rev 10186 : [mq]: prune_scavengable_nmethods

   1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   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.
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  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).
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/symbolTable.hpp"
  27 #include "classfile/systemDictionary.hpp"
  28 #include "classfile/vmSymbols.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc/shared/collectedHeap.inline.hpp"
  32 #include "gc/shared/collectorCounters.hpp"
  33 #include "gc/shared/gcId.hpp"
  34 #include "gc/shared/gcLocker.inline.hpp"
  35 #include "gc/shared/gcTrace.hpp"
  36 #include "gc/shared/gcTraceTime.inline.hpp"
  37 #include "gc/shared/genCollectedHeap.hpp"
  38 #include "gc/shared/genOopClosures.inline.hpp"
  39 #include "gc/shared/generationSpec.hpp"
  40 #include "gc/shared/space.hpp"
  41 #include "gc/shared/strongRootsScope.hpp"
  42 #include "gc/shared/vmGCOperations.hpp"
  43 #include "gc/shared/workgroup.hpp"
  44 #include "memory/filemap.hpp"
  45 #include "memory/resourceArea.hpp"
  46 #include "oops/oop.inline.hpp"
  47 #include "runtime/biasedLocking.hpp"
  48 #include "runtime/fprofiler.hpp"
  49 #include "runtime/handles.hpp"
  50 #include "runtime/handles.inline.hpp"
  51 #include "runtime/java.hpp"
  52 #include "runtime/vmThread.hpp"
  53 #include "services/management.hpp"
  54 #include "services/memoryService.hpp"
  55 #include "utilities/macros.hpp"
  56 #include "utilities/stack.inline.hpp"
  57 #include "utilities/vmError.hpp"
  58 #if INCLUDE_ALL_GCS
  59 #include "gc/cms/concurrentMarkSweepThread.hpp"
  60 #include "gc/cms/vmCMSOperations.hpp"
  61 #endif // INCLUDE_ALL_GCS
  62 
  63 NOT_PRODUCT(size_t GenCollectedHeap::_skip_header_HeapWords = 0;)
  64 
  65 // The set of potentially parallel tasks in root scanning.
  66 enum GCH_strong_roots_tasks {
  67   GCH_PS_Universe_oops_do,
  68   GCH_PS_JNIHandles_oops_do,
  69   GCH_PS_ObjectSynchronizer_oops_do,
  70   GCH_PS_FlatProfiler_oops_do,
  71   GCH_PS_Management_oops_do,
  72   GCH_PS_SystemDictionary_oops_do,
  73   GCH_PS_ClassLoaderDataGraph_oops_do,
  74   GCH_PS_jvmti_oops_do,
  75   GCH_PS_CodeCache_oops_do,
  76   GCH_PS_younger_gens,
  77   // Leave this one last.
  78   GCH_PS_NumElements
  79 };
  80 
  81 GenCollectedHeap::GenCollectedHeap(GenCollectorPolicy *policy) :
  82   CollectedHeap(),
  83   _rem_set(NULL),
  84   _gen_policy(policy),
  85   _process_strong_tasks(new SubTasksDone(GCH_PS_NumElements)),
  86   _full_collections_completed(0)
  87 {
  88   assert(policy != NULL, "Sanity check");
  89   if (UseConcMarkSweepGC) {
  90     _workers = new WorkGang("GC Thread", ParallelGCThreads,
  91                             /* are_GC_task_threads */true,
  92                             /* are_ConcurrentGC_threads */false);
  93     _workers->initialize_workers();
  94   } else {
  95     // Serial GC does not use workers.
  96     _workers = NULL;
  97   }
  98 }
  99 
 100 jint GenCollectedHeap::initialize() {
 101   CollectedHeap::pre_initialize();
 102 
 103   // While there are no constraints in the GC code that HeapWordSize
 104   // be any particular value, there are multiple other areas in the
 105   // system which believe this to be true (e.g. oop->object_size in some
 106   // cases incorrectly returns the size in wordSize units rather than
 107   // HeapWordSize).
 108   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
 109 
 110   // Allocate space for the heap.
 111 
 112   char* heap_address;
 113   ReservedSpace heap_rs;
 114 
 115   size_t heap_alignment = collector_policy()->heap_alignment();
 116 
 117   heap_address = allocate(heap_alignment, &heap_rs);
 118 
 119   if (!heap_rs.is_reserved()) {
 120     vm_shutdown_during_initialization(
 121       "Could not reserve enough space for object heap");
 122     return JNI_ENOMEM;
 123   }
 124 
 125   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
 126 
 127   _rem_set = collector_policy()->create_rem_set(reserved_region());
 128   set_barrier_set(rem_set()->bs());
 129 
 130   ReservedSpace young_rs = heap_rs.first_part(gen_policy()->young_gen_spec()->max_size(), false, false);
 131   _young_gen = gen_policy()->young_gen_spec()->init(young_rs, rem_set());
 132   heap_rs = heap_rs.last_part(gen_policy()->young_gen_spec()->max_size());
 133 
 134   ReservedSpace old_rs = heap_rs.first_part(gen_policy()->old_gen_spec()->max_size(), false, false);
 135   _old_gen = gen_policy()->old_gen_spec()->init(old_rs, 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   // Now figure out the total size.
 153   const size_t pageSize = UseLargePages ? os::large_page_size() : os::vm_page_size();
 154   assert(alignment % pageSize == 0, "Must be");
 155 
 156   GenerationSpec* young_spec = gen_policy()->young_gen_spec();
 157   GenerationSpec* old_spec = gen_policy()->old_gen_spec();
 158 
 159   // Check for overflow.
