1 /*
   2  * Copyright (c) 2000, 2015, 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/gcTrace.hpp"
  32 #include "gc_implementation/shared/gcTraceTime.hpp"
  33 #include "gc_implementation/shared/vmGCOperations.hpp"
  34 #include "gc_interface/collectedHeap.inline.hpp"
  35 #include "memory/filemap.hpp"
  36 #include "memory/gcLocker.inline.hpp"
  37 #include "memory/genCollectedHeap.hpp"
  38 #include "memory/genOopClosures.inline.hpp"
  39 #include "memory/generationSpec.hpp"
  40 #include "memory/resourceArea.hpp"
  41 #include "memory/sharedHeap.hpp"
  42 #include "memory/space.hpp"
  43 #include "oops/oop.inline.hpp"
  44 #include "runtime/biasedLocking.hpp"
  45 #include "runtime/fprofiler.hpp"
  46 #include "runtime/handles.hpp"
  47 #include "runtime/handles.inline.hpp"
  48 #include "runtime/java.hpp"
  49 #include "runtime/vmThread.hpp"
  50 #include "services/memoryService.hpp"
  51 #include "utilities/vmError.hpp"
  52 #include "utilities/workgroup.hpp"
  53 #include "utilities/macros.hpp"
  54 #if INCLUDE_ALL_GCS
  55 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
  56 #include "gc_implementation/concurrentMarkSweep/vmCMSOperations.hpp"
  57 #endif // INCLUDE_ALL_GCS
  58 
  59 GenCollectedHeap* GenCollectedHeap::_gch;
  60 NOT_PRODUCT(size_t GenCollectedHeap::_skip_header_HeapWords = 0;)
  61 
  62 // The set of potentially parallel tasks in root scanning.
  63 enum GCH_strong_roots_tasks {
  64   // We probably want to parallelize both of these internally, but for now...
  65   GCH_PS_younger_gens,
  66   // Leave this one last.
  67   GCH_PS_NumElements
  68 };
  69 
  70 GenCollectedHeap::GenCollectedHeap(GenCollectorPolicy *policy) :
  71   SharedHeap(policy),
  72   _rem_set(NULL),
  73   _gen_policy(policy),
  74   _gen_process_roots_tasks(new SubTasksDone(GCH_PS_NumElements)),
  75   _full_collections_completed(0)
  76 {
  77   if (_gen_process_roots_tasks == NULL ||
  78       !_gen_process_roots_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   assert(_n_gens == 2, "There is no support for more than two generations");
  90 
  91   // While there are no constraints in the GC code that HeapWordSize
  92   // be any particular value, there are multiple other areas in the
  93   // system which believe this to be true (e.g. oop->object_size in some
  94   // cases incorrectly returns the size in wordSize units rather than
  95   // HeapWordSize).
  96   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
  97 
  98   // The heap must be at least as aligned as generations.
  99   size_t gen_alignment = Generation::GenGrain;
 100 
 101   _gen_specs = gen_policy()->generations();
 102 
 103   // Make sure the sizes are all aligned.
 104   for (i = 0; i < _n_gens; i++) {
 105     _gen_specs[i]->align(gen_alignment);
 106   }
 107 
 108   // Allocate space for the heap.
 109 
 110   char* heap_address;
 111   ReservedSpace heap_rs;
 112 
 113   size_t heap_alignment = collector_policy()->heap_alignment();
 114 
 115   heap_address = allocate(heap_alignment, &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   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
 124 
 125   _rem_set = collector_policy()->create_rem_set(reserved_region());
 126   set_barrier_set(rem_set()->bs());
 127 
 128   _gch = this;
 129 
 130   ReservedSpace young_rs = heap_rs.first_part(_gen_specs[0]->max_size(), false, false);
 131   _young_gen = _gen_specs[0]->init(young_rs, 0, rem_set());
 132   heap_rs = heap_rs.last_part(_gen_specs[0]->max_size());
 133 
 134   ReservedSpace old_rs = heap_rs.first_part(_gen_specs[1]->max_size(), false, false);
 135   _old_gen = _gen_specs[1]->init(old_rs, 1, rem_set());
 136   clear_incremental_collection_failed();
 137 
 138 #if INCLUDE_ALL_GCS
 139   // If we are running CMS, create the collector responsible
 140   // for collecting the CMS generations.
 141   if (collector_policy()->is_concurrent_mark_sweep_policy()) {
 142     bool success = create_cms_collector();
 143     if (!success) return JNI_ENOMEM;
 144   }
 145 #endif // INCLUDE_ALL_GCS
 146 
 147   return JNI_OK;
 148 }
 149 
 150 char* GenCollectedHeap::allocate(size_t alignment,
 151                                  ReservedSpace* heap_rs){
 152   const char overflow_msg[] = "The size of the object heap + VM data exceeds "
 153     "the maximum representable size";
 154 
 155   // Now figure out the total size.
 156   size_t total_reserved = 0;
 157   const size_t pageSize = UseLargePages ?
 158       os::large_page_size() : os::vm_page_size();
 159 
 160   assert(alignment % pageSize == 0, "Must be");
 161 
 162   for (int i = 0; i < _n_gens; i++) {
 163     total_reserved += _gen_specs[i]->max_size();
 164     if (total_reserved < _gen_specs[i]->max_size()) {
 165       vm_exit_during_initialization(overflow_msg);
 166     }
 167   }
 168   assert(total_reserved % alignment == 0,
 169          err_msg("Gen size; total_reserved=" SIZE_FORMAT ", alignment="
 170                  SIZE_FORMAT, total_reserved, alignment));
 171 
 172   *heap_rs = Universe::reserve_heap(total_reserved, alignment);
 173   return heap_rs->base();
 174 }
 175 
 176 void GenCollectedHeap::post_initialize() {
 177   SharedHeap::post_initialize();
 178   GenCollectorPolicy *policy = (GenCollectorPolicy *)collector_policy();
 179   guarantee(policy->is_generation_policy(), "Illegal policy type");
 180   assert((_young_gen->kind() == Generation::DefNew) ||
 181          (_young_gen->kind() == Generation::ParNew),
 182     "Wrong youngest generation type");
 183   DefNewGeneration* def_new_gen = (DefNewGeneration*)_young_gen;
 184 
 185   assert(_old_gen->kind() == Generation::ConcurrentMarkSweep ||
 186          _old_gen->kind() == Generation::MarkSweepCompact,
 187     "Wrong generation kind");
 188 
 189   policy->initialize_size_policy(def_new_gen->eden()->capacity(),
 190                                  _old_gen->capacity(),
 191                                  def_new_gen->from()->capacity());
 192   policy->initialize_gc_policy_counters();
 193 }
 194 
 195 void GenCollectedHeap::ref_processing_init() {
 196   SharedHeap::ref_processing_init();
 197   _young_gen->ref_processor_init();
 198   _old_gen->ref_processor_init();
 199 }
 200 
 201 size_t GenCollectedHeap::capacity() const {
 202   return _young_gen->capacity() + _old_gen->capacity();
 203 }
 204 
 205 size_t GenCollectedHeap::used() const {
 206   return _young_gen->used() + _old_gen->used();
 207 }
 208 
 209 // Save the "used_region" for generations level and lower.
