }
4742 
4743       double start_time = os::elapsedTime();
4744 
4745       end = MIN2(end, _num_work_items);
4746 
4747       for (; cur < end; cur++) {
4748         bool is_young = _work_items[cur].is_young;
4749 
4750         do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4751 
4752         double end_time = os::elapsedTime();
4753         double time_taken = end_time - start_time;
4754         if (is_young) {
4755           young_time += time_taken;
4756           has_young_time = true;
4757         } else {
4758           non_young_time += time_taken;
4759           has_non_young_time = true;
4760         }
4761         start_time = end_time;
4762       }
4763     }
4764 
4765     if (has_young_time) {
4766       timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4767     }
4768     if (has_non_young_time) {
4769       timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, young_time);
4770     }
4771   }
4772 };
4773 
4774 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4775   _eden.clear();
4776 
4777   double free_cset_start_time = os::elapsedTime();
4778 
4779   {
4780     uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4781     uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4782 
4783     G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4784 
4785     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4786                         cl.name(),
4787                         num_workers,
4788                         _collection_set.region_length());
4789     workers()->run_task(&cl, num_workers);
4790   }
4791   g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4792 
4793   collection_set->clear();
4794 }
4795 
4796 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4797  private:
4798   FreeRegionList* _free_region_list;
4799   HeapRegionSet* _proxy_set;
4800   uint _humongous_objects_reclaimed;
4801   uint _humongous_regions_reclaimed;
4802   size_t _freed_bytes;
4803  public:
4804 
4805   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4806     _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4807   }
4808 
4809   virtual bool doHeapRegion(HeapRegion* r) {
4810     if (!r->is_starts_humongous()) {
4811       return false;
4812     }
4813 
4814     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4815 
4816     oop obj = (oop)r->bottom();
4817     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4818 
4819     // The following checks whether the humongous object is live are sufficient.
4820     // The main additional check (in addition to having a reference from the roots
4821     // or the young gen) is whether the humongous object has a remembered set entry.
4822     //
4823     // A humongous object cannot be live if there is no remembered set for it
4824     // because:
4825     // - there can be no references from within humongous starts regions referencing
4826     // the object because we never allocate other objects into them.
4827     // (I.e. there are no intra-region references that may be missed by the
4828     // remembered set)
4829     // - as soon there is a remembered set entry to the humongous starts region
4830     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4831     // until the end of a concurrent mark.
4832     //
4833     // It is not required to check whether the object has been found dead by marking
4834     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4835     // all objects allocated during that time are considered live.
4836     // SATB marking is even more conservative than the remembered set.
4837     // So if at this point in the collection there is no remembered set entry,
4838     // nobody has a reference to it.
4839     // At the start of collection we flush all refinement logs, and remembered sets
4840     // are completely up-to-date wrt to references to the humongous object.
4841     //
4842     // Other implementation considerations:
4843     // - never consider object arrays at this time because they would pose
4844     // considerable effort for cleaning up the the remembered sets. This is
4845     // required because stale remembered sets might reference locations that
4846     // are currently allocated into.
4847     uint region_idx = r->hrm_index();
4848     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4849         !r->rem_set()->is_empty()) {
4850       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",
4851                                region_idx,
4852                                (size_t)obj->size() * HeapWordSize,
4853                                p2i(r->bottom()),
4854                                r->rem_set()->occupied(),
4855                                r->rem_set()->strong_code_roots_list_length(),
4856                                next_bitmap->is_marked(r->bottom()),
4857                                g1h->is_humongous_reclaim_candidate(region_idx),
4858                                obj->is_typeArray()
4859                               );
4860       return false;
4861     }
4862 
4863     guarantee(obj->is_typeArray(),
4864               "Only eagerly reclaiming type arrays is supported, but the object "
4865               PTR_FORMAT " is not.", p2i(r->bottom()));
4866 
4867     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",
4868                              region_idx,
4869                              (size_t)obj->size() * HeapWordSize,
4870                              p2i(r->bottom()),
4871                              r->rem_set()->occupied(),
4872                              r->rem_set()->strong_code_roots_list_length(),
4873                              next_bitmap->is_marked(r->bottom()),
4874                              g1h->is_humongous_reclaim_candidate(region_idx),
4875                              obj->is_typeArray()
4876                             );
4877 
4878     // Need to clear mark bit of the humongous object if already set.
