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/systemDictionary.hpp"
  27 #include "gc/shared/allocTracer.hpp"
  28 #include "gc/shared/barrierSet.inline.hpp"
  29 #include "gc/shared/collectedHeap.hpp"
  30 #include "gc/shared/collectedHeap.inline.hpp"
  31 #include "gc/shared/gcHeapSummary.hpp"
  32 #include "gc/shared/gcTrace.hpp"
  33 #include "gc/shared/gcTraceTime.inline.hpp"
  34 #include "gc/shared/gcWhen.hpp"
  35 #include "gc/shared/vmGCOperations.hpp"
  36 #include "logging/log.hpp"
  37 #include "memory/metaspace.hpp"
  38 #include "memory/resourceArea.hpp"
  39 #include "oops/instanceMirrorKlass.hpp"
  40 #include "oops/oop.inline.hpp"
  41 #include "runtime/heapMonitoring.hpp"
  42 #include "runtime/init.hpp"
  43 #include "runtime/thread.inline.hpp"
  44 #include "services/heapDumper.hpp"
  45 #include "utilities/align.hpp"
  46 
  47 
  48 #ifdef ASSERT
  49 int CollectedHeap::_fire_out_of_memory_count = 0;
  50 #endif
  51 
  52 size_t CollectedHeap::_filler_array_max_size = 0;
  53 
  54 template <>
  55 void EventLogBase<GCMessage>::print(outputStream* st, GCMessage& m) {
  56   st->print_cr("GC heap %s", m.is_before ? "before" : "after");
  57   st->print_raw(m);
  58 }
  59 
  60 void GCHeapLog::log_heap(CollectedHeap* heap, bool before) {
  61   if (!should_log()) {
  62     return;
  63   }
  64 
  65   double timestamp = fetch_timestamp();
  66   MutexLockerEx ml(&_mutex, Mutex::_no_safepoint_check_flag);
  67   int index = compute_log_index();
  68   _records[index].thread = NULL; // Its the GC thread so it's not that interesting.
  69   _records[index].timestamp = timestamp;
  70   _records[index].data.is_before = before;
  71   stringStream st(_records[index].data.buffer(), _records[index].data.size());
  72 
  73   st.print_cr("{Heap %s GC invocations=%u (full %u):",
  74                  before ? "before" : "after",
  75                  heap->total_collections(),
  76                  heap->total_full_collections());
  77 
  78   heap->print_on(&st);
  79   st.print_cr("}");
  80 }
  81 
  82 VirtualSpaceSummary CollectedHeap::create_heap_space_summary() {
  83   size_t capacity_in_words = capacity() / HeapWordSize;
  84 
  85   return VirtualSpaceSummary(
  86     reserved_region().start(), reserved_region().start() + capacity_in_words, reserved_region().end());
  87 }
  88 
  89 GCHeapSummary CollectedHeap::create_heap_summary() {
  90   VirtualSpaceSummary heap_space = create_heap_space_summary();
  91   return GCHeapSummary(heap_space, used());
  92 }
  93 
  94 MetaspaceSummary CollectedHeap::create_metaspace_summary() {
  95   const MetaspaceSizes meta_space(
  96       MetaspaceAux::committed_bytes(),
  97       MetaspaceAux::used_bytes(),
  98       MetaspaceAux::reserved_bytes());
  99   const MetaspaceSizes data_space(
 100       MetaspaceAux::committed_bytes(Metaspace::NonClassType),
 101       MetaspaceAux::used_bytes(Metaspace::NonClassType),
 102       MetaspaceAux::reserved_bytes(Metaspace::NonClassType));
 103   const MetaspaceSizes class_space(
 104       MetaspaceAux::committed_bytes(Metaspace::ClassType),
 105       MetaspaceAux::used_bytes(Metaspace::ClassType),
 106       MetaspaceAux::reserved_bytes(Metaspace::ClassType));
 107 
 108   const MetaspaceChunkFreeListSummary& ms_chunk_free_list_summary =
 109     MetaspaceAux::chunk_free_list_summary(Metaspace::NonClassType);
 110   const MetaspaceChunkFreeListSummary& class_chunk_free_list_summary =
 111     MetaspaceAux::chunk_free_list_summary(Metaspace::ClassType);
 112 
