1 /*
   2  * Copyright (c) 2002, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/stringTable.hpp"
  27 #include "code/codeCache.hpp"
  28 #include "gc/parallel/cardTableExtension.hpp"
  29 #include "gc/parallel/gcTaskManager.hpp"
  30 #include "gc/parallel/parallelScavengeHeap.hpp"
  31 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
  32 #include "gc/parallel/psMarkSweep.hpp"
  33 #include "gc/parallel/psParallelCompact.hpp"
  34 #include "gc/parallel/psScavenge.inline.hpp"
  35 #include "gc/parallel/psTasks.hpp"
  36 #include "gc/shared/collectorPolicy.hpp"
  37 #include "gc/shared/gcCause.hpp"
  38 #include "gc/shared/gcHeapSummary.hpp"
  39 #include "gc/shared/gcLocker.inline.hpp"
  40 #include "gc/shared/gcTimer.hpp"
  41 #include "gc/shared/gcTrace.hpp"
  42 #include "gc/shared/gcTraceTime.hpp"
  43 #include "gc/shared/isGCActiveMark.hpp"
  44 #include "gc/shared/referencePolicy.hpp"
  45 #include "gc/shared/referenceProcessor.hpp"
  46 #include "gc/shared/spaceDecorator.hpp"
  47 #include "memory/resourceArea.hpp"
  48 #include "oops/oop.inline.hpp"
  49 #include "runtime/biasedLocking.hpp"
  50 #include "runtime/fprofiler.hpp"
  51 #include "runtime/handles.inline.hpp"
  52 #include "runtime/threadCritical.hpp"
  53 #include "runtime/vmThread.hpp"
  54 #include "runtime/vm_operations.hpp"
  55 #include "services/memoryService.hpp"
  56 #include "utilities/stack.inline.hpp"
  57 
  58 HeapWord*                  PSScavenge::_to_space_top_before_gc = NULL;
  59 int                        PSScavenge::_consecutive_skipped_scavenges = 0;
  60 ReferenceProcessor*        PSScavenge::_ref_processor = NULL;
  61 CardTableExtension*        PSScavenge::_card_table = NULL;
  62 bool                       PSScavenge::_survivor_overflow = false;
  63 uint                       PSScavenge::_tenuring_threshold = 0;
  64 HeapWord*                  PSScavenge::_young_generation_boundary = NULL;
  65 uintptr_t                  PSScavenge::_young_generation_boundary_compressed = 0;
  66 elapsedTimer               PSScavenge::_accumulated_time;
  67 STWGCTimer                 PSScavenge::_gc_timer;
  68 ParallelScavengeTracer     PSScavenge::_gc_tracer;
  69 Stack<markOop, mtGC>       PSScavenge::_preserved_mark_stack;
  70 Stack<oop, mtGC>           PSScavenge::_preserved_oop_stack;
  71 CollectorCounters*         PSScavenge::_counters = NULL;
  72 
  73 // Define before use
  74 class PSIsAliveClosure: public BoolObjectClosure {
  75 public:
  76   bool do_object_b(oop p) {
  77     return (!PSScavenge::is_obj_in_young(p)) || p->is_forwarded();
  78   }
  79 };
  80 
  81 PSIsAliveClosure PSScavenge::_is_alive_closure;
  82 
  83 class PSKeepAliveClosure: public OopClosure {
  84 protected:
  85   MutableSpace* _to_space;
  86   PSPromotionManager* _promotion_manager;
  87 
  88 public:
  89   PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
  90     ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
  91     _to_space = heap->young_gen()->to_space();
  92 
  93     assert(_promotion_manager != NULL, "Sanity");
  94   }
  95 
  96   template <class T> void do_oop_work(T* p) {
  97     assert (!oopDesc::is_null(*p), "expected non-null ref");
  98     assert ((oopDesc::load_decode_heap_oop_not_null(p))->is_oop(),
  99             "expected an oop while scanning weak refs");
 100 
 101     // Weak refs may be visited more than once.
