1 /*
   2  * Copyright (c) 2000, 2012, 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/symbolTable.hpp"
  27 #include "classfile/systemDictionary.hpp"
  28 #include "classfile/vmSymbols.hpp"
  29 #include "code/icBuffer.hpp"
  30 #include "gc_implementation/shared/collectorCounters.hpp"
  31 #include "gc_implementation/shared/vmGCOperations.hpp"
  32 #include "gc_interface/collectedHeap.inline.hpp"
  33 #include "memory/filemap.hpp"
  34 #include "memory/gcLocker.inline.hpp"
  35 #include "memory/genCollectedHeap.hpp"
  36 #include "memory/genOopClosures.inline.hpp"
  37 #include "memory/generation.inline.hpp"
  38 #include "memory/generationSpec.hpp"
  39 #include "memory/resourceArea.hpp"
  40 #include "memory/sharedHeap.hpp"
  41 #include "memory/space.hpp"
  42 #include "oops/oop.inline.hpp"
  43 #include "oops/oop.inline2.hpp"
  44 #include "runtime/aprofiler.hpp"
  45 #include "runtime/biasedLocking.hpp"
  46 #include "runtime/fprofiler.hpp"
  47 #include "runtime/handles.hpp"
  48 #include "runtime/handles.inline.hpp"
  49 #include "runtime/java.hpp"
  50 #include "runtime/vmThread.hpp"
  51 #include "services/memoryService.hpp"
  52 #include "utilities/vmError.hpp"
  53 #include "utilities/workgroup.hpp"
  54 #include "utilities/macros.hpp"
  55 #if INCLUDE_ALL_GCS
  56 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
  57 #include "gc_implementation/concurrentMarkSweep/vmCMSOperations.hpp"
  58 #endif // INCLUDE_ALL_GCS
  59 
  60 GenCollectedHeap* GenCollectedHeap::_gch;
  61 NOT_PRODUCT(size_t GenCollectedHeap::_skip_header_HeapWords = 0;)
  62 
  63 // The set of potentially parallel tasks in strong root scanning.
  64 enum GCH_process_strong_roots_tasks {
  65   // We probably want to parallelize both of these internally, but for now...
  66   GCH_PS_younger_gens,
  67   // Leave this one last.
  68   GCH_PS_NumElements
  69 };
  70 
  71 GenCollectedHeap::GenCollectedHeap(GenCollectorPolicy *policy) :
  72   SharedHeap(policy),
  73   _gen_policy(policy),
  74   _gen_process_strong_tasks(new SubTasksDone(GCH_PS_NumElements)),
  75   _full_collections_completed(0)
  76 {
  77   if (_gen_process_strong_tasks == NULL ||
  78       !_gen_process_strong_tasks->valid()) {
  79     vm_exit_during_initialization("Failed necessary allocation.");
  80   }
  81   assert(policy != NULL, "Sanity check");
  82 }
  83 
  84 jint GenCollectedHeap::initialize() {
  85   CollectedHeap::pre_initialize();
  86 
  87   int i;
  88   _n_gens = gen_policy()->number_of_generations();
  89 
  90   // While there are no constraints in the GC code that HeapWordSize
  91   // be any particular value, there are multiple other areas in the
  92   // system which believe this to be true (e.g. oop->object_size in some
  93   // cases incorrectly returns the size in wordSize units rather than
  94   // HeapWordSize).
  95   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
  96 
  97   // The heap must be at least as aligned as generations.
  98   size_t alignment = Generation::GenGrain;
  99 
 100   _gen_specs = gen_policy()->generations();
 101 
 102   // Make sure the sizes are all aligned.
 103   for (i = 0; i < _n_gens; i++) {
 104     _gen_specs[i]->align(alignment);
 105   }
 106 
 107   // Allocate space for the heap.
 108 
 109   char* heap_address;
 110   size_t total_reserved = 0;
 111   int n_covered_regions = 0;
 112   ReservedSpace heap_rs(0);
 113 
 114   heap_address = allocate(alignment, &total_reserved,
 115                           &n_covered_regions, &heap_rs);
 116 
 117   if (!heap_rs.is_reserved()) {
 118     vm_shutdown_during_initialization(
 119       "Could not reserve enough space for object heap");
 120     return JNI_ENOMEM;
 121   }
 122 
 123   _reserved = MemRegion((HeapWord*)heap_rs.base(),
 124                         (HeapWord*)(heap_rs.base() + heap_rs.size()));
 125 
 126   // It is important to do this in a way such that concurrent readers can't
 127   // temporarily think somethings in the heap.  (Seen this happen in asserts.)
 128   _reserved.set_word_size(0);
 129   _reserved.set_start((HeapWord*)heap_rs.base());
 130   size_t actual_heap_size = heap_rs.size();
 131   _reserved.set_end((HeapWord*)(heap_rs.base() + actual_heap_size));
 132 
 133   _rem_set = collector_policy()->create_rem_set(_reserved, n_covered_regions);
 134   set_barrier_set(rem_set()->bs());
 135 
 136   _gch = this;
 137 
 138   for (i = 0; i < _n_gens; i++) {
 139     ReservedSpace this_rs = heap_rs.first_part(_gen_specs[i]->max_size(), false, false);
 140     _gens[i] = _gen_specs[i]->init(this_rs, i, rem_set());
 141     heap_rs = heap_rs.last_part(_gen_specs[i]->max_size());
 142   }
 143   clear_incremental_collection_failed();
 144 
 145 #if INCLUDE_ALL_GCS
 146   // If we are running CMS, create the collector responsible
 147   // for collecting the CMS generations.
 148   if (collector_policy()->is_concurrent_mark_sweep_policy()) {
 149     bool success = create_cms_collector();
 150     if (!success) return JNI_ENOMEM;
 151   }
 152 #endif // INCLUDE_ALL_GCS
 153 
 154   return JNI_OK;
 155 }
 156 
 157 
 158 char* GenCollectedHeap::allocate(size_t alignment,
 159                                  size_t* _total_reserved,
 160                                  int* _n_covered_regions,
 161                                  ReservedSpace* heap_rs){
 162   const char overflow_msg[] = "The size of the object heap + VM data exceeds "
 163     "the maximum representable size";
 164 
 165   // Now figure out the total size.
 166   size_t total_reserved = 0;
 167   int n_covered_regions = 0;
 168   const size_t pageSize = UseLargePages ?