 113   return MetaspaceSummary(MetaspaceGC::capacity_until_GC(), meta_space, data_space, class_space,
 114                           ms_chunk_free_list_summary, class_chunk_free_list_summary);
 115 }
 116 
 117 void CollectedHeap::print_heap_before_gc() {
 118   Universe::print_heap_before_gc();
 119   if (_gc_heap_log != NULL) {
 120     _gc_heap_log->log_heap_before(this);
 121   }
 122 }
 123 
 124 void CollectedHeap::print_heap_after_gc() {
 125   Universe::print_heap_after_gc();
 126   if (_gc_heap_log != NULL) {
 127     _gc_heap_log->log_heap_after(this);
 128   }
 129 }
 130 
 131 void CollectedHeap::print_on_error(outputStream* st) const {
 132   st->print_cr("Heap:");
 133   print_extended_on(st);
 134   st->cr();
 135 
 136   _barrier_set->print_on(st);
 137 }
 138 
 139 void CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
 140   const GCHeapSummary& heap_summary = create_heap_summary();
 141   gc_tracer->report_gc_heap_summary(when, heap_summary);
 142 
 143   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
 144   gc_tracer->report_metaspace_summary(when, metaspace_summary);
 145 }
 146 
 147 void CollectedHeap::trace_heap_before_gc(const GCTracer* gc_tracer) {
 148   trace_heap(GCWhen::BeforeGC, gc_tracer);
 149 }
 150 
 151 void CollectedHeap::trace_heap_after_gc(const GCTracer* gc_tracer) {
 152   trace_heap(GCWhen::AfterGC, gc_tracer);
 153 }
 154 
 155 // WhiteBox API support for concurrent collectors.  These are the
 156 // default implementations, for collectors which don't support this
 157 // feature.
 158 bool CollectedHeap::supports_concurrent_phase_control() const {
 159   return false;
 160 }
 161 
 162 const char* const* CollectedHeap::concurrent_phases() const {
 163   static const char* const result[] = { NULL };
 164   return result;
 165 }
 166 
 167 bool CollectedHeap::request_concurrent_phase(const char* phase) {
 168   return false;
 169 }
 170 
 171 // Memory state functions.
 172 
 173 
 174 CollectedHeap::CollectedHeap() :
 175   _barrier_set(NULL),
 176   _is_gc_active(false),
 177   _total_collections(0),
 178   _total_full_collections(0),
 179   _gc_cause(GCCause::_no_gc),
 180   _gc_lastcause(GCCause::_no_gc),
 181   _defer_initial_card_mark(false) // strengthened by subclass in pre_initialize() below.
 182 {
 183   const size_t max_len = size_t(arrayOopDesc::max_array_length(T_INT));
 184   const size_t elements_per_word = HeapWordSize / sizeof(jint);
 185   _filler_array_max_size = align_object_size(filler_array_hdr_size() +
 186                                              max_len / elements_per_word);
 187 
 188   NOT_PRODUCT(_promotion_failure_alot_count = 0;)
 189   NOT_PRODUCT(_promotion_failure_alot_gc_number = 0;)
 190 
 191   if (UsePerfData) {
 192     EXCEPTION_MARK;
 193 
 194     // create the gc cause jvmstat counters
 195     _perf_gc_cause = PerfDataManager::create_string_variable(SUN_GC, "cause",
 196                              80, GCCause::to_string(_gc_cause), CHECK);
 197 
 198     _perf_gc_lastcause =
 199                 PerfDataManager::create_string_variable(SUN_GC, "lastCause",
 200                              80, GCCause::to_string(_gc_lastcause), CHECK);
 201   }
 202 
 203   // Create the ring log
 204   if (LogEvents) {
 205     _gc_heap_log = new GCHeapLog();
 206   } else {
 207     _gc_heap_log = NULL;
 208   }
 209 }
 210 
 211 // This interface assumes that it's being called by the
 212 // vm thread. It collects the heap assuming that the
 213 // heap lock is already held and that we are executing in
 214 // the context of the vm thread.
