1 /*
   2  * Copyright (c) 2000, 2016, 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 "aot/aotLoader.hpp"
  27 #include "classfile/symbolTable.hpp"
  28 #include "classfile/systemDictionary.hpp"
  29 #include "classfile/vmSymbols.hpp"
  30 #include "code/codeCache.hpp"
  31 #include "code/icBuffer.hpp"
  32 #include "gc/shared/collectedHeap.inline.hpp"
  33 #include "gc/shared/collectorCounters.hpp"
  34 #include "gc/shared/gcId.hpp"
  35 #include "gc/shared/gcLocker.inline.hpp"
  36 #include "gc/shared/gcTrace.hpp"
  37 #include "gc/shared/gcTraceTime.inline.hpp"
  38 #include "gc/shared/genCollectedHeap.hpp"
  39 #include "gc/shared/genOopClosures.inline.hpp"
  40 #include "gc/shared/generationSpec.hpp"
  41 #include "gc/shared/space.hpp"
  42 #include "gc/shared/strongRootsScope.hpp"
  43 #include "gc/shared/vmGCOperations.hpp"
  44 #include "gc/shared/workgroup.hpp"
  45 #include "memory/filemap.hpp"
  46 #include "memory/resourceArea.hpp"
  47 #include "oops/oop.inline.hpp"
  48 #include "runtime/biasedLocking.hpp"
  49 #include "runtime/fprofiler.hpp"
  50 #include "runtime/handles.hpp"
  51 #include "runtime/handles.inline.hpp"
  52 #include "runtime/java.hpp"
  53 #include "runtime/vmThread.hpp"
  54 #include "services/management.hpp"
  55 #include "services/memoryService.hpp"
  56 #include "utilities/macros.hpp"
  57 #include "utilities/stack.inline.hpp"
  58 #include "utilities/vmError.hpp"
  59 #if INCLUDE_ALL_GCS
  60 #include "gc/cms/concurrentMarkSweepThread.hpp"
  61 #include "gc/cms/vmCMSOperations.hpp"
  62 #endif // INCLUDE_ALL_GCS
  63 
  64 NOT_PRODUCT(size_t GenCollectedHeap::_skip_header_HeapWords = 0;)
  65 
  66 // The set of potentially parallel tasks in root scanning.
  67 enum GCH_strong_roots_tasks {
  68   GCH_PS_Universe_oops_do,
  69   GCH_PS_JNIHandles_oops_do,
  70   GCH_PS_ObjectSynchronizer_oops_do,
  71   GCH_PS_FlatProfiler_oops_do,
  72   GCH_PS_Management_oops_do,
  73   GCH_PS_SystemDictionary_oops_do,
  74   GCH_PS_ClassLoaderDataGraph_oops_do,
  75   GCH_PS_jvmti_oops_do,
  76   GCH_PS_CodeCache_oops_do,
  77   GCH_PS_aot_oops_do,
  78   GCH_PS_younger_gens,
  79   // Leave this one last.
  80   GCH_PS_NumElements
  81 };
  82 
  83 GenCollectedHeap::GenCollectedHeap(GenCollectorPolicy *policy) :
  84   CollectedHeap(),
  85   _rem_set(NULL),
  86   _gen_policy(policy),
  87   _process_strong_tasks(new SubTasksDone(GCH_PS_NumElements)),
  88   _full_collections_completed(0)
  89 {
  90   assert(policy != NULL, "Sanity check");
  91   if (UseConcMarkSweepGC) {
  92     _workers = new WorkGang("GC Thread", ParallelGCThreads,
  93                             /* are_GC_task_threads */true,
  94                             /* are_ConcurrentGC_threads */false);
  95     _workers->initialize_workers();
  96   } else {
  97     // Serial GC does not use workers.
  98     _workers = NULL;
  99   }
 100 }
 101 
 102 jint GenCollectedHeap::initialize() {
 103   CollectedHeap::pre_initialize();
 104 
 105   // While there are no constraints in the GC code that HeapWordSize
 106   // be any particular value, there are multiple other areas in the
 107   // system which believe this to be true (e.g. oop->object_size in some
 108   // cases incorrectly returns the size in wordSize units rather than
 109   // HeapWordSize).
 110   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
 111 
 112   // Allocate space for the heap.
 113 
 114   char* heap_address;
 115   ReservedSpace heap_rs;
 116 
 117   size_t heap_alignment = collector_policy()->heap_alignment();
 118 
 119   heap_address = allocate(heap_alignment, &heap_rs);
 120 
 121   if (!heap_rs.is_reserved()) {
 122     vm_shutdown_during_initialization(
 123       "Could not reserve enough space for object heap");
 124     return JNI_ENOMEM;
 125   }
 126 
 127   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
 128 
 129   _rem_set = collector_policy()->create_rem_set(reserved_region());
 130   set_barrier_set(rem_set()->bs());
 131 
 132   ReservedSpace young_rs = heap_rs.first_part(gen_policy()->young_gen_spec()->max_size(), false, false);
 133   _young_gen = gen_policy()->young_gen_spec()->init(young_rs, rem_set());
 134   heap_rs = heap_rs.last_part(gen_policy()->young_gen_spec()->max_size());
 135 
 136   ReservedSpace old_rs = heap_rs.first_part(gen_policy()->old_gen_spec()->max_size(), false, false);
 137   _old_gen = gen_policy()->old_gen_spec()->init(old_rs, rem_set());
 138   clear_incremental_collection_failed();
 139 
 140 #if INCLUDE_ALL_GCS
 141   // If we are running CMS, create the collector responsible
 142   // for collecting the CMS generations.
 143   if (collector_policy()->is_concurrent_mark_sweep_policy()) {
 144     bool success = create_cms_collector();
 145     if (!success) return JNI_ENOMEM;
 146   }
 147 #endif // INCLUDE_ALL_GCS
 148 
 149   return JNI_OK;
 150 }
 151 
 152 char* GenCollectedHeap::allocate(size_t alignment,
 153                                  ReservedSpace* heap_rs){
 154   // Now figure out the total size.
 155   const size_t pageSize = UseLargePages ? os::large_page_size() : os::vm_page_size();
 156   assert(alignment % pageSize == 0, "Must be");
 157 
 158   GenerationSpec* young_spec = gen_policy()->young_gen_spec();
 159   GenerationSpec* old_spec = gen_policy()->old_gen_spec();
 160 
 161   // Check for overflow.
