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 "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/gcHeapSummary.hpp"
  38 #include "gc_implementation/shared/gcTimer.hpp"
  39 #include "gc_implementation/shared/gcTrace.hpp"
  40 #include "gc_implementation/shared/gcTraceTime.hpp"
  41 #include "gc_implementation/shared/isGCActiveMark.hpp"
  42 #include "gc_implementation/shared/spaceDecorator.hpp"
  43 #include "gc_interface/gcCause.hpp"
  44 #include "memory/collectorPolicy.hpp"
  45 #include "memory/gcLocker.inline.hpp"
  46 #include "memory/referencePolicy.hpp"
  47 #include "memory/referenceProcessor.hpp"
  48 #include "memory/resourceArea.hpp"
  49 #include "oops/oop.inline.hpp"
  50 #include "oops/oop.psgc.inline.hpp"
  51 #include "runtime/biasedLocking.hpp"
  52 #include "runtime/fprofiler.hpp"
  53 #include "runtime/handles.inline.hpp"
  54 #include "runtime/threadCritical.hpp"
  55 #include "runtime/vmThread.hpp"
  56 #include "runtime/vm_operations.hpp"
  57 #include "services/memoryService.hpp"
  58 #include "utilities/stack.inline.hpp"
  59 
  60 
  61 HeapWord*                  PSScavenge::_to_space_top_before_gc = NULL;
  62 int                        PSScavenge::_consecutive_skipped_scavenges = 0;
  63 ReferenceProcessor*        PSScavenge::_ref_processor = NULL;
  64 CardTableExtension*        PSScavenge::_card_table = NULL;
  65 bool                       PSScavenge::_survivor_overflow = false;
  66 int                        PSScavenge::_tenuring_threshold = 0;
  67 HeapWord*                  PSScavenge::_young_generation_boundary = NULL;
  68 elapsedTimer               PSScavenge::_accumulated_time;
  69 STWGCTimer                 PSScavenge::_gc_timer;
  70 ParallelScavengeTracer     PSScavenge::_gc_tracer;
  71 Stack<markOop, mtGC>       PSScavenge::_preserved_mark_stack;
  72 Stack<oop, mtGC>           PSScavenge::_preserved_oop_stack;
  73 CollectorCounters*         PSScavenge::_counters = NULL;
  74 
  75 // Define before use
  76 class PSIsAliveClosure: public BoolObjectClosure {
  77 public:
  78   void do_object(oop p) {
  79     assert(false, "Do not call.");
  80   }
  81   bool do_object_b(oop p) {
  82     return (!PSScavenge::is_obj_in_young((HeapWord*) p)) || p->is_forwarded();
  83   }
  84 };
  85 
  86 PSIsAliveClosure PSScavenge::_is_alive_closure;
  87 
  88 class PSKeepAliveClosure: public OopClosure {
  89 protected:
  90   MutableSpace* _to_space;
  91   PSPromotionManager* _promotion_manager;
  92 
  93 public:
  94   PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
  95     ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  96     assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
  97     _to_space = heap->young_gen()->to_space();
  98 
  99     assert(_promotion_manager != NULL, "Sanity");
 100   }
 101 
 102   template <class T> void do_oop_work(T* p) {
 103     assert (!oopDesc::is_null(*p), "expected non-null ref");
 104     assert ((oopDesc::load_decode_heap_oop_not_null(p))->is_oop(),
 105             "expected an oop while scanning weak refs");
 106 
 107     // Weak refs may be visited more than once.