 215 void CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
 216   assert(Thread::current()->is_VM_thread(), "Precondition#1");
 217   assert(Heap_lock->is_locked(), "Precondition#2");
 218   GCCauseSetter gcs(this, cause);
 219   switch (cause) {
 220     case GCCause::_heap_inspection:
 221     case GCCause::_heap_dump:
 222     case GCCause::_metadata_GC_threshold : {
 223       HandleMark hm;
 224       do_full_collection(false);        // don't clear all soft refs
 225       break;
 226     }
 227     case GCCause::_metadata_GC_clear_soft_refs: {
 228       HandleMark hm;
 229       do_full_collection(true);         // do clear all soft refs
 230       break;
 231     }
 232     default:
 233       ShouldNotReachHere(); // Unexpected use of this function
 234   }
 235 }
 236 
 237 void CollectedHeap::set_barrier_set(BarrierSet* barrier_set) {
 238   _barrier_set = barrier_set;
 239   oopDesc::set_bs(_barrier_set);
 240 }
 241 
 242 void CollectedHeap::pre_initialize() {
 243   // Used for ReduceInitialCardMarks (when COMPILER2 is used);
 244   // otherwise remains unused.
 245 #if defined(COMPILER2) || INCLUDE_JVMCI
 246   _defer_initial_card_mark = is_server_compilation_mode_vm() &&  ReduceInitialCardMarks && can_elide_tlab_store_barriers()
 247                              && (DeferInitialCardMark || card_mark_must_follow_store());
 248 #else
 249   assert(_defer_initial_card_mark == false, "Who would set it?");
 250 #endif
 251 }
 252 
 253 #ifndef PRODUCT
 254 void CollectedHeap::check_for_bad_heap_word_value(HeapWord* addr, size_t size) {
 255   if (CheckMemoryInitialization && ZapUnusedHeapArea) {
 256     for (size_t slot = 0; slot < size; slot += 1) {
 257       assert((*(intptr_t*) (addr + slot)) != ((intptr_t) badHeapWordVal),
 258              "Found badHeapWordValue in post-allocation check");
 259     }
 260   }
 261 }
 262 
 263 void CollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr, size_t size) {
 264   if (CheckMemoryInitialization && ZapUnusedHeapArea) {
 265     for (size_t slot = 0; slot < size; slot += 1) {
 266       assert((*(intptr_t*) (addr + slot)) == ((intptr_t) badHeapWordVal),
 267              "Found non badHeapWordValue in pre-allocation check");
 268     }
 269   }
 270 }
 271 #endif // PRODUCT
 272 
 273 #ifdef ASSERT
 274 void CollectedHeap::check_for_valid_allocation_state() {
 275   Thread *thread = Thread::current();
 276   // How to choose between a pending exception and a potential
 277   // OutOfMemoryError?  Don't allow pending exceptions.
 278   // This is a VM policy failure, so how do we exhaustively test it?
 279   assert(!thread->has_pending_exception(),
 280          "shouldn't be allocating with pending exception");
 281   if (StrictSafepointChecks) {
 282     assert(thread->allow_allocation(),
 283            "Allocation done by thread for which allocation is blocked "
 284            "by No_Allocation_Verifier!");
 285     // Allocation of an oop can always invoke a safepoint,
 286     // hence, the true argument
 287     thread->check_for_valid_safepoint_state(true);
 288   }
 289 }
 290 #endif
 291 
 292 
 293 void CollectedHeap::sample_allocation(Thread* thread, HeapWord* obj,
 294                                       size_t size, size_t overflowed_words) {
 295   // Object is allocated, sample it now.
 296   HeapMonitoring::object_alloc_do_sample(thread,
 297                                          reinterpret_cast<oopDesc*>(obj),
 298                                          size * HeapWordSize);
 299   // Pick a next sample in this case, we allocated right.
 300   thread->tlab().pick_next_sample(overflowed_words);
 301 }
 302 
 303 HeapWord* CollectedHeap::allocate_sampled_object(Thread* thread, size_t size) {
 304   thread->tlab().set_back_actual_end();
 305 
 306   // The tlab could still have space after this sample.