 160   size_t total_reserved = young_spec->max_size() + old_spec->max_size();
 161   if (total_reserved < young_spec->max_size()) {
 162     vm_exit_during_initialization("The size of the object heap + VM data exceeds "
 163                                   "the maximum representable size");
 164   }
 165   assert(total_reserved % alignment == 0,
 166          "Gen size; total_reserved=" SIZE_FORMAT ", alignment="
 167          SIZE_FORMAT, total_reserved, alignment);
 168 
 169   *heap_rs = Universe::reserve_heap(total_reserved, alignment);
 170   return heap_rs->base();
 171 }
 172 
 173 void GenCollectedHeap::post_initialize() {
 174   CollectedHeap::post_initialize();
 175   ref_processing_init();
 176   assert((_young_gen->kind() == Generation::DefNew) ||
 177          (_young_gen->kind() == Generation::ParNew),
 178     "Wrong youngest generation type");
 179   DefNewGeneration* def_new_gen = (DefNewGeneration*)_young_gen;
 180 
 181   assert(_old_gen->kind() == Generation::ConcurrentMarkSweep ||
 182          _old_gen->kind() == Generation::MarkSweepCompact,
 183     "Wrong generation kind");
 184 
 185   _gen_policy->initialize_size_policy(def_new_gen->eden()->capacity(),
 186                                       _old_gen->capacity(),
 187                                       def_new_gen->from()->capacity());
 188   _gen_policy->initialize_gc_policy_counters();
 189 }
 190 
 191 void GenCollectedHeap::ref_processing_init() {
 192   _young_gen->ref_processor_init();
 193   _old_gen->ref_processor_init();
 194 }
 195 
 196 size_t GenCollectedHeap::capacity() const {
 197   return _young_gen->capacity() + _old_gen->capacity();
 198 }
 199 
 200 size_t GenCollectedHeap::used() const {
 201   return _young_gen->used() + _old_gen->used();
 202 }
 203 
 204 void GenCollectedHeap::save_used_regions() {
 205   _old_gen->save_used_region();
 206   _young_gen->save_used_region();
 207 }
 208 
 209 size_t GenCollectedHeap::max_capacity() const {
 210   return _young_gen->max_capacity() + _old_gen->max_capacity();
 211 }
 212 
 213 // Update the _full_collections_completed counter
 214 // at the end of a stop-world full GC.
 215 unsigned int GenCollectedHeap::update_full_collections_completed() {
 216   MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
 217   assert(_full_collections_completed <= _total_full_collections,
 218          "Can't complete more collections than were started");
 219   _full_collections_completed = _total_full_collections;
 220   ml.notify_all();
 221   return _full_collections_completed;
 222 }
 223 
 224 // Update the _full_collections_completed counter, as appropriate,
 225 // at the end of a concurrent GC cycle. Note the conditional update
 226 // below to allow this method to be called by a concurrent collector
 227 // without synchronizing in any manner with the VM thread (which
 228 // may already have initiated a STW full collection "concurrently").
 229 unsigned int GenCollectedHeap::update_full_collections_completed(unsigned int count) {
 230   MonitorLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
 231   assert((_full_collections_completed <= _total_full_collections) &&
 232          (count <= _total_full_collections),
 233          "Can't complete more collections than were started");
 234   if (count > _full_collections_completed) {
 235     _full_collections_completed = count;
 236     ml.notify_all();
 237   }
 238   return _full_collections_completed;
 239 }
 240 
 241 
 242 #ifndef PRODUCT
 243 // Override of memory state checking method in CollectedHeap:
 244 // Some collectors (CMS for example) can't have badHeapWordVal written
 245 // in the first two words of an object. (For instance , in the case of
 246 // CMS these words hold state used to synchronize between certain
 247 // (concurrent) GC steps and direct allocating mutators.)
 248 // The skip_header_HeapWords() method below, allows us to skip
 249 // over the requisite number of HeapWord's. Note that (for
 250 // generational collectors) this means that those many words are
 251 // skipped in each object, irrespective of the generation in which
 252 // that object lives. The resultant loss of precision seems to be
 253 // harmless and the pain of avoiding that imprecision appears somewhat
 254 // higher than we are prepared to pay for such rudimentary debugging
 255 // support.
 256 void GenCollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr,
 257                                                          size_t size) {
 258   if (CheckMemoryInitialization && ZapUnusedHeapArea) {
 259     // We are asked to check a size in HeapWords,
 260     // but the memory is mangled in juint words.
 261     juint* start = (juint*) (addr + skip_header_HeapWords());
 262     juint* end   = (juint*) (addr + size);
 263     for (juint* slot = start; slot < end; slot += 1) {
 264       assert(*slot == badHeapWordVal,
 265              "Found non badHeapWordValue in pre-allocation check");
 266     }
 267   }
 268 }
 269 #endif
 270 
 271 HeapWord* GenCollectedHeap::attempt_allocation(size_t size,
 272                                                bool is_tlab,
 273                                                bool first_only) {
 274   HeapWord* res = NULL;
 275 
 276   if (_young_gen->should_allocate(size, is_tlab)) {
 277     res = _young_gen->allocate(size, is_tlab);
 278     if (res != NULL || first_only) {
 279       return res;
 280     }
 281   }
 282 
 283   if (_old_gen->should_allocate(size, is_tlab)) {
 284     res = _old_gen->allocate(size, is_tlab);
 285   }
 286 
 287   return res;
 288 }
 289 
 290 HeapWord* GenCollectedHeap::mem_allocate(size_t size,
 291                                          bool* gc_overhead_limit_was_exceeded) {
 292   return gen_policy()->mem_allocate_work(size,
 293                                          false /* is_tlab */,
 294                                          gc_overhead_limit_was_exceeded);
 295 }
 296 
 297 bool GenCollectedHeap::must_clear_all_soft_refs() {
 298   return _gc_cause == GCCause::_last_ditch_collection;
 299 }
 300 
 301 bool GenCollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
 302   if (!UseConcMarkSweepGC) {
 303     return false;
 304   }
 305 
 306   switch (cause) {
 307     case GCCause::_gc_locker:           return GCLockerInvokesConcurrent;
 308     case GCCause::_java_lang_system_gc:
 309     case GCCause::_dcmd_gc_run:         return ExplicitGCInvokesConcurrent;
 310     default:                            return false;
 311   }
 312 }
 313 
 314 void GenCollectedHeap::collect_generation(Generation* gen, bool full, size_t size,
 315                                           bool is_tlab, bool run_verification, bool clear_soft_refs,
 316                                           bool restore_marks_for_biased_locking) {
 317   FormatBuffer<> title("Collect gen: %s", gen->short_name());
 318   GCTraceTime(Debug, gc) t1(title);
 319   TraceCollectorStats tcs(gen->counters());
 320   TraceMemoryManagerStats tmms(gen->kind(),gc_cause());
 321 
 322   gen->stat_record()->invocations++;
 323   gen->stat_record()->accumulated_time.start();
 324 
 325   // Must be done anew before each collection because
 326   // a previous collection will do mangling and will
 327   // change top of some spaces.