 102     if (PSScavenge::should_scavenge(p, _to_space)) {
 103       _promotion_manager->copy_and_push_safe_barrier<T, /*promote_immediately=*/false>(p);
 104     }
 105   }
 106   virtual void do_oop(oop* p)       { PSKeepAliveClosure::do_oop_work(p); }
 107   virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
 108 };
 109 
 110 class PSEvacuateFollowersClosure: public VoidClosure {
 111  private:
 112   PSPromotionManager* _promotion_manager;
 113  public:
 114   PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}
 115 
 116   virtual void do_void() {
 117     assert(_promotion_manager != NULL, "Sanity");
 118     _promotion_manager->drain_stacks(true);
 119     guarantee(_promotion_manager->stacks_empty(),
 120               "stacks should be empty at this point");
 121   }
 122 };
 123 
 124 class PSPromotionFailedClosure : public ObjectClosure {
 125   virtual void do_object(oop obj) {
 126     if (obj->is_forwarded()) {
 127       obj->init_mark();
 128     }
 129   }
 130 };
 131 
 132 class PSRefProcTaskProxy: public GCTask {
 133   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
 134   ProcessTask & _rp_task;
 135   uint          _work_id;
 136 public:
 137   PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id)
 138     : _rp_task(rp_task),
 139       _work_id(work_id)
 140   { }
 141 
 142 private:
 143   virtual char* name() { return (char *)"Process referents by policy in parallel"; }
 144   virtual void do_it(GCTaskManager* manager, uint which);
 145 };
 146 
 147 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which)
 148 {
 149   PSPromotionManager* promotion_manager =
 150     PSPromotionManager::gc_thread_promotion_manager(which);
 151   assert(promotion_manager != NULL, "sanity check");
 152   PSKeepAliveClosure keep_alive(promotion_manager);
 153   PSEvacuateFollowersClosure evac_followers(promotion_manager);
 154   PSIsAliveClosure is_alive;
 155   _rp_task.work(_work_id, is_alive, keep_alive, evac_followers);
 156 }
 157 
 158 class PSRefEnqueueTaskProxy: public GCTask {
 159   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
 160   EnqueueTask& _enq_task;
 161   uint         _work_id;
 162 
 163 public:
 164   PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id)
 165     : _enq_task(enq_task),
 166       _work_id(work_id)
 167   { }
 168 
 169   virtual char* name() { return (char *)"Enqueue reference objects in parallel"; }
 170   virtual void do_it(GCTaskManager* manager, uint which)
 171   {
 172     _enq_task.work(_work_id);
 173   }
 174 };
 175 
 176 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
 177   virtual void execute(ProcessTask& task);
 178   virtual void execute(EnqueueTask& task);
 179 };
 180 
 181 void PSRefProcTaskExecutor::execute(ProcessTask& task)
 182 {
 183   GCTaskQueue* q = GCTaskQueue::create();
 184   GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
 185   for(uint i=0; i < manager->active_workers(); i++) {
 186     q->enqueue(new PSRefProcTaskProxy(task, i));
 187   }
 188   ParallelTaskTerminator terminator(manager->active_workers(),
 189                  (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth());
 190   if (task.marks_oops_alive() && manager->active_workers() > 1) {
 191     for (uint j = 0; j < manager->active_workers(); j++) {
 192       q->enqueue(new StealTask(&terminator));
 193     }
 194   }
 195   manager->execute_and_wait(q);
 196 }
 197 
 198 
 199 void PSRefProcTaskExecutor::execute(EnqueueTask& task)
 200 {
 201   GCTaskQueue* q = GCTaskQueue::create();
 202   GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
 203   for(uint i=0; i < manager->active_workers(); i++) {
 204     q->enqueue(new PSRefEnqueueTaskProxy(task, i));
 205   }
 206   manager->execute_and_wait(q);
 207 }
 208 
 209 // This method contains all heap specific policy for invoking scavenge.
 210 // PSScavenge::invoke_no_policy() will do nothing but attempt to
 211 // scavenge. It will not clean up after failed promotions, bail out if
 212 // we've exceeded policy time limits, or any other special behavior.
 213 // All such policy should be placed here.
 214 //
 215 // Note that this method should only be called from the vm_thread while
 216 // at a safepoint!