 210 void GenCollectedHeap::save_used_regions(int level) {
 211   assert(level >= 0, "Illegal level parameter");
 212   assert(level < _n_gens, "Illegal level parameter");
 213   if (level == 1) {
 214     _old_gen->save_used_region();
 215   }
 216   _young_gen->save_used_region();
 217 }
 218 
 219 size_t GenCollectedHeap::max_capacity() const {
 220   return _young_gen->max_capacity() + _old_gen->max_capacity();
 221 }
 222 
 223 // Update the _full_collections_completed counter
 224 // at the end of a stop-world full GC.
 225 unsigned int GenCollectedHeap::update_full_collections_completed() {
 226   MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
 227   assert(_full_collections_completed <= _total_full_collections,
 228          "Can't complete more collections than were started");
 229   _full_collections_completed = _total_full_collections;
 230   ml.notify_all();
 231   return _full_collections_completed;
 232 }
 233 
 234 // Update the _full_collections_completed counter, as appropriate,
 235 // at the end of a concurrent GC cycle. Note the conditional update
 236 // below to allow this method to be called by a concurrent collector
 237 // without synchronizing in any manner with the VM thread (which
 238 // may already have initiated a STW full collection "concurrently").
 239 unsigned int GenCollectedHeap::update_full_collections_completed(unsigned int count) {
 240   MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
 241   assert((_full_collections_completed <= _total_full_collections) &&
 242          (count <= _total_full_collections),
 243          "Can't complete more collections than were started");
 244   if (count > _full_collections_completed) {
 245     _full_collections_completed = count;
 246     ml.notify_all();
 247   }
 248   return _full_collections_completed;
 249 }
 250 
 251 
 252 #ifndef PRODUCT
 253 // Override of memory state checking method in CollectedHeap:
 254 // Some collectors (CMS for example) can't have badHeapWordVal written
 255 // in the first two words of an object. (For instance , in the case of
 256 // CMS these words hold state used to synchronize between certain
 257 // (concurrent) GC steps and direct allocating mutators.)
 258 // The skip_header_HeapWords() method below, allows us to skip
 259 // over the requisite number of HeapWord's. Note that (for
 260 // generational collectors) this means that those many words are
 261 // skipped in each object, irrespective of the generation in which
 262 // that object lives. The resultant loss of precision seems to be
 263 // harmless and the pain of avoiding that imprecision appears somewhat
 264 // higher than we are prepared to pay for such rudimentary debugging
 265 // support.
 266 void GenCollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr,
 267                                                          size_t size) {
 268   if (CheckMemoryInitialization && ZapUnusedHeapArea) {
 269     // We are asked to check a size in HeapWords,
 270     // but the memory is mangled in juint words.
 271     juint* start = (juint*) (addr + skip_header_HeapWords());
 272     juint* end   = (juint*) (addr + size);
 273     for (juint* slot = start; slot < end; slot += 1) {
 274       assert(*slot == badHeapWordVal,
 275              "Found non badHeapWordValue in pre-allocation check");
 276     }
 277   }
 278 }
 279 #endif
 280 
 281 HeapWord* GenCollectedHeap::attempt_allocation(size_t size,
 282                                                bool is_tlab,
 283                                                bool first_only) {
 284   HeapWord* res = NULL;
 285 
 286   if (_young_gen->should_allocate(size, is_tlab)) {
 287     res = _young_gen->allocate(size, is_tlab);
 288     if (res != NULL || first_only) {
 289       return res;
 290     }
 291   }
 292 
 293   if (_old_gen->should_allocate(size, is_tlab)) {
 294     res = _old_gen->allocate(size, is_tlab);
 295   }
 296 
 297   return res;
 298 }
 299 
 300 HeapWord* GenCollectedHeap::mem_allocate(size_t size,
 301                                          bool* gc_overhead_limit_was_exceeded) {
 302   return collector_policy()->mem_allocate_work(size,
 303                                                false /* is_tlab */,
 304                                                gc_overhead_limit_was_exceeded);
 305 }
 306 
 307 bool GenCollectedHeap::must_clear_all_soft_refs() {
 308   return _gc_cause == GCCause::_last_ditch_collection;
 309 }
 310 
 311 bool GenCollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
 312   return UseConcMarkSweepGC &&
 313          ((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
 314           (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent));
 315 }
 316 
 317 void GenCollectedHeap::collect_generation(Generation* gen, bool full, size_t size,
 318                                           bool is_tlab, bool run_verification, bool clear_soft_refs,
 319                                           bool restore_marks_for_biased_locking) {
 320   // Timer for individual generations. Last argument is false: no CR
 321   // FIXME: We should try to start the timing earlier to cover more of the GC pause
 322   // The PrintGCDetails logging starts before we have incremented the GC id. We will do that later
 323   // so we can assume here that the next GC id is what we want.