 169       os::large_page_size() : os::vm_page_size();
 170 
 171   for (int i = 0; i < _n_gens; i++) {
 172     total_reserved += _gen_specs[i]->max_size();
 173     if (total_reserved < _gen_specs[i]->max_size()) {
 174       vm_exit_during_initialization(overflow_msg);
 175     }
 176     n_covered_regions += _gen_specs[i]->n_covered_regions();
 177   }
 178   assert(total_reserved % pageSize == 0,
 179          err_msg("Gen size; total_reserved=" SIZE_FORMAT ", pageSize="
 180                  SIZE_FORMAT, total_reserved, pageSize));
 181 
 182   // Needed until the cardtable is fixed to have the right number
 183   // of covered regions.
 184   n_covered_regions += 2;
 185 
 186   if (UseLargePages) {
 187     assert(total_reserved != 0, "total_reserved cannot be 0");
 188     total_reserved = round_to(total_reserved, os::large_page_size());
 189     if (total_reserved < os::large_page_size()) {
 190       vm_exit_during_initialization(overflow_msg);
 191     }
 192   }
 193 
 194       *_total_reserved = total_reserved;
 195       *_n_covered_regions = n_covered_regions;
 196   *heap_rs = Universe::reserve_heap(total_reserved, alignment);
 197   return heap_rs->base();
 198 }
 199 
 200 
 201 void GenCollectedHeap::post_initialize() {
 202   SharedHeap::post_initialize();
 203   TwoGenerationCollectorPolicy *policy =
 204     (TwoGenerationCollectorPolicy *)collector_policy();
 205   guarantee(policy->is_two_generation_policy(), "Illegal policy type");
 206   DefNewGeneration* def_new_gen = (DefNewGeneration*) get_gen(0);
 207   assert(def_new_gen->kind() == Generation::DefNew ||
 208          def_new_gen->kind() == Generation::ParNew ||
 209          def_new_gen->kind() == Generation::ASParNew,
 210          "Wrong generation kind");
 211 
 212   Generation* old_gen = get_gen(1);
 213   assert(old_gen->kind() == Generation::ConcurrentMarkSweep ||
 214          old_gen->kind() == Generation::ASConcurrentMarkSweep ||
 215          old_gen->kind() == Generation::MarkSweepCompact,
 216     "Wrong generation kind");
 217 
 218   policy->initialize_size_policy(def_new_gen->eden()->capacity(),
 219                                  old_gen->capacity(),
 220                                  def_new_gen->from()->capacity());
 221   policy->initialize_gc_policy_counters();
 222 }
 223 
 224 void GenCollectedHeap::ref_processing_init() {
 225   SharedHeap::ref_processing_init();
 226   for (int i = 0; i < _n_gens; i++) {
 227     _gens[i]->ref_processor_init();
 228   }
 229 }
 230 
 231 size_t GenCollectedHeap::capacity() const {
 232   size_t res = 0;
 233   for (int i = 0; i < _n_gens; i++) {
 234     res += _gens[i]->capacity();
 235   }
 236   return res;
 237 }
 238 
 239 size_t GenCollectedHeap::used() const {
 240   size_t res = 0;
 241   for (int i = 0; i < _n_gens; i++) {
 242     res += _gens[i]->used();
 243   }
 244   return res;
 245 }
 246 
 247 // Save the "used_region" for generations level and lower.
 248 void GenCollectedHeap::save_used_regions(int level) {
 249   assert(level < _n_gens, "Illegal level parameter");
 250   for (int i = level; i >= 0; i--) {
 251     _gens[i]->save_used_region();
 252   }
 253 }
 254 
 255 size_t GenCollectedHeap::max_capacity() const {
 256   size_t res = 0;
 257   for (int i = 0; i < _n_gens; i++) {
 258     res += _gens[i]->max_capacity();
 259   }
 260   return res;
 261 }
 262 
 263 // Update the _full_collections_completed counter
 264 // at the end of a stop-world full GC.
 265 unsigned int GenCollectedHeap::update_full_collections_completed() {
 266   MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
 267   assert(_full_collections_completed <= _total_full_collections,
 268          "Can't complete more collections than were started");
 269   _full_collections_completed = _total_full_collections;
 270   ml.notify_all();
 271   return _full_collections_completed;
 272 }
 273 
 274 // Update the _full_collections_completed counter, as appropriate,
 275 // at the end of a concurrent GC cycle. Note the conditional update
 276 // below to allow this method to be called by a concurrent collector
 277 // without synchronizing in any manner with the VM thread (which
 278 // may already have initiated a STW full collection "concurrently").
 279 unsigned int GenCollectedHeap::update_full_collections_completed(unsigned int count) {
 280   MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
 281   assert((_full_collections_completed <= _total_full_collections) &&
 282          (count <= _total_full_collections),
 283          "Can't complete more collections than were started");
 284   if (count > _full_collections_completed) {
 285     _full_collections_completed = count;
 286     ml.notify_all();
 287   }
 288   return _full_collections_completed;
 289 }
 290 
 291 
 292 #ifndef PRODUCT
 293 // Override of memory state checking method in CollectedHeap:
 294 // Some collectors (CMS for example) can't have badHeapWordVal written
 295 // in the first two words of an object. (For instance , in the case of
 296 // CMS these words hold state used to synchronize between certain
 297 // (concurrent) GC steps and direct allocating mutators.)
 298 // The skip_header_HeapWords() method below, allows us to skip
 299 // over the requisite number of HeapWord's. Note that (for
 300 // generational collectors) this means that those many words are
 301 // skipped in each object, irrespective of the generation in which
 302 // that object lives. The resultant loss of precision seems to be
 303 // harmless and the pain of avoiding that imprecision appears somewhat
 304 // higher than we are prepared to pay for such rudimentary debugging
 305 // support.
 306 void GenCollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr,
 307                                                          size_t size) {
 308   if (CheckMemoryInitialization && ZapUnusedHeapArea) {
 309     // We are asked to check a size in HeapWords,
 310     // but the memory is mangled in juint words.