 217 bool PSScavenge::invoke() {
 218   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 219   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
 220   assert(!ParallelScavengeHeap::heap()->is_gc_active(), "not reentrant");
 221 
 222   ParallelScavengeHeap* const heap = ParallelScavengeHeap::heap();
 223   PSAdaptiveSizePolicy* policy = heap->size_policy();
 224   IsGCActiveMark mark;
 225 
 226   const bool scavenge_done = PSScavenge::invoke_no_policy();
 227   const bool need_full_gc = !scavenge_done ||
 228     policy->should_full_GC(heap->old_gen()->free_in_bytes());
 229   bool full_gc_done = false;
 230 
 231   if (UsePerfData) {
 232     PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
 233     const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped;
 234     counters->update_full_follows_scavenge(ffs_val);
 235   }
 236 
 237   if (need_full_gc) {
 238     GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
 239     CollectorPolicy* cp = heap->collector_policy();
 240     const bool clear_all_softrefs = cp->should_clear_all_soft_refs();
 241 
 242     if (UseParallelOldGC) {
 243       full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs);
 244     } else {
 245       full_gc_done = PSMarkSweep::invoke_no_policy(clear_all_softrefs);
 246     }
 247   }
 248 
 249   return full_gc_done;
 250 }
 251 
 252 // This method contains no policy. You should probably
 253 // be calling invoke() instead.
 254 bool PSScavenge::invoke_no_policy() {
 255   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 256   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
 257 
 258   assert(_preserved_mark_stack.is_empty(), "should be empty");
 259   assert(_preserved_oop_stack.is_empty(), "should be empty");
 260 
 261   _gc_timer.register_gc_start();
 262 
 263   TimeStamp scavenge_entry;
 264   TimeStamp scavenge_midpoint;
 265   TimeStamp scavenge_exit;
 266 
 267   scavenge_entry.update();
 268 
 269   if (GC_locker::check_active_before_gc()) {
 270     return false;
 271   }
 272 
 273   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 274   GCCause::Cause gc_cause = heap->gc_cause();
 275 
 276   // Check for potential problems.
 277   if (!should_attempt_scavenge()) {
 278     return false;
 279   }
 280 
 281   _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
 282 
 283   bool promotion_failure_occurred = false;
 284 
 285   PSYoungGen* young_gen = heap->young_gen();
 286   PSOldGen* old_gen = heap->old_gen();
 287   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
 288 
 289   heap->increment_total_collections();
 290 
 291   AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
 292 
 293   if (AdaptiveSizePolicy::should_update_eden_stats(gc_cause)) {
 294     // Gather the feedback data for eden occupancy.
 295     young_gen->eden_space()->accumulate_statistics();
 296   }
 297 
 298   if (ZapUnusedHeapArea) {
 299     // Save information needed to minimize mangling
 300     heap->record_gen_tops_before_GC();
 301   }
 302 
 303   heap->print_heap_before_gc();
 304   heap->trace_heap_before_gc(&_gc_tracer);
 305 
 306   assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
 307   assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
 308 
 309   size_t prev_used = heap->used();
 310 
 311   // Fill in TLABs
 312   heap->accumulate_statistics_all_tlabs();
 313   heap->ensure_parsability(true);  // retire TLABs
 314 
 315   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
 316     HandleMark hm;  // Discard invalid handles created during verification
 317     Universe::verify(" VerifyBeforeGC:");
 318   }
 319 
 320   {
 321     ResourceMark rm;
 322     HandleMark hm;
 323 
 324     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
 325     GCTraceTime t1(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, NULL, _gc_tracer.gc_id());
 326     TraceCollectorStats tcs(counters());
 327     TraceMemoryManagerStats tms(false /* not full GC */,gc_cause);
 328 
 329     if (TraceYoungGenTime) accumulated_time()->start();
 330 
 331     // Let the size policy know we're starting
 332     size_policy->minor_collection_begin();
 333 
 334     // Verify the object start arrays.