 162   size_t total_reserved = young_spec->max_size() + old_spec->max_size();
 163   if (total_reserved < young_spec->max_size()) {
 164     vm_exit_during_initialization("The size of the object heap + VM data exceeds "
 165                                   "the maximum representable size");
 166   }
 167   assert(total_reserved % alignment == 0,
 168          "Gen size; total_reserved=" SIZE_FORMAT ", alignment="
 169          SIZE_FORMAT, total_reserved, alignment);
 170 
 171   *heap_rs = Universe::reserve_heap(total_reserved, alignment);
 172 
 173   os::trace_page_sizes("Heap",
 174                        collector_policy()->min_heap_byte_size(),
 175                        total_reserved,
 176                        alignment,
 177                        heap_rs->base(),
 178                        heap_rs->size());
 179 
 180   return heap_rs->base();
 181 }
 182 
 183 void GenCollectedHeap::post_initialize() {
 184   ref_processing_init();
 185   assert((_young_gen->kind() == Generation::DefNew) ||
 186          (_young_gen->kind() == Generation::ParNew),
 187     "Wrong youngest generation type");
 188   DefNewGeneration* def_new_gen = (DefNewGeneration*)_young_gen;
 189 
 190   assert(_old_gen->kind() == Generation::ConcurrentMarkSweep ||
 191          _old_gen->kind() == Generation::MarkSweepCompact,
 192     "Wrong generation kind");
 193 
 194   _gen_policy->initialize_size_policy(def_new_gen->eden()->capacity(),
 195                                       _old_gen->capacity(),
 196                                       def_new_gen->from()->capacity());
 197   _gen_policy->initialize_gc_policy_counters();
 198 }
 199 
 200 void GenCollectedHeap::ref_processing_init() {
 201   _young_gen->ref_processor_init();
 202   _old_gen->ref_processor_init();
 203 }
 204 
 205 size_t GenCollectedHeap::capacity() const {
 206   return _young_gen->capacity() + _old_gen->capacity();
 207 }
 208 
 209 size_t GenCollectedHeap::used() const {
 210   return _young_gen->used() + _old_gen->used();
 211 }
 212 
 213 void GenCollectedHeap::save_used_regions() {
 214   _old_gen->save_used_region();
 215   _young_gen->save_used_region();
 216 }
 217 
 218 size_t GenCollectedHeap::max_capacity() const {
 219   return _young_gen->max_capacity() + _old_gen->max_capacity();
 220 }
 221 
 222 // Update the _full_collections_completed counter
 223 // at the end of a stop-world full GC.
 224 unsigned int GenCollectedHeap::update_full_collections_completed() {
 225   MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
 226   assert(_full_collections_completed <= _total_full_collections,
 227          "Can't complete more collections than were started");
 228   _full_collections_completed = _total_full_collections;
 229   ml.notify_all();
 230   return _full_collections_completed;
 231 }
 232 
 233 // Update the _full_collections_completed counter, as appropriate,
 234 // at the end of a concurrent GC cycle. Note the conditional update
 235 // below to allow this method to be called by a concurrent collector
 236 // without synchronizing in any manner with the VM thread (which
 237 // may already have initiated a STW full collection "concurrently").
 238 unsigned int GenCollectedHeap::update_full_collections_completed(unsigned int count) {
 239   MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
 240   assert((_full_collections_completed <= _total_full_collections) &&
 241          (count <= _total_full_collections),
 242          "Can't complete more collections than were started");
 243   if (count > _full_collections_completed) {
 244     _full_collections_completed = count;
 245     ml.notify_all();
 246   }
 247   return _full_collections_completed;
 248 }
 249 
 250 
 251 #ifndef PRODUCT
 252 // Override of memory state checking method in CollectedHeap:
 253 // Some collectors (CMS for example) can't have badHeapWordVal written
 254 // in the first two words of an object. (For instance , in the case of
 255 // CMS these words hold state used to synchronize between certain
 256 // (concurrent) GC steps and direct allocating mutators.)
 257 // The skip_header_HeapWords() method below, allows us to skip
 258 // over the requisite number of HeapWord's. Note that (for
 259 // generational collectors) this means that those many words are
 260 // skipped in each object, irrespective of the generation in which
 261 // that object lives. The resultant loss of precision seems to be
 262 // harmless and the pain of avoiding that imprecision appears somewhat
 263 // higher than we are prepared to pay for such rudimentary debugging
 264 // support.
 265 void GenCollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr,
 266                                                          size_t size) {
 267   if (CheckMemoryInitialization && ZapUnusedHeapArea) {
 268     // We are asked to check a size in HeapWords,
 269     // but the memory is mangled in juint words.
 270     juint* start = (juint*) (addr + skip_header_HeapWords());
 271     juint* end   = (juint*) (addr + size);
 272     for (juint* slot = start; slot < end; slot += 1) {
 273       assert(*slot == badHeapWordVal,
 274              "Found non badHeapWordValue in pre-allocation check");
 275     }
 276   }
 277 }
 278 #endif
 279 
 280 HeapWord* GenCollectedHeap::attempt_allocation(size_t size,
 281                                                bool is_tlab,
 282                                                bool first_only) {
 283   HeapWord* res = NULL;
 284 
 285   if (_young_gen->should_allocate(size, is_tlab)) {
 286     res = _young_gen->allocate(size, is_tlab);
 287     if (res != NULL || first_only) {
 288       return res;
 289     }
 290   }
 291 
 292   if (_old_gen->should_allocate(size, is_tlab)) {
 293     res = _old_gen->allocate(size, is_tlab);
 294   }
 295 
 296   return res;
 297 }
 298 
 299 HeapWord* GenCollectedHeap::mem_allocate(size_t size,
 300                                          bool* gc_overhead_limit_was_exceeded) {
 301   return gen_policy()->mem_allocate_work(size,
 302                                          false /* is_tlab */,
 303                                          gc_overhead_limit_was_exceeded);
 304 }
 305 
 306 bool GenCollectedHeap::must_clear_all_soft_refs() {
 307   return _gc_cause == GCCause::_metadata_GC_clear_soft_refs ||
 308          _gc_cause == GCCause::_wb_full_gc;
 309 }
 310 
 311 bool GenCollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
 312   if (!UseConcMarkSweepGC) {
 313     return false;
 314   }
 315 
 316   switch (cause) {
 317     case GCCause::_gc_locker:           return GCLockerInvokesConcurrent;
 318     case GCCause::_java_lang_system_gc:
 319     case GCCause::_dcmd_gc_run:         return ExplicitGCInvokesConcurrent;
 320     default:                            return false;
 321   }
 322 }
 323 
 324 void GenCollectedHeap::collect_generation(Generation* gen, bool full, size_t size,
 325                                           bool is_tlab, bool run_verification, bool clear_soft_refs,
 326                                           bool restore_marks_for_biased_locking) {
 327   FormatBuffer<> title("Collect gen: %s", gen->short_name());
 328   GCTraceTime(Trace, gc, phases) t1(title);
 329   TraceCollectorStats tcs(gen->counters());
 330   TraceMemoryManagerStats tmms(gen->kind(),gc_cause());
 331 
 332   gen->stat_record()->invocations++;
 333   gen->stat_record()->accumulated_time.start();
 334 
 335   // Must be done anew before each collection because
 336   // a previous collection will do mangling and will
 337   // change top of some spaces.
