1 /*
   2  * Copyright (c) 2002, 2013, 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 "code/codeCache.hpp"
  28 #include "gc_implementation/parallelScavenge/cardTableExtension.hpp"
  29 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp"
  30 #include "gc_implementation/parallelScavenge/generationSizer.hpp"
  31 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp"
  32 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"
  33 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp"
  34 #include "gc_implementation/parallelScavenge/psParallelCompact.hpp"
  35 #include "gc_implementation/parallelScavenge/psScavenge.inline.hpp"
  36 #include "gc_implementation/parallelScavenge/psTasks.hpp"
  37 #include "gc_implementation/shared/isGCActiveMark.hpp"
  38 #include "gc_implementation/shared/spaceDecorator.hpp"
  39 #include "gc_interface/gcCause.hpp"
  40 #include "memory/collectorPolicy.hpp"
  41 #include "memory/gcLocker.inline.hpp"
  42 #include "memory/referencePolicy.hpp"
  43 #include "memory/referenceProcessor.hpp"
  44 #include "memory/resourceArea.hpp"
  45 #include "oops/oop.inline.hpp"
  46 #include "oops/oop.psgc.inline.hpp"
  47 #include "runtime/biasedLocking.hpp"
  48 #include "runtime/fprofiler.hpp"
  49 #include "runtime/handles.inline.hpp"
  50 #include "runtime/threadCritical.hpp"
  51 #include "runtime/vmThread.hpp"
  52 #include "runtime/vm_operations.hpp"
  53 #include "services/memoryService.hpp"
  54 #include "utilities/stack.inline.hpp"
  55 
  56 
  57 HeapWord*                  PSScavenge::_to_space_top_before_gc = NULL;
  58 int                        PSScavenge::_consecutive_skipped_scavenges = 0;
  59 ReferenceProcessor*        PSScavenge::_ref_processor = NULL;
  60 CardTableExtension*        PSScavenge::_card_table = NULL;
  61 bool                       PSScavenge::_survivor_overflow = false;
  62 uint                       PSScavenge::_tenuring_threshold = 0;
  63 HeapWord*                  PSScavenge::_young_generation_boundary = NULL;
  64 elapsedTimer               PSScavenge::_accumulated_time;
  65 Stack<markOop, mtGC>       PSScavenge::_preserved_mark_stack;
  66 Stack<oop, mtGC>           PSScavenge::_preserved_oop_stack;
  67 CollectorCounters*         PSScavenge::_counters = NULL;
  68 bool                       PSScavenge::_promotion_failed = false;
  69 
  70 // Define before use
  71 class PSIsAliveClosure: public BoolObjectClosure {
  72 public:
  73   void do_object(oop p) {
  74     assert(false, "Do not call.");
  75   }
  76   bool do_object_b(oop p) {
  77     return (!PSScavenge::is_obj_in_young((HeapWord*) 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*)Universe::heap();
  91     assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
  92     _to_space = heap->young_gen()->to_space();
  93 
  94     assert(_promotion_manager != NULL, "Sanity");
  95   }
  96 
  97   template <class T> void do_oop_work(T* p) {
  98     assert (!oopDesc::is_null(*p), "expected non-null ref");
  99     assert ((oopDesc::load_decode_heap_oop_not_null(p))->is_oop(),
 100             "expected an oop while scanning weak refs");
 101 
 102     // Weak refs may be visited more than once.