 307   return thread->tlab().allocate(size);
 308 }
 309 
 310 HeapWord* CollectedHeap::allocate_from_tlab_slow(Klass* klass, Thread* thread, size_t size) {
 311   // In case the tlab changes, remember if this one wanted a sample.
 312   bool should_sample = HeapMonitoring::enabled() && thread->tlab().should_sample();
 313 
 314   HeapWord* obj = NULL;
 315   if (should_sample) {
 316     // Remember the tlab end to fix up the sampling rate.
 317     HeapWord *tlab_old_end = thread->tlab().end();
 318     obj = allocate_sampled_object(thread, size);
 319 
 320     // If we did allocate in this tlab, sample it. Otherwise, we wait for the
 321     // new tlab's first allocation at the end of this method.
 322     if (obj != NULL) {
 323       // Fix sample rate by removing the extra words allocated in this last
 324       // sample.
 325       size_t overflowed_words = pointer_delta(thread->tlab().top(), tlab_old_end);
 326       sample_allocation(thread, obj, size, overflowed_words);
 327       return obj;
 328     }
 329   }
 330 
 331   // Retain tlab and allocate object in shared space if
 332   // the amount free in the tlab is too large to discard.
 333   if (thread->tlab().free() > thread->tlab().refill_waste_limit()) {
 334     thread->tlab().record_slow_allocation(size);
 335     return NULL;
 336   }
 337 
 338   // Discard tlab and allocate a new one.
 339   // To minimize fragmentation, the last TLAB may be smaller than the rest.
 340   size_t new_tlab_size = thread->tlab().compute_size(size);
 341 
 342   thread->tlab().clear_before_allocation();
 343 
 344   if (new_tlab_size == 0) {
 345     return NULL;
 346   }
 347 
 348   // Allocate a new TLAB...
 349   obj = Universe::heap()->allocate_new_tlab(new_tlab_size);
 350   if (obj == NULL) {
 351     return NULL;
 352   }
 353 
 354   AllocTracer::send_allocation_in_new_tlab_event(klass, new_tlab_size * HeapWordSize, size * HeapWordSize);
 355 
 356   if (ZeroTLAB) {
 357     // ..and clear it.
 358     Copy::zero_to_words(obj, new_tlab_size);
 359   } else {
 360     // ...and zap just allocated object.
 361 #ifdef ASSERT
 362     // Skip mangling the space corresponding to the object header to
 363     // ensure that the returned space is not considered parsable by
 364     // any concurrent GC thread.
 365     size_t hdr_size = oopDesc::header_size();
 366     Copy::fill_to_words(obj + hdr_size, new_tlab_size - hdr_size, badHeapWordVal);
 367 #endif // ASSERT
 368   }
 369   thread->tlab().fill(obj, obj + size, new_tlab_size);
 370 
 371   // Did we initially want to sample?
 372   if (should_sample) {
 373     sample_allocation(thread, obj, size);
 374   }
 375   return obj;
 376 }
 377 
 378 void CollectedHeap::flush_deferred_store_barrier(JavaThread* thread) {
 379   MemRegion deferred = thread->deferred_card_mark();
 380   if (!deferred.is_empty()) {
 381     assert(_defer_initial_card_mark, "Otherwise should be empty");
 382     {
 383       // Verify that the storage points to a parsable object in heap
 384       DEBUG_ONLY(oop old_obj = oop(deferred.start());)
 385       assert(is_in(old_obj), "Not in allocated heap");
 386       assert(!can_elide_initializing_store_barrier(old_obj),
 387              "Else should have been filtered in new_store_pre_barrier()");
 388       assert(oopDesc::is_oop(old_obj, true), "Not an oop");
 389       assert(deferred.word_size() == (size_t)(old_obj->size()),
 390              "Mismatch: multiple objects?");
 391     }
 392     BarrierSet* bs = barrier_set();
 393     bs->write_region(deferred);
 394     // "Clear" the deferred_card_mark field
 395     thread->set_deferred_card_mark(MemRegion());
 396   }
 397   assert(thread->deferred_card_mark().is_empty(), "invariant");
 398 }
 399 
 400 size_t CollectedHeap::max_tlab_size() const {
 401   // TLABs can't be bigger than we can fill with a int[Integer.MAX_VALUE].