 324   GCTraceTime t1(gen->short_name(), PrintGCDetails, false, NULL, GCId::peek());
 325   TraceCollectorStats tcs(gen->counters());
 326   TraceMemoryManagerStats tmms(gen->kind(),gc_cause());
 327 
 328   size_t prev_used = gen->used();
 329   gen->stat_record()->invocations++;
 330   gen->stat_record()->accumulated_time.start();
 331 
 332   // Must be done anew before each collection because
 333   // a previous collection will do mangling and will
 334   // change top of some spaces.
 335   record_gen_tops_before_GC();
 336 
 337   if (PrintGC && Verbose) {
 338     gclog_or_tty->print("level=%d invoke=%d size=" SIZE_FORMAT,
 339                         gen->level(),
 340                         gen->stat_record()->invocations,
 341                         size * HeapWordSize);
 342   }
 343 
 344   if (run_verification && VerifyBeforeGC) {
 345     HandleMark hm;  // Discard invalid handles created during verification
 346     Universe::verify(" VerifyBeforeGC:");
 347   }
 348   COMPILER2_PRESENT(DerivedPointerTable::clear());
 349 
 350   if (restore_marks_for_biased_locking) {
 351     // We perform this mark word preservation work lazily
 352     // because it's only at this point that we know whether we
 353     // absolutely have to do it; we want to avoid doing it for
 354     // scavenge-only collections where it's unnecessary
 355     BiasedLocking::preserve_marks();
 356   }
 357 
 358   // Do collection work
 359   {
 360     // Note on ref discovery: For what appear to be historical reasons,
 361     // GCH enables and disabled (by enqueing) refs discovery.
 362     // In the future this should be moved into the generation's
 363     // collect method so that ref discovery and enqueueing concerns
 364     // are local to a generation. The collect method could return
 365     // an appropriate indication in the case that notification on
 366     // the ref lock was needed. This will make the treatment of
 367     // weak refs more uniform (and indeed remove such concerns
 368     // from GCH). XXX
 369 
 370     HandleMark hm;  // Discard invalid handles created during gc
 371     save_marks();   // save marks for all gens
 372     // We want to discover references, but not process them yet.
 373     // This mode is disabled in process_discovered_references if the
 374     // generation does some collection work, or in
 375     // enqueue_discovered_references if the generation returns
 376     // without doing any work.
 377     ReferenceProcessor* rp = gen->ref_processor();
 378     // If the discovery of ("weak") refs in this generation is
 379     // atomic wrt other collectors in this configuration, we
 380     // are guaranteed to have empty discovered ref lists.
 381     if (rp->discovery_is_atomic()) {
 382       rp->enable_discovery();
 383       rp->setup_policy(clear_soft_refs);
 384     } else {
 385       // collect() below will enable discovery as appropriate
 386     }
 387     gen->collect(full, clear_soft_refs, size, is_tlab);
 388     if (!rp->enqueuing_is_done()) {
 389       rp->enqueue_discovered_references();
 390     } else {
 391       rp->set_enqueuing_is_done(false);
 392     }
 393     rp->verify_no_references_recorded();
 394   }
 395 
 396   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
 397 
 398   gen->stat_record()->accumulated_time.stop();
 399 
 400   update_gc_stats(gen->level(), full);
 401 
 402   if (run_verification && VerifyAfterGC) {
 403     HandleMark hm;  // Discard invalid handles created during verification
 404     Universe::verify(" VerifyAfterGC:");
 405   }
 406 
 407   if (PrintGCDetails) {
 408     gclog_or_tty->print(":");
 409     gen->print_heap_change(prev_used);
 410   }
 411 }
 412 
 413 void GenCollectedHeap::do_collection(bool   full,
 414                                      bool   clear_all_soft_refs,
 415                                      size_t size,
 416                                      bool   is_tlab,
 417                                      int    max_level) {
 418   ResourceMark rm;
 419   DEBUG_ONLY(Thread* my_thread = Thread::current();)
 420 
 421   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 422   assert(my_thread->is_VM_thread() ||
 423          my_thread->is_ConcurrentGC_thread(),
 424          "incorrect thread type capability");
 425   assert(Heap_lock->is_locked(),
 426          "the requesting thread should have the Heap_lock");
 427   guarantee(!is_gc_active(), "collection is not reentrant");
 428   assert(max_level < n_gens(), "sanity check");
 429 
 430   if (GC_locker::check_active_before_gc()) {
 431     return; // GC is disabled (e.g. JNI GetXXXCritical operation)
 432   }
 433 
 434   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
 435                           collector_policy()->should_clear_all_soft_refs();
 436 
 437   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
 438 
 439   const size_t metadata_prev_used = MetaspaceAux::used_bytes();
 440 
 441   print_heap_before_gc();
 442 
 443   {
 444     FlagSetting fl(_is_gc_active, true);
 445 
 446     bool complete = full && (max_level == (n_gens()-1));
 447     const char* gc_cause_prefix = complete ? "Full GC" : "GC";
 448     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
 449     // The PrintGCDetails logging starts before we have incremented the GC id. We will do that later
 450     // so we can assume here that the next GC id is what we want.
 451     GCTraceTime t(GCCauseString(gc_cause_prefix, gc_cause()), PrintGCDetails, false, NULL, GCId::peek());
 452 
 453     gc_prologue(complete);
 454     increment_total_collections(complete);
 455 
 456     size_t gch_prev_used = used();
 457     bool run_verification = total_collections() >= VerifyGCStartAt;
 458 
 459     bool prepared_for_verification = false;
 460     int max_level_collected = 0;
 461     bool old_collects_young = (max_level == 1) &&
 462                               full &&
 463                               _old_gen->full_collects_younger_generations();
 464     if (!old_collects_young &&
 465         _young_gen->should_collect(full, size, is_tlab)) {
 466       if (run_verification && VerifyGCLevel <= 0 && VerifyBeforeGC) {
 467         prepare_for_verify();
 468         prepared_for_verification = true;
 469       }
 470 
 471       assert(!_young_gen->performs_in_place_marking(), "No young generation do in place marking");
 472       collect_generation(_young_gen,
 473                          full,
 474                          size,
 475                          is_tlab,
 476                          run_verification && VerifyGCLevel <= 0,
 477                          do_clear_all_soft_refs,
 478                          false);
 479 
 480       if (size > 0 && (!is_tlab || _young_gen->supports_tlab_allocation()) &&
 481           size * HeapWordSize <= _young_gen->unsafe_max_alloc_nogc()) {
 482         // Allocation request was met by young GC.