 311     juint* start = (juint*) (addr + skip_header_HeapWords());
 312     juint* end   = (juint*) (addr + size);
 313     for (juint* slot = start; slot < end; slot += 1) {
 314       assert(*slot == badHeapWordVal,
 315              "Found non badHeapWordValue in pre-allocation check");
 316     }
 317   }
 318 }
 319 #endif
 320 
 321 HeapWord* GenCollectedHeap::attempt_allocation(size_t size,
 322                                                bool is_tlab,
 323                                                bool first_only) {
 324   HeapWord* res;
 325   for (int i = 0; i < _n_gens; i++) {
 326     if (_gens[i]->should_allocate(size, is_tlab)) {
 327       res = _gens[i]->allocate(size, is_tlab);
 328       if (res != NULL) return res;
 329       else if (first_only) break;
 330     }
 331   }
 332   // Otherwise...
 333   return NULL;
 334 }
 335 
 336 HeapWord* GenCollectedHeap::mem_allocate(size_t size,
 337                                          bool* gc_overhead_limit_was_exceeded) {
 338   return collector_policy()->mem_allocate_work(size,
 339                                                false /* is_tlab */,
 340                                                gc_overhead_limit_was_exceeded);
 341 }
 342 
 343 bool GenCollectedHeap::must_clear_all_soft_refs() {
 344   return _gc_cause == GCCause::_last_ditch_collection;
 345 }
 346 
 347 bool GenCollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
 348   return UseConcMarkSweepGC &&
 349          ((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
 350           (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent));
 351 }
 352 
 353 void GenCollectedHeap::do_collection(bool  full,
 354                                      bool   clear_all_soft_refs,
 355                                      size_t size,
 356                                      bool   is_tlab,
 357                                      int    max_level) {
 358   bool prepared_for_verification = false;
 359   ResourceMark rm;
 360   DEBUG_ONLY(Thread* my_thread = Thread::current();)
 361 
 362   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 363   assert(my_thread->is_VM_thread() ||
 364          my_thread->is_ConcurrentGC_thread(),
 365          "incorrect thread type capability");
 366   assert(Heap_lock->is_locked(),
 367          "the requesting thread should have the Heap_lock");
 368   guarantee(!is_gc_active(), "collection is not reentrant");
 369   assert(max_level < n_gens(), "sanity check");
 370 
 371   if (GC_locker::check_active_before_gc()) {
 372     return; // GC is disabled (e.g. JNI GetXXXCritical operation)
 373   }
 374 
 375   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
 376                           collector_policy()->should_clear_all_soft_refs();
 377 
 378   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
 379 
 380   const size_t metadata_prev_used = MetaspaceAux::allocated_used_bytes();
 381 
 382   print_heap_before_gc();
 383 
 384   {
 385     FlagSetting fl(_is_gc_active, true);
 386 
 387     bool complete = full && (max_level == (n_gens()-1));
 388     const char* gc_cause_prefix = complete ? "Full GC" : "GC";
 389     gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
 390     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
 391     TraceTime t(GCCauseString(gc_cause_prefix, gc_cause()), PrintGCDetails, false, gclog_or_tty);
 392 
 393     gc_prologue(complete);
 394     increment_total_collections(complete);
 395 
 396     size_t gch_prev_used = used();
 397 
 398     int starting_level = 0;
 399     if (full) {
 400       // Search for the oldest generation which will collect all younger
 401       // generations, and start collection loop there.
 402       for (int i = max_level; i >= 0; i--) {
 403         if (_gens[i]->full_collects_younger_generations()) {
 404           starting_level = i;
 405           break;
 406         }
 407       }
 408     }
 409 
 410     bool must_restore_marks_for_biased_locking = false;
 411 
 412     int max_level_collected = starting_level;
 413     for (int i = starting_level; i <= max_level; i++) {
 414       if (_gens[i]->should_collect(full, size, is_tlab)) {
 415         if (i == n_gens() - 1) {  // a major collection is to happen
 416           if (!complete) {
 417             // The full_collections increment was missed above.
 418             increment_total_full_collections();
 419           }
 420           pre_full_gc_dump();    // do any pre full gc dumps
 421         }
 422         // Timer for individual generations. Last argument is false: no CR
 423         TraceTime t1(_gens[i]->short_name(), PrintGCDetails, false, gclog_or_tty);
 424         TraceCollectorStats tcs(_gens[i]->counters());
 425         TraceMemoryManagerStats tmms(_gens[i]->kind(),gc_cause());
 426 
 427         size_t prev_used = _gens[i]->used();
 428         _gens[i]->stat_record()->invocations++;
 429         _gens[i]->stat_record()->accumulated_time.start();
 430 
 431         // Must be done anew before each collection because
 432         // a previous collection will do mangling and will
 433         // change top of some spaces.
 434         record_gen_tops_before_GC();
 435 
 436         if (PrintGC && Verbose) {
 437           gclog_or_tty->print("level=%d invoke=%d size=" SIZE_FORMAT,
 438                      i,
 439                      _gens[i]->stat_record()->invocations,
 440                      size*HeapWordSize);
 441         }
 442 
 443         if (VerifyBeforeGC && i >= VerifyGCLevel &&
 444             total_collections() >= VerifyGCStartAt) {
 445           HandleMark hm;  // Discard invalid handles created during verification
 446           if (!prepared_for_verification) {
 447             prepare_for_verify();
 448             prepared_for_verification = true;
 449           }
 450           Universe::verify(" VerifyBeforeGC:");
 451         }
 452         COMPILER2_PRESENT(DerivedPointerTable::clear());
 453 
 454         if (!must_restore_marks_for_biased_locking &&
 455             _gens[i]->performs_in_place_marking()) {
 456           // We perform this mark word preservation work lazily
 457           // because it's only at this point that we know whether we
 458           // absolutely have to do it; we want to avoid doing it for
 459           // scavenge-only collections where it's unnecessary
 460           must_restore_marks_for_biased_locking = true;
 461           BiasedLocking::preserve_marks();
 462         }
 463 
 464         // Do collection work
 465         {
 466           // Note on ref discovery: For what appear to be historical reasons,
 467           // GCH enables and disabled (by enqueing) refs discovery.
 468           // In the future this should be moved into the generation's
 469           // collect method so that ref discovery and enqueueing concerns
 470           // are local to a generation. The collect method could return
 471           // an appropriate indication in the case that notification on
 472           // the ref lock was needed. This will make the treatment of
 473           // weak refs more uniform (and indeed remove such concerns
 474           // from GCH). XXX
 475 
 476           HandleMark hm;  // Discard invalid handles created during gc
 477           save_marks();   // save marks for all gens
 478           // We want to discover references, but not process them yet.
 479           // This mode is disabled in process_discovered_references if the
 480           // generation does some collection work, or in
 481           // enqueue_discovered_references if the generation returns
 482           // without doing any work.