 338   record_gen_tops_before_GC();
 339 
 340   log_trace(gc)("%s invoke=%d size=" SIZE_FORMAT, heap()->is_young_gen(gen) ? "Young" : "Old", gen->stat_record()->invocations, size * HeapWordSize);
 341 
 342   if (run_verification && VerifyBeforeGC) {
 343     HandleMark hm;  // Discard invalid handles created during verification
 344     Universe::verify("Before GC");
 345   }
 346   COMPILER2_PRESENT(DerivedPointerTable::clear());
 347 
 348   if (restore_marks_for_biased_locking) {
 349     // We perform this mark word preservation work lazily
 350     // because it's only at this point that we know whether we
 351     // absolutely have to do it; we want to avoid doing it for
 352     // scavenge-only collections where it's unnecessary
 353     BiasedLocking::preserve_marks();
 354   }
 355 
 356   // Do collection work
 357   {
 358     // Note on ref discovery: For what appear to be historical reasons,
 359     // GCH enables and disabled (by enqueing) refs discovery.
 360     // In the future this should be moved into the generation's
 361     // collect method so that ref discovery and enqueueing concerns
 362     // are local to a generation. The collect method could return
 363     // an appropriate indication in the case that notification on
 364     // the ref lock was needed. This will make the treatment of
 365     // weak refs more uniform (and indeed remove such concerns
 366     // from GCH). XXX
 367 
 368     HandleMark hm;  // Discard invalid handles created during gc
 369     save_marks();   // save marks for all gens
 370     // We want to discover references, but not process them yet.
 371     // This mode is disabled in process_discovered_references if the
 372     // generation does some collection work, or in
 373     // enqueue_discovered_references if the generation returns
 374     // without doing any work.
 375     ReferenceProcessor* rp = gen->ref_processor();
 376     // If the discovery of ("weak") refs in this generation is
 377     // atomic wrt other collectors in this configuration, we
 378     // are guaranteed to have empty discovered ref lists.
 379     if (rp->discovery_is_atomic()) {
 380       rp->enable_discovery();
 381       rp->setup_policy(clear_soft_refs);
 382     } else {
 383       // collect() below will enable discovery as appropriate
 384     }
 385     gen->collect(full, clear_soft_refs, size, is_tlab);
 386     if (!rp->enqueuing_is_done()) {
 387       rp->enqueue_discovered_references();
 388     } else {
 389       rp->set_enqueuing_is_done(false);
 390     }
 391     rp->verify_no_references_recorded();
 392   }
 393 
 394   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
 395 
 396   gen->stat_record()->accumulated_time.stop();
 397 
 398   update_gc_stats(gen, full);
 399 
 400   if (run_verification && VerifyAfterGC) {
 401     HandleMark hm;  // Discard invalid handles created during verification
 402     Universe::verify("After GC");
 403   }
 404 }
 405 
 406 void GenCollectedHeap::do_collection(bool           full,
 407                                      bool           clear_all_soft_refs,
 408                                      size_t         size,
 409                                      bool           is_tlab,
 410                                      GenerationType max_generation) {
 411   ResourceMark rm;
 412   DEBUG_ONLY(Thread* my_thread = Thread::current();)
 413 
 414   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 415   assert(my_thread->is_VM_thread() ||
 416          my_thread->is_ConcurrentGC_thread(),
 417          "incorrect thread type capability");
 418   assert(Heap_lock->is_locked(),
 419          "the requesting thread should have the Heap_lock");
 420   guarantee(!is_gc_active(), "collection is not reentrant");
 421 
 422   if (GCLocker::check_active_before_gc()) {
 423     return; // GC is disabled (e.g. JNI GetXXXCritical operation)
 424   }
 425 
 426   GCIdMarkAndRestore gc_id_mark;
 427 
 428   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
 429                           collector_policy()->should_clear_all_soft_refs();
 430 
 431   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
 432 
 433   const size_t metadata_prev_used = MetaspaceAux::used_bytes();
 434 
 435   print_heap_before_gc();
 436 
 437   {
 438     FlagSetting fl(_is_gc_active, true);
 439 
 440     bool complete = full && (max_generation == OldGen);
 441     bool old_collects_young = complete && !ScavengeBeforeFullGC;
 442     bool do_young_collection = !old_collects_young && _young_gen->should_collect(full, size, is_tlab);
 443 
 444     FormatBuffer<> gc_string("%s", "Pause ");
 445     if (do_young_collection) {
 446       gc_string.append("Young");
 447     } else {
 448       gc_string.append("Full");
 449     }
 450 
 451     GCTraceCPUTime tcpu;
 452     GCTraceTime(Info, gc) t(gc_string, NULL, gc_cause(), true);
 453 
 454     gc_prologue(complete);
 455     increment_total_collections(complete);
 456 
 457     size_t young_prev_used = _young_gen->used();
 458     size_t old_prev_used = _old_gen->used();
 459 
 460     bool run_verification = total_collections() >= VerifyGCStartAt;
 461 
 462     bool prepared_for_verification = false;
 463     bool collected_old = false;
 464 
 465     if (do_young_collection) {
 466       if (run_verification && VerifyGCLevel <= 0 && VerifyBeforeGC) {
 467         prepare_for_verify();
 468         prepared_for_verification = true;
 469       }
 470 
 471       collect_generation(_young_gen,
 472                          full,
 473                          size,
 474                          is_tlab,
 475                          run_verification && VerifyGCLevel <= 0,
 476                          do_clear_all_soft_refs,
 477                          false);
 478 
 479       if (size > 0 && (!is_tlab || _young_gen->supports_tlab_allocation()) &&
 480           size * HeapWordSize <= _young_gen->unsafe_max_alloc_nogc()) {
 481         // Allocation request was met by young GC.
 482         size = 0;
 483       }
 484     }
 485 
 486     bool must_restore_marks_for_biased_locking = false;
 487 
 488     if (max_generation == OldGen && _old_gen->should_collect(full, size, is_tlab)) {
 489       if (!complete) {
 490         // The full_collections increment was missed above.
 491         increment_total_full_collections();
 492       }
 493 
 494       if (!prepared_for_verification && run_verification &&
 495           VerifyGCLevel <= 1 && VerifyBeforeGC) {
 496         prepare_for_verify();
 497       }
 498 
 499       if (do_young_collection) {
 500         // We did a young GC. Need a new GC id for the old GC.
 501         GCIdMarkAndRestore gc_id_mark;
 502         GCTraceTime(Info, gc) t("Pause Full", NULL, gc_cause(), true);
 503         collect_generation(_old_gen, full, size, is_tlab, run_verification && VerifyGCLevel <= 1, do_clear_all_soft_refs, true);
 504       } else {
 505         // No young GC done. Use the same GC id as was set up earlier in this method.
