1 /*
   2  * Copyright (c) 2001, 2018, 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.hpp"
  29 #include "gc/shared/collectedHeap.hpp"
  30 #include "gc/shared/collectedHeap.inline.hpp"
  31 #include "gc/shared/gcLocker.inline.hpp"
  32 #include "gc/shared/gcHeapSummary.hpp"
  33 #include "gc/shared/gcTrace.hpp"
  34 #include "gc/shared/gcTraceTime.inline.hpp"
  35 #include "gc/shared/gcWhen.hpp"
  36 #include "gc/shared/vmGCOperations.hpp"
  37 #include "logging/log.hpp"
  38 #include "memory/metaspace.hpp"
  39 #include "memory/resourceArea.hpp"
  40 #include "oops/instanceMirrorKlass.hpp"
  41 #include "oops/oop.inline.hpp"
  42 #include "runtime/handles.inline.hpp"
  43 #include "runtime/init.hpp"
  44 #include "runtime/thread.inline.hpp"
  45 #include "runtime/threadSMR.hpp"
  46 #include "runtime/vmThread.hpp"
  47 #include "services/heapDumper.hpp"
  48 #include "utilities/align.hpp"
  49 
  50 class ClassLoaderData;
  51 
  52 #ifdef ASSERT
  53 int CollectedHeap::_fire_out_of_memory_count = 0;
  54 #endif
  55 
  56 size_t CollectedHeap::_filler_array_max_size = 0;
  57 
  58 template <>
  59 void EventLogBase<GCMessage>::print(outputStream* st, GCMessage& m) {
  60   st->print_cr("GC heap %s", m.is_before ? "before" : "after");
  61   st->print_raw(m);
  62 }
  63 
  64 void GCHeapLog::log_heap(CollectedHeap* heap, bool before) {
  65   if (!should_log()) {
  66     return;
  67   }
  68 
  69   double timestamp = fetch_timestamp();
  70   MutexLockerEx ml(&_mutex, Mutex::_no_safepoint_check_flag);
  71   int index = compute_log_index();
  72   _records[index].thread = NULL; // Its the GC thread so it's not that interesting.
  73   _records[index].timestamp = timestamp;
  74   _records[index].data.is_before = before;
  75   stringStream st(_records[index].data.buffer(), _records[index].data.size());
  76 
  77   st.print_cr("{Heap %s GC invocations=%u (full %u):",
  78                  before ? "before" : "after",
  79                  heap->total_collections(),
  80                  heap->total_full_collections());
  81 
  82   heap->print_on(&st);
  83   st.print_cr("}");
  84 }
  85 
  86 VirtualSpaceSummary CollectedHeap::create_heap_space_summary() {
  87   size_t capacity_in_words = capacity() / HeapWordSize;
  88 
  89   return VirtualSpaceSummary(
  90     reserved_region().start(), reserved_region().start() + capacity_in_words, reserved_region().end());
  91 }
  92 
  93 GCHeapSummary CollectedHeap::create_heap_summary() {
  94   VirtualSpaceSummary heap_space = create_heap_space_summary();
  95   return GCHeapSummary(heap_space, used());
  96 }
  97 
  98 MetaspaceSummary CollectedHeap::create_metaspace_summary() {
  99   const MetaspaceSizes meta_space(
 100       MetaspaceUtils::committed_bytes(),
 101       MetaspaceUtils::used_bytes(),
 102       MetaspaceUtils::reserved_bytes());
 103   const MetaspaceSizes data_space(
 104       MetaspaceUtils::committed_bytes(Metaspace::NonClassType),
 105       MetaspaceUtils::used_bytes(Metaspace::NonClassType),
 106       MetaspaceUtils::reserved_bytes(Metaspace::NonClassType));
 107   const MetaspaceSizes class_space(
 108       MetaspaceUtils::committed_bytes(Metaspace::ClassType),
 109       MetaspaceUtils::used_bytes(Metaspace::ClassType),
 110       MetaspaceUtils::reserved_bytes(Metaspace::ClassType));
 111 
 112   const MetaspaceChunkFreeListSummary& ms_chunk_free_list_summary =
 113     MetaspaceUtils::chunk_free_list_summary(Metaspace::NonClassType);
 114   const MetaspaceChunkFreeListSummary& class_chunk_free_list_summary =