 103     if (PSScavenge::should_scavenge(p, _to_space)) {
 104       PSScavenge::copy_and_push_safe_barrier<T, /*promote_immediately=*/false>(_promotion_manager, p);
 105     }
 106   }
 107   virtual void do_oop(oop* p)       { PSKeepAliveClosure::do_oop_work(p); }
 108   virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
 109 };
 110 
 111 class PSEvacuateFollowersClosure: public VoidClosure {
 112  private:
 113   PSPromotionManager* _promotion_manager;
 114  public:
 115   PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}
 116 
 117   virtual void do_void() {
 118     assert(_promotion_manager != NULL, "Sanity");
 119     _promotion_manager->drain_stacks(true);
 120     guarantee(_promotion_manager->stacks_empty(),
 121               "stacks should be empty at this point");
 122   }
 123 };
 124 
 125 class PSPromotionFailedClosure : public ObjectClosure {
 126   virtual void do_object(oop obj) {
 127     if (obj->is_forwarded()) {
 128       obj->init_mark();
 129     }
 130   }
 131 };
 132 
 133 class PSRefProcTaskProxy: public GCTask {
 134   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
 135   ProcessTask & _rp_task;
 136   uint          _work_id;
 137 public:
 138   PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id)
 139     : _rp_task(rp_task),
 140       _work_id(work_id)
 141   { }
 142 
 143 private:
 144   virtual char* name() { return (char *)"Process referents by policy in parallel"; }
 145   virtual void do_it(GCTaskManager* manager, uint which);
 146 };
 147 
 148 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which)
 149 {
 150   PSPromotionManager* promotion_manager =
 151     PSPromotionManager::gc_thread_promotion_manager(which);
 152   assert(promotion_manager != NULL, "sanity check");
 153   PSKeepAliveClosure keep_alive(promotion_manager);
 154   PSEvacuateFollowersClosure evac_followers(promotion_manager);
 155   PSIsAliveClosure is_alive;
 156   _rp_task.work(_work_id, is_alive, keep_alive, evac_followers);
 157 }
 158 
 159 class PSRefEnqueueTaskProxy: public GCTask {
 160   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
 161   EnqueueTask& _enq_task;
 162   uint         _work_id;
 163 
 164 public:
 165   PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id)
 166     : _enq_task(enq_task),
 167       _work_id(work_id)
 168   { }
 169 
 170   virtual char* name() { return (char *)"Enqueue reference objects in parallel"; }
 171   virtual void do_it(GCTaskManager* manager, uint which)
 172   {
 173     _enq_task.work(_work_id);
 174   }
 175 };
 176 
 177 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
 178   virtual void execute(ProcessTask& task);
 179   virtual void execute(EnqueueTask& task);
 180 };
 181 
 182 void PSRefProcTaskExecutor::execute(ProcessTask& task)
 183 {
 184   GCTaskQueue* q = GCTaskQueue::create();
 185   GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
 186   for(uint i=0; i < manager->active_workers(); i++) {
 187     q->enqueue(new PSRefProcTaskProxy(task, i));
 188   }
 189   ParallelTaskTerminator terminator(manager->active_workers(),
 190                  (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth());
 191   if (task.marks_oops_alive() && manager->active_workers() > 1) {
 192     for (uint j = 0; j < manager->active_workers(); j++) {
 193       q->enqueue(new StealTask(&terminator));
 194     }
 195   }
 196   manager->execute_and_wait(q);
 197 }
 198 
 199 
 200 void PSRefProcTaskExecutor::execute(EnqueueTask& task)
 201 {
 202   GCTaskQueue* q = GCTaskQueue::create();
 203   GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
 204   for(uint i=0; i < manager->active_workers(); i++) {
 205     q->enqueue(new PSRefEnqueueTaskProxy(task, i));
 206   }
 207   manager->execute_and_wait(q);
 208 }
 209 
 210 // This method contains all heap specific policy for invoking scavenge.
 211 // PSScavenge::invoke_no_policy() will do nothing but attempt to
 212 // scavenge. It will not clean up after failed promotions, bail out if
 213 // we've exceeded policy time limits, or any other special behavior.
 214 // All such policy should be placed here.
 215 //
 216 // Note that this method should only be called from the vm_thread while
 217 // at a safepoint!
 218 bool PSScavenge::invoke() {
 219   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 220   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
 221   assert(!Universe::heap()->is_gc_active(), "not reentrant");
 222 
 223   ParallelScavengeHeap* const heap = (ParallelScavengeHeap*)Universe::heap();
 224   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 225 
 226   PSAdaptiveSizePolicy* policy = heap->size_policy();
 227   IsGCActiveMark mark;
 228 
 229   const bool scavenge_done = PSScavenge::invoke_no_policy();
 230   const bool need_full_gc = !scavenge_done ||
 231     policy->should_full_GC(heap->old_gen()->free_in_bytes());
 232   bool full_gc_done = false;
 233 
 234   if (UsePerfData) {
 235     PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
 236     const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped;
 237     counters->update_full_follows_scavenge(ffs_val);
 238   }
 239 
 240   if (need_full_gc) {
 241     GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
 242     CollectorPolicy* cp = heap->collector_policy();
 243     const bool clear_all_softrefs = cp->should_clear_all_soft_refs();
 244 
 245     if (UseParallelOldGC) {
 246       full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs);
 247     } else {
 248       full_gc_done = PSMarkSweep::invoke_no_policy(clear_all_softrefs);
 249     }
 250   }
 251 
 252   return full_gc_done;
 253 }
 254 
 255 // This method contains no policy. You should probably
 256 // be calling invoke() instead.