 506         collect_generation(_old_gen, full, size, is_tlab, run_verification && VerifyGCLevel <= 1, do_clear_all_soft_refs, true);
 507       }
 508 
 509       must_restore_marks_for_biased_locking = true;
 510       collected_old = true;
 511     }
 512 
 513     // Update "complete" boolean wrt what actually transpired --
 514     // for instance, a promotion failure could have led to
 515     // a whole heap collection.
 516     complete = complete || collected_old;
 517 
 518     print_heap_change(young_prev_used, old_prev_used);
 519     MetaspaceAux::print_metaspace_change(metadata_prev_used);
 520 
 521     // Adjust generation sizes.
 522     if (collected_old) {
 523       _old_gen->compute_new_size();
 524     }
 525     _young_gen->compute_new_size();
 526 
 527     if (complete) {
 528       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
 529       ClassLoaderDataGraph::purge();
 530       MetaspaceAux::verify_metrics();
 531       // Resize the metaspace capacity after full collections
 532       MetaspaceGC::compute_new_size();
 533       update_full_collections_completed();
 534     }
 535 
 536     // Track memory usage and detect low memory after GC finishes
 537     MemoryService::track_memory_usage();
 538 
 539     gc_epilogue(complete);
 540 
 541     if (must_restore_marks_for_biased_locking) {
 542       BiasedLocking::restore_marks();
 543     }
 544   }
 545 
 546   print_heap_after_gc();
 547 
 548 #ifdef TRACESPINNING
 549   ParallelTaskTerminator::print_termination_counts();
 550 #endif
 551 }
 552 
 553 HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
 554   return gen_policy()->satisfy_failed_allocation(size, is_tlab);
 555 }
 556 
 557 #ifdef ASSERT
 558 class AssertNonScavengableClosure: public OopClosure {
 559 public:
 560   virtual void do_oop(oop* p) {
 561     assert(!GenCollectedHeap::heap()->is_in_partial_collection(*p),
 562       "Referent should not be scavengable.");  }
 563   virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
 564 };
 565 static AssertNonScavengableClosure assert_is_non_scavengable_closure;
 566 #endif
 567 
 568 void GenCollectedHeap::process_roots(StrongRootsScope* scope,
 569                                      ScanningOption so,
 570                                      OopClosure* strong_roots,
 571                                      OopClosure* weak_roots,
 572                                      CLDClosure* strong_cld_closure,
 573                                      CLDClosure* weak_cld_closure,
 574                                      CodeBlobToOopClosure* code_roots) {
 575   // General roots.
 576   assert(Threads::thread_claim_parity() != 0, "must have called prologue code");
 577   assert(code_roots != NULL, "code root closure should always be set");
 578   // _n_termination for _process_strong_tasks should be set up stream
 579   // in a method not running in a GC worker.  Otherwise the GC worker
 580   // could be trying to change the termination condition while the task
 581   // is executing in another GC worker.
 582 
 583   if (!_process_strong_tasks->is_task_claimed(GCH_PS_ClassLoaderDataGraph_oops_do)) {
 584     ClassLoaderDataGraph::roots_cld_do(strong_cld_closure, weak_cld_closure);
 585   }
 586 
 587   // Only process code roots from thread stacks if we aren't visiting the entire CodeCache anyway
 588   CodeBlobToOopClosure* roots_from_code_p = (so & SO_AllCodeCache) ? NULL : code_roots;
 589 
 590   bool is_par = scope->n_threads() > 1;
 591   Threads::possibly_parallel_oops_do(is_par, strong_roots, roots_from_code_p);
 592 
 593   if (!_process_strong_tasks->is_task_claimed(GCH_PS_Universe_oops_do)) {
 594     Universe::oops_do(strong_roots);
 595   }
 596   // Global (strong) JNI handles
 597   if (!_process_strong_tasks->is_task_claimed(GCH_PS_JNIHandles_oops_do)) {
 598     JNIHandles::oops_do(strong_roots);
 599   }
 600 
 601   if (!_process_strong_tasks->is_task_claimed(GCH_PS_ObjectSynchronizer_oops_do)) {
 602     ObjectSynchronizer::oops_do(strong_roots);
 603   }
 604   if (!_process_strong_tasks->is_task_claimed(GCH_PS_FlatProfiler_oops_do)) {
 605     FlatProfiler::oops_do(strong_roots);
 606   }
 607   if (!_process_strong_tasks->is_task_claimed(GCH_PS_Management_oops_do)) {
 608     Management::oops_do(strong_roots);
 609   }
 610   if (!_process_strong_tasks->is_task_claimed(GCH_PS_jvmti_oops_do)) {
 611     JvmtiExport::oops_do(strong_roots);
 612   }
 613   if (UseAOT && !_process_strong_tasks->is_task_claimed(GCH_PS_aot_oops_do)) {
 614     AOTLoader::oops_do(strong_roots);
 615   }
 616 
 617   if (!_process_strong_tasks->is_task_claimed(GCH_PS_SystemDictionary_oops_do)) {
 618     SystemDictionary::roots_oops_do(strong_roots, weak_roots);
 619   }
 620 
 621   if (!_process_strong_tasks->is_task_claimed(GCH_PS_CodeCache_oops_do)) {
 622     if (so & SO_ScavengeCodeCache) {
 623       assert(code_roots != NULL, "must supply closure for code cache");
 624 
 625       // We only visit parts of the CodeCache when scavenging.
 626       CodeCache::scavenge_root_nmethods_do(code_roots);
 627     }
 628     if (so & SO_AllCodeCache) {
 629       assert(code_roots != NULL, "must supply closure for code cache");
 630 
 631       // CMSCollector uses this to do intermediate-strength collections.
 632       // We scan the entire code cache, since CodeCache::do_unloading is not called.
 633       CodeCache::blobs_do(code_roots);
 634     }
 635     // Verify that the code cache contents are not subject to
 636     // movement by a scavenging collection.
 637     DEBUG_ONLY(CodeBlobToOopClosure assert_code_is_non_scavengable(&assert_is_non_scavengable_closure, !CodeBlobToOopClosure::FixRelocations));
 638     DEBUG_ONLY(CodeCache::asserted_non_scavengable_nmethods_do(&assert_code_is_non_scavengable));
 639   }
 640 }
 641 
 642 void GenCollectedHeap::process_string_table_roots(StrongRootsScope* scope,
 643                                                   OopClosure* root_closure) {
 644   assert(root_closure != NULL, "Must be set");
 645   // All threads execute the following. A specific chunk of buckets
 646   // from the StringTable are the individual tasks.
