1 /*
   2  * Copyright (c) 2002, 2012, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/symbolTable.hpp"
  27 #include "gc_implementation/parallelScavenge/cardTableExtension.hpp"
  28 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp"
  29 #include "gc_implementation/parallelScavenge/generationSizer.hpp"
  30 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp"
  31 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"
  32 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp"
  33 #include "gc_implementation/parallelScavenge/psParallelCompact.hpp"
  34 #include "gc_implementation/parallelScavenge/psScavenge.inline.hpp"
  35 #include "gc_implementation/parallelScavenge/psTasks.hpp"
  36 #include "gc_implementation/shared/isGCActiveMark.hpp"
  37 #include "gc_implementation/shared/spaceDecorator.hpp"
  38 #include "gc_interface/gcCause.hpp"
  39 #include "memory/collectorPolicy.hpp"
  40 #include "memory/gcLocker.inline.hpp"
  41 #include "memory/referencePolicy.hpp"
  42 #include "memory/referenceProcessor.hpp"
  43 #include "memory/resourceArea.hpp"
  44 #include "oops/oop.inline.hpp"
  45 #include "oops/oop.psgc.inline.hpp"
  46 #include "runtime/biasedLocking.hpp"
  47 #include "runtime/fprofiler.hpp"
  48 #include "runtime/handles.inline.hpp"
  49 #include "runtime/threadCritical.hpp"
  50 #include "runtime/vmThread.hpp"
  51 #include "runtime/vm_operations.hpp"
  52 #include "services/memoryService.hpp"
  53 #include "utilities/stack.inline.hpp"
  54 
  55 
  56 HeapWord*                  PSScavenge::_to_space_top_before_gc = NULL;
  57 int                        PSScavenge::_consecutive_skipped_scavenges = 0;
  58 ReferenceProcessor*        PSScavenge::_ref_processor = NULL;
  59 CardTableExtension*        PSScavenge::_card_table = NULL;
  60 bool                       PSScavenge::_survivor_overflow = false;
  61 int                        PSScavenge::_tenuring_threshold = 0;
  62 HeapWord*                  PSScavenge::_young_generation_boundary = NULL;
  63 elapsedTimer               PSScavenge::_accumulated_time;
  64 Stack<markOop>             PSScavenge::_preserved_mark_stack;
  65 Stack<oop>                 PSScavenge::_preserved_oop_stack;
  66 CollectorCounters*         PSScavenge::_counters = NULL;
  67 bool                       PSScavenge::_promotion_failed = false;
  68 
  69 // Define before use
  70 class PSIsAliveClosure: public BoolObjectClosure {
  71 public:
  72   void do_object(oop p) {
  73     assert(false, "Do not call.");
  74   }
  75   bool do_object_b(oop p) {
  76     return (!PSScavenge::is_obj_in_young((HeapWord*) p)) || p->is_forwarded();
  77   }
  78 };
  79 
  80 PSIsAliveClosure PSScavenge::_is_alive_closure;
  81 
  82 class PSKeepAliveClosure: public OopClosure {
  83 protected:
  84   MutableSpace* _to_space;
  85   PSPromotionManager* _promotion_manager;
  86 
  87 public:
  88   PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
  89     ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  90     assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
  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       PSScavenge::copy_and_push_safe_barrier(_promotion_manager, 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 void 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(!Universe::heap()->is_gc_active(), "not reentrant");
 221 
 222   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 223   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 224 
 225   PSAdaptiveSizePolicy* policy = heap->size_policy();
 226   IsGCActiveMark mark;
 227 
 228   bool scavenge_was_done = PSScavenge::invoke_no_policy();
 229 
 230   PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 231   if (UsePerfData)
 232     counters->update_full_follows_scavenge(0);
 233   if (!scavenge_was_done ||
 234       policy->should_full_GC(heap->old_gen()->free_in_bytes())) {
 235     if (UsePerfData)
 236       counters->update_full_follows_scavenge(full_follows_scavenge);
 237     GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
 238     CollectorPolicy* cp = heap->collector_policy();
 239     const bool clear_all_softrefs = cp->should_clear_all_soft_refs();
 240 
 241     if (UseParallelOldGC) {
 242       PSParallelCompact::invoke_no_policy(clear_all_softrefs);
 243     } else {
 244       PSMarkSweep::invoke_no_policy(clear_all_softrefs);
 245     }
 246   }
 247 }
 248 
 249 // This method contains no policy. You should probably
 250 // be calling invoke() instead.