 257 bool PSScavenge::invoke_no_policy() {
 258   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 259   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
 260 
 261   assert(_preserved_mark_stack.is_empty(), "should be empty");
 262   assert(_preserved_oop_stack.is_empty(), "should be empty");
 263 
 264   TimeStamp scavenge_entry;
 265   TimeStamp scavenge_midpoint;
 266   TimeStamp scavenge_exit;
 267 
 268   scavenge_entry.update();
 269 
 270   if (GC_locker::check_active_before_gc()) {
 271     return false;
 272   }
 273 
 274   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 275   GCCause::Cause gc_cause = heap->gc_cause();
 276   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 277 
 278   // Check for potential problems.
 279   if (!should_attempt_scavenge()) {
 280     return false;
 281   }
 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   heap->increment_total_collections();
 289 
 290   AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
 291 
 292   if ((gc_cause != GCCause::_java_lang_system_gc) ||
 293        UseAdaptiveSizePolicyWithSystemGC) {
 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 
 305   assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
 306   assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
 307 
 308   size_t prev_used = heap->used();
 309   assert(promotion_failed() == false, "Sanity");
 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     gclog_or_tty->print(" VerifyBeforeGC:");
 318     Universe::verify();
 319   }
 320 
 321   {
 322     ResourceMark rm;
 323     HandleMark hm;
 324 
 325     gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
 326     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
 327     TraceTime t1(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, gclog_or_tty);
 328     TraceCollectorStats tcs(counters());
 329     TraceMemoryManagerStats tms(false /* not full GC */,gc_cause);
 330 
 331     if (TraceGen0Time) accumulated_time()->start();
 332 
 333     // Let the size policy know we're starting
 334     size_policy->minor_collection_begin();
 335 
 336     // Verify the object start arrays.
 337     if (VerifyObjectStartArray &&
 338         VerifyBeforeGC) {
 339       old_gen->verify_object_start_array();
 340     }
 341 
 342     // Verify no unmarked old->young roots
 343     if (VerifyRememberedSets) {
 344       CardTableExtension::verify_all_young_refs_imprecise();
 345     }
 346 
 347     if (!ScavengeWithObjectsInToSpace) {
 348       assert(young_gen->to_space()->is_empty(),
 349              "Attempt to scavenge with live objects in to_space");
 350       young_gen->to_space()->clear(SpaceDecorator::Mangle);
 351     } else if (ZapUnusedHeapArea) {
 352       young_gen->to_space()->mangle_unused_area();
 353     }
 354     save_to_space_top_before_gc();
 355 
 356     COMPILER2_PRESENT(DerivedPointerTable::clear());
 357 
 358     reference_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
 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     heap->set_par_threads(active_workers);
 387 
 388     PSPromotionManager::pre_scavenge();
 389 
 390     // We'll use the promotion manager again later.
 391     PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
 392     {
 393       // TraceTime("Roots");
 394       ParallelScavengeHeap::ParStrongRootsScope psrs;
 395 
 396       GCTaskQueue* q = GCTaskQueue::create();
 397 
 398       if (!old_gen->object_space()->is_empty()) {
 399         // There are only old-to-young pointers if there are objects
 400         // in the old gen.
 401         uint stripe_total = active_workers;
 402         for(uint i=0; i < stripe_total; i++) {
 403           q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));
 404         }
 405       }
 406 
 407       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
 408       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
 409       // We scan the thread roots in parallel
 410       Threads::create_thread_roots_tasks(q);
 411       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
 412       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));
 413       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
 414       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
 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       reference_processor()->setup_policy(false); // not always_clear
 435       reference_processor()->set_active_mt_degree(active_workers);
 436       PSKeepAliveClosure keep_alive(promotion_manager);
 437       PSEvacuateFollowersClosure evac_followers(promotion_manager);
 438       if (reference_processor()->processing_is_mt()) {
 439         PSRefProcTaskExecutor task_executor;
 440         reference_processor()->process_discovered_references(
 441           &_is_alive_closure, &keep_alive, &evac_followers, &task_executor);
 442       } else {
 443         reference_processor()->process_discovered_references(
 444           &_is_alive_closure, &keep_alive, &evac_followers, NULL);
 445       }
 446     }
 447 
 448     // Enqueue reference objects discovered during scavenge.