 647   if (scope->n_threads() > 1) {
 648     StringTable::possibly_parallel_oops_do(root_closure);
 649   } else {
 650     StringTable::oops_do(root_closure);
 651   }
 652 }
 653 
 654 void GenCollectedHeap::young_process_roots(StrongRootsScope* scope,
 655                                            OopsInGenClosure* root_closure,
 656                                            OopsInGenClosure* old_gen_closure,
 657                                            CLDClosure* cld_closure) {
 658   MarkingCodeBlobClosure mark_code_closure(root_closure, CodeBlobToOopClosure::FixRelocations);
 659 
 660   process_roots(scope, SO_ScavengeCodeCache, root_closure, root_closure,
 661                 cld_closure, cld_closure, &mark_code_closure);
 662   process_string_table_roots(scope, root_closure);
 663 
 664   if (!_process_strong_tasks->is_task_claimed(GCH_PS_younger_gens)) {
 665     root_closure->reset_generation();
 666   }
 667 
 668   // When collection is parallel, all threads get to cooperate to do
 669   // old generation scanning.
 670   old_gen_closure->set_generation(_old_gen);
 671   rem_set()->younger_refs_iterate(_old_gen, old_gen_closure, scope->n_threads());
 672   old_gen_closure->reset_generation();
 673 
 674   _process_strong_tasks->all_tasks_completed(scope->n_threads());
 675 }
 676 
 677 void GenCollectedHeap::cms_process_roots(StrongRootsScope* scope,
 678                                          bool young_gen_as_roots,
 679                                          ScanningOption so,
 680                                          bool only_strong_roots,
 681                                          OopsInGenClosure* root_closure,
 682                                          CLDClosure* cld_closure) {
 683   MarkingCodeBlobClosure mark_code_closure(root_closure, !CodeBlobToOopClosure::FixRelocations);
 684   OopsInGenClosure* weak_roots = only_strong_roots ? NULL : root_closure;
 685   CLDClosure* weak_cld_closure = only_strong_roots ? NULL : cld_closure;
 686 
 687   process_roots(scope, so, root_closure, weak_roots, cld_closure, weak_cld_closure, &mark_code_closure);
 688   if (!only_strong_roots) {
 689     process_string_table_roots(scope, root_closure);
 690   }
 691 
 692   if (young_gen_as_roots &&
 693       !_process_strong_tasks->is_task_claimed(GCH_PS_younger_gens)) {
 694     root_closure->set_generation(_young_gen);
 695     _young_gen->oop_iterate(root_closure);
 696     root_closure->reset_generation();
 697   }
 698 
 699   _process_strong_tasks->all_tasks_completed(scope->n_threads());
 700 }
 701 
 702 void GenCollectedHeap::full_process_roots(StrongRootsScope* scope,
 703                                           bool is_adjust_phase,
 704                                           ScanningOption so,
 705                                           bool only_strong_roots,
 706                                           OopsInGenClosure* root_closure,
 707                                           CLDClosure* cld_closure) {
 708   MarkingCodeBlobClosure mark_code_closure(root_closure, is_adjust_phase);
 709   OopsInGenClosure* weak_roots = only_strong_roots ? NULL : root_closure;
 710   CLDClosure* weak_cld_closure = only_strong_roots ? NULL : cld_closure;
 711 
 712   process_roots(scope, so, root_closure, weak_roots, cld_closure, weak_cld_closure, &mark_code_closure);
 713   if (is_adjust_phase) {
 714     // We never treat the string table as roots during marking
 715     // for the full gc, so we only need to process it during
 716     // the adjust phase.
 717     process_string_table_roots(scope, root_closure);
 718   }
 719 
 720   _process_strong_tasks->all_tasks_completed(scope->n_threads());
 721 }
 722 
 723 void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure) {
 724   JNIHandles::weak_oops_do(root_closure);
 725   _young_gen->ref_processor()->weak_oops_do(root_closure);
 726   _old_gen->ref_processor()->weak_oops_do(root_closure);
 727 }
 728 
 729 #define GCH_SINCE_SAVE_MARKS_ITERATE_DEFN(OopClosureType, nv_suffix)    \
 730 void GenCollectedHeap::                                                 \
 731 oop_since_save_marks_iterate(GenerationType gen,                        \
 732                              OopClosureType* cur,                       \
 733                              OopClosureType* older) {                   \
 734   if (gen == YoungGen) {                              \
 735     _young_gen->oop_since_save_marks_iterate##nv_suffix(cur);           \
 736     _old_gen->oop_since_save_marks_iterate##nv_suffix(older);           \
 737   } else {                                                              \
 738     _old_gen->oop_since_save_marks_iterate##nv_suffix(cur);             \
 739   }                                                                     \
 740 }
 741 
 742 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DEFN)
 743 
 744 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DEFN
 745 
 746 bool GenCollectedHeap::no_allocs_since_save_marks() {
 747   return _young_gen->no_allocs_since_save_marks() &&
 748          _old_gen->no_allocs_since_save_marks();
 749 }
 750 
 751 bool GenCollectedHeap::supports_inline_contig_alloc() const {
 752   return _young_gen->supports_inline_contig_alloc();
 753 }
 754 
 755 HeapWord* volatile* GenCollectedHeap::top_addr() const {
 756   return _young_gen->top_addr();
 757 }
 758 
 759 HeapWord** GenCollectedHeap::end_addr() const {
 760   return _young_gen->end_addr();
 761 }
 762 
 763 // public collection interfaces
 764 
 765 void GenCollectedHeap::collect(GCCause::Cause cause) {
 766   if (should_do_concurrent_full_gc(cause)) {
 767 #if INCLUDE_ALL_GCS
 768     // Mostly concurrent full collection.
 769     collect_mostly_concurrent(cause);
 770 #else  // INCLUDE_ALL_GCS
 771     ShouldNotReachHere();
 772 #endif // INCLUDE_ALL_GCS
 773   } else if (cause == GCCause::_wb_young_gc) {
 774     // Young collection for the WhiteBox API.
 775     collect(cause, YoungGen);
 776   } else {
 777 #ifdef ASSERT
 778   if (cause == GCCause::_scavenge_alot) {
 779     // Young collection only.
 780     collect(cause, YoungGen);
 781   } else {
 782     // Stop-the-world full collection.
 783     collect(cause, OldGen);
 784   }
 785 #else
 786     // Stop-the-world full collection.
 787     collect(cause, OldGen);
 788 #endif
 789   }
 790 }
 791 
 792 void GenCollectedHeap::collect(GCCause::Cause cause, GenerationType max_generation) {
 793   // The caller doesn't have the Heap_lock
 794   assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
 795   MutexLocker ml(Heap_lock);
 796   collect_locked(cause, max_generation);
 797 }
 798 
 799 void GenCollectedHeap::collect_locked(GCCause::Cause cause) {
 800   // The caller has the Heap_lock
 801   assert(Heap_lock->owned_by_self(), "this thread should own the Heap_lock");
 802   collect_locked(cause, OldGen);
 803 }
 804 
 805 // this is the private collection interface
 806 // The Heap_lock is expected to be held on entry.