 251 bool PSScavenge::invoke_no_policy() {
 252   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 253   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
 254 
 255   assert(_preserved_mark_stack.is_empty(), "should be empty");
 256   assert(_preserved_oop_stack.is_empty(), "should be empty");
 257 
 258   TimeStamp scavenge_entry;
 259   TimeStamp scavenge_midpoint;
 260   TimeStamp scavenge_exit;
 261 
 262   scavenge_entry.update();
 263 
 264   if (GC_locker::check_active_before_gc()) {
 265     return false;
 266   }
 267 
 268   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 269   GCCause::Cause gc_cause = heap->gc_cause();
 270   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 271 
 272   // Check for potential problems.
 273   if (!should_attempt_scavenge()) {
 274     return false;
 275   }
 276 
 277   bool promotion_failure_occurred = false;
 278 
 279   PSYoungGen* young_gen = heap->young_gen();
 280   PSOldGen* old_gen = heap->old_gen();
 281   PSPermGen* perm_gen = heap->perm_gen();
 282   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
 283   heap->increment_total_collections();
 284 
 285   AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
 286 
 287   if ((gc_cause != GCCause::_java_lang_system_gc) ||
 288        UseAdaptiveSizePolicyWithSystemGC) {
 289     // Gather the feedback data for eden occupancy.
 290     young_gen->eden_space()->accumulate_statistics();
 291   }
 292 
 293   if (ZapUnusedHeapArea) {
 294     // Save information needed to minimize mangling
 295     heap->record_gen_tops_before_GC();
 296   }
 297 
 298   heap->print_heap_before_gc();
 299 
 300   assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
 301   assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
 302 
 303   size_t prev_used = heap->used();
 304   assert(promotion_failed() == false, "Sanity");
 305 
 306   // Fill in TLABs
 307   heap->accumulate_statistics_all_tlabs();
 308   heap->ensure_parsability(true);  // retire TLABs
 309 
 310   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
 311     HandleMark hm;  // Discard invalid handles created during verification
 312     gclog_or_tty->print(" VerifyBeforeGC:");
 313     Universe::verify(true);
 314   }
 315 
 316   {
 317     ResourceMark rm;
 318     HandleMark hm;
 319 
 320     gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
 321     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
 322     TraceTime t1("GC", PrintGC, !PrintGCDetails, gclog_or_tty);
 323     TraceCollectorStats tcs(counters());
 324     TraceMemoryManagerStats tms(false /* not full GC */,gc_cause);
 325 
 326     if (TraceGen0Time) accumulated_time()->start();
 327 
 328     // Let the size policy know we're starting
 329     size_policy->minor_collection_begin();
 330 
 331     // Verify the object start arrays.
 332     if (VerifyObjectStartArray &&
 333         VerifyBeforeGC) {
 334       old_gen->verify_object_start_array();
 335       perm_gen->verify_object_start_array();
 336     }
 337 
 338     // Verify no unmarked old->young roots
 339     if (VerifyRememberedSets) {
 340       CardTableExtension::verify_all_young_refs_imprecise();
 341     }
 342 
 343     if (!ScavengeWithObjectsInToSpace) {
 344       assert(young_gen->to_space()->is_empty(),
 345              "Attempt to scavenge with live objects in to_space");
 346       young_gen->to_space()->clear(SpaceDecorator::Mangle);
 347     } else if (ZapUnusedHeapArea) {
 348       young_gen->to_space()->mangle_unused_area();
 349     }
 350     save_to_space_top_before_gc();
 351 
 352     COMPILER2_PRESENT(DerivedPointerTable::clear());
 353 
 354     reference_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
 355     reference_processor()->setup_policy(false);
 356 
 357     // We track how much was promoted to the next generation for
 358     // the AdaptiveSizePolicy.
 359     size_t old_gen_used_before = old_gen->used_in_bytes();
 360 
 361     // For PrintGCDetails
 362     size_t young_gen_used_before = young_gen->used_in_bytes();
 363 
 364     // Reset our survivor overflow.
 365     set_survivor_overflow(false);
 366 
 367     // We need to save the old/perm top values before
 368     // creating the promotion_manager. We pass the top
 369     // values to the card_table, to prevent it from
 370     // straying into the promotion labs.