 108     if (PSScavenge::should_scavenge(p, _to_space)) {
 109       PSScavenge::copy_and_push_safe_barrier<T, /*promote_immediately=*/false>(_promotion_manager, p);
 110     }
 111   }
 112   virtual void do_oop(oop* p)       { PSKeepAliveClosure::do_oop_work(p); }
 113   virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
 114 };
 115 
 116 class PSEvacuateFollowersClosure: public VoidClosure {
 117  private:
 118   PSPromotionManager* _promotion_manager;
 119  public:
 120   PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}
 121 
 122   virtual void do_void() {
 123     assert(_promotion_manager != NULL, "Sanity");
 124     _promotion_manager->drain_stacks(true);
 125     guarantee(_promotion_manager->stacks_empty(),
 126               "stacks should be empty at this point");
 127   }
 128 };
 129 
 130 class PSPromotionFailedClosure : public ObjectClosure {
 131   virtual void do_object(oop obj) {
 132     if (obj->is_forwarded()) {
 133       obj->init_mark();
 134     }
 135   }
 136 };
 137 
 138 class PSRefProcTaskProxy: public GCTask {
 139   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
 140   ProcessTask & _rp_task;
 141   uint          _work_id;
 142 public:
 143   PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id)
 144     : _rp_task(rp_task),
 145       _work_id(work_id)
 146   { }
 147 
 148 private:
 149   virtual char* name() { return (char *)"Process referents by policy in parallel"; }
 150   virtual void do_it(GCTaskManager* manager, uint which);
 151 };
 152 
 153 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which)
 154 {
 155   PSPromotionManager* promotion_manager =
 156     PSPromotionManager::gc_thread_promotion_manager(which);
 157   assert(promotion_manager != NULL, "sanity check");
 158   PSKeepAliveClosure keep_alive(promotion_manager);
 159   PSEvacuateFollowersClosure evac_followers(promotion_manager);
 160   PSIsAliveClosure is_alive;
 161   _rp_task.work(_work_id, is_alive, keep_alive, evac_followers);
 162 }
 163 
 164 class PSRefEnqueueTaskProxy: public GCTask {
 165   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
 166   EnqueueTask& _enq_task;
 167   uint         _work_id;
 168 
 169 public:
 170   PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id)
 171     : _enq_task(enq_task),
 172       _work_id(work_id)
 173   { }
 174 
 175   virtual char* name() { return (char *)"Enqueue reference objects in parallel"; }
 176   virtual void do_it(GCTaskManager* manager, uint which)
 177   {
 178     _enq_task.work(_work_id);
 179   }
 180 };
 181 
 182 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
 183   virtual void execute(ProcessTask& task);
 184   virtual void execute(EnqueueTask& task);
 185 };
 186 
 187 void PSRefProcTaskExecutor::execute(ProcessTask& task)
 188 {
 189   GCTaskQueue* q = GCTaskQueue::create();
 190   GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
 191   for(uint i=0; i < manager->active_workers(); i++) {
 192     q->enqueue(new PSRefProcTaskProxy(task, i));
 193   }
 194   ParallelTaskTerminator terminator(manager->active_workers(),
 195                  (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth());
 196   if (task.marks_oops_alive() && manager->active_workers() > 1) {
 197     for (uint j = 0; j < manager->active_workers(); j++) {
 198       q->enqueue(new StealTask(&terminator));
 199     }
 200   }
 201   manager->execute_and_wait(q);
 202 }
 203 
 204 
 205 void PSRefProcTaskExecutor::execute(EnqueueTask& task)
 206 {
 207   GCTaskQueue* q = GCTaskQueue::create();
 208   GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
 209   for(uint i=0; i < manager->active_workers(); i++) {
 210     q->enqueue(new PSRefEnqueueTaskProxy(task, i));
 211   }
 212   manager->execute_and_wait(q);
 213 }
 214 
 215 // This method contains all heap specific policy for invoking scavenge.
 216 // PSScavenge::invoke_no_policy() will do nothing but attempt to
 217 // scavenge. It will not clean up after failed promotions, bail out if
 218 // we've exceeded policy time limits, or any other special behavior.
 219 // All such policy should be placed here.
 220 //
 221 // Note that this method should only be called from the vm_thread while
 222 // at a safepoint!