 402   // This restriction could be removed by enabling filling with multiple arrays.
 403   // If we compute that the reasonable way as
 404   //    header_size + ((sizeof(jint) * max_jint) / HeapWordSize)
 405   // we'll overflow on the multiply, so we do the divide first.
 406   // We actually lose a little by dividing first,
 407   // but that just makes the TLAB  somewhat smaller than the biggest array,
 408   // which is fine, since we'll be able to fill that.
 409   size_t max_int_size = typeArrayOopDesc::header_size(T_INT) +
 410               sizeof(jint) *
 411               ((juint) max_jint / (size_t) HeapWordSize);
 412   return align_down(max_int_size, MinObjAlignment);
 413 }
 414 
 415 // Helper for ReduceInitialCardMarks. For performance,
 416 // compiled code may elide card-marks for initializing stores
 417 // to a newly allocated object along the fast-path. We
 418 // compensate for such elided card-marks as follows:
 419 // (a) Generational, non-concurrent collectors, such as
 420 //     GenCollectedHeap(ParNew,DefNew,Tenured) and
 421 //     ParallelScavengeHeap(ParallelGC, ParallelOldGC)
 422 //     need the card-mark if and only if the region is
 423 //     in the old gen, and do not care if the card-mark
 424 //     succeeds or precedes the initializing stores themselves,
 425 //     so long as the card-mark is completed before the next
 426 //     scavenge. For all these cases, we can do a card mark
 427 //     at the point at which we do a slow path allocation
 428 //     in the old gen, i.e. in this call.
 429 // (b) GenCollectedHeap(ConcurrentMarkSweepGeneration) requires
 430 //     in addition that the card-mark for an old gen allocated
 431 //     object strictly follow any associated initializing stores.
 432 //     In these cases, the memRegion remembered below is
 433 //     used to card-mark the entire region either just before the next
 434 //     slow-path allocation by this thread or just before the next scavenge or
 435 //     CMS-associated safepoint, whichever of these events happens first.
 436 //     (The implicit assumption is that the object has been fully
 437 //     initialized by this point, a fact that we assert when doing the
 438 //     card-mark.)
 439 // (c) G1CollectedHeap(G1) uses two kinds of write barriers. When a
 440 //     G1 concurrent marking is in progress an SATB (pre-write-)barrier
 441 //     is used to remember the pre-value of any store. Initializing
 442 //     stores will not need this barrier, so we need not worry about
 443 //     compensating for the missing pre-barrier here. Turning now
 444 //     to the post-barrier, we note that G1 needs a RS update barrier
 445 //     which simply enqueues a (sequence of) dirty cards which may
 446 //     optionally be refined by the concurrent update threads. Note
 447 //     that this barrier need only be applied to a non-young write,
 448 //     but, like in CMS, because of the presence of concurrent refinement
 449 //     (much like CMS' precleaning), must strictly follow the oop-store.
 450 //     Thus, using the same protocol for maintaining the intended
 451 //     invariants turns out, serendepitously, to be the same for both
 452 //     G1 and CMS.
 453 //
 454 // For any future collector, this code should be reexamined with
 455 // that specific collector in mind, and the documentation above suitably
 456 // extended and updated.
 457 oop CollectedHeap::new_store_pre_barrier(JavaThread* thread, oop new_obj) {
 458   // If a previous card-mark was deferred, flush it now.
 459   flush_deferred_store_barrier(thread);
 460   if (can_elide_initializing_store_barrier(new_obj) ||
 461       new_obj->is_typeArray()) {
 462     // Arrays of non-references don't need a pre-barrier.
 463     // The deferred_card_mark region should be empty
 464     // following the flush above.