 483         size = 0;
 484       }
 485     }
 486 
 487     bool must_restore_marks_for_biased_locking = false;
 488 
 489     if (max_level == 1 && _old_gen->should_collect(full, size, is_tlab)) {
 490       if (!complete) {
 491         // The full_collections increment was missed above.
 492         increment_total_full_collections();
 493       }
 494 
 495       pre_full_gc_dump(NULL);    // do any pre full gc dumps
 496 
 497       if (!prepared_for_verification && run_verification &&
 498           VerifyGCLevel <= 1 && VerifyBeforeGC) {
 499         prepare_for_verify();
 500       }
 501 
 502       assert(_old_gen->performs_in_place_marking(), "All old generations do in place marking");
 503       collect_generation(_old_gen,
 504                          full,
 505                          size,
 506                          is_tlab,
 507                          run_verification && VerifyGCLevel <= 1,
 508                          do_clear_all_soft_refs,
 509                          true);
 510 
 511       must_restore_marks_for_biased_locking = true;
 512       max_level_collected = 1;
 513     }
 514 
 515     // Update "complete" boolean wrt what actually transpired --
 516     // for instance, a promotion failure could have led to
 517     // a whole heap collection.
 518     complete = complete || (max_level_collected == n_gens() - 1);
 519 
 520     if (complete) { // We did a "major" collection
 521       // FIXME: See comment at pre_full_gc_dump call
 522       post_full_gc_dump(NULL);   // do any post full gc dumps
 523     }
 524 
 525     if (PrintGCDetails) {
 526       print_heap_change(gch_prev_used);
 527 
 528       // Print metaspace info for full GC with PrintGCDetails flag.
 529       if (complete) {
 530         MetaspaceAux::print_metaspace_change(metadata_prev_used);
 531       }
 532     }
 533 
 534     // Adjust generation sizes.
 535     if (max_level_collected == 1) {
 536       _old_gen->compute_new_size();
 537     }
 538     _young_gen->compute_new_size();
 539 
 540     if (complete) {
 541       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
 542       ClassLoaderDataGraph::purge();
 543       MetaspaceAux::verify_metrics();
 544       // Resize the metaspace capacity after full collections
 545       MetaspaceGC::compute_new_size();
 546       update_full_collections_completed();
 547     }
 548 
 549     // Track memory usage and detect low memory after GC finishes
 550     MemoryService::track_memory_usage();
 551 
 552     gc_epilogue(complete);
 553 
 554     if (must_restore_marks_for_biased_locking) {
 555       BiasedLocking::restore_marks();
 556     }
 557   }
 558 
 559   print_heap_after_gc();
 560 
 561 #ifdef TRACESPINNING
 562   ParallelTaskTerminator::print_termination_counts();
 563 #endif
 564 }
 565 
 566 HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
 567   return collector_policy()->satisfy_failed_allocation(size, is_tlab);
 568 }
 569 
 570 void GenCollectedHeap::set_par_threads(uint t) {
 571   SharedHeap::set_par_threads(t);
 572   _gen_process_roots_tasks->set_n_threads(t);
 573 }
 574 
 575 void GenCollectedHeap::
 576 gen_process_roots(int level,
 577                   bool younger_gens_as_roots,
 578                   bool activate_scope,
 579                   SharedHeap::ScanningOption so,
 580                   OopsInGenClosure* not_older_gens,
 581                   OopsInGenClosure* weak_roots,
 582                   OopsInGenClosure* older_gens,
 583                   CLDClosure* cld_closure,
 584                   CLDClosure* weak_cld_closure,
 585                   CodeBlobClosure* code_closure) {
 586 
 587   // General roots.
 588   SharedHeap::process_roots(activate_scope, so,
 589                             not_older_gens, weak_roots,
 590                             cld_closure, weak_cld_closure,
 591                             code_closure);
 592 
 593   if (younger_gens_as_roots) {
 594     if (!_gen_process_roots_tasks->is_task_claimed(GCH_PS_younger_gens)) {
 595       if (level == 1) {
 596         not_older_gens->set_generation(_young_gen);
 597         _young_gen->oop_iterate(not_older_gens);
 598       }
 599       not_older_gens->reset_generation();
 600     }
 601   }
 602   // When collection is parallel, all threads get to cooperate to do
 603   // older-gen scanning.