 115     MetaspaceUtils::chunk_free_list_summary(Metaspace::ClassType);
 116 
 117   return MetaspaceSummary(MetaspaceGC::capacity_until_GC(), meta_space, data_space, class_space,
 118                           ms_chunk_free_list_summary, class_chunk_free_list_summary);
 119 }
 120 
 121 void CollectedHeap::print_heap_before_gc() {
 122   Universe::print_heap_before_gc();
 123   if (_gc_heap_log != NULL) {
 124     _gc_heap_log->log_heap_before(this);
 125   }
 126 }
 127 
 128 void CollectedHeap::print_heap_after_gc() {
 129   Universe::print_heap_after_gc();
 130   if (_gc_heap_log != NULL) {
 131     _gc_heap_log->log_heap_after(this);
 132   }
 133 }
 134 
 135 void CollectedHeap::print_on_error(outputStream* st) const {
 136   st->print_cr("Heap:");
 137   print_extended_on(st);
 138   st->cr();
 139 
 140   _barrier_set->print_on(st);
 141 }
 142 
 143 void CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
 144   const GCHeapSummary& heap_summary = create_heap_summary();
 145   gc_tracer->report_gc_heap_summary(when, heap_summary);
 146 
 147   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
 148   gc_tracer->report_metaspace_summary(when, metaspace_summary);
 149 }
 150 
 151 void CollectedHeap::trace_heap_before_gc(const GCTracer* gc_tracer) {
 152   trace_heap(GCWhen::BeforeGC, gc_tracer);
 153 }
 154 
 155 void CollectedHeap::trace_heap_after_gc(const GCTracer* gc_tracer) {
 156   trace_heap(GCWhen::AfterGC, gc_tracer);
 157 }
 158 
 159 // WhiteBox API support for concurrent collectors.  These are the
 160 // default implementations, for collectors which don't support this
 161 // feature.
 162 bool CollectedHeap::supports_concurrent_phase_control() const {
 163   return false;
 164 }
 165 
 166 const char* const* CollectedHeap::concurrent_phases() const {
 167   static const char* const result[] = { NULL };
 168   return result;
 169 }
 170 
 171 bool CollectedHeap::request_concurrent_phase(const char* phase) {
 172   return false;
 173 }
 174 
 175 // Memory state functions.
 176 
 177 
 178 CollectedHeap::CollectedHeap() :
 179   _barrier_set(NULL),
 180   _is_gc_active(false),
 181   _total_collections(0),
 182   _total_full_collections(0),
 183   _gc_cause(GCCause::_no_gc),
 184   _gc_lastcause(GCCause::_no_gc)
 185 {
 186   const size_t max_len = size_t(arrayOopDesc::max_array_length(T_INT));
 187   const size_t elements_per_word = HeapWordSize / sizeof(jint);
 188   _filler_array_max_size = align_object_size(filler_array_hdr_size() +
 189                                              max_len / elements_per_word);
 190 
 191   NOT_PRODUCT(_promotion_failure_alot_count = 0;)
 192   NOT_PRODUCT(_promotion_failure_alot_gc_number = 0;)
 193 
 194   if (UsePerfData) {
 195     EXCEPTION_MARK;
 196 
 197     // create the gc cause jvmstat counters
 198     _perf_gc_cause = PerfDataManager::create_string_variable(SUN_GC, "cause",
 199                              80, GCCause::to_string(_gc_cause), CHECK);
 200 
 201     _perf_gc_lastcause =
 202                 PerfDataManager::create_string_variable(SUN_GC, "lastCause",
 203                              80, GCCause::to_string(_gc_lastcause), CHECK);
 204   }
 205 
 206   // Create the ring log
 207   if (LogEvents) {
 208     _gc_heap_log = new GCHeapLog();
 209   } else {
 210     _gc_heap_log = NULL;
 211   }
 212 }
 213 
 214 // This interface assumes that it's being called by the
 215 // vm thread. It collects the heap assuming that the
 216 // heap lock is already held and that we are executing in
 217 // the context of the vm thread.