 807 
 808 void GenCollectedHeap::collect_locked(GCCause::Cause cause, GenerationType max_generation) {
 809   // Read the GC count while holding the Heap_lock
 810   unsigned int gc_count_before      = total_collections();
 811   unsigned int full_gc_count_before = total_full_collections();
 812   {
 813     MutexUnlocker mu(Heap_lock);  // give up heap lock, execute gets it back
 814     VM_GenCollectFull op(gc_count_before, full_gc_count_before,
 815                          cause, max_generation);
 816     VMThread::execute(&op);
 817   }
 818 }
 819 
 820 #if INCLUDE_ALL_GCS
 821 bool GenCollectedHeap::create_cms_collector() {
 822 
 823   assert(_old_gen->kind() == Generation::ConcurrentMarkSweep,
 824          "Unexpected generation kinds");
 825   // Skip two header words in the block content verification
 826   NOT_PRODUCT(_skip_header_HeapWords = CMSCollector::skip_header_HeapWords();)
 827   assert(_gen_policy->is_concurrent_mark_sweep_policy(), "Unexpected policy type");
 828   CMSCollector* collector =
 829     new CMSCollector((ConcurrentMarkSweepGeneration*)_old_gen,
 830                      _rem_set,
 831                      _gen_policy->as_concurrent_mark_sweep_policy());
 832 
 833   if (collector == NULL || !collector->completed_initialization()) {
 834     if (collector) {
 835       delete collector;  // Be nice in embedded situation
 836     }
 837     vm_shutdown_during_initialization("Could not create CMS collector");
 838     return false;
 839   }
 840   return true;  // success
 841 }
 842 
 843 void GenCollectedHeap::collect_mostly_concurrent(GCCause::Cause cause) {
 844   assert(!Heap_lock->owned_by_self(), "Should not own Heap_lock");
 845 
 846   MutexLocker ml(Heap_lock);
 847   // Read the GC counts while holding the Heap_lock
 848   unsigned int full_gc_count_before = total_full_collections();
 849   unsigned int gc_count_before      = total_collections();
 850   {
 851     MutexUnlocker mu(Heap_lock);
 852     VM_GenCollectFullConcurrent op(gc_count_before, full_gc_count_before, cause);
 853     VMThread::execute(&op);
 854   }
 855 }
 856 #endif // INCLUDE_ALL_GCS
 857 
 858 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs) {
 859    do_full_collection(clear_all_soft_refs, OldGen);
 860 }
 861 
 862 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs,
 863                                           GenerationType last_generation) {
 864   GenerationType local_last_generation;
 865   if (!incremental_collection_will_fail(false /* don't consult_young */) &&
 866       gc_cause() == GCCause::_gc_locker) {
 867     local_last_generation = YoungGen;
 868   } else {
 869     local_last_generation = last_generation;
 870   }
 871 
 872   do_collection(true,                   // full
 873                 clear_all_soft_refs,    // clear_all_soft_refs
 874                 0,                      // size
 875                 false,                  // is_tlab
 876                 local_last_generation); // last_generation
 877   // Hack XXX FIX ME !!!
 878   // A scavenge may not have been attempted, or may have
 879   // been attempted and failed, because the old gen was too full
 880   if (local_last_generation == YoungGen && gc_cause() == GCCause::_gc_locker &&
 881       incremental_collection_will_fail(false /* don't consult_young */)) {
 882     log_debug(gc, jni)("GC locker: Trying a full collection because scavenge failed");
 883     // This time allow the old gen to be collected as well
 884     do_collection(true,                // full
 885                   clear_all_soft_refs, // clear_all_soft_refs
 886                   0,                   // size
 887                   false,               // is_tlab
 888                   OldGen);             // last_generation
 889   }
 890 }
 891 
 892 bool GenCollectedHeap::is_in_young(oop p) {
 893   bool result = ((HeapWord*)p) < _old_gen->reserved().start();
 894   assert(result == _young_gen->is_in_reserved(p),
 895          "incorrect test - result=%d, p=" INTPTR_FORMAT, result, p2i((void*)p));
 896   return result;
 897 }
 898 
 899 // Returns "TRUE" iff "p" points into the committed areas of the heap.
 900 bool GenCollectedHeap::is_in(const void* p) const {
 901   return _young_gen->is_in(p) || _old_gen->is_in(p);
 902 }
 903 
 904 #ifdef ASSERT
 905 // Don't implement this by using is_in_young().  This method is used
 906 // in some cases to check that is_in_young() is correct.
 907 bool GenCollectedHeap::is_in_partial_collection(const void* p) {
 908   assert(is_in_reserved(p) || p == NULL,
 909     "Does not work if address is non-null and outside of the heap");
 910   return p < _young_gen->reserved().end() && p != NULL;
 911 }
 912 #endif
 913 
 914 void GenCollectedHeap::oop_iterate_no_header(OopClosure* cl) {
 915   NoHeaderExtendedOopClosure no_header_cl(cl);
 916   oop_iterate(&no_header_cl);
 917 }
 918 
 919 void GenCollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
 920   _young_gen->oop_iterate(cl);
 921   _old_gen->oop_iterate(cl);
 922 }
 923 
 924 void GenCollectedHeap::object_iterate(ObjectClosure* cl) {
 925   _young_gen->object_iterate(cl);
 926   _old_gen->object_iterate(cl);
 927 }
 928 
 929 void GenCollectedHeap::safe_object_iterate(ObjectClosure* cl) {
 930   _young_gen->safe_object_iterate(cl);
 931   _old_gen->safe_object_iterate(cl);
 932 }
 933 
 934 Space* GenCollectedHeap::space_containing(const void* addr) const {
 935   Space* res = _young_gen->space_containing(addr);
 936   if (res != NULL) {
 937     return res;
 938   }
 939   res = _old_gen->space_containing(addr);
 940   assert(res != NULL, "Could not find containing space");
 941   return res;
 942 }
 943 
 944 HeapWord* GenCollectedHeap::block_start(const void* addr) const {
 945   assert(is_in_reserved(addr), "block_start of address outside of heap");
 946   if (_young_gen->is_in_reserved(addr)) {
 947     assert(_young_gen->is_in(addr), "addr should be in allocated part of generation");