 223 bool PSScavenge::invoke() {
 224   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 225   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
 226   assert(!Universe::heap()->is_gc_active(), "not reentrant");
 227 
 228   ParallelScavengeHeap* const heap = (ParallelScavengeHeap*)Universe::heap();
 229   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 230 
 231   PSAdaptiveSizePolicy* policy = heap->size_policy();
 232   IsGCActiveMark mark;
 233 
 234   const bool scavenge_done = PSScavenge::invoke_no_policy();
 235   const bool need_full_gc = !scavenge_done ||
 236     policy->should_full_GC(heap->old_gen()->free_in_bytes());
 237   bool full_gc_done = false;
 238 
 239   if (UsePerfData) {
 240     PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
 241     const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped;
 242     counters->update_full_follows_scavenge(ffs_val);
 243   }
 244 
 245   if (need_full_gc) {
 246     GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
 247     CollectorPolicy* cp = heap->collector_policy();
 248     const bool clear_all_softrefs = cp->should_clear_all_soft_refs();
 249 
 250     if (UseParallelOldGC) {
 251       full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs);
 252     } else {
 253       full_gc_done = PSMarkSweep::invoke_no_policy(clear_all_softrefs);
 254     }
 255   }
 256 
 257   return full_gc_done;
 258 }
 259 
 260 // This method contains no policy. You should probably
 261 // be calling invoke() instead.
 262 bool PSScavenge::invoke_no_policy() {
 263   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 264   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
 265 
 266   assert(_preserved_mark_stack.is_empty(), "should be empty");
 267   assert(_preserved_oop_stack.is_empty(), "should be empty");
 268 
 269   _gc_timer.register_gc_start(os::elapsed_counter());
 270 
 271   TimeStamp scavenge_entry;
 272   TimeStamp scavenge_midpoint;
 273   TimeStamp scavenge_exit;
 274 
 275   scavenge_entry.update();
 276 
 277   if (GC_locker::check_active_before_gc()) {
 278     return false;
 279   }
 280 
 281   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 282   GCCause::Cause gc_cause = heap->gc_cause();
 283   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 284 
 285   // Check for potential problems.
 286   if (!should_attempt_scavenge()) {
 287     return false;
 288   }
 289 
 290   _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
 291 
 292   bool promotion_failure_occurred = false;
 293 
 294   PSYoungGen* young_gen = heap->young_gen();
 295   PSOldGen* old_gen = heap->old_gen();
 296   PSPermGen* perm_gen = heap->perm_gen();
 297   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
 298 
 299   heap->increment_total_collections();
 300 
 301   AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
 302 
 303   if ((gc_cause != GCCause::_java_lang_system_gc) ||
 304        UseAdaptiveSizePolicyWithSystemGC) {
 305     // Gather the feedback data for eden occupancy.
 306     young_gen->eden_space()->accumulate_statistics();
 307   }
 308 
 309   if (ZapUnusedHeapArea) {
 310     // Save information needed to minimize mangling
 311     heap->record_gen_tops_before_GC();
 312   }
 313 
 314   heap->print_heap_before_gc();
 315   heap->trace_heap_before_gc(&_gc_tracer);
 316 
 317   assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
 318   assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
 319 
 320   size_t prev_used = heap->used();
 321 
 322   // Fill in TLABs
 323   heap->accumulate_statistics_all_tlabs();
 324   heap->ensure_parsability(true);  // retire TLABs
 325 
 326   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
 327     HandleMark hm;  // Discard invalid handles created during verification
 328     gclog_or_tty->print(" VerifyBeforeGC:");
 329     Universe::verify();
 330   }
 331 
 332   {
 333     ResourceMark rm;
 334     HandleMark hm;
 335 
 336     gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
 337     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
 338     GCTraceTime t1(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, NULL);
 339     TraceCollectorStats tcs(counters());
 340     TraceMemoryManagerStats tms(false /* not full GC */,gc_cause);
 341 
 342     if (TraceGen0Time) accumulated_time()->start();
 343 
 344     // Let the size policy know we're starting
 345     size_policy->minor_collection_begin();
 346 
 347     // Verify the object start arrays.