 449     if (reference_processor()->processing_is_mt()) {
 450       PSRefProcTaskExecutor task_executor;
 451       reference_processor()->enqueue_discovered_references(&task_executor);
 452     } else {
 453       reference_processor()->enqueue_discovered_references(NULL);
 454     }
 455 
 456       // Unlink any dead interned Strings
 457       StringTable::unlink(&_is_alive_closure);
 458       // Process the remaining live ones
 459       PSScavengeRootsClosure root_closure(promotion_manager);
 460       StringTable::oops_do(&root_closure);
 461 
 462     // Finally, flush the promotion_manager's labs, and deallocate its stacks.
 463     PSPromotionManager::post_scavenge();
 464 
 465     promotion_failure_occurred = promotion_failed();
 466     if (promotion_failure_occurred) {
 467       clean_up_failed_promotion();
 468       if (PrintGC) {
 469         gclog_or_tty->print("--");
 470       }
 471     }
 472 
 473     // Let the size policy know we're done.  Note that we count promotion
 474     // failure cleanup time as part of the collection (otherwise, we're
 475     // implicitly saying it's mutator time).
 476     size_policy->minor_collection_end(gc_cause);
 477 
 478     if (!promotion_failure_occurred) {
 479       // Swap the survivor spaces.
 480 
 481 
 482       young_gen->eden_space()->clear(SpaceDecorator::Mangle);
 483       young_gen->from_space()->clear(SpaceDecorator::Mangle);
 484       young_gen->swap_spaces();
 485 
 486       size_t survived = young_gen->from_space()->used_in_bytes();
 487       size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
 488       size_policy->update_averages(_survivor_overflow, survived, promoted);
 489 
 490       // A successful scavenge should restart the GC time limit count which is
 491       // for full GC's.
 492       size_policy->reset_gc_overhead_limit_count();
 493       if (UseAdaptiveSizePolicy) {
 494         // Calculate the new survivor size and tenuring threshold
 495 
 496         if (PrintAdaptiveSizePolicy) {
 497           gclog_or_tty->print("AdaptiveSizeStart: ");
 498           gclog_or_tty->stamp();
 499           gclog_or_tty->print_cr(" collection: %d ",
 500                          heap->total_collections());
 501 
 502           if (Verbose) {
 503             gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d",
 504               old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
 505           }
 506         }
 507 
 508 
 509         if (UsePerfData) {
 510           PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 511           counters->update_old_eden_size(
 512             size_policy->calculated_eden_size_in_bytes());
 513           counters->update_old_promo_size(
 514             size_policy->calculated_promo_size_in_bytes());
 515           counters->update_old_capacity(old_gen->capacity_in_bytes());
 516           counters->update_young_capacity(young_gen->capacity_in_bytes());
 517           counters->update_survived(survived);
 518           counters->update_promoted(promoted);
 519           counters->update_survivor_overflowed(_survivor_overflow);
 520         }
 521 
 522         size_t survivor_limit =
 523           size_policy->max_survivor_size(young_gen->max_size());
 524         _tenuring_threshold =
 525           size_policy->compute_survivor_space_size_and_threshold(
 526                                                            _survivor_overflow,
 527                                                            _tenuring_threshold,
 528                                                            survivor_limit);
 529 
 530        if (PrintTenuringDistribution) {
 531          gclog_or_tty->cr();
 532          gclog_or_tty->print_cr("Desired survivor size " SIZE_FORMAT " bytes, new threshold %u (max %u)",
 533                                 size_policy->calculated_survivor_size_in_bytes(),
 534                                 _tenuring_threshold, MaxTenuringThreshold);
 535        }
 536 
 537         if (UsePerfData) {
 538           PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 539           counters->update_tenuring_threshold(_tenuring_threshold);
 540           counters->update_survivor_size_counters();
 541         }
 542 
 543         // Do call at minor collections?
 544         // Don't check if the size_policy is ready at this
 545         // level.  Let the size_policy check that internally.