 604   if (level == 0) {
 605     older_gens->set_generation(_old_gen);
 606     rem_set()->younger_refs_iterate(_old_gen, older_gens);
 607     older_gens->reset_generation();
 608   }
 609 
 610   _gen_process_roots_tasks->all_tasks_completed();
 611 }
 612 
 613 void GenCollectedHeap::
 614 gen_process_roots(int level,
 615                   bool younger_gens_as_roots,
 616                   bool activate_scope,
 617                   SharedHeap::ScanningOption so,
 618                   bool only_strong_roots,
 619                   OopsInGenClosure* not_older_gens,
 620                   OopsInGenClosure* older_gens,
 621                   CLDClosure* cld_closure) {
 622 
 623   const bool is_adjust_phase = !only_strong_roots && !younger_gens_as_roots;
 624 
 625   bool is_moving_collection = false;
 626   if (level == 0 || is_adjust_phase) {
 627     // young collections are always moving
 628     is_moving_collection = true;
 629   }
 630 
 631   MarkingCodeBlobClosure mark_code_closure(not_older_gens, is_moving_collection);
 632   CodeBlobClosure* code_closure = &mark_code_closure;
 633 
 634   gen_process_roots(level,
 635                     younger_gens_as_roots,
 636                     activate_scope, so,
 637                     not_older_gens, only_strong_roots ? NULL : not_older_gens,
 638                     older_gens,
 639                     cld_closure, only_strong_roots ? NULL : cld_closure,
 640                     code_closure);
 641 
 642 }
 643 
 644 void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure) {
 645   SharedHeap::process_weak_roots(root_closure);
 646   // "Local" "weak" refs
 647   _young_gen->ref_processor()->weak_oops_do(root_closure);
 648   _old_gen->ref_processor()->weak_oops_do(root_closure);
 649 }
 650 
 651 #define GCH_SINCE_SAVE_MARKS_ITERATE_DEFN(OopClosureType, nv_suffix)    \
 652 void GenCollectedHeap::                                                 \
 653 oop_since_save_marks_iterate(int level,                                 \
 654                              OopClosureType* cur,                       \
 655                              OopClosureType* older) {                   \
 656   if (level == 0) {                                                     \
 657     _young_gen->oop_since_save_marks_iterate##nv_suffix(cur);           \
 658     _old_gen->oop_since_save_marks_iterate##nv_suffix(older);           \
 659   } else {                                                              \
 660     _old_gen->oop_since_save_marks_iterate##nv_suffix(cur);             \
 661   }                                                                     \
 662 }
 663 
 664 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DEFN)
 665 
 666 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DEFN
 667 
 668 bool GenCollectedHeap::no_allocs_since_save_marks(int level) {
 669   if (level == 0 && !_young_gen->no_allocs_since_save_marks()) {
 670     return false;
 671   }
 672   return _old_gen->no_allocs_since_save_marks();
 673 }
 674 
 675 bool GenCollectedHeap::supports_inline_contig_alloc() const {
 676   return _young_gen->supports_inline_contig_alloc();
 677 }
 678 
 679 HeapWord** GenCollectedHeap::top_addr() const {
 680   return _young_gen->top_addr();
 681 }
 682 
 683 HeapWord** GenCollectedHeap::end_addr() const {
 684   return _young_gen->end_addr();
 685 }
 686 
 687 // public collection interfaces
 688 
 689 void GenCollectedHeap::collect(GCCause::Cause cause) {
 690   if (should_do_concurrent_full_gc(cause)) {
 691 #if INCLUDE_ALL_GCS
 692     // mostly concurrent full collection
 693     collect_mostly_concurrent(cause);
 694 #else  // INCLUDE_ALL_GCS
 695     ShouldNotReachHere();
 696 #endif // INCLUDE_ALL_GCS
 697   } else if (cause == GCCause::_wb_young_gc) {
 698     // minor collection for WhiteBox API
 699     collect(cause, 0);
 700   } else {
 701 #ifdef ASSERT
 702   if (cause == GCCause::_scavenge_alot) {
 703     // minor collection only
 704     collect(cause, 0);
 705   } else {
 706     // Stop-the-world full collection
 707     collect(cause, n_gens() - 1);
 708   }
 709 #else
 710     // Stop-the-world full collection
 711     collect(cause, n_gens() - 1);
 712 #endif
 713   }
 714 }
 715 
 716 void GenCollectedHeap::collect(GCCause::Cause cause, int max_level) {
 717   // The caller doesn't have the Heap_lock
 718   assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
 719   MutexLocker ml(Heap_lock);
 720   collect_locked(cause, max_level);
 721 }
 722 
 723 void GenCollectedHeap::collect_locked(GCCause::Cause cause) {
 724   // The caller has the Heap_lock
 725   assert(Heap_lock->owned_by_self(), "this thread should own the Heap_lock");
 726   collect_locked(cause, n_gens() - 1);
 727 }
 728 
 729 // this is the private collection interface
 730 // The Heap_lock is expected to be held on entry.
 731 
 732 void GenCollectedHeap::collect_locked(GCCause::Cause cause, int max_level) {
 733   // Read the GC count while holding the Heap_lock
 734   unsigned int gc_count_before      = total_collections();
 735   unsigned int full_gc_count_before = total_full_collections();
 736   {
 737     MutexUnlocker mu(Heap_lock);  // give up heap lock, execute gets it back
 738     VM_GenCollectFull op(gc_count_before, full_gc_count_before,
 739                          cause, max_level);
 740     VMThread::execute(&op);
 741   }
 742 }
 743 
 744 #if INCLUDE_ALL_GCS
 745 bool GenCollectedHeap::create_cms_collector() {
 746 
 747   assert(_old_gen->kind() == Generation::ConcurrentMarkSweep,
 748          "Unexpected generation kinds");
 749   // Skip two header words in the block content verification
 750   NOT_PRODUCT(_skip_header_HeapWords = CMSCollector::skip_header_HeapWords();)
 751   CMSCollector* collector = new CMSCollector(
 752     (ConcurrentMarkSweepGeneration*)_old_gen,
 753     _rem_set->as_CardTableRS(),
 754     (ConcurrentMarkSweepPolicy*) collector_policy());
 755 
 756   if (collector == NULL || !collector->completed_initialization()) {
 757     if (collector) {
 758       delete collector;  // Be nice in embedded situation
 759     }
 760     vm_shutdown_during_initialization("Could not create CMS collector");
 761     return false;
 762   }
 763   return true;  // success
 764 }
 765 
 766 void GenCollectedHeap::collect_mostly_concurrent(GCCause::Cause cause) {
 767   assert(!Heap_lock->owned_by_self(), "Should not own Heap_lock");
 768 
 769   MutexLocker ml(Heap_lock);
 770   // Read the GC counts while holding the Heap_lock
 771   unsigned int full_gc_count_before = total_full_collections();
 772   unsigned int gc_count_before      = total_collections();
 773   {
 774     MutexUnlocker mu(Heap_lock);
 775     VM_GenCollectFullConcurrent op(gc_count_before, full_gc_count_before, cause);
 776     VMThread::execute(&op);
 777   }
 778 }
 779 #endif // INCLUDE_ALL_GCS
 780 
 781 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs) {
 782    do_full_collection(clear_all_soft_refs, _n_gens - 1);
 783 }
 784 
 785 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs,
 786                                           int max_level) {
 787   int local_max_level;
 788   if (!incremental_collection_will_fail(false /* don't consult_young */) &&
 789       gc_cause() == GCCause::_gc_locker) {
 790     local_max_level = 0;
 791   } else {
 792     local_max_level = max_level;
 793   }
 794 
 795   do_collection(true                 /* full */,
 796                 clear_all_soft_refs  /* clear_all_soft_refs */,
 797                 0                    /* size */,
 798                 false                /* is_tlab */,
 799                 local_max_level      /* max_level */);
 800   // Hack XXX FIX ME !!!