 483           ReferenceProcessor* rp = _gens[i]->ref_processor();
 484           // If the discovery of ("weak") refs in this generation is
 485           // atomic wrt other collectors in this configuration, we
 486           // are guaranteed to have empty discovered ref lists.
 487           if (rp->discovery_is_atomic()) {
 488             rp->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
 489             rp->setup_policy(do_clear_all_soft_refs);
 490           } else {
 491             // collect() below will enable discovery as appropriate
 492           }
 493           _gens[i]->collect(full, do_clear_all_soft_refs, size, is_tlab);
 494           if (!rp->enqueuing_is_done()) {
 495             rp->enqueue_discovered_references();
 496           } else {
 497             rp->set_enqueuing_is_done(false);
 498           }
 499           rp->verify_no_references_recorded();
 500         }
 501         max_level_collected = i;
 502 
 503         // Determine if allocation request was met.
 504         if (size > 0) {
 505           if (!is_tlab || _gens[i]->supports_tlab_allocation()) {
 506             if (size*HeapWordSize <= _gens[i]->unsafe_max_alloc_nogc()) {
 507               size = 0;
 508             }
 509           }
 510         }
 511 
 512         COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
 513 
 514         _gens[i]->stat_record()->accumulated_time.stop();
 515 
 516         update_gc_stats(i, full);
 517 
 518         if (VerifyAfterGC && i >= VerifyGCLevel &&
 519             total_collections() >= VerifyGCStartAt) {
 520           HandleMark hm;  // Discard invalid handles created during verification
 521           Universe::verify(" VerifyAfterGC:");
 522         }
 523 
 524         if (PrintGCDetails) {
 525           gclog_or_tty->print(":");
 526           _gens[i]->print_heap_change(prev_used);
 527         }
 528       }
 529     }
 530 
 531     // Update "complete" boolean wrt what actually transpired --
 532     // for instance, a promotion failure could have led to
 533     // a whole heap collection.
 534     complete = complete || (max_level_collected == n_gens() - 1);
 535 
 536     if (complete) { // We did a "major" collection
 537       post_full_gc_dump();   // do any post full gc dumps
 538     }
 539 
 540     if (PrintGCDetails) {
 541       print_heap_change(gch_prev_used);
 542 
 543       // Print metaspace info for full GC with PrintGCDetails flag.
 544       if (complete) {
 545         MetaspaceAux::print_metaspace_change(metadata_prev_used);
 546       }
 547     }
 548 
 549     for (int j = max_level_collected; j >= 0; j -= 1) {
 550       // Adjust generation sizes.
 551       _gens[j]->compute_new_size();
 552     }
 553 
 554     if (complete) {
 555       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
 556       ClassLoaderDataGraph::purge();
 557       MetaspaceAux::verify_metrics();
 558       // Resize the metaspace capacity after full collections
 559       MetaspaceGC::compute_new_size();
 560       update_full_collections_completed();
 561     }
 562 
 563     // Track memory usage and detect low memory after GC finishes
 564     MemoryService::track_memory_usage();
 565 
 566     gc_epilogue(complete);
 567 
 568     if (must_restore_marks_for_biased_locking) {
 569       BiasedLocking::restore_marks();
 570     }
 571   }
 572 
 573   AdaptiveSizePolicy* sp = gen_policy()->size_policy();
 574   AdaptiveSizePolicyOutput(sp, total_collections());
 575 
 576   print_heap_after_gc();
 577 
 578 #ifdef TRACESPINNING
 579   ParallelTaskTerminator::print_termination_counts();
 580 #endif
 581 }
 582 
 583 HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
 584   return collector_policy()->satisfy_failed_allocation(size, is_tlab);
 585 }
 586 
 587 void GenCollectedHeap::set_par_threads(uint t) {
 588   SharedHeap::set_par_threads(t);
 589   _gen_process_strong_tasks->set_n_threads(t);
 590 }
 591 
 592 void GenCollectedHeap::
 593 gen_process_strong_roots(int level,
 594                          bool younger_gens_as_roots,
 595                          bool activate_scope,
 596                          bool is_scavenging,
 597                          SharedHeap::ScanningOption so,
 598                          OopsInGenClosure* not_older_gens,
 599                          bool do_code_roots,
 600                          OopsInGenClosure* older_gens,
 601                          KlassClosure* klass_closure) {
 602   // General strong roots.
 603 
 604   if (!do_code_roots) {
 605     SharedHeap::process_strong_roots(activate_scope, is_scavenging, so,
 606                                      not_older_gens, NULL, klass_closure);
 607   } else {
 608     bool do_code_marking = (activate_scope || nmethod::oops_do_marking_is_active());
 609     CodeBlobToOopClosure code_roots(not_older_gens, /*do_marking=*/ do_code_marking);
 610     SharedHeap::process_strong_roots(activate_scope, is_scavenging, so,
 611                                      not_older_gens, &code_roots, klass_closure);
 612   }
 613 
 614   if (younger_gens_as_roots) {
 615     if (!_gen_process_strong_tasks->is_task_claimed(GCH_PS_younger_gens)) {
 616       for (int i = 0; i < level; i++) {
 617         not_older_gens->set_generation(_gens[i]);
 618         _gens[i]->oop_iterate(not_older_gens);
 619       }
 620       not_older_gens->reset_generation();
 621     }
 622   }
 623   // When collection is parallel, all threads get to cooperate to do
 624   // older-gen scanning.