 348     if (VerifyObjectStartArray &&
 349         VerifyBeforeGC) {
 350       old_gen->verify_object_start_array();
 351       perm_gen->verify_object_start_array();
 352     }
 353 
 354     // Verify no unmarked old->young roots
 355     if (VerifyRememberedSets) {
 356       CardTableExtension::verify_all_young_refs_imprecise();
 357     }
 358 
 359     if (!ScavengeWithObjectsInToSpace) {
 360       assert(young_gen->to_space()->is_empty(),
 361              "Attempt to scavenge with live objects in to_space");
 362       young_gen->to_space()->clear(SpaceDecorator::Mangle);
 363     } else if (ZapUnusedHeapArea) {
 364       young_gen->to_space()->mangle_unused_area();
 365     }
 366     save_to_space_top_before_gc();
 367 
 368     COMPILER2_PRESENT(DerivedPointerTable::clear());
 369 
 370     reference_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
 371     reference_processor()->setup_policy(false);
 372 
 373     // We track how much was promoted to the next generation for
 374     // the AdaptiveSizePolicy.
 375     size_t old_gen_used_before = old_gen->used_in_bytes();
 376 
 377     // For PrintGCDetails
 378     size_t young_gen_used_before = young_gen->used_in_bytes();
 379 
 380     // Reset our survivor overflow.
 381     set_survivor_overflow(false);
 382 
 383     // We need to save the old/perm top values before
 384     // creating the promotion_manager. We pass the top
 385     // values to the card_table, to prevent it from
 386     // straying into the promotion labs.
 387     HeapWord* old_top = old_gen->object_space()->top();
 388     HeapWord* perm_top = perm_gen->object_space()->top();
 389 
 390     // Release all previously held resources
 391     gc_task_manager()->release_all_resources();
 392 
 393     // Set the number of GC threads to be used in this collection
 394     gc_task_manager()->set_active_gang();
 395     gc_task_manager()->task_idle_workers();
 396     // Get the active number of workers here and use that value
 397     // throughout the methods.
 398     uint active_workers = gc_task_manager()->active_workers();
 399     heap->set_par_threads(active_workers);
 400 
 401     PSPromotionManager::pre_scavenge();
 402 
 403     // We'll use the promotion manager again later.
 404     PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
 405     {
 406       GCTraceTime tm("Scavenge", false, false, &_gc_timer);
 407       ParallelScavengeHeap::ParStrongRootsScope psrs;
 408 
 409       GCTaskQueue* q = GCTaskQueue::create();
 410 
 411       uint stripe_total = active_workers;
 412       for(uint i=0; i < stripe_total; i++) {
 413         q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));
 414       }
 415 
 416       q->enqueue(new SerialOldToYoungRootsTask(perm_gen, perm_top));
 417 
 418       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
 419       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
 420       // We scan the thread roots in parallel
 421       Threads::create_thread_roots_tasks(q);
 422       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
 423       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));
 424       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
 425       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
 426       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
 427       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
 428 
 429       ParallelTaskTerminator terminator(
 430         active_workers,
 431                   (TaskQueueSetSuper*) promotion_manager->stack_array_depth());
 432       if (active_workers > 1) {
 433         for (uint j = 0; j < active_workers; j++) {
 434           q->enqueue(new StealTask(&terminator));
 435         }
 436       }
 437 
 438       gc_task_manager()->execute_and_wait(q);
 439     }
 440 
 441     scavenge_midpoint.update();
 442 
 443     // Process reference objects discovered during scavenge
 444     {
 445       GCTraceTime tm("References", false, false, &_gc_timer);
 446 
 447       reference_processor()->setup_policy(false); // not always_clear
 448       reference_processor()->set_active_mt_degree(active_workers);
 449       PSKeepAliveClosure keep_alive(promotion_manager);
 450       PSEvacuateFollowersClosure evac_followers(promotion_manager);
 451       ReferenceProcessorStats stats;
 452       if (reference_processor()->processing_is_mt()) {
 453         PSRefProcTaskExecutor task_executor;
 454         stats = reference_processor()->process_discovered_references(
 455           &_is_alive_closure, &keep_alive, &evac_followers, &task_executor,
 456           &_gc_timer);
 457       } else {
 458         stats = reference_processor()->process_discovered_references(
 459           &_is_alive_closure, &keep_alive, &evac_followers, NULL, &_gc_timer);
 460       }
 461 
 462       _gc_tracer.report_gc_reference_stats(stats);
 463 
 464       // Enqueue reference objects discovered during scavenge.