 371     HeapWord* old_top = old_gen->object_space()->top();
 372     HeapWord* perm_top = perm_gen->object_space()->top();
 373 
 374     // Release all previously held resources
 375     gc_task_manager()->release_all_resources();
 376 
 377     // Set the number of GC threads to be used in this collection
 378     gc_task_manager()->set_active_gang();
 379     gc_task_manager()->task_idle_workers();
 380     // Get the active number of workers here and use that value
 381     // throughout the methods.
 382     uint active_workers = gc_task_manager()->active_workers();
 383     heap->set_par_threads(active_workers);
 384 
 385     PSPromotionManager::pre_scavenge();
 386 
 387     // We'll use the promotion manager again later.
 388     PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
 389     {
 390       // TraceTime("Roots");
 391       ParallelScavengeHeap::ParStrongRootsScope psrs;
 392 
 393       GCTaskQueue* q = GCTaskQueue::create();
 394 
 395       uint stripe_total = active_workers;
 396       for(uint i=0; i < stripe_total; i++) {
 397         q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));
 398       }
 399 
 400       q->enqueue(new SerialOldToYoungRootsTask(perm_gen, perm_top));
 401 
 402       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
 403       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
 404       // We scan the thread roots in parallel
 405       Threads::create_thread_roots_tasks(q);
 406       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
 407       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));
 408       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
 409       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
 410       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
 411       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
 412 
 413       ParallelTaskTerminator terminator(
 414         active_workers,
 415                   (TaskQueueSetSuper*) promotion_manager->stack_array_depth());
 416       if (active_workers > 1) {
 417         for (uint j = 0; j < active_workers; j++) {
 418           q->enqueue(new StealTask(&terminator));
 419         }
 420       }
 421 
 422       gc_task_manager()->execute_and_wait(q);
 423     }
 424 
 425     scavenge_midpoint.update();
 426 
 427     // Process reference objects discovered during scavenge
 428     {
 429       reference_processor()->setup_policy(false); // not always_clear
 430       reference_processor()->set_active_mt_degree(active_workers);
 431       PSKeepAliveClosure keep_alive(promotion_manager);
 432       PSEvacuateFollowersClosure evac_followers(promotion_manager);
 433       if (reference_processor()->processing_is_mt()) {
 434         PSRefProcTaskExecutor task_executor;
 435         reference_processor()->process_discovered_references(
 436           &_is_alive_closure, &keep_alive, &evac_followers, &task_executor);
 437       } else {
 438         reference_processor()->process_discovered_references(
 439           &_is_alive_closure, &keep_alive, &evac_followers, NULL);
 440       }
 441     }
 442 
 443     // Enqueue reference objects discovered during scavenge.
 444     if (reference_processor()->processing_is_mt()) {
 445       PSRefProcTaskExecutor task_executor;
 446       reference_processor()->enqueue_discovered_references(&task_executor);
 447     } else {
 448       reference_processor()->enqueue_discovered_references(NULL);
 449     }
 450 
 451     if (!JavaObjectsInPerm) {
 452       // Unlink any dead interned Strings
 453       StringTable::unlink(&_is_alive_closure);
 454       // Process the remaining live ones
 455       PSScavengeRootsClosure root_closure(promotion_manager);
 456       StringTable::oops_do(&root_closure);
 457     }
 458 
 459     // Finally, flush the promotion_manager's labs, and deallocate its stacks.
 460     PSPromotionManager::post_scavenge();
 461 
 462     promotion_failure_occurred = promotion_failed();
 463     if (promotion_failure_occurred) {
 464       clean_up_failed_promotion();
 465       if (PrintGC) {
 466         gclog_or_tty->print("--");
 467       }
 468     }
 469 
 470     // Let the size policy know we're done.  Note that we count promotion
 471     // failure cleanup time as part of the collection (otherwise, we're
 472     // implicitly saying it's mutator time).
 473     size_policy->minor_collection_end(gc_cause);
 474 
 475     if (!promotion_failure_occurred) {
 476       // Swap the survivor spaces.
 477 
 478 
 479       young_gen->eden_space()->clear(SpaceDecorator::Mangle);
 480       young_gen->from_space()->clear(SpaceDecorator::Mangle);
 481       young_gen->swap_spaces();
 482 
 483       size_t survived = young_gen->from_space()->used_in_bytes();
 484       size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
 485       size_policy->update_averages(_survivor_overflow, survived, promoted);
 486 
 487       // A successful scavenge should restart the GC time limit count which is
 488       // for full GC's.