 625   for (int i = level+1; i < _n_gens; i++) {
 626     older_gens->set_generation(_gens[i]);
 627     rem_set()->younger_refs_iterate(_gens[i], older_gens);
 628     older_gens->reset_generation();
 629   }
 630 
 631   _gen_process_strong_tasks->all_tasks_completed();
 632 }
 633 
 634 void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure,
 635                                               CodeBlobClosure* code_roots) {
 636   SharedHeap::process_weak_roots(root_closure, code_roots);
 637   // "Local" "weak" refs
 638   for (int i = 0; i < _n_gens; i++) {
 639     _gens[i]->ref_processor()->weak_oops_do(root_closure);
 640   }
 641 }
 642 
 643 #define GCH_SINCE_SAVE_MARKS_ITERATE_DEFN(OopClosureType, nv_suffix)    \
 644 void GenCollectedHeap::                                                 \
 645 oop_since_save_marks_iterate(int level,                                 \
 646                              OopClosureType* cur,                       \
 647                              OopClosureType* older) {                   \
 648   _gens[level]->oop_since_save_marks_iterate##nv_suffix(cur);           \
 649   for (int i = level+1; i < n_gens(); i++) {                            \
 650     _gens[i]->oop_since_save_marks_iterate##nv_suffix(older);           \
 651   }                                                                     \
 652 }
 653 
 654 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DEFN)
 655 
 656 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DEFN
 657 
 658 bool GenCollectedHeap::no_allocs_since_save_marks(int level) {
 659   for (int i = level; i < _n_gens; i++) {
 660     if (!_gens[i]->no_allocs_since_save_marks()) return false;
 661   }
 662   return true;
 663 }
 664 
 665 bool GenCollectedHeap::supports_inline_contig_alloc() const {
 666   return _gens[0]->supports_inline_contig_alloc();
 667 }
 668 
 669 HeapWord** GenCollectedHeap::top_addr() const {
 670   return _gens[0]->top_addr();
 671 }
 672 
 673 HeapWord** GenCollectedHeap::end_addr() const {
 674   return _gens[0]->end_addr();
 675 }
 676 
 677 size_t GenCollectedHeap::unsafe_max_alloc() {
 678   return _gens[0]->unsafe_max_alloc_nogc();
 679 }
 680 
 681 // public collection interfaces
 682 
 683 void GenCollectedHeap::collect(GCCause::Cause cause) {
 684   if (should_do_concurrent_full_gc(cause)) {
 685 #if INCLUDE_ALL_GCS
 686     // mostly concurrent full collection
 687     collect_mostly_concurrent(cause);
 688 #else  // INCLUDE_ALL_GCS
 689     ShouldNotReachHere();
 690 #endif // INCLUDE_ALL_GCS
 691   } else {
 692 #ifdef ASSERT
 693     if (cause == GCCause::_scavenge_alot) {
 694       // minor collection only
 695       collect(cause, 0);
 696     } else {
 697       // Stop-the-world full collection
 698       collect(cause, n_gens() - 1);
 699     }
 700 #else
 701     // Stop-the-world full collection
 702     collect(cause, n_gens() - 1);
 703 #endif
 704   }
 705 }
 706 
 707 void GenCollectedHeap::collect(GCCause::Cause cause, int max_level) {
 708   // The caller doesn't have the Heap_lock
 709   assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
 710   MutexLocker ml(Heap_lock);
 711   collect_locked(cause, max_level);
 712 }
 713 
 714 void GenCollectedHeap::collect_locked(GCCause::Cause cause) {
 715   // The caller has the Heap_lock
 716   assert(Heap_lock->owned_by_self(), "this thread should own the Heap_lock");
 717   collect_locked(cause, n_gens() - 1);
 718 }
 719 
 720 // this is the private collection interface
 721 // The Heap_lock is expected to be held on entry.
 722 
 723 void GenCollectedHeap::collect_locked(GCCause::Cause cause, int max_level) {
 724   // Read the GC count while holding the Heap_lock
 725   unsigned int gc_count_before      = total_collections();
 726   unsigned int full_gc_count_before = total_full_collections();
 727   {
 728     MutexUnlocker mu(Heap_lock);  // give up heap lock, execute gets it back
 729     VM_GenCollectFull op(gc_count_before, full_gc_count_before,
 730                          cause, max_level);
 731     VMThread::execute(&op);
 732   }
 733 }
 734 
 735 #if INCLUDE_ALL_GCS
 736 bool GenCollectedHeap::create_cms_collector() {
 737 
 738   assert(((_gens[1]->kind() == Generation::ConcurrentMarkSweep) ||
 739          (_gens[1]->kind() == Generation::ASConcurrentMarkSweep)),
 740          "Unexpected generation kinds");
 741   // Skip two header words in the block content verification
 742   NOT_PRODUCT(_skip_header_HeapWords = CMSCollector::skip_header_HeapWords();)
 743   CMSCollector* collector = new CMSCollector(
 744     (ConcurrentMarkSweepGeneration*)_gens[1],
 745     _rem_set->as_CardTableRS(),
 746     (ConcurrentMarkSweepPolicy*) collector_policy());
 747 
 748   if (collector == NULL || !collector->completed_initialization()) {
 749     if (collector) {
 750       delete collector;  // Be nice in embedded situation
 751     }
 752     vm_shutdown_during_initialization("Could not create CMS collector");
 753     return false;
 754   }
 755   return true;  // success
 756 }
 757 
 758 void GenCollectedHeap::collect_mostly_concurrent(GCCause::Cause cause) {
 759   assert(!Heap_lock->owned_by_self(), "Should not own Heap_lock");
 760 
 761   MutexLocker ml(Heap_lock);
 762   // Read the GC counts while holding the Heap_lock
 763   unsigned int full_gc_count_before = total_full_collections();
 764   unsigned int gc_count_before      = total_collections();
 765   {
 766     MutexUnlocker mu(Heap_lock);
 767     VM_GenCollectFullConcurrent op(gc_count_before, full_gc_count_before, cause);
 768     VMThread::execute(&op);
 769   }
 770 }
 771 #endif // INCLUDE_ALL_GCS
 772 
 773 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs) {
 774    do_full_collection(clear_all_soft_refs, _n_gens - 1);
 775 }
 776 
 777 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs,
 778                                           int max_level) {
 779   int local_max_level;
 780   if (!incremental_collection_will_fail(false /* don't consult_young */) &&
 781       gc_cause() == GCCause::_gc_locker) {
 782     local_max_level = 0;
 783   } else {
 784     local_max_level = max_level;
 785   }
 786 
 787   do_collection(true                 /* full */,
 788                 clear_all_soft_refs  /* clear_all_soft_refs */,
 789                 0                    /* size */,
 790                 false                /* is_tlab */,
 791                 local_max_level      /* max_level */);
 792   // Hack XXX FIX ME !!!