 948     return _young_gen->block_start(addr);
 949   }
 950 
 951   assert(_old_gen->is_in_reserved(addr), "Some generation should contain the address");
 952   assert(_old_gen->is_in(addr), "addr should be in allocated part of generation");
 953   return _old_gen->block_start(addr);
 954 }
 955 
 956 size_t GenCollectedHeap::block_size(const HeapWord* addr) const {
 957   assert(is_in_reserved(addr), "block_size of address outside of heap");
 958   if (_young_gen->is_in_reserved(addr)) {
 959     assert(_young_gen->is_in(addr), "addr should be in allocated part of generation");
 960     return _young_gen->block_size(addr);
 961   }
 962 
 963   assert(_old_gen->is_in_reserved(addr), "Some generation should contain the address");
 964   assert(_old_gen->is_in(addr), "addr should be in allocated part of generation");
 965   return _old_gen->block_size(addr);
 966 }
 967 
 968 bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const {
 969   assert(is_in_reserved(addr), "block_is_obj of address outside of heap");
 970   assert(block_start(addr) == addr, "addr must be a block start");
 971   if (_young_gen->is_in_reserved(addr)) {
 972     return _young_gen->block_is_obj(addr);
 973   }
 974 
 975   assert(_old_gen->is_in_reserved(addr), "Some generation should contain the address");
 976   return _old_gen->block_is_obj(addr);
 977 }
 978 
 979 bool GenCollectedHeap::supports_tlab_allocation() const {
 980   assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
 981   return _young_gen->supports_tlab_allocation();
 982 }
 983 
 984 size_t GenCollectedHeap::tlab_capacity(Thread* thr) const {
 985   assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
 986   if (_young_gen->supports_tlab_allocation()) {
 987     return _young_gen->tlab_capacity();
 988   }
 989   return 0;
 990 }
 991 
 992 size_t GenCollectedHeap::tlab_used(Thread* thr) const {
 993   assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
 994   if (_young_gen->supports_tlab_allocation()) {
 995     return _young_gen->tlab_used();
 996   }
 997   return 0;
 998 }
 999 
1000 size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const {
1001   assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
1002   if (_young_gen->supports_tlab_allocation()) {
1003     return _young_gen->unsafe_max_tlab_alloc();
1004   }
1005   return 0;
1006 }
1007 
1008 HeapWord* GenCollectedHeap::allocate_new_tlab(size_t size) {
1009   bool gc_overhead_limit_was_exceeded;
1010   return gen_policy()->mem_allocate_work(size /* size */,
1011                                          true /* is_tlab */,
1012                                          &gc_overhead_limit_was_exceeded);
1013 }
1014 
1015 // Requires "*prev_ptr" to be non-NULL.  Deletes and a block of minimal size
1016 // from the list headed by "*prev_ptr".
1017 static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) {
1018   bool first = true;
1019   size_t min_size = 0;   // "first" makes this conceptually infinite.
1020   ScratchBlock **smallest_ptr, *smallest;
1021   ScratchBlock  *cur = *prev_ptr;
1022   while (cur) {
1023     assert(*prev_ptr == cur, "just checking");
1024     if (first || cur->num_words < min_size) {
1025       smallest_ptr = prev_ptr;
1026       smallest     = cur;
1027       min_size     = smallest->num_words;
1028       first        = false;
1029     }
1030     prev_ptr = &cur->next;
1031     cur     =  cur->next;
1032   }
1033   smallest      = *smallest_ptr;
1034   *smallest_ptr = smallest->next;
1035   return smallest;
1036 }
1037 
1038 // Sort the scratch block list headed by res into decreasing size order,
1039 // and set "res" to the result.
1040 static void sort_scratch_list(ScratchBlock*& list) {
1041   ScratchBlock* sorted = NULL;
1042   ScratchBlock* unsorted = list;
1043   while (unsorted) {
1044     ScratchBlock *smallest = removeSmallestScratch(&unsorted);
1045     smallest->next  = sorted;
1046     sorted          = smallest;
1047   }
1048   list = sorted;
1049 }
1050 
1051 ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor,
1052                                                size_t max_alloc_words) {
1053   ScratchBlock* res = NULL;
1054   _young_gen->contribute_scratch(res, requestor, max_alloc_words);
1055   _old_gen->contribute_scratch(res, requestor, max_alloc_words);
1056   sort_scratch_list(res);
1057   return res;
1058 }
1059 
1060 void GenCollectedHeap::release_scratch() {
1061   _young_gen->reset_scratch();
1062   _old_gen->reset_scratch();
1063 }
1064 
1065 class GenPrepareForVerifyClosure: public GenCollectedHeap::GenClosure {
1066   void do_generation(Generation* gen) {
1067     gen->prepare_for_verify();
1068   }
1069 };
1070 
1071 void GenCollectedHeap::prepare_for_verify() {
1072   ensure_parsability(false);        // no need to retire TLABs
1073   GenPrepareForVerifyClosure blk;
1074   generation_iterate(&blk, false);
1075 }
1076 
1077 void GenCollectedHeap::generation_iterate(GenClosure* cl,
1078                                           bool old_to_young) {
1079   if (old_to_young) {
1080     cl->do_generation(_old_gen);
1081     cl->do_generation(_young_gen);
1082   } else {
1083     cl->do_generation(_young_gen);
1084     cl->do_generation(_old_gen);
1085   }
1086 }
1087 
1088 bool GenCollectedHeap::is_maximal_no_gc() const {
1089   return _young_gen->is_maximal_no_gc() && _old_gen->is_maximal_no_gc();
1090 }
1091 
1092 void GenCollectedHeap::save_marks() {
1093   _young_gen->save_marks();
1094   _old_gen->save_marks();
1095 }
1096 
1097 GenCollectedHeap* GenCollectedHeap::heap() {
1098   CollectedHeap* heap = Universe::heap();
1099   assert(heap != NULL, "Uninitialized access to GenCollectedHeap::heap()");
1100   assert(heap->kind() == CollectedHeap::GenCollectedHeap, "Not a GenCollectedHeap");
1101   return (GenCollectedHeap*)heap;
1102 }
1103 
1104 void GenCollectedHeap::prepare_for_compaction() {
1105   // Start by compacting into same gen.