 489       size_policy->reset_gc_overhead_limit_count();
 490       if (UseAdaptiveSizePolicy) {
 491         // Calculate the new survivor size and tenuring threshold
 492 
 493         if (PrintAdaptiveSizePolicy) {
 494           gclog_or_tty->print("AdaptiveSizeStart: ");
 495           gclog_or_tty->stamp();
 496           gclog_or_tty->print_cr(" collection: %d ",
 497                          heap->total_collections());
 498 
 499           if (Verbose) {
 500             gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d"
 501               " perm_gen_capacity: %d ",
 502               old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes(),
 503               perm_gen->capacity_in_bytes());
 504           }
 505         }
 506 
 507 
 508         if (UsePerfData) {
 509           PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 510           counters->update_old_eden_size(
 511             size_policy->calculated_eden_size_in_bytes());
 512           counters->update_old_promo_size(
 513             size_policy->calculated_promo_size_in_bytes());
 514           counters->update_old_capacity(old_gen->capacity_in_bytes());
 515           counters->update_young_capacity(young_gen->capacity_in_bytes());
 516           counters->update_survived(survived);
 517           counters->update_promoted(promoted);
 518           counters->update_survivor_overflowed(_survivor_overflow);
 519         }
 520 
 521         size_t survivor_limit =
 522           size_policy->max_survivor_size(young_gen->max_size());
 523         _tenuring_threshold =
 524           size_policy->compute_survivor_space_size_and_threshold(
 525                                                            _survivor_overflow,
 526                                                            _tenuring_threshold,
 527                                                            survivor_limit);
 528 
 529        if (PrintTenuringDistribution) {
 530          gclog_or_tty->cr();
 531          gclog_or_tty->print_cr("Desired survivor size %ld bytes, new threshold %d (max %d)",
 532                                 size_policy->calculated_survivor_size_in_bytes(),
 533                                 _tenuring_threshold, MaxTenuringThreshold);
 534        }
 535 
 536         if (UsePerfData) {
 537           PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 538           counters->update_tenuring_threshold(_tenuring_threshold);
 539           counters->update_survivor_size_counters();
 540         }
 541 
 542         // Do call at minor collections?
 543         // Don't check if the size_policy is ready at this
 544         // level.  Let the size_policy check that internally.
 545         if (UseAdaptiveSizePolicy &&
 546             UseAdaptiveGenerationSizePolicyAtMinorCollection &&
 547             ((gc_cause != GCCause::_java_lang_system_gc) ||
 548               UseAdaptiveSizePolicyWithSystemGC)) {
 549 
 550           // Calculate optimial free space amounts
 551           assert(young_gen->max_size() >
 552             young_gen->from_space()->capacity_in_bytes() +
 553             young_gen->to_space()->capacity_in_bytes(),
 554             "Sizes of space in young gen are out-of-bounds");
 555           size_t max_eden_size = young_gen->max_size() -
 556             young_gen->from_space()->capacity_in_bytes() -
 557             young_gen->to_space()->capacity_in_bytes();
 558           size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
 559                                    young_gen->eden_space()->used_in_bytes(),
 560                                    old_gen->used_in_bytes(),
 561                                    perm_gen->used_in_bytes(),
 562                                    young_gen->eden_space()->capacity_in_bytes(),
 563                                    old_gen->max_gen_size(),
 564                                    max_eden_size,
 565                                    false  /* full gc*/,
 566                                    gc_cause,
 567                                    heap->collector_policy());
 568 
 569         }
 570         // Resize the young generation at every collection
 571         // even if new sizes have not been calculated.  This is
 572         // to allow resizes that may have been inhibited by the
 573         // relative location of the "to" and "from" spaces.
 574 
 575         // Resizing the old gen at minor collects can cause increases
 576         // that don't feed back to the generation sizing policy until
 577         // a major collection.  Don't resize the old gen here.
 578 
 579         heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
 580                         size_policy->calculated_survivor_size_in_bytes());
 581 
 582         if (PrintAdaptiveSizePolicy) {
 583           gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
 584                          heap->total_collections());
 585         }
 586       }
 587 
 588       // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
 589       // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
 590       // Also update() will case adaptive NUMA chunk resizing.