 801   // A scavenge may not have been attempted, or may have
 802   // been attempted and failed, because the old gen was too full
 803   if (local_max_level == 0 && gc_cause() == GCCause::_gc_locker &&
 804       incremental_collection_will_fail(false /* don't consult_young */)) {
 805     if (PrintGCDetails) {
 806       gclog_or_tty->print_cr("GC locker: Trying a full collection "
 807                              "because scavenge failed");
 808     }
 809     // This time allow the old gen to be collected as well
 810     do_collection(true                 /* full */,
 811                   clear_all_soft_refs  /* clear_all_soft_refs */,
 812                   0                    /* size */,
 813                   false                /* is_tlab */,
 814                   n_gens() - 1         /* max_level */);
 815   }
 816 }
 817 
 818 bool GenCollectedHeap::is_in_young(oop p) {
 819   bool result = ((HeapWord*)p) < _old_gen->reserved().start();
 820   assert(result == _young_gen->is_in_reserved(p),
 821          err_msg("incorrect test - result=%d, p=" INTPTR_FORMAT, result, p2i((void*)p)));
 822   return result;
 823 }
 824 
 825 // Returns "TRUE" iff "p" points into the committed areas of the heap.
 826 bool GenCollectedHeap::is_in(const void* p) const {
 827   #ifndef ASSERT
 828   guarantee(VerifyBeforeGC      ||
 829             VerifyDuringGC      ||
 830             VerifyBeforeExit    ||
 831             VerifyDuringStartup ||
 832             PrintAssembly       ||
 833             tty->count() != 0   ||   // already printing
 834             VerifyAfterGC       ||
 835     VMError::fatal_error_in_progress(), "too expensive");
 836 
 837   #endif
 838   return _young_gen->is_in(p) || _old_gen->is_in(p);
 839 }
 840 
 841 #ifdef ASSERT
 842 // Don't implement this by using is_in_young().  This method is used
 843 // in some cases to check that is_in_young() is correct.
 844 bool GenCollectedHeap::is_in_partial_collection(const void* p) {
 845   assert(is_in_reserved(p) || p == NULL,
 846     "Does not work if address is non-null and outside of the heap");
 847   return p < _young_gen->reserved().end() && p != NULL;
 848 }
 849 #endif
 850 
 851 void GenCollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
 852   _young_gen->oop_iterate(cl);
 853   _old_gen->oop_iterate(cl);
 854 }
 855 
 856 void GenCollectedHeap::object_iterate(ObjectClosure* cl) {
 857   _young_gen->object_iterate(cl);
 858   _old_gen->object_iterate(cl);
 859 }
 860 
 861 void GenCollectedHeap::safe_object_iterate(ObjectClosure* cl) {
 862   _young_gen->safe_object_iterate(cl);
 863   _old_gen->safe_object_iterate(cl);
 864 }
 865 
 866 Space* GenCollectedHeap::space_containing(const void* addr) const {
 867   Space* res = _young_gen->space_containing(addr);
 868   if (res != NULL) {
 869     return res;
 870   }
 871   res = _old_gen->space_containing(addr);
 872   assert(res != NULL, "Could not find containing space");
 873   return res;
 874 }
 875 
 876 HeapWord* GenCollectedHeap::block_start(const void* addr) const {
 877   assert(is_in_reserved(addr), "block_start of address outside of heap");
 878   if (_young_gen->is_in_reserved(addr)) {
 879     assert(_young_gen->is_in(addr), "addr should be in allocated part of generation");
 880     return _young_gen->block_start(addr);
 881   }
 882 
 883   assert(_old_gen->is_in_reserved(addr), "Some generation should contain the address");
 884   assert(_old_gen->is_in(addr), "addr should be in allocated part of generation");
 885   return _old_gen->block_start(addr);
 886 }
 887 
 888 size_t GenCollectedHeap::block_size(const HeapWord* addr) const {
 889   assert(is_in_reserved(addr), "block_size of address outside of heap");
 890   if (_young_gen->is_in_reserved(addr)) {
 891     assert(_young_gen->is_in(addr), "addr should be in allocated part of generation");
 892     return _young_gen->block_size(addr);
 893   }
 894 
 895   assert(_old_gen->is_in_reserved(addr), "Some generation should contain the address");
 896   assert(_old_gen->is_in(addr), "addr should be in allocated part of generation");
 897   return _old_gen->block_size(addr);
 898 }
 899 
 900 bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const {
 901   assert(is_in_reserved(addr), "block_is_obj of address outside of heap");
 902   assert(block_start(addr) == addr, "addr must be a block start");
 903   if (_young_gen->is_in_reserved(addr)) {
 904     return _young_gen->block_is_obj(addr);
 905   }
 906 
 907   assert(_old_gen->is_in_reserved(addr), "Some generation should contain the address");
 908   return _old_gen->block_is_obj(addr);
 909 }
 910 
 911 bool GenCollectedHeap::supports_tlab_allocation() const {
 912   assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
 913   return _young_gen->supports_tlab_allocation();
 914 }
 915 
 916 size_t GenCollectedHeap::tlab_capacity(Thread* thr) const {
 917   assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
 918   if (_young_gen->supports_tlab_allocation()) {
 919     return _young_gen->tlab_capacity();
 920   }
 921   return 0;
 922 }
 923 
 924 size_t GenCollectedHeap::tlab_used(Thread* thr) const {
 925   assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
 926   if (_young_gen->supports_tlab_allocation()) {
 927     return _young_gen->tlab_used();
 928   }
 929   return 0;
 930 }
 931 
 932 size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const {
 933   assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
 934   if (_young_gen->supports_tlab_allocation()) {
 935     return _young_gen->unsafe_max_tlab_alloc();
 936   }
 937   return 0;
 938 }
 939 
 940 HeapWord* GenCollectedHeap::allocate_new_tlab(size_t size) {
 941   bool gc_overhead_limit_was_exceeded;
 942   return collector_policy()->mem_allocate_work(size /* size */,
 943                                                true /* is_tlab */,
 944                                                &gc_overhead_limit_was_exceeded);
 945 }
 946 
 947 // Requires "*prev_ptr" to be non-NULL.  Deletes and a block of minimal size
 948 // from the list headed by "*prev_ptr".