 328   record_gen_tops_before_GC();
 329 
 330   log_trace(gc)("%s invoke=%d size=" SIZE_FORMAT, heap()->is_young_gen(gen) ? "Young" : "Old", gen->stat_record()->invocations, size * HeapWordSize);
 331 
 332   if (run_verification && VerifyBeforeGC) {
 333     HandleMark hm;  // Discard invalid handles created during verification
 334     Universe::verify("Before GC");
 335   }
 336   COMPILER2_PRESENT(DerivedPointerTable::clear());
 337 
 338   if (restore_marks_for_biased_locking) {
 339     // We perform this mark word preservation work lazily
 340     // because it's only at this point that we know whether we
 341     // absolutely have to do it; we want to avoid doing it for
 342     // scavenge-only collections where it's unnecessary
 343     BiasedLocking::preserve_marks();
 344   }
 345 
 346   // Do collection work
 347   {
 348     // Note on ref discovery: For what appear to be historical reasons,
 349     // GCH enables and disabled (by enqueing) refs discovery.
 350     // In the future this should be moved into the generation's
 351     // collect method so that ref discovery and enqueueing concerns
 352     // are local to a generation. The collect method could return
 353     // an appropriate indication in the case that notification on
 354     // the ref lock was needed. This will make the treatment of
 355     // weak refs more uniform (and indeed remove such concerns
 356     // from GCH). XXX
 357 
 358     HandleMark hm;  // Discard invalid handles created during gc
 359     save_marks();   // save marks for all gens
 360     // We want to discover references, but not process them yet.
 361     // This mode is disabled in process_discovered_references if the
 362     // generation does some collection work, or in
 363     // enqueue_discovered_references if the generation returns
 364     // without doing any work.
 365     ReferenceProcessor* rp = gen->ref_processor();
 366     // If the discovery of ("weak") refs in this generation is
 367     // atomic wrt other collectors in this configuration, we
 368     // are guaranteed to have empty discovered ref lists.
 369     if (rp->discovery_is_atomic()) {
 370       rp->enable_discovery();
 371       rp->setup_policy(clear_soft_refs);
 372     } else {
 373       // collect() below will enable discovery as appropriate
 374     }
 375     gen->collect(full, clear_soft_refs, size, is_tlab);
 376     if (!rp->enqueuing_is_done()) {
 377       rp->enqueue_discovered_references();
 378     } else {
 379       rp->set_enqueuing_is_done(false);
 380     }
 381     rp->verify_no_references_recorded();
 382   }
 383 
 384   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
 385 
 386   gen->stat_record()->accumulated_time.stop();
 387 
 388   update_gc_stats(gen, full);
 389 
 390   if (run_verification && VerifyAfterGC) {
 391     HandleMark hm;  // Discard invalid handles created during verification
 392     Universe::verify("After GC");
 393   }
 394 }
 395 
 396 void GenCollectedHeap::do_collection(bool           full,
 397                                      bool           clear_all_soft_refs,
 398                                      size_t         size,
 399                                      bool           is_tlab,
 400                                      GenerationType max_generation) {
 401   ResourceMark rm;
 402   DEBUG_ONLY(Thread* my_thread = Thread::current();)
 403 
 404   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 405   assert(my_thread->is_VM_thread() ||
 406          my_thread->is_ConcurrentGC_thread(),
 407          "incorrect thread type capability");
 408   assert(Heap_lock->is_locked(),
 409          "the requesting thread should have the Heap_lock");
 410   guarantee(!is_gc_active(), "collection is not reentrant");
 411 
 412   if (GCLocker::check_active_before_gc()) {
 413     return; // GC is disabled (e.g. JNI GetXXXCritical operation)
 414   }
 415 
 416   GCIdMarkAndRestore gc_id_mark;
 417 
 418   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
 419                           collector_policy()->should_clear_all_soft_refs();
 420 
 421   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
 422 
 423   const size_t metadata_prev_used = MetaspaceAux::used_bytes();
 424 
 425   print_heap_before_gc();
 426 
 427   {
 428     FlagSetting fl(_is_gc_active, true);
 429 
 430     bool complete = full && (max_generation == OldGen);
 431     bool old_collects_young = complete && !ScavengeBeforeFullGC;
 432     bool do_young_collection = !old_collects_young && _young_gen->should_collect(full, size, is_tlab);
 433 
 434     FormatBuffer<> gc_string("%s", "Pause ");
 435     if (do_young_collection) {
 436       gc_string.append("Young");
 437     } else {
 438       gc_string.append("Full");
 439     }
 440 
 441     GCTraceCPUTime tcpu;
 442     GCTraceTime(Info, gc) t(gc_string, NULL, gc_cause(), true);
 443 
 444     gc_prologue(complete);
 445     increment_total_collections(complete);
 446 
 447     size_t young_prev_used = _young_gen->used();
 448     size_t old_prev_used = _old_gen->used();
 449 
 450     bool run_verification = total_collections() >= VerifyGCStartAt;
 451 
 452     bool prepared_for_verification = false;
 453     bool collected_old = false;
 454 
 455     if (do_young_collection) {
 456       if (run_verification && VerifyGCLevel <= 0 && VerifyBeforeGC) {
 457         prepare_for_verify();
 458         prepared_for_verification = true;
 459       }
 460 
 461       collect_generation(_young_gen,
 462                          full,
 463                          size,
 464                          is_tlab,
 465                          run_verification && VerifyGCLevel <= 0,
 466                          do_clear_all_soft_refs,
 467                          false);
 468 
 469       if (size > 0 && (!is_tlab || _young_gen->supports_tlab_allocation()) &&
 470           size * HeapWordSize <= _young_gen->unsafe_max_alloc_nogc()) {
 471         // Allocation request was met by young GC.
 472         size = 0;
 473       }
 474     }
 475 
 476     bool must_restore_marks_for_biased_locking = false;
 477 
 478     if (max_generation == OldGen && _old_gen->should_collect(full, size, is_tlab)) {
 479       if (!complete) {
 480         // The full_collections increment was missed above.
 481         increment_total_full_collections();
 482       }
 483 
 484       if (!prepared_for_verification && run_verification &&
 485           VerifyGCLevel <= 1 && VerifyBeforeGC) {
 486         prepare_for_verify();
 487       }
 488 
 489       if (do_young_collection) {
 490         // We did a young GC. Need a new GC id for the old GC.
 491         GCIdMarkAndRestore gc_id_mark;
 492         GCTraceTime(Info, gc) t("Pause Full", NULL, gc_cause(), true);
 493         collect_generation(_old_gen, full, size, is_tlab, run_verification && VerifyGCLevel <= 1, do_clear_all_soft_refs, true);
 494       } else {
 495         // No young GC done. Use the same GC id as was set up earlier in this method.