 335     if (VerifyObjectStartArray &&
 336         VerifyBeforeGC) {
 337       old_gen->verify_object_start_array();
 338     }
 339 
 340     // Verify no unmarked old->young roots
 341     if (VerifyRememberedSets) {
 342       CardTableExtension::verify_all_young_refs_imprecise();
 343     }
 344 
 345     if (!ScavengeWithObjectsInToSpace) {
 346       assert(young_gen->to_space()->is_empty(),
 347              "Attempt to scavenge with live objects in to_space");
 348       young_gen->to_space()->clear(SpaceDecorator::Mangle);
 349     } else if (ZapUnusedHeapArea) {
 350       young_gen->to_space()->mangle_unused_area();
 351     }
 352     save_to_space_top_before_gc();
 353 
 354 #if defined(COMPILER2) || INCLUDE_JVMCI
 355     DerivedPointerTable::clear();
 356 #endif
 357 
 358     reference_processor()->enable_discovery();
 359     reference_processor()->setup_policy(false);
 360 
 361     // We track how much was promoted to the next generation for
 362     // the AdaptiveSizePolicy.
 363     size_t old_gen_used_before = old_gen->used_in_bytes();
 364 
 365     // For PrintGCDetails
 366     size_t young_gen_used_before = young_gen->used_in_bytes();
 367 
 368     // Reset our survivor overflow.
 369     set_survivor_overflow(false);
 370 
 371     // We need to save the old top values before
 372     // creating the promotion_manager. We pass the top
 373     // values to the card_table, to prevent it from
 374     // straying into the promotion labs.
 375     HeapWord* old_top = old_gen->object_space()->top();
 376 
 377     // Release all previously held resources
 378     gc_task_manager()->release_all_resources();
 379 
 380     // Set the number of GC threads to be used in this collection
 381     gc_task_manager()->set_active_gang();
 382     gc_task_manager()->task_idle_workers();
 383     // Get the active number of workers here and use that value
 384     // throughout the methods.
 385     uint active_workers = gc_task_manager()->active_workers();
 386 
 387     PSPromotionManager::pre_scavenge();
 388 
 389     // We'll use the promotion manager again later.
 390     PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
 391     {
 392       GCTraceTime tm("Scavenge", false, false, &_gc_timer, _gc_tracer.gc_id());
 393       ParallelScavengeHeap::ParStrongRootsScope psrs;
 394 
 395       GCTaskQueue* q = GCTaskQueue::create();
 396 
 397       if (!old_gen->object_space()->is_empty()) {
 398         // There are only old-to-young pointers if there are objects
 399         // in the old gen.
 400         uint stripe_total = active_workers;
 401         for(uint i=0; i < stripe_total; i++) {
 402           q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));
 403         }
 404       }
 405 
 406       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
 407       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
 408       // We scan the thread roots in parallel
 409       Threads::create_thread_roots_tasks(q);
 410       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
 411       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));
 412       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
 413       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
 414       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::class_loader_data));
 415       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
 416       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
 417 
 418       ParallelTaskTerminator terminator(
 419         active_workers,
 420                   (TaskQueueSetSuper*) promotion_manager->stack_array_depth());
 421       if (active_workers > 1) {
 422         for (uint j = 0; j < active_workers; j++) {
 423           q->enqueue(new StealTask(&terminator));
 424         }
 425       }
 426 
 427       gc_task_manager()->execute_and_wait(q);
 428     }
 429 
 430     scavenge_midpoint.update();
 431 
 432     // Process reference objects discovered during scavenge
 433     {
 434       GCTraceTime tm("References", false, false, &_gc_timer, _gc_tracer.gc_id());
 435 
 436       reference_processor()->setup_policy(false); // not always_clear
 437       reference_processor()->set_active_mt_degree(active_workers);
 438       PSKeepAliveClosure keep_alive(promotion_manager);
 439       PSEvacuateFollowersClosure evac_followers(promotion_manager);
 440       ReferenceProcessorStats stats;
 441       if (reference_processor()->processing_is_mt()) {
 442         PSRefProcTaskExecutor task_executor;
 443         stats = reference_processor()->process_discovered_references(
 444           &_is_alive_closure, &keep_alive, &evac_followers, &task_executor,
 445           &_gc_timer, _gc_tracer.gc_id());
 446       } else {
 447         stats = reference_processor()->process_discovered_references(
 448           &_is_alive_closure, &keep_alive, &evac_followers, NULL, &_gc_timer, _gc_tracer.gc_id());
 449       }
 450 
 451       _gc_tracer.report_gc_reference_stats(stats);
 452 
 453       // Enqueue reference objects discovered during scavenge.