 949 static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) {
 950   bool first = true;
 951   size_t min_size = 0;   // "first" makes this conceptually infinite.
 952   ScratchBlock **smallest_ptr, *smallest;
 953   ScratchBlock  *cur = *prev_ptr;
 954   while (cur) {
 955     assert(*prev_ptr == cur, "just checking");
 956     if (first || cur->num_words < min_size) {
 957       smallest_ptr = prev_ptr;
 958       smallest     = cur;
 959       min_size     = smallest->num_words;
 960       first        = false;
 961     }
 962     prev_ptr = &cur->next;
 963     cur     =  cur->next;
 964   }
 965   smallest      = *smallest_ptr;
 966   *smallest_ptr = smallest->next;
 967   return smallest;
 968 }
 969 
 970 // Sort the scratch block list headed by res into decreasing size order,
 971 // and set "res" to the result.
 972 static void sort_scratch_list(ScratchBlock*& list) {
 973   ScratchBlock* sorted = NULL;
 974   ScratchBlock* unsorted = list;
 975   while (unsorted) {
 976     ScratchBlock *smallest = removeSmallestScratch(&unsorted);
 977     smallest->next  = sorted;
 978     sorted          = smallest;
 979   }
 980   list = sorted;
 981 }
 982 
 983 ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor,
 984                                                size_t max_alloc_words) {
 985   ScratchBlock* res = NULL;
 986   _young_gen->contribute_scratch(res, requestor, max_alloc_words);
 987   _old_gen->contribute_scratch(res, requestor, max_alloc_words);
 988   sort_scratch_list(res);
 989   return res;
 990 }
 991 
 992 void GenCollectedHeap::release_scratch() {
 993   _young_gen->reset_scratch();
 994   _old_gen->reset_scratch();
 995 }
 996 
 997 class GenPrepareForVerifyClosure: public GenCollectedHeap::GenClosure {
 998   void do_generation(Generation* gen) {
 999     gen->prepare_for_verify();
1000   }
1001 };
1002 
1003 void GenCollectedHeap::prepare_for_verify() {
1004   ensure_parsability(false);        // no need to retire TLABs
1005   GenPrepareForVerifyClosure blk;
1006   generation_iterate(&blk, false);
1007 }
1008 
1009 void GenCollectedHeap::generation_iterate(GenClosure* cl,
1010                                           bool old_to_young) {
1011   if (old_to_young) {
1012     cl->do_generation(_old_gen);
1013     cl->do_generation(_young_gen);
1014   } else {
1015     cl->do_generation(_young_gen);
1016     cl->do_generation(_old_gen);
1017   }
1018 }
1019 
1020 void GenCollectedHeap::space_iterate(SpaceClosure* cl) {
1021   _young_gen->space_iterate(cl, true);
1022   _old_gen->space_iterate(cl, true);
1023 }
1024 
1025 bool GenCollectedHeap::is_maximal_no_gc() const {
1026   return _young_gen->is_maximal_no_gc() && _old_gen->is_maximal_no_gc();
1027 }
1028 
1029 void GenCollectedHeap::save_marks() {
1030   _young_gen->save_marks();
1031   _old_gen->save_marks();
1032 }
1033 
1034 GenCollectedHeap* GenCollectedHeap::heap() {
1035   assert(_gch != NULL, "Uninitialized access to GenCollectedHeap::heap()");
1036   assert(_gch->kind() == CollectedHeap::GenCollectedHeap, "not a generational heap");
1037   return _gch;
1038 }
1039 
1040 
1041 void GenCollectedHeap::prepare_for_compaction() {
1042   guarantee(_n_gens = 2, "Wrong number of generations");
1043   // Start by compacting into same gen.
1044   CompactPoint cp(_old_gen);
1045   _old_gen->prepare_for_compaction(&cp);
1046   _young_gen->prepare_for_compaction(&cp);
1047 }
1048 
1049 GCStats* GenCollectedHeap::gc_stats(int level) const {
1050   if (level == 0) {
1051     return _young_gen->gc_stats();
1052   } else {
1053     return _old_gen->gc_stats();
1054   }
1055 }
1056 
1057 void GenCollectedHeap::verify(bool silent, VerifyOption option /* ignored */) {
1058   if (!silent) {
1059     gclog_or_tty->print("%s", _old_gen->name());
1060     gclog_or_tty->print(" ");
1061   }
1062   _old_gen->verify();
1063 
1064   if (!silent) {
1065     gclog_or_tty->print("%s", _young_gen->name());
1066     gclog_or_tty->print(" ");
1067   }
1068   _young_gen->verify();
1069 
1070   if (!silent) {
1071     gclog_or_tty->print("remset ");
1072   }
1073   rem_set()->verify();
1074 }
1075 
1076 void GenCollectedHeap::print_on(outputStream* st) const {
1077   _young_gen->print_on(st);
1078   _old_gen->print_on(st);
1079   MetaspaceAux::print_on(st);
1080 }
1081 
1082 void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const {
1083   if (workers() != NULL) {
1084     workers()->threads_do(tc);
1085   }
1086 #if INCLUDE_ALL_GCS
1087   if (UseConcMarkSweepGC) {
1088     ConcurrentMarkSweepThread::threads_do(tc);
1089   }
1090 #endif // INCLUDE_ALL_GCS
1091 }
1092 
1093 void GenCollectedHeap::print_gc_threads_on(outputStream* st) const {
1094 #if INCLUDE_ALL_GCS
1095   if (UseConcMarkSweepGC) {
1096     workers()->print_worker_threads_on(st);
1097     ConcurrentMarkSweepThread::print_all_on(st);
1098   }
1099 #endif // INCLUDE_ALL_GCS
1100 }
1101 
1102 void GenCollectedHeap::print_on_error(outputStream* st) const {
1103   this->CollectedHeap::print_on_error(st);
1104 
1105 #if INCLUDE_ALL_GCS
1106   if (UseConcMarkSweepGC) {
1107     st->cr();
1108     CMSCollector::print_on_error(st);
1109   }
1110 #endif // INCLUDE_ALL_GCS
1111 }
1112 
1113 void GenCollectedHeap::print_tracing_info() const {
1114   if (TraceYoungGenTime) {