 465     assert(thread->deferred_card_mark().is_empty(), "Error");
 466   } else {
 467     MemRegion mr((HeapWord*)new_obj, new_obj->size());
 468     assert(!mr.is_empty(), "Error");
 469     if (_defer_initial_card_mark) {
 470       // Defer the card mark
 471       thread->set_deferred_card_mark(mr);
 472     } else {
 473       // Do the card mark
 474       BarrierSet* bs = barrier_set();
 475       bs->write_region(mr);
 476     }
 477   }
 478   return new_obj;
 479 }
 480 
 481 size_t CollectedHeap::filler_array_hdr_size() {
 482   return align_object_offset(arrayOopDesc::header_size(T_INT)); // align to Long
 483 }
 484 
 485 size_t CollectedHeap::filler_array_min_size() {
 486   return align_object_size(filler_array_hdr_size()); // align to MinObjAlignment
 487 }
 488 
 489 #ifdef ASSERT
 490 void CollectedHeap::fill_args_check(HeapWord* start, size_t words)
 491 {
 492   assert(words >= min_fill_size(), "too small to fill");
 493   assert(is_object_aligned(words), "unaligned size");
 494   assert(Universe::heap()->is_in_reserved(start), "not in heap");
 495   assert(Universe::heap()->is_in_reserved(start + words - 1), "not in heap");
 496 }
 497 
 498 void CollectedHeap::zap_filler_array(HeapWord* start, size_t words, bool zap)
 499 {
 500   if (ZapFillerObjects && zap) {
 501     Copy::fill_to_words(start + filler_array_hdr_size(),
 502                         words - filler_array_hdr_size(), 0XDEAFBABE);
 503   }
 504 }
 505 #endif // ASSERT
 506 
 507 void
 508 CollectedHeap::fill_with_array(HeapWord* start, size_t words, bool zap)
 509 {
 510   assert(words >= filler_array_min_size(), "too small for an array");
 511   assert(words <= filler_array_max_size(), "too big for a single object");
 512 
 513   const size_t payload_size = words - filler_array_hdr_size();
 514   const size_t len = payload_size * HeapWordSize / sizeof(jint);
 515   assert((int)len >= 0, "size too large " SIZE_FORMAT " becomes %d", words, (int)len);
 516 
 517   // Set the length first for concurrent GC.
 518   ((arrayOop)start)->set_length((int)len);
 519   post_allocation_setup_common(Universe::intArrayKlassObj(), start);
 520   DEBUG_ONLY(zap_filler_array(start, words, zap);)
 521 }
 522 
 523 void
 524 CollectedHeap::fill_with_object_impl(HeapWord* start, size_t words, bool zap)
 525 {
 526   assert(words <= filler_array_max_size(), "too big for a single object");
 527 
 528   if (words >= filler_array_min_size()) {
 529     fill_with_array(start, words, zap);
 530   } else if (words > 0) {
 531     assert(words == min_fill_size(), "unaligned size");
 532     post_allocation_setup_common(SystemDictionary::Object_klass(), start);
 533   }
 534 }
 535 
 536 void CollectedHeap::fill_with_object(HeapWord* start, size_t words, bool zap)
 537 {
 538   DEBUG_ONLY(fill_args_check(start, words);)
 539   HandleMark hm;  // Free handles before leaving.
 540   fill_with_object_impl(start, words, zap);
 541 }
 542 
 543 void CollectedHeap::fill_with_objects(HeapWord* start, size_t words, bool zap)
 544 {
 545   DEBUG_ONLY(fill_args_check(start, words);)
 546   HandleMark hm;  // Free handles before leaving.
 547 
 548   // Multiple objects may be required depending on the filler array maximum size. Fill
 549   // the range up to that with objects that are filler_array_max_size sized. The
 550   // remainder is filled with a single object.
 551   const size_t min = min_fill_size();
 552   const size_t max = filler_array_max_size();
 553   while (words > max) {
 554     const size_t cur = (words - max) >= min ? max : max - min;
 555     fill_with_array(start, cur, zap);
 556     start += cur;
 557     words -= cur;
 558   }
 559 
 560   fill_with_object_impl(start, words, zap);
 561 }
 562 
 563 HeapWord* CollectedHeap::allocate_new_tlab(size_t size) {
 564   guarantee(false, "thread-local allocation buffers not supported");
 565   return NULL;
 566 }
 567 
 568 void CollectedHeap::ensure_parsability(bool retire_tlabs) {
 569   // The second disjunct in the assertion below makes a concession
 570   // for the start-up verification done while the VM is being
 571   // created. Callers be careful that you know that mutators
 572   // aren't going to interfere -- for instance, this is permissible
 573   // if we are still single-threaded and have either not yet
 574   // started allocating (nothing much to verify) or we have
 575   // started allocating but are now a full-fledged JavaThread
 576   // (and have thus made our TLAB's) available for filling.