 496         collect_generation(_old_gen, full, size, is_tlab, run_verification && VerifyGCLevel <= 1, do_clear_all_soft_refs, true);
 497       }
 498 
 499       must_restore_marks_for_biased_locking = true;
 500       collected_old = true;
 501     }
 502 
 503     // Update "complete" boolean wrt what actually transpired --
 504     // for instance, a promotion failure could have led to
 505     // a whole heap collection.
 506     complete = complete || collected_old;
 507 
 508     print_heap_change(young_prev_used, old_prev_used);
 509     MetaspaceAux::print_metaspace_change(metadata_prev_used);
 510 
 511     // Adjust generation sizes.
 512     if (collected_old) {
 513       _old_gen->compute_new_size();
 514     }
 515     _young_gen->compute_new_size();
 516 
 517     if (complete) {
 518       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
 519       ClassLoaderDataGraph::purge();
 520       MetaspaceAux::verify_metrics();
 521       // Resize the metaspace capacity after full collections
 522       MetaspaceGC::compute_new_size();
 523       update_full_collections_completed();
 524     }
 525 
 526     // Track memory usage and detect low memory after GC finishes
 527     MemoryService::track_memory_usage();
 528 
 529     gc_epilogue(complete);
 530 
 531     if (must_restore_marks_for_biased_locking) {
 532       BiasedLocking::restore_marks();
 533     }
 534   }
 535 
 536   print_heap_after_gc();
 537 
 538 #ifdef TRACESPINNING
 539   ParallelTaskTerminator::print_termination_counts();
 540 #endif
 541 }
 542 
 543 HeapWord* GenCollectedHeap::satisfy_failed_allocation(size_t size, bool is_tlab) {
 544   return gen_policy()->satisfy_failed_allocation(size, is_tlab);
 545 }
 546 
 547 #ifdef ASSERT
 548 class AssertNonScavengableClosure: public OopClosure {
 549 public:
 550   virtual void do_oop(oop* p) {
 551     assert(!GenCollectedHeap::heap()->is_in_partial_collection(*p),
 552       "Referent should not be scavengable.");  }
 553   virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
 554 };
 555 static AssertNonScavengableClosure assert_is_non_scavengable_closure;
 556 #endif
 557 
 558 void GenCollectedHeap::process_roots(StrongRootsScope* scope,
 559                                      ScanningOption so,
 560                                      OopClosure* strong_roots,
 561                                      OopClosure* weak_roots,
 562                                      CLDClosure* strong_cld_closure,
 563                                      CLDClosure* weak_cld_closure,
 564                                      CodeBlobClosure* code_roots) {
 565   // General roots.
 566   assert(Threads::thread_claim_parity() != 0, "must have called prologue code");
 567   assert(code_roots != NULL, "code root closure should always be set");
 568   // _n_termination for _process_strong_tasks should be set up stream
 569   // in a method not running in a GC worker.  Otherwise the GC worker
 570   // could be trying to change the termination condition while the task
 571   // is executing in another GC worker.
 572 
 573   if (!_process_strong_tasks->is_task_claimed(GCH_PS_ClassLoaderDataGraph_oops_do)) {
 574     ClassLoaderDataGraph::roots_cld_do(strong_cld_closure, weak_cld_closure);
 575   }
 576 
 577   // Some CLDs contained in the thread frames should be considered strong.
 578   // Don't process them if they will be processed during the ClassLoaderDataGraph phase.
 579   CLDClosure* roots_from_clds_p = (strong_cld_closure != weak_cld_closure) ? strong_cld_closure : NULL;
 580   // Only process code roots from thread stacks if we aren't visiting the entire CodeCache anyway
 581   CodeBlobClosure* roots_from_code_p = (so & SO_AllCodeCache) ? NULL : code_roots;
 582 
 583   bool is_par = scope->n_threads() > 1;
 584   Threads::possibly_parallel_oops_do(is_par, strong_roots, roots_from_clds_p, roots_from_code_p);
 585 
 586   if (!_process_strong_tasks->is_task_claimed(GCH_PS_Universe_oops_do)) {
 587     Universe::oops_do(strong_roots);
 588   }
 589   // Global (strong) JNI handles
 590   if (!_process_strong_tasks->is_task_claimed(GCH_PS_JNIHandles_oops_do)) {
 591     JNIHandles::oops_do(strong_roots);
 592   }
 593 
 594   if (!_process_strong_tasks->is_task_claimed(GCH_PS_ObjectSynchronizer_oops_do)) {
 595     ObjectSynchronizer::oops_do(strong_roots);
 596   }
 597   if (!_process_strong_tasks->is_task_claimed(GCH_PS_FlatProfiler_oops_do)) {
 598     FlatProfiler::oops_do(strong_roots);
 599   }
 600   if (!_process_strong_tasks->is_task_claimed(GCH_PS_Management_oops_do)) {
 601     Management::oops_do(strong_roots);
 602   }
 603   if (!_process_strong_tasks->is_task_claimed(GCH_PS_jvmti_oops_do)) {
 604     JvmtiExport::oops_do(strong_roots);
 605   }
 606 
 607   if (!_process_strong_tasks->is_task_claimed(GCH_PS_SystemDictionary_oops_do)) {
 608     SystemDictionary::roots_oops_do(strong_roots, weak_roots);
 609   }
 610 
 611   // All threads execute the following. A specific chunk of buckets
 612   // from the StringTable are the individual tasks.
 613   if (weak_roots != NULL) {
 614     if (is_par) {
 615       StringTable::possibly_parallel_oops_do(weak_roots);
 616     } else {
 617       StringTable::oops_do(weak_roots);
 618     }
 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::gen_process_roots(StrongRootsScope* scope,
 643                                          GenerationType type,
 644                                          bool young_gen_as_roots,
 645                                          ScanningOption so,
 646                                          bool only_strong_roots,
 647                                          OopsInGenClosure* not_older_gens,
 648                                          OopsInGenClosure* older_gens,
 649                                          CLDClosure* cld_closure) {
 650   const bool is_adjust_phase = !only_strong_roots && !young_gen_as_roots;
 651 
 652   bool is_moving_collection = false;
 653   if (type == YoungGen || is_adjust_phase) {
 654     // young collections are always moving
 655     is_moving_collection = true;
 656   }
 657 
 658   MarkingCodeBlobClosure mark_code_closure(not_older_gens, is_moving_collection);
 659   OopsInGenClosure* weak_roots = only_strong_roots ? NULL : not_older_gens;
 660   CLDClosure* weak_cld_closure = only_strong_roots ? NULL : cld_closure;
 661 
 662   process_roots(scope, so,
 663                 not_older_gens, weak_roots,
 664                 cld_closure, weak_cld_closure,
 665                 &mark_code_closure);
 666 
 667   if (young_gen_as_roots) {
 668     if (!_process_strong_tasks->is_task_claimed(GCH_PS_younger_gens)) {
 669       if (type == OldGen) {
 670         not_older_gens->set_generation(_young_gen);
 671         _young_gen->oop_iterate(not_older_gens);
 672       }
 673       not_older_gens->reset_generation();
 674     }
 675   }
 676   // When collection is parallel, all threads get to cooperate to do
 677   // old generation scanning.