1115     _young_gen->print_summary_info();
1116   }
1117   if (TraceOldGenTime) {
1118     _old_gen->print_summary_info();
1119   }
1120 }
1121 
1122 void GenCollectedHeap::print_heap_change(size_t prev_used) const {
1123   if (PrintGCDetails && Verbose) {
1124     gclog_or_tty->print(" "  SIZE_FORMAT
1125                         "->" SIZE_FORMAT
1126                         "("  SIZE_FORMAT ")",
1127                         prev_used, used(), capacity());
1128   } else {
1129     gclog_or_tty->print(" "  SIZE_FORMAT "K"
1130                         "->" SIZE_FORMAT "K"
1131                         "("  SIZE_FORMAT "K)",
1132                         prev_used / K, used() / K, capacity() / K);
1133   }
1134 }
1135 
1136 class GenGCPrologueClosure: public GenCollectedHeap::GenClosure {
1137  private:
1138   bool _full;
1139  public:
1140   void do_generation(Generation* gen) {
1141     gen->gc_prologue(_full);
1142   }
1143   GenGCPrologueClosure(bool full) : _full(full) {};
1144 };
1145 
1146 void GenCollectedHeap::gc_prologue(bool full) {
1147   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
1148 
1149   always_do_update_barrier = false;
1150   // Fill TLAB's and such
1151   CollectedHeap::accumulate_statistics_all_tlabs();
1152   ensure_parsability(true);   // retire TLABs
1153 
1154   // Walk generations
1155   GenGCPrologueClosure blk(full);
1156   generation_iterate(&blk, false);  // not old-to-young.
1157 };
1158 
1159 class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure {
1160  private:
1161   bool _full;
1162  public:
1163   void do_generation(Generation* gen) {
1164     gen->gc_epilogue(_full);
1165   }
1166   GenGCEpilogueClosure(bool full) : _full(full) {};
1167 };
1168 
1169 void GenCollectedHeap::gc_epilogue(bool full) {
1170 #ifdef COMPILER2
1171   assert(DerivedPointerTable::is_empty(), "derived pointer present");
1172   size_t actual_gap = pointer_delta((HeapWord*) (max_uintx-3), *(end_addr()));
1173   guarantee(actual_gap > (size_t)FastAllocateSizeLimit, "inline allocation wraps");
1174 #endif /* COMPILER2 */
1175 
1176   resize_all_tlabs();
1177 
1178   GenGCEpilogueClosure blk(full);
1179   generation_iterate(&blk, false);  // not old-to-young.
1180 
1181   if (!CleanChunkPoolAsync) {
1182     Chunk::clean_chunk_pool();
1183   }
1184 
1185   MetaspaceCounters::update_performance_counters();
1186   CompressedClassSpaceCounters::update_performance_counters();
1187 
1188   always_do_update_barrier = UseConcMarkSweepGC;
1189 };
1190 
1191 #ifndef PRODUCT
1192 class GenGCSaveTopsBeforeGCClosure: public GenCollectedHeap::GenClosure {
1193  private:
1194  public:
1195   void do_generation(Generation* gen) {
1196     gen->record_spaces_top();
1197   }
1198 };
1199 
1200 void GenCollectedHeap::record_gen_tops_before_GC() {
1201   if (ZapUnusedHeapArea) {
1202     GenGCSaveTopsBeforeGCClosure blk;
1203     generation_iterate(&blk, false);  // not old-to-young.
1204   }
1205 }
1206 #endif  // not PRODUCT
1207 
1208 class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure {
1209  public:
1210   void do_generation(Generation* gen) {
1211     gen->ensure_parsability();
1212   }
1213 };
1214 
1215 void GenCollectedHeap::ensure_parsability(bool retire_tlabs) {
1216   CollectedHeap::ensure_parsability(retire_tlabs);
1217   GenEnsureParsabilityClosure ep_cl;
1218   generation_iterate(&ep_cl, false);
1219 }
1220 
1221 oop GenCollectedHeap::handle_failed_promotion(Generation* old_gen,
1222                                               oop obj,
1223                                               size_t obj_size) {
1224   guarantee(old_gen->level() == 1, "We only get here with an old generation");
1225   assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1226   HeapWord* result = NULL;
1227 
1228   result = old_gen->expand_and_allocate(obj_size, false);
1229 
1230   if (result != NULL) {
1231     Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size);
1232   }
1233   return oop(result);
1234 }
1235 
1236 class GenTimeOfLastGCClosure: public GenCollectedHeap::GenClosure {
1237   jlong _time;   // in ms
1238   jlong _now;    // in ms
1239 
1240  public:
1241   GenTimeOfLastGCClosure(jlong now) : _time(now), _now(now) { }
1242 
1243   jlong time() { return _time; }
1244 
1245   void do_generation(Generation* gen) {
1246     _time = MIN2(_time, gen->time_of_last_gc(_now));
1247   }
1248 };
1249 
1250 jlong GenCollectedHeap::millis_since_last_gc() {
1251   // We need a monotonically non-decreasing time in ms but
1252   // os::javaTimeMillis() does not guarantee monotonicity.
1253   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
1254   GenTimeOfLastGCClosure tolgc_cl(now);
1255   // iterate over generations getting the oldest
1256   // time that a generation was collected
1257   generation_iterate(&tolgc_cl, false);
1258 
1259   // javaTimeNanos() is guaranteed to be monotonically non-decreasing
1260   // provided the underlying platform provides such a time source
1261   // (and it is bug free). So we still have to guard against getting
1262   // back a time later than 'now'.
1263   jlong retVal = now - tolgc_cl.time();
1264   if (retVal < 0) {
1265     NOT_PRODUCT(warning("time warp: "INT64_FORMAT, (int64_t) retVal);)
1266     return 0;
1267   }
1268   return retVal;
1269 }