4879     if (next_bitmap->is_marked(r->bottom())) {
4880       next_bitmap->clear(r->bottom());
4881     }
4882     _humongous_objects_reclaimed++;
4883     do {
4884       HeapRegion* next = g1h->next_region_in_humongous(r);
4885       _freed_bytes += r->used();
4886       r->set_containing_set(NULL);
4887       _humongous_regions_reclaimed++;
4888       g1h->free_humongous_region(r, _free_region_list, false /* skip_remset */ );
4889       r = next;
4890     } while (r != NULL);
4891 
4892     return false;
4893   }
4894 
4895   uint humongous_objects_reclaimed() {
4896     return _humongous_objects_reclaimed;
4897   }
4898 
4899   uint humongous_regions_reclaimed() {
4900     return _humongous_regions_reclaimed;
4901   }
4902 
4903   size_t bytes_freed() const {
4904     return _freed_bytes;
4905   }
4906 };
4907 
4908 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4909   assert_at_safepoint(true);
4910 
4911   if (!G1EagerReclaimHumongousObjects ||
4912       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4913     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4914     return;
4915   }
4916 
4917   double start_time = os::elapsedTime();
4918 
4919   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4920 
4921   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4922   heap_region_iterate(&cl);
4923 
4924   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4925 
4926   G1HRPrinter* hrp = hr_printer();
4927   if (hrp->is_active()) {
4928     FreeRegionListIterator iter(&local_cleanup_list);
4929     while (iter.more_available()) {
4930       HeapRegion* hr = iter.get_next();
4931       hrp->cleanup(hr);
4932     }
4933   }
4934 
4935   prepend_to_freelist(&local_cleanup_list);
4936   decrement_summary_bytes(cl.bytes_freed());
4937 
4938   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4939                                                                     cl.humongous_objects_reclaimed());
4940 }
4941 
4942 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4943 public:
4944   virtual bool doHeapRegion(HeapRegion* r) {
4945     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4946     G1CollectedHeap::heap()->clear_in_cset(r);
4947     r->set_young_index_in_cset(-1);
4948     return false;
4949   }
4950 };
4951 
4952 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4953   G1AbandonCollectionSetClosure cl;
4954   collection_set->iterate(&cl);
4955 
4956   collection_set->clear();
4957   collection_set->stop_incremental_building();
4958 }
4959 
4960 void G1CollectedHeap::set_free_regions_coming() {
4961   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
4962 
4963   assert(!free_regions_coming(), "pre-condition");
4964   _free_regions_coming = true;
4965 }
4966 
4967 void G1CollectedHeap::reset_free_regions_coming() {
4968   assert(free_regions_coming(), "pre-condition");
4969 
4970   {
4971     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4972     _free_regions_coming = false;
4973     SecondaryFreeList_lock->notify_all();
4974   }
4975 
4976   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
4977 }
4978 
4979 void G1CollectedHeap::wait_while_free_regions_coming() {
4980   // Most of the time we won't have to wait, so let's do a quick test
4981   // first before we take the lock.