 218 void CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
 219   assert(Thread::current()->is_VM_thread(), "Precondition#1");
 220   assert(Heap_lock->is_locked(), "Precondition#2");
 221   GCCauseSetter gcs(this, cause);
 222   switch (cause) {
 223     case GCCause::_heap_inspection:
 224     case GCCause::_heap_dump:
 225     case GCCause::_metadata_GC_threshold : {
 226       HandleMark hm;
 227       do_full_collection(false);        // don't clear all soft refs
 228       break;
 229     }
 230     case GCCause::_metadata_GC_clear_soft_refs: {
 231       HandleMark hm;
 232       do_full_collection(true);         // do clear all soft refs
 233       break;
 234     }
 235     default:
 236       ShouldNotReachHere(); // Unexpected use of this function
 237   }
 238 }
 239 
 240 MetaWord* CollectedHeap::satisfy_failed_metadata_allocation(ClassLoaderData* loader_data,
 241                                                             size_t word_size,
 242                                                             Metaspace::MetadataType mdtype) {
 243   uint loop_count = 0;
 244   uint gc_count = 0;
 245   uint full_gc_count = 0;
 246 
 247   assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
 248 
 249   do {
 250     MetaWord* result = loader_data->metaspace_non_null()->allocate(word_size, mdtype);
 251     if (result != NULL) {
 252       return result;
 253     }
 254 
 255     if (GCLocker::is_active_and_needs_gc()) {
 256       // If the GCLocker is active, just expand and allocate.
 257       // If that does not succeed, wait if this thread is not
 258       // in a critical section itself.
 259       result = loader_data->metaspace_non_null()->expand_and_allocate(word_size, mdtype);
 260       if (result != NULL) {
 261         return result;
 262       }
 263       JavaThread* jthr = JavaThread::current();
 264       if (!jthr->in_critical()) {
 265         // Wait for JNI critical section to be exited
 266         GCLocker::stall_until_clear();
 267         // The GC invoked by the last thread leaving the critical
 268         // section will be a young collection and a full collection
 269         // is (currently) needed for unloading classes so continue
 270         // to the next iteration to get a full GC.
 271         continue;
 272       } else {
 273         if (CheckJNICalls) {
 274           fatal("Possible deadlock due to allocating while"
 275                 " in jni critical section");
 276         }
 277         return NULL;
 278       }
 279     }
 280 
 281     {  // Need lock to get self consistent gc_count's
 282       MutexLocker ml(Heap_lock);
 283       gc_count      = Universe::heap()->total_collections();
 284       full_gc_count = Universe::heap()->total_full_collections();
 285     }
 286 
 287     // Generate a VM operation
 288     VM_CollectForMetadataAllocation op(loader_data,
 289                                        word_size,
 290                                        mdtype,
 291                                        gc_count,
 292                                        full_gc_count,
 293                                        GCCause::_metadata_GC_threshold);
 294     VMThread::execute(&op);
 295 
 296     // If GC was locked out, try again. Check before checking success because the
 297     // prologue could have succeeded and the GC still have been locked out.
 298     if (op.gc_locked()) {
 299       continue;
 300     }
 301 
 302     if (op.prologue_succeeded()) {
 303       return op.result();
 304     }
 305     loop_count++;
 306     if ((QueuedAllocationWarningCount > 0) &&
 307         (loop_count % QueuedAllocationWarningCount == 0)) {
 308       log_warning(gc, ergo)("satisfy_failed_metadata_allocation() retries %d times,"
 309                             " size=" SIZE_FORMAT, loop_count, word_size);
 310     }
 311   } while (true);  // Until a GC is done
 312 }
 313 
 314 void CollectedHeap::set_barrier_set(BarrierSet* barrier_set) {
 315   _barrier_set = barrier_set;
 316   BarrierSet::set_bs(barrier_set);
 317 }
 318 
 319 #ifndef PRODUCT
 320 void CollectedHeap::check_for_bad_heap_word_value(HeapWord* addr, size_t size) {
 321   if (CheckMemoryInitialization && ZapUnusedHeapArea) {
 322     for (size_t slot = 0; slot < size; slot += 1) {
 323       assert((*(intptr_t*) (addr + slot)) != ((intptr_t) badHeapWordVal),
 324              "Found badHeapWordValue in post-allocation check");
 325     }
 326   }
 327 }
 328 
 329 void CollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr, size_t size) {
 330   if (CheckMemoryInitialization && ZapUnusedHeapArea) {
 331     for (size_t slot = 0; slot < size; slot += 1) {
 332       assert((*(intptr_t*) (addr + slot)) == ((intptr_t) badHeapWordVal),
 333              "Found non badHeapWordValue in pre-allocation check");
 334     }
 335   }
 336 }
 337 #endif // PRODUCT
 338 
 339 #ifdef ASSERT
 340 void CollectedHeap::check_for_valid_allocation_state() {
 341   Thread *thread = Thread::current();
 342   // How to choose between a pending exception and a potential
 343   // OutOfMemoryError?  Don't allow pending exceptions.
 344   // This is a VM policy failure, so how do we exhaustively test it?