 678   if (type == YoungGen) {
 679     older_gens->set_generation(_old_gen);
 680     rem_set()->younger_refs_iterate(_old_gen, older_gens, scope->n_threads());
 681     older_gens->reset_generation();
 682   }
 683 
 684   _process_strong_tasks->all_tasks_completed(scope->n_threads());
 685 }
 686 
 687 
 688 class AlwaysTrueClosure: public BoolObjectClosure {
 689 public:
 690   bool do_object_b(oop p) { return true; }
 691 };
 692 static AlwaysTrueClosure always_true;
 693 
 694 void GenCollectedHeap::gen_process_weak_roots(OopClosure* root_closure) {
 695   JNIHandles::weak_oops_do(&always_true, root_closure);
 696   _young_gen->ref_processor()->weak_oops_do(root_closure);
 697   _old_gen->ref_processor()->weak_oops_do(root_closure);
 698 }
 699 
 700 #define GCH_SINCE_SAVE_MARKS_ITERATE_DEFN(OopClosureType, nv_suffix)    \
 701 void GenCollectedHeap::                                                 \
 702 oop_since_save_marks_iterate(GenerationType gen,                        \
 703                              OopClosureType* cur,                       \
 704                              OopClosureType* older) {                   \
 705   if (gen == YoungGen) {                              \
 706     _young_gen->oop_since_save_marks_iterate##nv_suffix(cur);           \
 707     _old_gen->oop_since_save_marks_iterate##nv_suffix(older);           \
 708   } else {                                                              \
 709     _old_gen->oop_since_save_marks_iterate##nv_suffix(cur);             \
 710   }                                                                     \
 711 }
 712 
 713 ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DEFN)
 714 
 715 #undef GCH_SINCE_SAVE_MARKS_ITERATE_DEFN
 716 
 717 bool GenCollectedHeap::no_allocs_since_save_marks() {
 718   return _young_gen->no_allocs_since_save_marks() &&
 719          _old_gen->no_allocs_since_save_marks();
 720 }
 721 
 722 bool GenCollectedHeap::supports_inline_contig_alloc() const {
 723   return _young_gen->supports_inline_contig_alloc();
 724 }
 725 
 726 HeapWord** GenCollectedHeap::top_addr() const {
 727   return _young_gen->top_addr();
 728 }
 729 
 730 HeapWord** GenCollectedHeap::end_addr() const {
 731   return _young_gen->end_addr();
 732 }
 733 
 734 // public collection interfaces
 735 
 736 void GenCollectedHeap::collect(GCCause::Cause cause) {
 737   if (should_do_concurrent_full_gc(cause)) {
 738 #if INCLUDE_ALL_GCS
 739     // Mostly concurrent full collection.
 740     collect_mostly_concurrent(cause);
 741 #else  // INCLUDE_ALL_GCS
 742     ShouldNotReachHere();
 743 #endif // INCLUDE_ALL_GCS
 744   } else if (cause == GCCause::_wb_young_gc) {
 745     // Young collection for the WhiteBox API.
 746     collect(cause, YoungGen);
 747   } else {
 748 #ifdef ASSERT
 749   if (cause == GCCause::_scavenge_alot) {
 750     // Young collection only.
 751     collect(cause, YoungGen);
 752   } else {
 753     // Stop-the-world full collection.
 754     collect(cause, OldGen);
 755   }
 756 #else
 757     // Stop-the-world full collection.
 758     collect(cause, OldGen);
 759 #endif
 760   }
 761 }
 762 
 763 void GenCollectedHeap::collect(GCCause::Cause cause, GenerationType max_generation) {
 764   // The caller doesn't have the Heap_lock
 765   assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
 766   MutexLocker ml(Heap_lock);
 767   collect_locked(cause, max_generation);
 768 }
 769 
 770 void GenCollectedHeap::collect_locked(GCCause::Cause cause) {
 771   // The caller has the Heap_lock
 772   assert(Heap_lock->owned_by_self(), "this thread should own the Heap_lock");
 773   collect_locked(cause, OldGen);
 774 }
 775 
 776 // this is the private collection interface
 777 // The Heap_lock is expected to be held on entry.
 778 
 779 void GenCollectedHeap::collect_locked(GCCause::Cause cause, GenerationType max_generation) {
 780   // Read the GC count while holding the Heap_lock
 781   unsigned int gc_count_before      = total_collections();
 782   unsigned int full_gc_count_before = total_full_collections();
 783   {
 784     MutexUnlocker mu(Heap_lock);  // give up heap lock, execute gets it back
 785     VM_GenCollectFull op(gc_count_before, full_gc_count_before,
 786                          cause, max_generation);
 787     VMThread::execute(&op);
 788   }
 789 }
 790 
 791 #if INCLUDE_ALL_GCS
 792 bool GenCollectedHeap::create_cms_collector() {
 793 
 794   assert(_old_gen->kind() == Generation::ConcurrentMarkSweep,
 795          "Unexpected generation kinds");
 796   // Skip two header words in the block content verification
 797   NOT_PRODUCT(_skip_header_HeapWords = CMSCollector::skip_header_HeapWords();)
 798   assert(_gen_policy->is_concurrent_mark_sweep_policy(), "Unexpected policy type");
 799   CMSCollector* collector =
 800     new CMSCollector((ConcurrentMarkSweepGeneration*)_old_gen,
 801                      _rem_set,
 802                      _gen_policy->as_concurrent_mark_sweep_policy());
 803 
 804   if (collector == NULL || !collector->completed_initialization()) {
 805     if (collector) {
 806       delete collector;  // Be nice in embedded situation
 807     }
 808     vm_shutdown_during_initialization("Could not create CMS collector");
 809     return false;
 810   }
 811   return true;  // success
 812 }
 813 
 814 void GenCollectedHeap::collect_mostly_concurrent(GCCause::Cause cause) {
 815   assert(!Heap_lock->owned_by_self(), "Should not own Heap_lock");
 816 
 817   MutexLocker ml(Heap_lock);
 818   // Read the GC counts while holding the Heap_lock
 819   unsigned int full_gc_count_before = total_full_collections();
 820   unsigned int gc_count_before      = total_collections();
 821   {
 822     MutexUnlocker mu(Heap_lock);
 823     VM_GenCollectFullConcurrent op(gc_count_before, full_gc_count_before, cause);
 824     VMThread::execute(&op);
 825   }
 826 }
 827 #endif // INCLUDE_ALL_GCS
 828 
 829 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs) {
 830    do_full_collection(clear_all_soft_refs, OldGen);
 831 }
 832 
 833 void GenCollectedHeap::do_full_collection(bool clear_all_soft_refs,
 834                                           GenerationType last_generation) {
 835   GenerationType local_last_generation;
 836   if (!incremental_collection_will_fail(false /* don't consult_young */) &&
 837       gc_cause() == GCCause::_gc_locker) {
 838     local_last_generation = YoungGen;
 839   } else {
 840     local_last_generation = last_generation;
 841   }
 842 
 843   do_collection(true,                   // full
 844                 clear_all_soft_refs,    // clear_all_soft_refs
 845                 0,                      // size
 846                 false,                  // is_tlab
 847                 local_last_generation); // last_generation
 848   // Hack XXX FIX ME !!!