 793   // A scavenge may not have been attempted, or may have
 794   // been attempted and failed, because the old gen was too full
 795   if (local_max_level == 0 && gc_cause() == GCCause::_gc_locker &&
 796       incremental_collection_will_fail(false /* don't consult_young */)) {
 797     if (PrintGCDetails) {
 798       gclog_or_tty->print_cr("GC locker: Trying a full collection "
 799                              "because scavenge failed");
 800     }
 801     // This time allow the old gen to be collected as well
 802     do_collection(true                 /* full */,
 803                   clear_all_soft_refs  /* clear_all_soft_refs */,
 804                   0                    /* size */,
 805                   false                /* is_tlab */,
 806                   n_gens() - 1         /* max_level */);
 807   }
 808 }
 809 
 810 bool GenCollectedHeap::is_in_young(oop p) {
 811   bool result = ((HeapWord*)p) < _gens[_n_gens - 1]->reserved().start();
 812   assert(result == _gens[0]->is_in_reserved(p),
 813          err_msg("incorrect test - result=%d, p=" PTR_FORMAT, result, (void*)p));
 814   return result;
 815 }
 816 
 817 // Returns "TRUE" iff "p" points into the committed areas of the heap.
 818 bool GenCollectedHeap::is_in(const void* p) const {
 819   #ifndef ASSERT
 820   guarantee(VerifyBeforeGC      ||
 821             VerifyDuringGC      ||
 822             VerifyBeforeExit    ||
 823             VerifyDuringStartup ||
 824             PrintAssembly       ||
 825             tty->count() != 0   ||   // already printing
 826             VerifyAfterGC       ||
 827     VMError::fatal_error_in_progress(), "too expensive");
 828 
 829   #endif
 830   // This might be sped up with a cache of the last generation that
 831   // answered yes.
 832   for (int i = 0; i < _n_gens; i++) {
 833     if (_gens[i]->is_in(p)) return true;
 834   }
 835   // Otherwise...
 836   return false;
 837 }
 838 
 839 #ifdef ASSERT
 840 // Don't implement this by using is_in_young().  This method is used
 841 // in some cases to check that is_in_young() is correct.
 842 bool GenCollectedHeap::is_in_partial_collection(const void* p) {
 843   assert(is_in_reserved(p) || p == NULL,
 844     "Does not work if address is non-null and outside of the heap");
 845   return p < _gens[_n_gens - 2]->reserved().end() && p != NULL;
 846 }
 847 #endif
 848 
 849 void GenCollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
 850   for (int i = 0; i < _n_gens; i++) {
 851     _gens[i]->oop_iterate(cl);
 852   }
 853 }
 854 
 855 void GenCollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
 856   for (int i = 0; i < _n_gens; i++) {
 857     _gens[i]->oop_iterate(mr, cl);
 858   }
 859 }
 860 
 861 void GenCollectedHeap::object_iterate(ObjectClosure* cl) {
 862   for (int i = 0; i < _n_gens; i++) {
 863     _gens[i]->object_iterate(cl);
 864   }
 865 }
 866 
 867 void GenCollectedHeap::safe_object_iterate(ObjectClosure* cl) {
 868   for (int i = 0; i < _n_gens; i++) {
 869     _gens[i]->safe_object_iterate(cl);
 870   }
 871 }
 872 
 873 void GenCollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
 874   for (int i = 0; i < _n_gens; i++) {
 875     _gens[i]->object_iterate_since_last_GC(cl);
 876   }
 877 }
 878 
 879 Space* GenCollectedHeap::space_containing(const void* addr) const {
 880   for (int i = 0; i < _n_gens; i++) {
 881     Space* res = _gens[i]->space_containing(addr);
 882     if (res != NULL) return res;
 883   }
 884   // Otherwise...
 885   assert(false, "Could not find containing space");
 886   return NULL;
 887 }
 888 
 889 
 890 HeapWord* GenCollectedHeap::block_start(const void* addr) const {
 891   assert(is_in_reserved(addr), "block_start of address outside of heap");
 892   for (int i = 0; i < _n_gens; i++) {
 893     if (_gens[i]->is_in_reserved(addr)) {
 894       assert(_gens[i]->is_in(addr),
 895              "addr should be in allocated part of generation");
 896       return _gens[i]->block_start(addr);
 897     }
 898   }
 899   assert(false, "Some generation should contain the address");
 900   return NULL;
 901 }
 902 
 903 size_t GenCollectedHeap::block_size(const HeapWord* addr) const {
 904   assert(is_in_reserved(addr), "block_size of address outside of heap");
 905   for (int i = 0; i < _n_gens; i++) {
 906     if (_gens[i]->is_in_reserved(addr)) {
 907       assert(_gens[i]->is_in(addr),
 908              "addr should be in allocated part of generation");
 909       return _gens[i]->block_size(addr);
 910     }
 911   }
 912   assert(false, "Some generation should contain the address");
 913   return 0;
 914 }
 915 
 916 bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const {
 917   assert(is_in_reserved(addr), "block_is_obj of address outside of heap");
 918   assert(block_start(addr) == addr, "addr must be a block start");
 919   for (int i = 0; i < _n_gens; i++) {
 920     if (_gens[i]->is_in_reserved(addr)) {
 921       return _gens[i]->block_is_obj(addr);
 922     }
 923   }
 924   assert(false, "Some generation should contain the address");
 925   return false;
 926 }
 927 
 928 bool GenCollectedHeap::supports_tlab_allocation() const {
 929   for (int i = 0; i < _n_gens; i += 1) {
 930     if (_gens[i]->supports_tlab_allocation()) {
 931       return true;
 932     }
 933   }
 934   return false;
 935 }
 936 
 937 size_t GenCollectedHeap::tlab_capacity(Thread* thr) const {
 938   size_t result = 0;
 939   for (int i = 0; i < _n_gens; i += 1) {
 940     if (_gens[i]->supports_tlab_allocation()) {
 941       result += _gens[i]->tlab_capacity();
 942     }
 943   }
 944   return result;
 945 }
 946 
 947 size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const {
 948   size_t result = 0;
 949   for (int i = 0; i < _n_gens; i += 1) {
 950     if (_gens[i]->supports_tlab_allocation()) {
 951       result += _gens[i]->unsafe_max_tlab_alloc();
 952     }
 953   }
 954   return result;
 955 }
 956 
 957 HeapWord* GenCollectedHeap::allocate_new_tlab(size_t size) {
 958   bool gc_overhead_limit_was_exceeded;
 959   return collector_policy()->mem_allocate_work(size /* size */,
 960                                                true /* is_tlab */,
 961                                                &gc_overhead_limit_was_exceeded);
 962 }
 963 
 964 // Requires "*prev_ptr" to be non-NULL.  Deletes and a block of minimal size
 965 // from the list headed by "*prev_ptr".
 966 static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) {
 967   bool first = true;
 968   size_t min_size = 0;   // "first" makes this conceptually infinite.