 454       if (reference_processor()->processing_is_mt()) {
 455         PSRefProcTaskExecutor task_executor;
 456         reference_processor()->enqueue_discovered_references(&task_executor);
 457       } else {
 458         reference_processor()->enqueue_discovered_references(NULL);
 459       }
 460     }
 461 
 462     {
 463       GCTraceTime tm("StringTable", false, false, &_gc_timer, _gc_tracer.gc_id());
 464       // Unlink any dead interned Strings and process the remaining live ones.
 465       PSScavengeRootsClosure root_closure(promotion_manager);
 466       StringTable::unlink_or_oops_do(&_is_alive_closure, &root_closure);
 467     }
 468 
 469     // Finally, flush the promotion_manager's labs, and deallocate its stacks.
 470     promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer);
 471     if (promotion_failure_occurred) {
 472       clean_up_failed_promotion();
 473       if (PrintGC) {
 474         gclog_or_tty->print("--");
 475       }
 476     }
 477 
 478     // Let the size policy know we're done.  Note that we count promotion
 479     // failure cleanup time as part of the collection (otherwise, we're
 480     // implicitly saying it's mutator time).
 481     size_policy->minor_collection_end(gc_cause);
 482 
 483     if (!promotion_failure_occurred) {
 484       // Swap the survivor spaces.
 485       young_gen->eden_space()->clear(SpaceDecorator::Mangle);
 486       young_gen->from_space()->clear(SpaceDecorator::Mangle);
 487       young_gen->swap_spaces();
 488 
 489       size_t survived = young_gen->from_space()->used_in_bytes();
 490       size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
 491       size_policy->update_averages(_survivor_overflow, survived, promoted);
 492 
 493       // A successful scavenge should restart the GC time limit count which is
 494       // for full GC's.
 495       size_policy->reset_gc_overhead_limit_count();
 496       if (UseAdaptiveSizePolicy) {
 497         // Calculate the new survivor size and tenuring threshold
 498 
 499         if (PrintAdaptiveSizePolicy) {
 500           gclog_or_tty->print("AdaptiveSizeStart: ");
 501           gclog_or_tty->stamp();
 502           gclog_or_tty->print_cr(" collection: %d ",
 503                          heap->total_collections());
 504 
 505           if (Verbose) {
 506             gclog_or_tty->print("old_gen_capacity: " SIZE_FORMAT
 507               " young_gen_capacity: " SIZE_FORMAT,
 508               old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
 509           }
 510         }
 511 
 512 
 513         if (UsePerfData) {
 514           PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 515           counters->update_old_eden_size(
 516             size_policy->calculated_eden_size_in_bytes());
 517           counters->update_old_promo_size(
 518             size_policy->calculated_promo_size_in_bytes());
 519           counters->update_old_capacity(old_gen->capacity_in_bytes());
 520           counters->update_young_capacity(young_gen->capacity_in_bytes());
 521           counters->update_survived(survived);
 522           counters->update_promoted(promoted);
 523           counters->update_survivor_overflowed(_survivor_overflow);
 524         }
 525 
 526         size_t max_young_size = young_gen->max_size();
 527 
 528         // Deciding a free ratio in the young generation is tricky, so if
 529         // MinHeapFreeRatio or MaxHeapFreeRatio are in use (implicating
 530         // that the old generation size may have been limited because of them) we
 531         // should then limit our young generation size using NewRatio to have it
 532         // follow the old generation size.