 849   // A scavenge may not have been attempted, or may have
 850   // been attempted and failed, because the old gen was too full
 851   if (local_last_generation == YoungGen && gc_cause() == GCCause::_gc_locker &&
 852       incremental_collection_will_fail(false /* don't consult_young */)) {
 853     log_debug(gc, jni)("GC locker: Trying a full collection because scavenge failed");
 854     // This time allow the old gen to be collected as well
 855     do_collection(true,                // full
 856                   clear_all_soft_refs, // clear_all_soft_refs
 857                   0,                   // size
 858                   false,               // is_tlab
 859                   OldGen);             // last_generation
 860   }
 861 }
 862 
 863 bool GenCollectedHeap::is_in_young(oop p) {
 864   bool result = ((HeapWord*)p) < _old_gen->reserved().start();
 865   assert(result == _young_gen->is_in_reserved(p),
 866          "incorrect test - result=%d, p=" INTPTR_FORMAT, result, p2i((void*)p));
 867   return result;
 868 }
 869 
 870 // Returns "TRUE" iff "p" points into the committed areas of the heap.
 871 bool GenCollectedHeap::is_in(const void* p) const {
 872   return _young_gen->is_in(p) || _old_gen->is_in(p);
 873 }
 874 
 875 #ifdef ASSERT
 876 // Don't implement this by using is_in_young().  This method is used
 877 // in some cases to check that is_in_young() is correct.
 878 bool GenCollectedHeap::is_in_partial_collection(const void* p) {
 879   assert(is_in_reserved(p) || p == NULL,
 880     "Does not work if address is non-null and outside of the heap");
 881   return p < _young_gen->reserved().end() && p != NULL;
 882 }
 883 #endif
 884 
 885 void GenCollectedHeap::oop_iterate_no_header(OopClosure* cl) {
 886   NoHeaderExtendedOopClosure no_header_cl(cl);
 887   oop_iterate(&no_header_cl);
 888 }
 889 
 890 void GenCollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
 891   _young_gen->oop_iterate(cl);
 892   _old_gen->oop_iterate(cl);
 893 }
 894 
 895 void GenCollectedHeap::object_iterate(ObjectClosure* cl) {
 896   _young_gen->object_iterate(cl);
 897   _old_gen->object_iterate(cl);
 898 }
 899 
 900 void GenCollectedHeap::safe_object_iterate(ObjectClosure* cl) {
 901   _young_gen->safe_object_iterate(cl);
 902   _old_gen->safe_object_iterate(cl);
 903 }
 904 
 905 Space* GenCollectedHeap::space_containing(const void* addr) const {
 906   Space* res = _young_gen->space_containing(addr);
 907   if (res != NULL) {
 908     return res;
 909   }
 910   res = _old_gen->space_containing(addr);
 911   assert(res != NULL, "Could not find containing space");
 912   return res;
 913 }
 914 
 915 HeapWord* GenCollectedHeap::block_start(const void* addr) const {
 916   assert(is_in_reserved(addr), "block_start of address outside of heap");
 917   if (_young_gen->is_in_reserved(addr)) {
 918     assert(_young_gen->is_in(addr), "addr should be in allocated part of generation");
 919     return _young_gen->block_start(addr);
 920   }
 921 
 922   assert(_old_gen->is_in_reserved(addr), "Some generation should contain the address");
 923   assert(_old_gen->is_in(addr), "addr should be in allocated part of generation");
 924   return _old_gen->block_start(addr);
 925 }
 926 
 927 size_t GenCollectedHeap::block_size(const HeapWord* addr) const {
 928   assert(is_in_reserved(addr), "block_size of address outside of heap");
 929   if (_young_gen->is_in_reserved(addr)) {
 930     assert(_young_gen->is_in(addr), "addr should be in allocated part of generation");
 931     return _young_gen->block_size(addr);
 932   }
 933 
 934   assert(_old_gen->is_in_reserved(addr), "Some generation should contain the address");
 935   assert(_old_gen->is_in(addr), "addr should be in allocated part of generation");
 936   return _old_gen->block_size(addr);
 937 }
 938 
 939 bool GenCollectedHeap::block_is_obj(const HeapWord* addr) const {
 940   assert(is_in_reserved(addr), "block_is_obj of address outside of heap");
 941   assert(block_start(addr) == addr, "addr must be a block start");
 942   if (_young_gen->is_in_reserved(addr)) {
 943     return _young_gen->block_is_obj(addr);
 944   }
 945 
 946   assert(_old_gen->is_in_reserved(addr), "Some generation should contain the address");
 947   return _old_gen->block_is_obj(addr);
 948 }
 949 
 950 bool GenCollectedHeap::supports_tlab_allocation() const {
 951   assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
 952   return _young_gen->supports_tlab_allocation();
 953 }
 954 
 955 size_t GenCollectedHeap::tlab_capacity(Thread* thr) const {
 956   assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
 957   if (_young_gen->supports_tlab_allocation()) {
 958     return _young_gen->tlab_capacity();
 959   }
 960   return 0;
 961 }
 962 
 963 size_t GenCollectedHeap::tlab_used(Thread* thr) const {
 964   assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
 965   if (_young_gen->supports_tlab_allocation()) {
 966     return _young_gen->tlab_used();
 967   }
 968   return 0;
 969 }
 970 
 971 size_t GenCollectedHeap::unsafe_max_tlab_alloc(Thread* thr) const {
 972   assert(!_old_gen->supports_tlab_allocation(), "Old gen supports TLAB allocation?!");
 973   if (_young_gen->supports_tlab_allocation()) {
 974     return _young_gen->unsafe_max_tlab_alloc();
 975   }
 976   return 0;
 977 }
 978 
 979 HeapWord* GenCollectedHeap::allocate_new_tlab(size_t size) {
 980   bool gc_overhead_limit_was_exceeded;
 981   return gen_policy()->mem_allocate_work(size /* size */,
 982                                          true /* is_tlab */,
 983                                          &gc_overhead_limit_was_exceeded);
 984 }
 985 
 986 // Requires "*prev_ptr" to be non-NULL.  Deletes and a block of minimal size
 987 // from the list headed by "*prev_ptr".