4982   if (!free_regions_coming()) {
4983     return;
4984   }
4985 
4986   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
4987 
4988   {
4989     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
4990     while (free_regions_coming()) {
4991       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
4992     }
4993   }
4994 
4995   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
4996 }
4997 
4998 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4999   return _allocator->is_retained_old_region(hr);
5000 }
5001 
5002 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5003   _eden.add(hr);
5004   _g1_policy->set_region_eden(hr);
5005 }
5006 
5007 #ifdef ASSERT
5008 
5009 class NoYoungRegionsClosure: public HeapRegionClosure {
5010 private:
5011   bool _success;
5012 public:
5013   NoYoungRegionsClosure() : _success(true) { }
5014   bool doHeapRegion(HeapRegion* r) {
5015     if (r->is_young()) {
5016       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5017                             p2i(r->bottom()), p2i(r->end()));
5018       _success = false;
5019     }
5020     return false;
5021   }
5022   bool success() { return _success; }
5023 };
5024 
5025 bool G1CollectedHeap::check_young_list_empty() {
5026   bool ret = (young_regions_count() == 0);
5027 
5028   NoYoungRegionsClosure closure;
5029   heap_region_iterate(&closure);
5030   ret = ret && closure.success();
5031 
5032   return ret;
5033 }
5034 
5035 #endif // ASSERT
5036 
5037 class TearDownRegionSetsClosure : public HeapRegionClosure {
5038 private:
5039   HeapRegionSet *_old_set;
5040 
5041 public:
5042   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5043 
5044   bool doHeapRegion(HeapRegion* r) {
5045     if (r->is_old()) {
5046       _old_set->remove(r);
5047     } else if(r->is_young()) {
5048       r->uninstall_surv_rate_group();
5049     } else {
5050       // We ignore free regions, we'll empty the free list afterwards.
5051       // We ignore humongous regions, we're not tearing down the
5052       // humongous regions set.
5053       assert(r->is_free() || r->is_humongous(),
5054              "it cannot be another type");
5055     }
5056     return false;
5057   }
5058 
5059   ~TearDownRegionSetsClosure() {
5060     assert(_old_set->is_empty(), "post-condition");
5061   }
5062 };
5063 
5064 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5065   assert_at_safepoint(true /* should_be_vm_thread */);
5066 
5067   if (!free_list_only) {
5068     TearDownRegionSetsClosure cl(&_old_set);
5069     heap_region_iterate(&cl);
5070 
5071     // Note that emptying the _young_list is postponed and instead done as
5072     // the first step when rebuilding the regions sets again. The reason for
5073     // this is that during a full GC string deduplication needs to know if
5074     // a collected region was young or old when the full GC was initiated.
5075   }
5076   _hrm.remove_all_free_regions();
5077 }
5078 
5079 void G1CollectedHeap::increase_used(size_t bytes) {
5080   _summary_bytes_used += bytes;
5081 }
5082 
5083 void G1CollectedHeap::decrease_used(size_t bytes) {
5084   assert(_summary_bytes_used >= bytes,
5085          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5086          _summary_bytes_used, bytes);
5087   _summary_bytes_used -= bytes;
5088 }
5089 
5090 void G1CollectedHeap::set_used(size_t bytes) {
5091   _summary_bytes_used = bytes;
5092 }
5093 
5094 class RebuildRegionSetsClosure : public HeapRegionClosure {
5095 private:
5096   bool            _free_list_only;
5097   HeapRegionSet*   _old_set;
5098   HeapRegionManager*   _hrm;
5099   size_t          _total_used;
5100 
5101 public:
5102   RebuildRegionSetsClosure(bool free_list_only,
5103                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
5104     _free_list_only(free_list_only),
5105     _old_set(old_set), _hrm(hrm), _total_used(0) {
5106     assert(_hrm->num_free_regions() == 0, "pre-condition");
5107     if (!free_list_only) {
5108       assert(_old_set->is_empty(), "pre-condition");
5109     }
5110   }
5111 
5112   bool doHeapRegion(HeapRegion* r) {
5113     if (r->is_empty()) {
5114       // Add free regions to the free list
5115       r->set_free();
5116       r->set_allocation_context(AllocationContext::system());
5117       _hrm->insert_into_free_list(r);
5118     } else if (!_free_list_only) {
5119 
5120       if (r->is_humongous()) {
5121         // We ignore humongous regions. We left the humongous set unchanged.