 969   ScratchBlock **smallest_ptr, *smallest;
 970   ScratchBlock  *cur = *prev_ptr;
 971   while (cur) {
 972     assert(*prev_ptr == cur, "just checking");
 973     if (first || cur->num_words < min_size) {
 974       smallest_ptr = prev_ptr;
 975       smallest     = cur;
 976       min_size     = smallest->num_words;
 977       first        = false;
 978     }
 979     prev_ptr = &cur->next;
 980     cur     =  cur->next;
 981   }
 982   smallest      = *smallest_ptr;
 983   *smallest_ptr = smallest->next;
 984   return smallest;
 985 }
 986 
 987 // Sort the scratch block list headed by res into decreasing size order,
 988 // and set "res" to the result.
 989 static void sort_scratch_list(ScratchBlock*& list) {
 990   ScratchBlock* sorted = NULL;
 991   ScratchBlock* unsorted = list;
 992   while (unsorted) {
 993     ScratchBlock *smallest = removeSmallestScratch(&unsorted);
 994     smallest->next  = sorted;
 995     sorted          = smallest;
 996   }
 997   list = sorted;
 998 }
 999 
1000 ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor,
1001                                                size_t max_alloc_words) {
1002   ScratchBlock* res = NULL;
1003   for (int i = 0; i < _n_gens; i++) {
1004     _gens[i]->contribute_scratch(res, requestor, max_alloc_words);
1005   }
1006   sort_scratch_list(res);
1007   return res;
1008 }
1009 
1010 void GenCollectedHeap::release_scratch() {
1011   for (int i = 0; i < _n_gens; i++) {
1012     _gens[i]->reset_scratch();
1013   }
1014 }
1015 
1016 class GenPrepareForVerifyClosure: public GenCollectedHeap::GenClosure {
1017   void do_generation(Generation* gen) {
1018     gen->prepare_for_verify();
1019   }
1020 };
1021 
1022 void GenCollectedHeap::prepare_for_verify() {
1023   ensure_parsability(false);        // no need to retire TLABs
1024   GenPrepareForVerifyClosure blk;
1025   generation_iterate(&blk, false);
1026 }
1027 
1028 
1029 void GenCollectedHeap::generation_iterate(GenClosure* cl,
1030                                           bool old_to_young) {
1031   if (old_to_young) {
1032     for (int i = _n_gens-1; i >= 0; i--) {
1033       cl->do_generation(_gens[i]);
1034     }
1035   } else {
1036     for (int i = 0; i < _n_gens; i++) {
1037       cl->do_generation(_gens[i]);
1038     }
1039   }
1040 }
1041 
1042 void GenCollectedHeap::space_iterate(SpaceClosure* cl) {
1043   for (int i = 0; i < _n_gens; i++) {
1044     _gens[i]->space_iterate(cl, true);
1045   }
1046 }
1047 
1048 bool GenCollectedHeap::is_maximal_no_gc() const {
1049   for (int i = 0; i < _n_gens; i++) {
1050     if (!_gens[i]->is_maximal_no_gc()) {
1051       return false;
1052     }
1053   }
1054   return true;
1055 }
1056 
1057 void GenCollectedHeap::save_marks() {
1058   for (int i = 0; i < _n_gens; i++) {
1059     _gens[i]->save_marks();
1060   }
1061 }
1062 
1063 void GenCollectedHeap::compute_new_generation_sizes(int collectedGen) {
1064   for (int i = 0; i <= collectedGen; i++) {
1065     _gens[i]->compute_new_size();
1066   }
1067 }
1068 
1069 GenCollectedHeap* GenCollectedHeap::heap() {
1070   assert(_gch != NULL, "Uninitialized access to GenCollectedHeap::heap()");
1071   assert(_gch->kind() == CollectedHeap::GenCollectedHeap, "not a generational heap");
1072   return _gch;
1073 }
1074 
1075 
1076 void GenCollectedHeap::prepare_for_compaction() {
1077   Generation* scanning_gen = _gens[_n_gens-1];
1078   // Start by compacting into same gen.
1079   CompactPoint cp(scanning_gen, NULL, NULL);
1080   while (scanning_gen != NULL) {
1081     scanning_gen->prepare_for_compaction(&cp);
1082     scanning_gen = prev_gen(scanning_gen);
1083   }
1084 }
1085 
1086 GCStats* GenCollectedHeap::gc_stats(int level) const {
1087   return _gens[level]->gc_stats();
1088 }
1089 
1090 void GenCollectedHeap::verify(bool silent, VerifyOption option /* ignored */) {
1091   for (int i = _n_gens-1; i >= 0; i--) {
1092     Generation* g = _gens[i];
1093     if (!silent) {
1094       gclog_or_tty->print(g->name());
1095       gclog_or_tty->print(" ");
1096     }
1097     g->verify();
1098   }
1099   if (!silent) {
1100     gclog_or_tty->print("remset ");
1101   }
1102   rem_set()->verify();
1103 }
1104 
1105 void GenCollectedHeap::print_on(outputStream* st) const {
1106   for (int i = 0; i < _n_gens; i++) {
1107     _gens[i]->print_on(st);
1108   }
1109   MetaspaceAux::print_on(st);
1110 }
1111 
1112 void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const {
1113   if (workers() != NULL) {
1114     workers()->threads_do(tc);
1115   }
1116 #if INCLUDE_ALL_GCS
1117   if (UseConcMarkSweepGC) {
1118     ConcurrentMarkSweepThread::threads_do(tc);
1119   }
1120 #endif // INCLUDE_ALL_GCS
1121 }
1122 
1123 void GenCollectedHeap::print_gc_threads_on(outputStream* st) const {
1124 #if INCLUDE_ALL_GCS
1125   if (UseParNewGC) {
1126     workers()->print_worker_threads_on(st);
1127   }
1128   if (UseConcMarkSweepGC) {
1129     ConcurrentMarkSweepThread::print_all_on(st);
1130   }
1131 #endif // INCLUDE_ALL_GCS
1132 }
1133 
1134 void GenCollectedHeap::print_on_error(outputStream* st) const {
1135   this->CollectedHeap::print_on_error(st);
1136 
1137 #if INCLUDE_ALL_GCS
1138   if (UseConcMarkSweepGC) {
1139     st->cr();
1140     CMSCollector::print_on_error(st);
1141   }
1142 #endif // INCLUDE_ALL_GCS
1143 }
1144 
1145 void GenCollectedHeap::print_tracing_info() const {
1146   if (TraceGen0Time) {
1147     get_gen(0)->print_summary_info();
1148   }
1149   if (TraceGen1Time) {
1150     get_gen(1)->print_summary_info();
1151   }
1152 }
1153 
1154 void GenCollectedHeap::print_heap_change(size_t prev_used) const {
1155   if (PrintGCDetails && Verbose) {
1156     gclog_or_tty->print(" "  SIZE_FORMAT
1157                         "->" SIZE_FORMAT
1158                         "("  SIZE_FORMAT ")",
1159                         prev_used, used(), capacity());
1160   } else {
1161     gclog_or_tty->print(" "  SIZE_FORMAT "K"
1162                         "->" SIZE_FORMAT "K"
1163                         "("  SIZE_FORMAT "K)",
1164                         prev_used / K, used() / K, capacity() / K);
1165   }
1166 }
1167 
1168 class GenGCPrologueClosure: public GenCollectedHeap::GenClosure {
1169  private:
1170   bool _full;
1171  public:
1172   void do_generation(Generation* gen) {
1173     gen->gc_prologue(_full);
1174   }
1175   GenGCPrologueClosure(bool full) : _full(full) {};
1176 };
1177 
1178 void GenCollectedHeap::gc_prologue(bool full) {
1179   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
1180 
1181   always_do_update_barrier = false;
1182   // Fill TLAB's and such
1183   CollectedHeap::accumulate_statistics_all_tlabs();
1184   ensure_parsability(true);   // retire TLABs
1185 
1186   // Call allocation profiler
1187   AllocationProfiler::iterate_since_last_gc();
1188   // Walk generations
1189   GenGCPrologueClosure blk(full);
1190   generation_iterate(&blk, false);  // not old-to-young.