 988 static ScratchBlock *removeSmallestScratch(ScratchBlock **prev_ptr) {
 989   bool first = true;
 990   size_t min_size = 0;   // "first" makes this conceptually infinite.
 991   ScratchBlock **smallest_ptr, *smallest;
 992   ScratchBlock  *cur = *prev_ptr;
 993   while (cur) {
 994     assert(*prev_ptr == cur, "just checking");
 995     if (first || cur->num_words < min_size) {
 996       smallest_ptr = prev_ptr;
 997       smallest     = cur;
 998       min_size     = smallest->num_words;
 999       first        = false;
1000     }
1001     prev_ptr = &cur->next;
1002     cur     =  cur->next;
1003   }
1004   smallest      = *smallest_ptr;
1005   *smallest_ptr = smallest->next;
1006   return smallest;
1007 }
1008 
1009 // Sort the scratch block list headed by res into decreasing size order,
1010 // and set "res" to the result.
1011 static void sort_scratch_list(ScratchBlock*& list) {
1012   ScratchBlock* sorted = NULL;
1013   ScratchBlock* unsorted = list;
1014   while (unsorted) {
1015     ScratchBlock *smallest = removeSmallestScratch(&unsorted);
1016     smallest->next  = sorted;
1017     sorted          = smallest;
1018   }
1019   list = sorted;
1020 }
1021 
1022 ScratchBlock* GenCollectedHeap::gather_scratch(Generation* requestor,
1023                                                size_t max_alloc_words) {
1024   ScratchBlock* res = NULL;
1025   _young_gen->contribute_scratch(res, requestor, max_alloc_words);
1026   _old_gen->contribute_scratch(res, requestor, max_alloc_words);
1027   sort_scratch_list(res);
1028   return res;
1029 }
1030 
1031 void GenCollectedHeap::release_scratch() {
1032   _young_gen->reset_scratch();
1033   _old_gen->reset_scratch();
1034 }
1035 
1036 class GenPrepareForVerifyClosure: public GenCollectedHeap::GenClosure {
1037   void do_generation(Generation* gen) {
1038     gen->prepare_for_verify();
1039   }
1040 };
1041 
1042 void GenCollectedHeap::prepare_for_verify() {
1043   ensure_parsability(false);        // no need to retire TLABs
1044   GenPrepareForVerifyClosure blk;
1045   generation_iterate(&blk, false);
1046 }
1047 
1048 void GenCollectedHeap::generation_iterate(GenClosure* cl,
1049                                           bool old_to_young) {
1050   if (old_to_young) {
1051     cl->do_generation(_old_gen);
1052     cl->do_generation(_young_gen);
1053   } else {
1054     cl->do_generation(_young_gen);
1055     cl->do_generation(_old_gen);
1056   }
1057 }
1058 
1059 bool GenCollectedHeap::is_maximal_no_gc() const {
1060   return _young_gen->is_maximal_no_gc() && _old_gen->is_maximal_no_gc();
1061 }
1062 
1063 void GenCollectedHeap::save_marks() {
1064   _young_gen->save_marks();
1065   _old_gen->save_marks();
1066 }
1067 
1068 GenCollectedHeap* GenCollectedHeap::heap() {
1069   CollectedHeap* heap = Universe::heap();
1070   assert(heap != NULL, "Uninitialized access to GenCollectedHeap::heap()");
1071   assert(heap->kind() == CollectedHeap::GenCollectedHeap, "Not a GenCollectedHeap");
1072   return (GenCollectedHeap*)heap;
1073 }
1074 
1075 void GenCollectedHeap::prepare_for_compaction() {
1076   // Start by compacting into same gen.
1077   CompactPoint cp(_old_gen);
1078   _old_gen->prepare_for_compaction(&cp);
1079   _young_gen->prepare_for_compaction(&cp);
1080 }
1081 
1082 void GenCollectedHeap::verify(VerifyOption option /* ignored */) {
1083   log_debug(gc, verify)("%s", _old_gen->name());
1084   _old_gen->verify();
1085 
1086   log_debug(gc, verify)("%s", _old_gen->name());
1087   _young_gen->verify();
1088 
1089   log_debug(gc, verify)("RemSet");
1090   rem_set()->verify();
1091 }
1092 
1093 void GenCollectedHeap::print_on(outputStream* st) const {
1094   _young_gen->print_on(st);
1095   _old_gen->print_on(st);
1096   MetaspaceAux::print_on(st);
1097 }
1098 
1099 void GenCollectedHeap::gc_threads_do(ThreadClosure* tc) const {
1100   if (workers() != NULL) {
1101     workers()->threads_do(tc);
1102   }
1103 #if INCLUDE_ALL_GCS
1104   if (UseConcMarkSweepGC) {
1105     ConcurrentMarkSweepThread::threads_do(tc);
1106   }
1107 #endif // INCLUDE_ALL_GCS
1108 }
1109 
1110 void GenCollectedHeap::print_gc_threads_on(outputStream* st) const {
1111 #if INCLUDE_ALL_GCS
1112   if (UseConcMarkSweepGC) {
1113     workers()->print_worker_threads_on(st);
1114     ConcurrentMarkSweepThread::print_all_on(st);
1115   }
1116 #endif // INCLUDE_ALL_GCS
1117 }
1118 
1119 void GenCollectedHeap::print_on_error(outputStream* st) const {
1120   this->CollectedHeap::print_on_error(st);
1121 
1122 #if INCLUDE_ALL_GCS
1123   if (UseConcMarkSweepGC) {
1124     st->cr();
1125     CMSCollector::print_on_error(st);
1126   }
1127 #endif // INCLUDE_ALL_GCS
1128 }
1129 
1130 void GenCollectedHeap::print_tracing_info() const {
1131   if (TraceYoungGenTime) {
1132     _young_gen->print_summary_info();
1133   }
1134   if (TraceOldGenTime) {
1135     _old_gen->print_summary_info();
1136   }
1137 }
1138 
1139 void GenCollectedHeap::print_heap_change(size_t young_prev_used, size_t old_prev_used) const {
1140   log_info(gc, heap)("%s: " SIZE_FORMAT "K->" SIZE_FORMAT "K("  SIZE_FORMAT "K)",
1141                      _young_gen->short_name(), young_prev_used / K, _young_gen->used() /K, _young_gen->capacity() /K);
1142   log_info(gc, heap)("%s: " SIZE_FORMAT "K->" SIZE_FORMAT "K("  SIZE_FORMAT "K)",
1143                      _old_gen->short_name(), old_prev_used / K, _old_gen->used() /K, _old_gen->capacity() /K);
1144 }
1145 
1146 class GenGCPrologueClosure: public GenCollectedHeap::GenClosure {
1147  private:
1148   bool _full;
1149  public:
1150   void do_generation(Generation* gen) {
1151     gen->gc_prologue(_full);
1152   }
1153   GenGCPrologueClosure(bool full) : _full(full) {};
1154 };
1155 
1156 void GenCollectedHeap::gc_prologue(bool full) {
1157   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
1158 
1159   always_do_update_barrier = false;
1160   // Fill TLAB's and such
1161   CollectedHeap::accumulate_statistics_all_tlabs();
1162   ensure_parsability(true);   // retire TLABs
1163 
1164   // Walk generations
1165   GenGCPrologueClosure blk(full);
1166   generation_iterate(&blk, false);  // not old-to-young.