5122       } else {
5123         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
5124         // We now move all (non-humongous, non-old) regions to old gen, and register them as such.
5125         r->move_to_old();
5126         _old_set->add(r);
5127       }
5128       _total_used += r->used();
5129     }
5130 
5131     return false;
5132   }
5133 
5134   size_t total_used() {
5135     return _total_used;
5136   }
5137 };
5138 
5139 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5140   assert_at_safepoint(true /* should_be_vm_thread */);
5141 
5142   if (!free_list_only) {
5143     _eden.clear();
5144     _survivor.clear();
5145   }
5146 
5147   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5148   heap_region_iterate(&cl);
5149 
5150   if (!free_list_only) {
5151     set_used(cl.total_used());
5152     if (_archive_allocator != NULL) {
5153       _archive_allocator->clear_used();
5154     }
5155   }
5156   assert(used_unlocked() == recalculate_used(),
5157          "inconsistent used_unlocked(), "
5158          "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5159          used_unlocked(), recalculate_used());
5160 }
5161 
5162 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5163   HeapRegion* hr = heap_region_containing(p);
5164   return hr->is_in(p);
5165 }
5166 
5167 // Methods for the mutator alloc region
5168 
5169 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5170                                                       bool force) {
5171   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5172   bool should_allocate = g1_policy()->should_allocate_mutator_region();
5173   if (force || should_allocate) {
5174     HeapRegion* new_alloc_region = new_region(word_size,
5175                                               false /* is_old */,
5176                                               false /* do_expand */);
5177     if (new_alloc_region != NULL) {
5178       set_region_short_lived_locked(new_alloc_region);
5179       _hr_printer.alloc(new_alloc_region, !should_allocate);
5180       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5181       return new_alloc_region;
5182     }
5183   }
5184   return NULL;
5185 }
5186 
5187 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5188                                                   size_t allocated_bytes) {
5189   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5190   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5191 
5192   collection_set()->add_eden_region(alloc_region);
5193   increase_used(allocated_bytes);
5194   _hr_printer.retire(alloc_region);
5195   // We update the eden sizes here, when the region is retired,
5196   // instead of when it's allocated, since this is the point that its
5197   // used space has been recored in _summary_bytes_used.
5198   g1mm()->update_eden_size();
5199 }
5200 
5201 // Methods for the GC alloc regions
5202 
5203 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
5204   if (dest.is_old()) {
5205     return true;
5206   } else {
5207     return survivor_regions_count() < g1_policy()->max_survivor_regions();
5208   }
5209 }
5210 
5211 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
5212   assert(FreeList_lock->owned_by_self(), "pre-condition");
5213 
5214   if (!has_more_regions(dest)) {
5215     return NULL;
5216   }
5217 
5218   const bool is_survivor = dest.is_young();
5219 
5220   HeapRegion* new_alloc_region = new_region(word_size,
5221                                             !is_survivor,
5222                                             true /* do_expand */);
5223   if (new_alloc_region != NULL) {
5224     // We really only need to do this for old regions given that we
5225     // should never scan survivors. But it doesn't hurt to do it
5226     // for survivors too.