1191 };
1192 
1193 class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure {
1194  private:
1195   bool _full;
1196  public:
1197   void do_generation(Generation* gen) {
1198     gen->gc_epilogue(_full);
1199   }
1200   GenGCEpilogueClosure(bool full) : _full(full) {};
1201 };
1202 
1203 void GenCollectedHeap::gc_epilogue(bool full) {
1204 #ifdef COMPILER2
1205   assert(DerivedPointerTable::is_empty(), "derived pointer present");
1206   size_t actual_gap = pointer_delta((HeapWord*) (max_uintx-3), *(end_addr()));
1207   guarantee(actual_gap > (size_t)FastAllocateSizeLimit, "inline allocation wraps");
1208 #endif /* COMPILER2 */
1209 
1210   resize_all_tlabs();
1211 
1212   GenGCEpilogueClosure blk(full);
1213   generation_iterate(&blk, false);  // not old-to-young.
1214 
1215   if (!CleanChunkPoolAsync) {
1216     Chunk::clean_chunk_pool();
1217   }
1218 
1219   MetaspaceCounters::update_performance_counters();
1220 
1221   always_do_update_barrier = UseConcMarkSweepGC;
1222 };
1223 
1224 #ifndef PRODUCT
1225 class GenGCSaveTopsBeforeGCClosure: public GenCollectedHeap::GenClosure {
1226  private:
1227  public:
1228   void do_generation(Generation* gen) {
1229     gen->record_spaces_top();
1230   }
1231 };
1232 
1233 void GenCollectedHeap::record_gen_tops_before_GC() {
1234   if (ZapUnusedHeapArea) {
1235     GenGCSaveTopsBeforeGCClosure blk;
1236     generation_iterate(&blk, false);  // not old-to-young.
1237   }
1238 }
1239 #endif  // not PRODUCT
1240 
1241 class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure {
1242  public:
1243   void do_generation(Generation* gen) {
1244     gen->ensure_parsability();
1245   }
1246 };
1247 
1248 void GenCollectedHeap::ensure_parsability(bool retire_tlabs) {
1249   CollectedHeap::ensure_parsability(retire_tlabs);
1250   GenEnsureParsabilityClosure ep_cl;
1251   generation_iterate(&ep_cl, false);
1252 }
1253 
1254 oop GenCollectedHeap::handle_failed_promotion(Generation* gen,
1255                                               oop obj,
1256                                               size_t obj_size) {
1257   assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1258   HeapWord* result = NULL;
1259 
1260   // First give each higher generation a chance to allocate the promoted object.
1261   Generation* allocator = next_gen(gen);
1262   if (allocator != NULL) {
1263     do {
1264       result = allocator->allocate(obj_size, false);
1265     } while (result == NULL && (allocator = next_gen(allocator)) != NULL);
1266   }
1267 
1268   if (result == NULL) {
1269     // Then give gen and higher generations a chance to expand and allocate the
1270     // object.
1271     do {
1272       result = gen->expand_and_allocate(obj_size, false);
1273     } while (result == NULL && (gen = next_gen(gen)) != NULL);
1274   }
1275 
1276   if (result != NULL) {
1277     Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size);
1278   }
1279   return oop(result);
1280 }
1281 
1282 class GenTimeOfLastGCClosure: public GenCollectedHeap::GenClosure {
1283   jlong _time;   // in ms
1284   jlong _now;    // in ms
1285 
1286  public:
1287   GenTimeOfLastGCClosure(jlong now) : _time(now), _now(now) { }
1288 
1289   jlong time() { return _time; }
1290 
1291   void do_generation(Generation* gen) {
1292     _time = MIN2(_time, gen->time_of_last_gc(_now));
1293   }
1294 };
1295 
1296 jlong GenCollectedHeap::millis_since_last_gc() {
1297   // We need a monotonically non-deccreasing time in ms but
1298   // os::javaTimeMillis() does not guarantee monotonicity.
1299   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
1300   GenTimeOfLastGCClosure tolgc_cl(now);
1301   // iterate over generations getting the oldest
1302   // time that a generation was collected
1303   generation_iterate(&tolgc_cl, false);
1304 
1305   // javaTimeNanos() is guaranteed to be monotonically non-decreasing
1306   // provided the underlying platform provides such a time source
1307   // (and it is bug free). So we still have to guard against getting
1308   // back a time later than 'now'.
1309   jlong retVal = now - tolgc_cl.time();
1310   if (retVal < 0) {
1311     NOT_PRODUCT(warning("time warp: "INT64_FORMAT, retVal);)
1312     return 0;
1313   }
1314   return retVal;
1315 }