 577   assert(SafepointSynchronize::is_at_safepoint() ||
 578          !is_init_completed(),
 579          "Should only be called at a safepoint or at start-up"
 580          " otherwise concurrent mutator activity may make heap "
 581          " unparsable again");
 582   const bool use_tlab = UseTLAB;
 583   const bool deferred = _defer_initial_card_mark;
 584   // The main thread starts allocating via a TLAB even before it
 585   // has added itself to the threads list at vm boot-up.
 586   assert(!use_tlab || Threads::first() != NULL,
 587          "Attempt to fill tlabs before main thread has been added"
 588          " to threads list is doomed to failure!");
 589   for (JavaThread *thread = Threads::first(); thread; thread = thread->next()) {
 590      if (use_tlab) thread->tlab().make_parsable(retire_tlabs);
 591 #if defined(COMPILER2) || INCLUDE_JVMCI
 592      // The deferred store barriers must all have been flushed to the
 593      // card-table (or other remembered set structure) before GC starts
 594      // processing the card-table (or other remembered set).
 595      if (deferred) flush_deferred_store_barrier(thread);
 596 #else
 597      assert(!deferred, "Should be false");
 598      assert(thread->deferred_card_mark().is_empty(), "Should be empty");
 599 #endif
 600   }
 601 }
 602 
 603 void CollectedHeap::accumulate_statistics_all_tlabs() {
 604   if (UseTLAB) {
 605     assert(SafepointSynchronize::is_at_safepoint() ||
 606          !is_init_completed(),
 607          "should only accumulate statistics on tlabs at safepoint");
 608 
 609     ThreadLocalAllocBuffer::accumulate_statistics_before_gc();
 610   }
 611 }
 612 
 613 void CollectedHeap::resize_all_tlabs() {
 614   if (UseTLAB) {
 615     assert(SafepointSynchronize::is_at_safepoint() ||
 616          !is_init_completed(),
 617          "should only resize tlabs at safepoint");
 618 
 619     ThreadLocalAllocBuffer::resize_all_tlabs();
 620   }
 621 }
 622 
 623 void CollectedHeap::full_gc_dump(GCTimer* timer, bool before) {
 624   assert(timer != NULL, "timer is null");
 625   if ((HeapDumpBeforeFullGC && before) || (HeapDumpAfterFullGC && !before)) {
 626     GCTraceTime(Info, gc) tm(before ? "Heap Dump (before full gc)" : "Heap Dump (after full gc)", timer);
 627     HeapDumper::dump_heap();
 628   }
 629 
 630   LogTarget(Trace, gc, classhisto) lt;
 631   if (lt.is_enabled()) {
 632     GCTraceTime(Trace, gc, classhisto) tm(before ? "Class Histogram (before full gc)" : "Class Histogram (after full gc)", timer);
 633     ResourceMark rm;
 634     LogStream ls(lt);
 635     VM_GC_HeapInspection inspector(&ls, false /* ! full gc */);
 636     inspector.doit();
 637   }
 638 }
 639 
 640 void CollectedHeap::pre_full_gc_dump(GCTimer* timer) {
 641   full_gc_dump(timer, true);
 642 }
 643 
 644 void CollectedHeap::post_full_gc_dump(GCTimer* timer) {
 645   full_gc_dump(timer, false);
 646 }
 647 
 648 void CollectedHeap::initialize_reserved_region(HeapWord *start, HeapWord *end) {
 649   // It is important to do this in a way such that concurrent readers can't
 650   // temporarily think something is in the heap.  (Seen this happen in asserts.)
 651   _reserved.set_word_size(0);
 652   _reserved.set_start(start);
 653   _reserved.set_end(end);
 654 }