 345   assert(!thread->has_pending_exception(),
 346          "shouldn't be allocating with pending exception");
 347   if (StrictSafepointChecks) {
 348     assert(thread->allow_allocation(),
 349            "Allocation done by thread for which allocation is blocked "
 350            "by No_Allocation_Verifier!");
 351     // Allocation of an oop can always invoke a safepoint,
 352     // hence, the true argument
 353     thread->check_for_valid_safepoint_state(true);
 354   }
 355 }
 356 #endif
 357 
 358 HeapWord* CollectedHeap::allocate_from_tlab_slow(Klass* klass, Thread* thread, size_t size) {
 359   HeapWord* obj = NULL;
 360 
 361   if (ThreadHeapSampler::enabled()) {
 362     // Try to allocate the sampled object from TLAB, it is possible a sample
 363     // point was put and the TLAB still has space.
 364     obj = thread->tlab().allocate_sampled_object(size);
 365 
 366     if (obj != NULL) {
 367       return obj;
 368     }
 369   }
 370 
 371   // Retain tlab and allocate object in shared space if
 372   // the amount free in the tlab is too large to discard.
 373   if (thread->tlab().free() > thread->tlab().refill_waste_limit()) {
 374     thread->tlab().record_slow_allocation(size);
 375     return NULL;
 376   }
 377 
 378   // Discard tlab and allocate a new one.
 379   // To minimize fragmentation, the last TLAB may be smaller than the rest.
 380   size_t new_tlab_size = thread->tlab().compute_size(size);
 381 
 382   thread->tlab().clear_before_allocation();
 383 
 384   if (new_tlab_size == 0) {
 385     return NULL;
 386   }
 387 
 388   // Allocate a new TLAB...
 389   obj = Universe::heap()->allocate_new_tlab(new_tlab_size);
 390   if (obj == NULL) {
 391     return NULL;
 392   }
 393 
 394   AllocTracer::send_allocation_in_new_tlab(klass, obj, new_tlab_size * HeapWordSize, size * HeapWordSize, thread);
 395 
 396   if (ZeroTLAB) {
 397     // ..and clear it.
 398     Copy::zero_to_words(obj, new_tlab_size);
 399   } else {
 400     // ...and zap just allocated object.
 401 #ifdef ASSERT
 402     // Skip mangling the space corresponding to the object header to
 403     // ensure that the returned space is not considered parsable by
 404     // any concurrent GC thread.
 405     size_t hdr_size = oopDesc::header_size();
 406     Copy::fill_to_words(obj + hdr_size, new_tlab_size - hdr_size, badHeapWordVal);
 407 #endif // ASSERT
 408   }
 409 
 410   // Send the thread information about this allocation in case a sample is
 411   // requested.
 412   if (ThreadHeapSampler::enabled()) {
 413     size_t tlab_bytes_since_last_sample = thread->tlab().bytes_since_last_sample_point();
 414     thread->heap_sampler().check_for_sampling(obj, size, tlab_bytes_since_last_sample);
 415   }
 416 
 417   thread->tlab().fill(obj, obj + size, new_tlab_size);
 418   return obj;
 419 }
 420 
 421 size_t CollectedHeap::max_tlab_size() const {
 422   // TLABs can't be bigger than we can fill with a int[Integer.MAX_VALUE].
 423   // This restriction could be removed by enabling filling with multiple arrays.
 424   // If we compute that the reasonable way as
 425   //    header_size + ((sizeof(jint) * max_jint) / HeapWordSize)
 426   // we'll overflow on the multiply, so we do the divide first.
 427   // We actually lose a little by dividing first,
 428   // but that just makes the TLAB  somewhat smaller than the biggest array,
 429   // which is fine, since we'll be able to fill that.