1106   CompactPoint cp(_old_gen);
1107   _old_gen->prepare_for_compaction(&cp);
1108   _young_gen->prepare_for_compaction(&cp);
1109 }
1110 
1111 void GenCollectedHeap::verify(VerifyOption option /* ignored */) {
1112   log_debug(gc, verify)("%s", _old_gen->name());
1113   _old_gen->verify();
1114 
1115   log_debug(gc, verify)("%s", _old_gen->name());
1116   _young_gen->verify();
1117 
1118   log_debug(gc, verify)("RemSet");
1119   rem_set()->verify();
1120 }
1121 
1122 void GenCollectedHeap::print_on(outputStream* st) const {
1123   _young_gen->print_on(st);
1124   _old_gen->print_on(st);
1125   MetaspaceAux::print_on(st);
1126 }
1127 
1128 void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const {
1129   if (workers() != NULL) {
1130     workers()->threads_do(tc);
1131   }
1132 #if INCLUDE_ALL_GCS
1133   if (UseConcMarkSweepGC) {
1134     ConcurrentMarkSweepThread::threads_do(tc);
1135   }
1136 #endif // INCLUDE_ALL_GCS
1137 }
1138 
1139 void GenCollectedHeap::print_gc_threads_on(outputStream* st) const {
1140 #if INCLUDE_ALL_GCS
1141   if (UseConcMarkSweepGC) {
1142     workers()->print_worker_threads_on(st);
1143     ConcurrentMarkSweepThread::print_all_on(st);
1144   }
1145 #endif // INCLUDE_ALL_GCS
1146 }
1147 
1148 void GenCollectedHeap::print_on_error(outputStream* st) const {
1149   this->CollectedHeap::print_on_error(st);
1150 
1151 #if INCLUDE_ALL_GCS
1152   if (UseConcMarkSweepGC) {
1153     st->cr();
1154     CMSCollector::print_on_error(st);
1155   }
1156 #endif // INCLUDE_ALL_GCS
1157 }
1158 
1159 void GenCollectedHeap::print_tracing_info() const {
1160   if (TraceYoungGenTime) {
1161     _young_gen->print_summary_info();
1162   }
1163   if (TraceOldGenTime) {
1164     _old_gen->print_summary_info();
1165   }
1166 }
1167 
1168 void GenCollectedHeap::print_heap_change(size_t young_prev_used, size_t old_prev_used) const {
1169   log_info(gc, heap)("%s: " SIZE_FORMAT "K->" SIZE_FORMAT "K("  SIZE_FORMAT "K)",
1170                      _young_gen->short_name(), young_prev_used / K, _young_gen->used() /K, _young_gen->capacity() /K);
1171   log_info(gc, heap)("%s: " SIZE_FORMAT "K->" SIZE_FORMAT "K("  SIZE_FORMAT "K)",
1172                      _old_gen->short_name(), old_prev_used / K, _old_gen->used() /K, _old_gen->capacity() /K);
1173 }
1174 
1175 class GenGCPrologueClosure: public GenCollectedHeap::GenClosure {
1176  private:
1177   bool _full;
1178  public:
1179   void do_generation(Generation* gen) {
1180     gen->gc_prologue(_full);
1181   }
1182   GenGCPrologueClosure(bool full) : _full(full) {};
1183 };
1184 
1185 void GenCollectedHeap::gc_prologue(bool full) {
1186   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
1187 
1188   always_do_update_barrier = false;
1189   // Fill TLAB's and such
1190   CollectedHeap::accumulate_statistics_all_tlabs();
1191   ensure_parsability(true);   // retire TLABs
1192 
1193   // Walk generations
1194   GenGCPrologueClosure blk(full);
1195   generation_iterate(&blk, false);  // not old-to-young.
1196 };
1197 
1198 class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure {
1199  private:
1200   bool _full;
1201  public:
1202   void do_generation(Generation* gen) {
1203     gen->gc_epilogue(_full);
1204   }
1205   GenGCEpilogueClosure(bool full) : _full(full) {};
1206 };
1207 
1208 void GenCollectedHeap::gc_epilogue(bool full) {
1209 #if defined(COMPILER2) || INCLUDE_JVMCI
1210   assert(DerivedPointerTable::is_empty(), "derived pointer present");
1211   size_t actual_gap = pointer_delta((HeapWord*) (max_uintx-3), *(end_addr()));
1212   guarantee(is_client_compilation_mode_vm() || actual_gap > (size_t)FastAllocateSizeLimit, "inline allocation wraps");
1213 #endif /* COMPILER2 || INCLUDE_JVMCI */
1214 
1215   resize_all_tlabs();
1216 
1217   GenGCEpilogueClosure blk(full);
1218   generation_iterate(&blk, false);  // not old-to-young.
1219 
1220   if (!CleanChunkPoolAsync) {
1221     Chunk::clean_chunk_pool();
1222   }
1223 
1224   MetaspaceCounters::update_performance_counters();
1225   CompressedClassSpaceCounters::update_performance_counters();
1226 
1227   always_do_update_barrier = UseConcMarkSweepGC;
1228 };
1229 
1230 #ifndef PRODUCT
1231 class GenGCSaveTopsBeforeGCClosure: public GenCollectedHeap::GenClosure {
1232  private:
1233  public:
1234   void do_generation(Generation* gen) {
1235     gen->record_spaces_top();
1236   }
1237 };
1238 
1239 void GenCollectedHeap::record_gen_tops_before_GC() {
1240   if (ZapUnusedHeapArea) {
1241     GenGCSaveTopsBeforeGCClosure blk;
1242     generation_iterate(&blk, false);  // not old-to-young.
1243   }
1244 }
1245 #endif  // not PRODUCT
1246 
1247 class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure {
1248  public:
1249   void do_generation(Generation* gen) {
1250     gen->ensure_parsability();
1251   }
1252 };
1253 
1254 void GenCollectedHeap::ensure_parsability(bool retire_tlabs) {
1255   CollectedHeap::ensure_parsability(retire_tlabs);
1256   GenEnsureParsabilityClosure ep_cl;
1257   generation_iterate(&ep_cl, false);
1258 }
1259 
1260 oop GenCollectedHeap::handle_failed_promotion(Generation* old_gen,
1261                                               oop obj,
1262                                               size_t obj_size) {
1263   guarantee(old_gen == _old_gen, "We only get here with an old generation");
1264   assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1265   HeapWord* result = NULL;
1266 
1267   result = old_gen->expand_and_allocate(obj_size, false);
1268 
1269   if (result != NULL) {
1270     Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size);
1271   }
1272   return oop(result);
1273 }
1274 
1275 class GenTimeOfLastGCClosure: public GenCollectedHeap::GenClosure {
1276   jlong _time;   // in ms
1277   jlong _now;    // in ms
1278 
1279  public:
1280   GenTimeOfLastGCClosure(jlong now) : _time(now), _now(now) { }
1281 
1282   jlong time() { return _time; }
1283 
1284   void do_generation(Generation* gen) {
1285     _time = MIN2(_time, gen->time_of_last_gc(_now));
1286   }
1287 };
1288 
1289 jlong GenCollectedHeap::millis_since_last_gc() {
1290   // javaTimeNanos() is guaranteed to be monotonically non-decreasing
1291   // provided the underlying platform provides such a time source
1292   // (and it is bug free). So we still have to guard against getting
1293   // back a time later than 'now'.
1294   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
1295   GenTimeOfLastGCClosure tolgc_cl(now);
1296   // iterate over generations getting the oldest
1297   // time that a generation was collected
1298   generation_iterate(&tolgc_cl, false);
1299 
1300   jlong retVal = now - tolgc_cl.time();
1301   if (retVal < 0) {
1302     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
1303        ". returning zero instead.", retVal);
1304     return 0;
1305   }
1306   return retVal;
1307 }
1308 
1309 void GenCollectedHeap::stop() {
1310 #if INCLUDE_ALL_GCS
1311   if (UseConcMarkSweepGC) {
1312     ConcurrentMarkSweepThread::cmst()->stop();
1313   }
1314 #endif
1315 }