 546         if (UseAdaptiveSizePolicy &&
 547             UseAdaptiveGenerationSizePolicyAtMinorCollection &&
 548             ((gc_cause != GCCause::_java_lang_system_gc) ||
 549               UseAdaptiveSizePolicyWithSystemGC)) {
 550 
 551           // Calculate optimial free space amounts
 552           assert(young_gen->max_size() >
 553             young_gen->from_space()->capacity_in_bytes() +
 554             young_gen->to_space()->capacity_in_bytes(),
 555             "Sizes of space in young gen are out-of-bounds");
 556           size_t max_eden_size = young_gen->max_size() -
 557             young_gen->from_space()->capacity_in_bytes() -
 558             young_gen->to_space()->capacity_in_bytes();
 559           size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
 560                                    young_gen->eden_space()->used_in_bytes(),
 561                                    old_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     CodeCache::prune_scavenge_root_nmethods();
 606 
 607     // Re-verify object start arrays
 608     if (VerifyObjectStartArray &&
 609         VerifyAfterGC) {
 610       old_gen->verify_object_start_array();
 611     }
 612 
 613     // Verify all old -> young cards are now precise
 614     if (VerifyRememberedSets) {
 615       // Precise verification will give false positives. Until this is fixed,
 616       // use imprecise verification.
 617       // CardTableExtension::verify_all_young_refs_precise();
 618       CardTableExtension::verify_all_young_refs_imprecise();
 619     }
 620 
 621     if (TraceGen0Time) accumulated_time()->stop();
 622 
 623     if (PrintGC) {
 624       if (PrintGCDetails) {
 625         // Don't print a GC timestamp here.  This is after the GC so
 626         // would be confusing.
 627         young_gen->print_used_change(young_gen_used_before);
 628       }
 629       heap->print_heap_change(prev_used);
 630     }
 631 
 632     // Track memory usage and detect low memory
 633     MemoryService::track_memory_usage();
 634     heap->update_counters();
 635 
 636     gc_task_manager()->release_idle_workers();
 637   }
 638 
 639   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
 640     HandleMark hm;  // Discard invalid handles created during verification
 641     gclog_or_tty->print(" VerifyAfterGC:");
 642     Universe::verify();
 643   }
 644 
 645   heap->print_heap_after_gc();
 646 
 647   if (ZapUnusedHeapArea) {
 648     young_gen->eden_space()->check_mangled_unused_area_complete();
 649     young_gen->from_space()->check_mangled_unused_area_complete();
 650     young_gen->to_space()->check_mangled_unused_area_complete();
 651   }
 652 
 653   scavenge_exit.update();
 654 
 655   if (PrintGCTaskTimeStamps) {
 656     tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,
 657                   scavenge_entry.ticks(), scavenge_midpoint.ticks(),
 658                   scavenge_exit.ticks());
 659     gc_task_manager()->print_task_time_stamps();
 660   }
 661 
 662 #ifdef TRACESPINNING
 663   ParallelTaskTerminator::print_termination_counts();
 664 #endif
 665 
 666   return !promotion_failure_occurred;
 667 }
 668 
 669 // This method iterates over all objects in the young generation,
 670 // unforwarding markOops. It then restores any preserved mark oops,
 671 // and clears the _preserved_mark_stack.
 672 void PSScavenge::clean_up_failed_promotion() {
 673   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 674   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 675   assert(promotion_failed(), "Sanity");
 676 
 677   PSYoungGen* young_gen = heap->young_gen();
 678 
 679   {
 680     ResourceMark rm;
 681 
 682     // Unforward all pointers in the young gen.
 683     PSPromotionFailedClosure unforward_closure;
 684     young_gen->object_iterate(&unforward_closure);
 685 
 686     if (PrintGC && Verbose) {
 687       gclog_or_tty->print_cr("Restoring %d marks", _preserved_oop_stack.size());
 688     }
 689 
 690     // Restore any saved marks.
 691     while (!_preserved_oop_stack.is_empty()) {
 692       oop obj      = _preserved_oop_stack.pop();
 693       markOop mark = _preserved_mark_stack.pop();
 694       obj->set_mark(mark);
 695     }
 696 
 697     // Clear the preserved mark and oop stack caches.
 698     _preserved_mark_stack.clear(true);
 699     _preserved_oop_stack.clear(true);
 700     _promotion_failed = false;
 701   }
 702 
 703   // Reset the PromotionFailureALot counters.
 704   NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
 705 }
 706 
 707 // This method is called whenever an attempt to promote an object
 708 // fails. Some markOops will need preservation, some will not. Note
 709 // that the entire eden is traversed after a failed promotion, with
 710 // all forwarded headers replaced by the default markOop. This means
 711 // it is not neccessary to preserve most markOops.