1167 };
1168 
1169 class GenGCEpilogueClosure: public GenCollectedHeap::GenClosure {
1170  private:
1171   bool _full;
1172  public:
1173   void do_generation(Generation* gen) {
1174     gen->gc_epilogue(_full);
1175   }
1176   GenGCEpilogueClosure(bool full) : _full(full) {};
1177 };
1178 
1179 void GenCollectedHeap::gc_epilogue(bool full) {
1180 #if defined(COMPILER2) || INCLUDE_JVMCI
1181   assert(DerivedPointerTable::is_empty(), "derived pointer present");
1182   size_t actual_gap = pointer_delta((HeapWord*) (max_uintx-3), *(end_addr()));
1183   guarantee(actual_gap > (size_t)FastAllocateSizeLimit, "inline allocation wraps");
1184 #endif /* COMPILER2 || INCLUDE_JVMCI */
1185 
1186   resize_all_tlabs();
1187 
1188   GenGCEpilogueClosure blk(full);
1189   generation_iterate(&blk, false);  // not old-to-young.
1190 
1191   if (!CleanChunkPoolAsync) {
1192     Chunk::clean_chunk_pool();
1193   }
1194 
1195   MetaspaceCounters::update_performance_counters();
1196   CompressedClassSpaceCounters::update_performance_counters();
1197 
1198   always_do_update_barrier = UseConcMarkSweepGC;
1199 };
1200 
1201 #ifndef PRODUCT
1202 class GenGCSaveTopsBeforeGCClosure: public GenCollectedHeap::GenClosure {
1203  private:
1204  public:
1205   void do_generation(Generation* gen) {
1206     gen->record_spaces_top();
1207   }
1208 };
1209 
1210 void GenCollectedHeap::record_gen_tops_before_GC() {
1211   if (ZapUnusedHeapArea) {
1212     GenGCSaveTopsBeforeGCClosure blk;
1213     generation_iterate(&blk, false);  // not old-to-young.
1214   }
1215 }
1216 #endif  // not PRODUCT
1217 
1218 class GenEnsureParsabilityClosure: public GenCollectedHeap::GenClosure {
1219  public:
1220   void do_generation(Generation* gen) {
1221     gen->ensure_parsability();
1222   }
1223 };
1224 
1225 void GenCollectedHeap::ensure_parsability(bool retire_tlabs) {
1226   CollectedHeap::ensure_parsability(retire_tlabs);
1227   GenEnsureParsabilityClosure ep_cl;
1228   generation_iterate(&ep_cl, false);
1229 }
1230 
1231 oop GenCollectedHeap::handle_failed_promotion(Generation* old_gen,
1232                                               oop obj,
1233                                               size_t obj_size) {
1234   guarantee(old_gen == _old_gen, "We only get here with an old generation");
1235   assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
1236   HeapWord* result = NULL;
1237 
1238   result = old_gen->expand_and_allocate(obj_size, false);
1239 
1240   if (result != NULL) {
1241     Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size);
1242   }
1243   return oop(result);
1244 }
1245 
1246 class GenTimeOfLastGCClosure: public GenCollectedHeap::GenClosure {
1247   jlong _time;   // in ms
1248   jlong _now;    // in ms
1249 
1250  public:
1251   GenTimeOfLastGCClosure(jlong now) : _time(now), _now(now) { }
1252 
1253   jlong time() { return _time; }
1254 
1255   void do_generation(Generation* gen) {
1256     _time = MIN2(_time, gen->time_of_last_gc(_now));
1257   }
1258 };
1259 
1260 jlong GenCollectedHeap::millis_since_last_gc() {
1261   // We need a monotonically non-decreasing time in ms but
1262   // os::javaTimeMillis() does not guarantee monotonicity.
1263   jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
1264   GenTimeOfLastGCClosure tolgc_cl(now);
1265   // iterate over generations getting the oldest
1266   // time that a generation was collected
1267   generation_iterate(&tolgc_cl, false);
1268 
1269   // javaTimeNanos() is guaranteed to be monotonically non-decreasing
1270   // provided the underlying platform provides such a time source
1271   // (and it is bug free). So we still have to guard against getting
1272   // back a time later than 'now'.
1273   jlong retVal = now - tolgc_cl.time();
1274   if (retVal < 0) {
1275     NOT_PRODUCT(warning("time warp: " JLONG_FORMAT, retVal);)
1276     return 0;
1277   }
1278   return retVal;
1279 }
1280 
1281 void GenCollectedHeap::stop() {
1282 #if INCLUDE_ALL_GCS
1283   if (UseConcMarkSweepGC) {
1284     ConcurrentMarkSweepThread::stop();
1285   }
1286 #endif
1287 }
--- EOF ---