 430   size_t max_int_size = typeArrayOopDesc::header_size(T_INT) +
 431               sizeof(jint) *
 432               ((juint) max_jint / (size_t) HeapWordSize);
 433   return align_down(max_int_size, MinObjAlignment);
 434 }
 435 
 436 size_t CollectedHeap::filler_array_hdr_size() {
 437   return align_object_offset(arrayOopDesc::header_size(T_INT)); // align to Long
 438 }
 439 
 440 size_t CollectedHeap::filler_array_min_size() {
 441   return align_object_size(filler_array_hdr_size()); // align to MinObjAlignment
 442 }
 443 
 444 #ifdef ASSERT
 445 void CollectedHeap::fill_args_check(HeapWord* start, size_t words)
 446 {
 447   assert(words >= min_fill_size(), "too small to fill");
 448   assert(is_object_aligned(words), "unaligned size");
 449   assert(Universe::heap()->is_in_reserved(start), "not in heap");
 450   assert(Universe::heap()->is_in_reserved(start + words - 1), "not in heap");
 451 }
 452 
 453 void CollectedHeap::zap_filler_array(HeapWord* start, size_t words, bool zap)
 454 {
 455   if (ZapFillerObjects && zap) {
 456     Copy::fill_to_words(start + filler_array_hdr_size(),
 457                         words - filler_array_hdr_size(), 0XDEAFBABE);
 458   }
 459 }
 460 #endif // ASSERT
 461 
 462 void
 463 CollectedHeap::fill_with_array(HeapWord* start, size_t words, bool zap)
 464 {
 465   assert(words >= filler_array_min_size(), "too small for an array");
 466   assert(words <= filler_array_max_size(), "too big for a single object");
 467 
 468   const size_t payload_size = words - filler_array_hdr_size();
 469   const size_t len = payload_size * HeapWordSize / sizeof(jint);
 470   assert((int)len >= 0, "size too large " SIZE_FORMAT " becomes %d", words, (int)len);
 471 
 472   // Set the length first for concurrent GC.
 473   ((arrayOop)start)->set_length((int)len);
 474   post_allocation_setup_common(Universe::intArrayKlassObj(), start);
 475   DEBUG_ONLY(zap_filler_array(start, words, zap);)
 476 }
 477 
 478 void
 479 CollectedHeap::fill_with_object_impl(HeapWord* start, size_t words, bool zap)
 480 {
 481   assert(words <= filler_array_max_size(), "too big for a single object");
 482 
 483   if (words >= filler_array_min_size()) {
 484     fill_with_array(start, words, zap);
 485   } else if (words > 0) {
 486     assert(words == min_fill_size(), "unaligned size");
 487     post_allocation_setup_common(SystemDictionary::Object_klass(), start);
 488   }
 489 }
 490 
 491 void CollectedHeap::fill_with_object(HeapWord* start, size_t words, bool zap)
 492 {
 493   DEBUG_ONLY(fill_args_check(start, words);)
 494   HandleMark hm;  // Free handles before leaving.
 495   fill_with_object_impl(start, words, zap);
 496 }
 497 
 498 void CollectedHeap::fill_with_objects(HeapWord* start, size_t words, bool zap)
 499 {
 500   DEBUG_ONLY(fill_args_check(start, words);)
 501   HandleMark hm;  // Free handles before leaving.
 502 
 503   // Multiple objects may be required depending on the filler array maximum size. Fill
 504   // the range up to that with objects that are filler_array_max_size sized. The
 505   // remainder is filled with a single object.
 506   const size_t min = min_fill_size();
 507   const size_t max = filler_array_max_size();
 508   while (words > max) {
 509     const size_t cur = (words - max) >= min ? max : max - min;
 510     fill_with_array(start, cur, zap);
 511     start += cur;
 512     words -= cur;
 513   }
 514 
 515   fill_with_object_impl(start, words, zap);
 516 }
 517 
 518 HeapWord* CollectedHeap::allocate_new_tlab(size_t size) {
 519   guarantee(false, "thread-local allocation buffers not supported");
 520   return NULL;
 521 }
 522 
 523 void CollectedHeap::ensure_parsability(bool retire_tlabs) {
 524   // The second disjunct in the assertion below makes a concession
 525   // for the start-up verification done while the VM is being
 526   // created. Callers be careful that you know that mutators
 527   // aren't going to interfere -- for instance, this is permissible
 528   // if we are still single-threaded and have either not yet
 529   // started allocating (nothing much to verify) or we have
 530   // started allocating but are now a full-fledged JavaThread
 531   // (and have thus made our TLAB's) available for filling.
 532   assert(SafepointSynchronize::is_at_safepoint() ||
 533          !is_init_completed(),
 534          "Should only be called at a safepoint or at start-up"
 535          " otherwise concurrent mutator activity may make heap "
 536          " unparsable again");
 537   const bool use_tlab = UseTLAB;
 538   // The main thread starts allocating via a TLAB even before it
 539   // has added itself to the threads list at vm boot-up.