 591       assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
 592       young_gen->eden_space()->update();
 593 
 594       heap->gc_policy_counters()->update_counters();
 595 
 596       heap->resize_all_tlabs();
 597 
 598       assert(young_gen->to_space()->is_empty(), "to space should be empty now");
 599     }
 600 
 601     COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
 602 
 603     NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
 604 
 605     // Re-verify object start arrays
 606     if (VerifyObjectStartArray &&
 607         VerifyAfterGC) {
 608       old_gen->verify_object_start_array();
 609       perm_gen->verify_object_start_array();
 610     }
 611 
 612     // Verify all old -> young cards are now precise
 613     if (VerifyRememberedSets) {
 614       // Precise verification will give false positives. Until this is fixed,
 615       // use imprecise verification.
 616       // CardTableExtension::verify_all_young_refs_precise();
 617       CardTableExtension::verify_all_young_refs_imprecise();
 618     }
 619 
 620     if (TraceGen0Time) accumulated_time()->stop();
 621 
 622     if (PrintGC) {
 623       if (PrintGCDetails) {
 624         // Don't print a GC timestamp here.  This is after the GC so
 625         // would be confusing.
 626         young_gen->print_used_change(young_gen_used_before);
 627       }
 628       heap->print_heap_change(prev_used);
 629     }
 630 
 631     // Track memory usage and detect low memory
 632     MemoryService::track_memory_usage();
 633     heap->update_counters();
 634 
 635     gc_task_manager()->release_idle_workers();
 636   }
 637 
 638   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
 639     HandleMark hm;  // Discard invalid handles created during verification
 640     gclog_or_tty->print(" VerifyAfterGC:");
 641     Universe::verify(false);
 642   }
 643 
 644   heap->print_heap_after_gc();
 645 
 646   if (ZapUnusedHeapArea) {
 647     young_gen->eden_space()->check_mangled_unused_area_complete();
 648     young_gen->from_space()->check_mangled_unused_area_complete();
 649     young_gen->to_space()->check_mangled_unused_area_complete();
 650   }
 651 
 652   scavenge_exit.update();
 653 
 654   if (PrintGCTaskTimeStamps) {
 655     tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,
 656                   scavenge_entry.ticks(), scavenge_midpoint.ticks(),
 657                   scavenge_exit.ticks());
 658     gc_task_manager()->print_task_time_stamps();
 659   }
 660 
 661 #ifdef TRACESPINNING
 662   ParallelTaskTerminator::print_termination_counts();
 663 #endif
 664 
 665   return !promotion_failure_occurred;
 666 }
 667 
 668 // This method iterates over all objects in the young generation,
 669 // unforwarding markOops. It then restores any preserved mark oops,
 670 // and clears the _preserved_mark_stack.
 671 void PSScavenge::clean_up_failed_promotion() {
 672   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 673   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 674   assert(promotion_failed(), "Sanity");
 675 
 676   PSYoungGen* young_gen = heap->young_gen();
 677 
 678   {
 679     ResourceMark rm;
 680 
 681     // Unforward all pointers in the young gen.
 682     PSPromotionFailedClosure unforward_closure;
 683     young_gen->object_iterate(&unforward_closure);
 684 
 685     if (PrintGC && Verbose) {
 686       gclog_or_tty->print_cr("Restoring %d marks", _preserved_oop_stack.size());
 687     }
 688 
 689     // Restore any saved marks.
 690     while (!_preserved_oop_stack.is_empty()) {
 691       oop obj      = _preserved_oop_stack.pop();
 692       markOop mark = _preserved_mark_stack.pop();
 693       obj->set_mark(mark);
 694     }
 695 
 696     // Clear the preserved mark and oop stack caches.
 697     _preserved_mark_stack.clear(true);
 698     _preserved_oop_stack.clear(true);
 699     _promotion_failed = false;
 700   }
 701 
 702   // Reset the PromotionFailureALot counters.
 703   NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
 704 }
 705 
 706 // This method is called whenever an attempt to promote an object
 707 // fails. Some markOops will need preservation, some will not. Note
 708 // that the entire eden is traversed after a failed promotion, with
 709 // all forwarded headers replaced by the default markOop. This means
 710 // it is not neccessary to preserve most markOops.
 711 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
 712   _promotion_failed = true;
 713   if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
 714     // Should use per-worker private stakcs hetre rather than
 715     // locking a common pair of stacks.