5227     new_alloc_region->record_timestamp();
5228     if (is_survivor) {
5229       new_alloc_region->set_survivor();
5230       _survivor.add(new_alloc_region);
5231       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5232     } else {
5233       new_alloc_region->set_old();
5234       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5235     }
5236     _hr_printer.alloc(new_alloc_region);
5237     bool during_im = collector_state()->during_initial_mark_pause();
5238     new_alloc_region->note_start_of_copying(during_im);
5239     return new_alloc_region;
5240   }
5241   return NULL;
5242 }
5243 
5244 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5245                                              size_t allocated_bytes,
5246                                              InCSetState dest) {
5247   bool during_im = collector_state()->during_initial_mark_pause();
5248   alloc_region->note_end_of_copying(during_im);
5249   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5250   if (dest.is_old()) {
5251     _old_set.add(alloc_region);
5252   }
5253   _hr_printer.retire(alloc_region);
5254 }
5255 
5256 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5257   bool expanded = false;
5258   uint index = _hrm.find_highest_free(&expanded);
5259 
5260   if (index != G1_NO_HRM_INDEX) {
5261     if (expanded) {
5262       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5263                                 HeapRegion::GrainWords * HeapWordSize);
5264     }
5265     _hrm.allocate_free_regions_starting_at(index, 1);
5266     return region_at(index);
5267   }
5268   return NULL;
5269 }
5270 
5271 // Optimized nmethod scanning
5272 
5273 class RegisterNMethodOopClosure: public OopClosure {
5274   G1CollectedHeap* _g1h;
5275   nmethod* _nm;
5276 
5277   template <class T> void do_oop_work(T* p) {
5278     T heap_oop = oopDesc::load_heap_oop(p);
5279     if (!oopDesc::is_null(heap_oop)) {
5280       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5281       HeapRegion* hr = _g1h->heap_region_containing(obj);
5282       assert(!hr->is_continues_humongous(),
5283              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5284              " starting at " HR_FORMAT,
5285              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5286 
5287       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5288       hr->add_strong_code_root_locked(_nm);
5289     }
5290   }
5291 
5292 public:
5293   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5294     _g1h(g1h), _nm(nm) {}
5295 
5296   void do_oop(oop* p)       { do_oop_work(p); }
5297   void do_oop(narrowOop* p) { do_oop_work(p); }
5298 };
5299 
5300 class UnregisterNMethodOopClosure: public OopClosure {
5301   G1CollectedHeap* _g1h;
5302   nmethod* _nm;
5303 
5304   template <class T> void do_oop_work(T* p) {
5305     T heap_oop = oopDesc::load_heap_oop(p);
5306     if (!oopDesc::is_null(heap_oop)) {
5307       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5308       HeapRegion* hr = _g1h->heap_region_containing(obj);
5309       assert(!hr->is_continues_humongous(),
5310              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5311              " starting at " HR_FORMAT,
5312              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5313 
5314       hr->remove_strong_code_root(_nm);
5315     }
5316   }
5317 
5318 public:
5319   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5320     _g1h(g1h), _nm(nm) {}
5321 
5322   void do_oop(oop* p)       { do_oop_work(p); }
5323   void do_oop(narrowOop* p) { do_oop_work(p); }
5324 };
5325 
5326 // Returns true if the reference points to an object that
5327 // can move in an incremental collection.
5328 bool G1CollectedHeap::is_scavengable(oop obj) {
5329   HeapRegion* hr = heap_region_containing(obj);
5330   return !hr->is_pinned();
5331 }
5332 
5333 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5334   guarantee(nm != NULL, "sanity");
5335   RegisterNMethodOopClosure reg_cl(this, nm);
5336   nm->oops_do(&reg_cl);
5337 }
5338 
5339 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5340   guarantee(nm != NULL, "sanity");
5341   UnregisterNMethodOopClosure reg_cl(this, nm);
5342   nm->oops_do(&reg_cl, true);
5343 }
5344 
5345 void G1CollectedHeap::purge_code_root_memory() {
5346   double purge_start = os::elapsedTime();
5347   G1CodeRootSet::purge();
5348   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5349   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5350 }
5351 
5352 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5353   G1CollectedHeap* _g1h;
5354 
5355 public:
5356   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5357     _g1h(g1h) {}
5358 
5359   void do_code_blob(CodeBlob* cb) {
5360     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5361     if (nm == NULL) {
5362       return;
5363     }
5364 
5365     if (ScavengeRootsInCode) {
5366       _g1h->register_nmethod(nm);
5367     }
5368   }
5369 };
5370 
5371 void G1CollectedHeap::rebuild_strong_code_roots() {
5372   RebuildStrongCodeRootClosure blob_cl(this);
5373   CodeCache::blobs_do(&blob_cl);
5374 }