 533         if (MinHeapFreeRatio != 0 || MaxHeapFreeRatio != 100) {
 534           max_young_size = MIN2(old_gen->capacity_in_bytes() / NewRatio, young_gen->max_size());
 535         }
 536 
 537         size_t survivor_limit =
 538           size_policy->max_survivor_size(max_young_size);
 539         _tenuring_threshold =
 540           size_policy->compute_survivor_space_size_and_threshold(
 541                                                            _survivor_overflow,
 542                                                            _tenuring_threshold,
 543                                                            survivor_limit);
 544 
 545        if (PrintTenuringDistribution) {
 546          gclog_or_tty->cr();
 547          gclog_or_tty->print_cr("Desired survivor size " SIZE_FORMAT " bytes, new threshold %u"
 548                                 " (max threshold " UINTX_FORMAT ")",
 549                                 size_policy->calculated_survivor_size_in_bytes(),
 550                                 _tenuring_threshold, MaxTenuringThreshold);
 551        }
 552 
 553         if (UsePerfData) {
 554           PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 555           counters->update_tenuring_threshold(_tenuring_threshold);
 556           counters->update_survivor_size_counters();
 557         }
 558 
 559         // Do call at minor collections?
 560         // Don't check if the size_policy is ready at this
 561         // level.  Let the size_policy check that internally.
 562         if (UseAdaptiveGenerationSizePolicyAtMinorCollection &&
 563             (AdaptiveSizePolicy::should_update_eden_stats(gc_cause))) {
 564           // Calculate optimal free space amounts
 565           assert(young_gen->max_size() >
 566             young_gen->from_space()->capacity_in_bytes() +
 567             young_gen->to_space()->capacity_in_bytes(),
 568             "Sizes of space in young gen are out-of-bounds");
 569 
 570           size_t young_live = young_gen->used_in_bytes();
 571           size_t eden_live = young_gen->eden_space()->used_in_bytes();
 572           size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
 573           size_t max_old_gen_size = old_gen->max_gen_size();
 574           size_t max_eden_size = max_young_size -
 575             young_gen->from_space()->capacity_in_bytes() -
 576             young_gen->to_space()->capacity_in_bytes();
 577 
 578           // Used for diagnostics
 579           size_policy->clear_generation_free_space_flags();
 580 
 581           size_policy->compute_eden_space_size(young_live,
 582                                                eden_live,
 583                                                cur_eden,
 584                                                max_eden_size,
 585                                                false /* not full gc*/);
 586 
 587           size_policy->check_gc_overhead_limit(young_live,
 588                                                eden_live,
 589                                                max_old_gen_size,
 590                                                max_eden_size,
 591                                                false /* not full gc*/,
 592                                                gc_cause,
 593                                                heap->collector_policy());
 594 
 595           size_policy->decay_supplemental_growth(false /* not full gc*/);
 596         }
 597         // Resize the young generation at every collection
 598         // even if new sizes have not been calculated.  This is
 599         // to allow resizes that may have been inhibited by the
 600         // relative location of the "to" and "from" spaces.
 601 
 602         // Resizing the old gen at young collections can cause increases
 603         // that don't feed back to the generation sizing policy until
 604         // a full collection.  Don't resize the old gen here.
 605 
 606         heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
 607                         size_policy->calculated_survivor_size_in_bytes());
 608 
 609         if (PrintAdaptiveSizePolicy) {
 610           gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
 611                          heap->total_collections());
 612         }
 613       }
 614 
 615       // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
 616       // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
 617       // Also update() will case adaptive NUMA chunk resizing.
 618       assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
 619       young_gen->eden_space()->update();
 620 
 621       heap->gc_policy_counters()->update_counters();
 622 
 623       heap->resize_all_tlabs();
 624 
 625       assert(young_gen->to_space()->is_empty(), "to space should be empty now");
 626     }
 627 
 628 #if defined(COMPILER2) || INCLUDE_JVMCI
 629     DerivedPointerTable::update_pointers();
 630 #endif
 631 
 632     NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
 633 
 634     {
 635       GCTraceTime tm("Prune Scavenge Root Methods", false, false, &_gc_timer, _gc_tracer.gc_id());
 636 
 637       CodeCache::prune_scavenge_root_nmethods();
 638     }
 639 
 640     // Re-verify object start arrays
 641     if (VerifyObjectStartArray &&
 642         VerifyAfterGC) {
 643       old_gen->verify_object_start_array();
 644     }
 645 
 646     // Verify all old -> young cards are now precise
 647     if (VerifyRememberedSets) {
 648       // Precise verification will give false positives. Until this is fixed,
 649       // use imprecise verification.