 712 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
 713   _promotion_failed = true;
 714   if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
 715     // Should use per-worker private stakcs hetre rather than
 716     // locking a common pair of stacks.
 717     ThreadCritical tc;
 718     _preserved_oop_stack.push(obj);
 719     _preserved_mark_stack.push(obj_mark);
 720   }
 721 }
 722 
 723 bool PSScavenge::should_attempt_scavenge() {
 724   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 725   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 726   PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 727 
 728   if (UsePerfData) {
 729     counters->update_scavenge_skipped(not_skipped);
 730   }
 731 
 732   PSYoungGen* young_gen = heap->young_gen();
 733   PSOldGen* old_gen = heap->old_gen();
 734 
 735   if (!ScavengeWithObjectsInToSpace) {
 736     // Do not attempt to promote unless to_space is empty
 737     if (!young_gen->to_space()->is_empty()) {
 738       _consecutive_skipped_scavenges++;
 739       if (UsePerfData) {
 740         counters->update_scavenge_skipped(to_space_not_empty);
 741       }
 742       return false;
 743     }
 744   }
 745 
 746   // Test to see if the scavenge will likely fail.
 747   PSAdaptiveSizePolicy* policy = heap->size_policy();
 748 
 749   // A similar test is done in the policy's should_full_GC().  If this is
 750   // changed, decide if that test should also be changed.
 751   size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
 752   size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
 753   bool result = promotion_estimate < old_gen->free_in_bytes();
 754 
 755   if (PrintGCDetails && Verbose) {
 756     gclog_or_tty->print(result ? "  do scavenge: " : "  skip scavenge: ");
 757     gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
 758       " padded_average_promoted " SIZE_FORMAT
 759       " free in old gen " SIZE_FORMAT,
 760       (size_t) policy->average_promoted_in_bytes(),
 761       (size_t) policy->padded_average_promoted_in_bytes(),
 762       old_gen->free_in_bytes());
 763     if (young_gen->used_in_bytes() <
 764         (size_t) policy->padded_average_promoted_in_bytes()) {
 765       gclog_or_tty->print_cr(" padded_promoted_average is greater"
 766         " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
 767     }
 768   }
 769 
 770   if (result) {
 771     _consecutive_skipped_scavenges = 0;
 772   } else {
 773     _consecutive_skipped_scavenges++;
 774     if (UsePerfData) {
 775       counters->update_scavenge_skipped(promoted_too_large);
 776     }
 777   }
 778   return result;
 779 }
 780 
 781   // Used to add tasks
 782 GCTaskManager* const PSScavenge::gc_task_manager() {
 783   assert(ParallelScavengeHeap::gc_task_manager() != NULL,
 784    "shouldn't return NULL");
 785   return ParallelScavengeHeap::gc_task_manager();
 786 }
 787 
 788 void PSScavenge::initialize() {
 789   // Arguments must have been parsed
 790 
 791   if (AlwaysTenure) {
 792     _tenuring_threshold = 0;
 793   } else if (NeverTenure) {
 794     _tenuring_threshold = markOopDesc::max_age + 1;
 795   } else {
 796     // We want to smooth out our startup times for the AdaptiveSizePolicy
 797     _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
 798                                                     MaxTenuringThreshold;
 799   }
 800 
 801   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 802   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 803 
 804   PSYoungGen* young_gen = heap->young_gen();
 805   PSOldGen* old_gen = heap->old_gen();
 806 
 807   // Set boundary between young_gen and old_gen
 808   assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
 809          "old above young");
 810   _young_generation_boundary = young_gen->eden_space()->bottom();
 811 
 812   // Initialize ref handling object for scavenging.
 813   MemRegion mr = young_gen->reserved();
 814 
 815   _ref_processor =
 816     new ReferenceProcessor(mr,                         // span
 817                            ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
 818                            (int) ParallelGCThreads,    // mt processing degree
 819                            true,                       // mt discovery
 820                            (int) ParallelGCThreads,    // mt discovery degree
 821                            true,                       // atomic_discovery
 822                            NULL,                       // header provides liveness info
 823                            false);                     // next field updates do not need write barrier
 824 
 825   // Cache the cardtable
 826   BarrierSet* bs = Universe::heap()->barrier_set();
 827   assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
 828   _card_table = (CardTableExtension*)bs;
 829 
 830   _counters = new CollectorCounters("PSScavenge", 0);
 831 }