 716     ThreadCritical tc;
 717     _preserved_oop_stack.push(obj);
 718     _preserved_mark_stack.push(obj_mark);
 719   }
 720 }
 721 
 722 bool PSScavenge::should_attempt_scavenge() {
 723   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 724   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 725   PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 726 
 727   if (UsePerfData) {
 728     counters->update_scavenge_skipped(not_skipped);
 729   }
 730 
 731   PSYoungGen* young_gen = heap->young_gen();
 732   PSOldGen* old_gen = heap->old_gen();
 733 
 734   if (!ScavengeWithObjectsInToSpace) {
 735     // Do not attempt to promote unless to_space is empty
 736     if (!young_gen->to_space()->is_empty()) {
 737       _consecutive_skipped_scavenges++;
 738       if (UsePerfData) {
 739         counters->update_scavenge_skipped(to_space_not_empty);
 740       }
 741       return false;
 742     }
 743   }
 744 
 745   // Test to see if the scavenge will likely fail.
 746   PSAdaptiveSizePolicy* policy = heap->size_policy();
 747 
 748   // A similar test is done in the policy's should_full_GC().  If this is
 749   // changed, decide if that test should also be changed.
 750   size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
 751   size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
 752   bool result = promotion_estimate < old_gen->free_in_bytes();
 753 
 754   if (PrintGCDetails && Verbose) {
 755     gclog_or_tty->print(result ? "  do scavenge: " : "  skip scavenge: ");
 756     gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
 757       " padded_average_promoted " SIZE_FORMAT
 758       " free in old gen " SIZE_FORMAT,
 759       (size_t) policy->average_promoted_in_bytes(),
 760       (size_t) policy->padded_average_promoted_in_bytes(),
 761       old_gen->free_in_bytes());
 762     if (young_gen->used_in_bytes() <
 763         (size_t) policy->padded_average_promoted_in_bytes()) {
 764       gclog_or_tty->print_cr(" padded_promoted_average is greater"
 765         " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
 766     }
 767   }
 768 
 769   if (result) {
 770     _consecutive_skipped_scavenges = 0;
 771   } else {
 772     _consecutive_skipped_scavenges++;
 773     if (UsePerfData) {
 774       counters->update_scavenge_skipped(promoted_too_large);
 775     }
 776   }
 777   return result;
 778 }
 779 
 780   // Used to add tasks
 781 GCTaskManager* const PSScavenge::gc_task_manager() {
 782   assert(ParallelScavengeHeap::gc_task_manager() != NULL,
 783    "shouldn't return NULL");
 784   return ParallelScavengeHeap::gc_task_manager();
 785 }
 786 
 787 void PSScavenge::initialize() {
 788   // Arguments must have been parsed
 789 
 790   if (AlwaysTenure) {
 791     _tenuring_threshold = 0;
 792   } else if (NeverTenure) {
 793     _tenuring_threshold = markOopDesc::max_age + 1;
 794   } else {
 795     // We want to smooth out our startup times for the AdaptiveSizePolicy
 796     _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
 797                                                     MaxTenuringThreshold;
 798   }
 799 
 800   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 801   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 802 
 803   PSYoungGen* young_gen = heap->young_gen();
 804   PSOldGen* old_gen = heap->old_gen();
 805   PSPermGen* perm_gen = heap->perm_gen();
 806 
 807   // Set boundary between young_gen and old_gen
 808   assert(perm_gen->reserved().end() <= old_gen->object_space()->bottom(),
 809          "perm above old");
 810   assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
 811          "old above young");
 812   _young_generation_boundary = young_gen->eden_space()->bottom();
 813 
 814   // Initialize ref handling object for scavenging.
 815   MemRegion mr = young_gen->reserved();
 816 
 817   _ref_processor =
 818     new ReferenceProcessor(mr,                         // span
 819                            ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
 820                            (int) ParallelGCThreads,    // mt processing degree
 821                            true,                       // mt discovery
 822                            (int) ParallelGCThreads,    // mt discovery degree
 823                            true,                       // atomic_discovery
 824                            NULL,                       // header provides liveness info
 825                            false);                     // next field updates do not need write barrier
 826 
 827   // Cache the cardtable
 828   BarrierSet* bs = Universe::heap()->barrier_set();
 829   assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
 830   _card_table = (CardTableExtension*)bs;
 831 
 832   _counters = new CollectorCounters("PSScavenge", 0);
 833 }