 650       // CardTableExtension::verify_all_young_refs_precise();
 651       CardTableExtension::verify_all_young_refs_imprecise();
 652     }
 653 
 654     if (TraceYoungGenTime) accumulated_time()->stop();
 655 
 656     if (PrintGC) {
 657       if (PrintGCDetails) {
 658         // Don't print a GC timestamp here.  This is after the GC so
 659         // would be confusing.
 660         young_gen->print_used_change(young_gen_used_before);
 661       }
 662       heap->print_heap_change(prev_used);
 663     }
 664 
 665     // Track memory usage and detect low memory
 666     MemoryService::track_memory_usage();
 667     heap->update_counters();
 668 
 669     gc_task_manager()->release_idle_workers();
 670   }
 671 
 672   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
 673     HandleMark hm;  // Discard invalid handles created during verification
 674     Universe::verify(" VerifyAfterGC:");
 675   }
 676 
 677   heap->print_heap_after_gc();
 678   heap->trace_heap_after_gc(&_gc_tracer);
 679   _gc_tracer.report_tenuring_threshold(tenuring_threshold());
 680 
 681   if (ZapUnusedHeapArea) {
 682     young_gen->eden_space()->check_mangled_unused_area_complete();
 683     young_gen->from_space()->check_mangled_unused_area_complete();
 684     young_gen->to_space()->check_mangled_unused_area_complete();
 685   }
 686 
 687   scavenge_exit.update();
 688 
 689   if (PrintGCTaskTimeStamps) {
 690     tty->print_cr("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT,
 691                   scavenge_entry.ticks(), scavenge_midpoint.ticks(),
 692                   scavenge_exit.ticks());
 693     gc_task_manager()->print_task_time_stamps();
 694   }
 695 
 696 #ifdef TRACESPINNING
 697   ParallelTaskTerminator::print_termination_counts();
 698 #endif
 699 
 700 
 701   _gc_timer.register_gc_end();
 702 
 703   _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
 704 
 705   return !promotion_failure_occurred;
 706 }
 707 
 708 // This method iterates over all objects in the young generation,
 709 // unforwarding markOops. It then restores any preserved mark oops,
 710 // and clears the _preserved_mark_stack.
 711 void PSScavenge::clean_up_failed_promotion() {
 712   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 713   PSYoungGen* young_gen = heap->young_gen();
 714 
 715   {
 716     ResourceMark rm;
 717 
 718     // Unforward all pointers in the young gen.
 719     PSPromotionFailedClosure unforward_closure;
 720     young_gen->object_iterate(&unforward_closure);
 721 
 722     if (PrintGC && Verbose) {
 723       gclog_or_tty->print_cr("Restoring " SIZE_FORMAT " marks", _preserved_oop_stack.size());
 724     }
 725 
 726     // Restore any saved marks.
 727     while (!_preserved_oop_stack.is_empty()) {
 728       oop obj      = _preserved_oop_stack.pop();
 729       markOop mark = _preserved_mark_stack.pop();
 730       obj->set_mark(mark);
 731     }
 732 
 733     // Clear the preserved mark and oop stack caches.
 734     _preserved_mark_stack.clear(true);
 735     _preserved_oop_stack.clear(true);
 736   }
 737 
 738   // Reset the PromotionFailureALot counters.
 739   NOT_PRODUCT(heap->reset_promotion_should_fail();)
 740 }
 741 
 742 // This method is called whenever an attempt to promote an object
 743 // fails. Some markOops will need preservation, some will not. Note
 744 // that the entire eden is traversed after a failed promotion, with
 745 // all forwarded headers replaced by the default markOop. This means
 746 // it is not necessary to preserve most markOops.
 747 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
 748   if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
 749     // Should use per-worker private stacks here rather than
 750     // locking a common pair of stacks.