 540   JavaThreadIteratorWithHandle jtiwh;
 541   assert(!use_tlab || jtiwh.length() > 0,
 542          "Attempt to fill tlabs before main thread has been added"
 543          " to threads list is doomed to failure!");
 544   BarrierSet *bs = barrier_set();
 545   for (; JavaThread *thread = jtiwh.next(); ) {
 546      if (use_tlab) thread->tlab().make_parsable(retire_tlabs);
 547      bs->make_parsable(thread);
 548   }
 549 }
 550 
 551 void CollectedHeap::accumulate_statistics_all_tlabs() {
 552   if (UseTLAB) {
 553     assert(SafepointSynchronize::is_at_safepoint() ||
 554          !is_init_completed(),
 555          "should only accumulate statistics on tlabs at safepoint");
 556 
 557     ThreadLocalAllocBuffer::accumulate_statistics_before_gc();
 558   }
 559 }
 560 
 561 void CollectedHeap::resize_all_tlabs() {
 562   if (UseTLAB) {
 563     assert(SafepointSynchronize::is_at_safepoint() ||
 564          !is_init_completed(),
 565          "should only resize tlabs at safepoint");
 566 
 567     ThreadLocalAllocBuffer::resize_all_tlabs();
 568   }
 569 }
 570 
 571 void CollectedHeap::full_gc_dump(GCTimer* timer, bool before) {
 572   assert(timer != NULL, "timer is null");
 573   if ((HeapDumpBeforeFullGC && before) || (HeapDumpAfterFullGC && !before)) {
 574     GCTraceTime(Info, gc) tm(before ? "Heap Dump (before full gc)" : "Heap Dump (after full gc)", timer);
 575     HeapDumper::dump_heap();
 576   }
 577 
 578   LogTarget(Trace, gc, classhisto) lt;
 579   if (lt.is_enabled()) {
 580     GCTraceTime(Trace, gc, classhisto) tm(before ? "Class Histogram (before full gc)" : "Class Histogram (after full gc)", timer);
 581     ResourceMark rm;
 582     LogStream ls(lt);
 583     VM_GC_HeapInspection inspector(&ls, false /* ! full gc */);
 584     inspector.doit();
 585   }
 586 }
 587 
 588 void CollectedHeap::pre_full_gc_dump(GCTimer* timer) {
 589   full_gc_dump(timer, true);
 590 }
 591 
 592 void CollectedHeap::post_full_gc_dump(GCTimer* timer) {
 593   full_gc_dump(timer, false);
 594 }
 595 
 596 void CollectedHeap::initialize_reserved_region(HeapWord *start, HeapWord *end) {
 597   // It is important to do this in a way such that concurrent readers can't
 598   // temporarily think something is in the heap.  (Seen this happen in asserts.)
 599   _reserved.set_word_size(0);
 600   _reserved.set_start(start);
 601   _reserved.set_end(end);
 602 }
 603 
 604 void CollectedHeap::post_initialize() {
 605   initialize_serviceability();
 606 }
 607 
 608 #ifndef PRODUCT
 609 
 610 bool CollectedHeap::promotion_should_fail(volatile size_t* count) {
 611   // Access to count is not atomic; the value does not have to be exact.
 612   if (PromotionFailureALot) {
 613     const size_t gc_num = total_collections();
 614     const size_t elapsed_gcs = gc_num - _promotion_failure_alot_gc_number;
 615     if (elapsed_gcs >= PromotionFailureALotInterval) {
 616       // Test for unsigned arithmetic wrap-around.
 617       if (++*count >= PromotionFailureALotCount) {
 618         *count = 0;
 619         return true;
 620       }
 621     }
 622   }
 623   return false;
 624 }
 625 
 626 bool CollectedHeap::promotion_should_fail() {
 627   return promotion_should_fail(&_promotion_failure_alot_count);
 628 }
 629 
 630 void CollectedHeap::reset_promotion_should_fail(volatile size_t* count) {
 631   if (PromotionFailureALot) {
 632     _promotion_failure_alot_gc_number = total_collections();
 633     *count = 0;
 634   }
 635 }
 636 
 637 void CollectedHeap::reset_promotion_should_fail() {
 638   reset_promotion_should_fail(&_promotion_failure_alot_count);
 639 }
 640 
 641 #endif  // #ifndef PRODUCT
 642 
 643 oop CollectedHeap::pin_object(JavaThread* thread, oop o) {
 644   Handle handle(thread, o);
 645   GCLocker::lock_critical(thread);
 646   return handle();
 647 }
 648 
 649 void CollectedHeap::unpin_object(JavaThread* thread, oop o) {
 650   GCLocker::unlock_critical(thread);
 651 }