 751     ThreadCritical tc;
 752     _preserved_oop_stack.push(obj);
 753     _preserved_mark_stack.push(obj_mark);
 754   }
 755 }
 756 
 757 bool PSScavenge::should_attempt_scavenge() {
 758   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 759   PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 760 
 761   if (UsePerfData) {
 762     counters->update_scavenge_skipped(not_skipped);
 763   }
 764 
 765   PSYoungGen* young_gen = heap->young_gen();
 766   PSOldGen* old_gen = heap->old_gen();
 767 
 768   if (!ScavengeWithObjectsInToSpace) {
 769     // Do not attempt to promote unless to_space is empty
 770     if (!young_gen->to_space()->is_empty()) {
 771       _consecutive_skipped_scavenges++;
 772       if (UsePerfData) {
 773         counters->update_scavenge_skipped(to_space_not_empty);
 774       }
 775       return false;
 776     }
 777   }
 778 
 779   // Test to see if the scavenge will likely fail.
 780   PSAdaptiveSizePolicy* policy = heap->size_policy();
 781 
 782   // A similar test is done in the policy's should_full_GC().  If this is
 783   // changed, decide if that test should also be changed.
 784   size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
 785   size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
 786   bool result = promotion_estimate < old_gen->free_in_bytes();
 787 
 788   if (PrintGCDetails && Verbose) {
 789     gclog_or_tty->print(result ? "  do scavenge: " : "  skip scavenge: ");
 790     gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
 791       " padded_average_promoted " SIZE_FORMAT
 792       " free in old gen " SIZE_FORMAT,
 793       (size_t) policy->average_promoted_in_bytes(),
 794       (size_t) policy->padded_average_promoted_in_bytes(),
 795       old_gen->free_in_bytes());
 796     if (young_gen->used_in_bytes() <
 797         (size_t) policy->padded_average_promoted_in_bytes()) {
 798       gclog_or_tty->print_cr(" padded_promoted_average is greater"
 799         " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
 800     }
 801   }
 802 
 803   if (result) {
 804     _consecutive_skipped_scavenges = 0;
 805   } else {
 806     _consecutive_skipped_scavenges++;
 807     if (UsePerfData) {
 808       counters->update_scavenge_skipped(promoted_too_large);
 809     }
 810   }
 811   return result;
 812 }
 813 
 814   // Used to add tasks
 815 GCTaskManager* const PSScavenge::gc_task_manager() {
 816   assert(ParallelScavengeHeap::gc_task_manager() != NULL,
 817    "shouldn't return NULL");
 818   return ParallelScavengeHeap::gc_task_manager();
 819 }
 820 
 821 void PSScavenge::initialize() {
 822   // Arguments must have been parsed
 823 
 824   if (AlwaysTenure || NeverTenure) {
 825     assert(MaxTenuringThreshold == 0 || MaxTenuringThreshold == markOopDesc::max_age + 1,
 826         err_msg("MaxTenuringThreshold should be 0 or markOopDesc::max_age + 1, but is %d", (int) MaxTenuringThreshold));
 827     _tenuring_threshold = MaxTenuringThreshold;
 828   } else {
 829     // We want to smooth out our startup times for the AdaptiveSizePolicy
 830     _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
 831                                                     MaxTenuringThreshold;
 832   }
 833 
 834   ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
 835   PSYoungGen* young_gen = heap->young_gen();
 836   PSOldGen* old_gen = heap->old_gen();
 837 
 838   // Set boundary between young_gen and old_gen
 839   assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
 840          "old above young");
 841   set_young_generation_boundary(young_gen->eden_space()->bottom());
 842 
 843   // Initialize ref handling object for scavenging.
 844   MemRegion mr = young_gen->reserved();
 845 
 846   _ref_processor =
 847     new ReferenceProcessor(mr,                         // span
 848                            ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
 849                            ParallelGCThreads,          // mt processing degree
 850                            true,                       // mt discovery
 851                            ParallelGCThreads,          // mt discovery degree
 852                            true,                       // atomic_discovery
 853                            NULL);                      // header provides liveness info
 854 
 855   // Cache the cardtable
 856   _card_table = barrier_set_cast<CardTableExtension>(heap->barrier_set());
 857 
 858   _counters = new CollectorCounters("PSScavenge", 0);
 859 }
--- EOF ---