 465       if (reference_processor()->processing_is_mt()) {
 466         PSRefProcTaskExecutor task_executor;
 467         reference_processor()->enqueue_discovered_references(&task_executor);
 468       } else {
 469         reference_processor()->enqueue_discovered_references(NULL);
 470       }
 471     }
 472 
 473     if (!JavaObjectsInPerm) {
 474       GCTraceTime tm("StringTable", false, false, &_gc_timer);
 475       // Unlink any dead interned Strings
 476       StringTable::unlink(&_is_alive_closure);
 477       // Process the remaining live ones
 478       PSScavengeRootsClosure root_closure(promotion_manager);
 479       StringTable::oops_do(&root_closure);
 480     }
 481 
 482     // Finally, flush the promotion_manager's labs, and deallocate its stacks.
 483     promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer);
 484     if (promotion_failure_occurred) {
 485       clean_up_failed_promotion();
 486       if (PrintGC) {
 487         gclog_or_tty->print("--");
 488       }
 489     }
 490 
 491     // Let the size policy know we're done.  Note that we count promotion
 492     // failure cleanup time as part of the collection (otherwise, we're
 493     // implicitly saying it's mutator time).
 494     size_policy->minor_collection_end(gc_cause);
 495 
 496     if (!promotion_failure_occurred) {
 497       // Swap the survivor spaces.
 498       young_gen->eden_space()->clear(SpaceDecorator::Mangle);
 499       young_gen->from_space()->clear(SpaceDecorator::Mangle);
 500       young_gen->swap_spaces();
 501 
 502       size_t survived = young_gen->from_space()->used_in_bytes();
 503       size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
 504       size_policy->update_averages(_survivor_overflow, survived, promoted);
 505 
 506       // A successful scavenge should restart the GC time limit count which is
 507       // for full GC's.
 508       size_policy->reset_gc_overhead_limit_count();
 509       if (UseAdaptiveSizePolicy) {
 510         // Calculate the new survivor size and tenuring threshold
 511 
 512         if (PrintAdaptiveSizePolicy) {
 513           gclog_or_tty->print("AdaptiveSizeStart: ");
 514           gclog_or_tty->stamp();
 515           gclog_or_tty->print_cr(" collection: %d ",
 516                          heap->total_collections());
 517 
 518           if (Verbose) {
 519             gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d"
 520               " perm_gen_capacity: %d ",
 521               old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes(),
 522               perm_gen->capacity_in_bytes());
 523           }
 524         }
 525 
 526 
 527         if (UsePerfData) {
 528           PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 529           counters->update_old_eden_size(
 530             size_policy->calculated_eden_size_in_bytes());
 531           counters->update_old_promo_size(
 532             size_policy->calculated_promo_size_in_bytes());
 533           counters->update_old_capacity(old_gen->capacity_in_bytes());
 534           counters->update_young_capacity(young_gen->capacity_in_bytes());
 535           counters->update_survived(survived);
 536           counters->update_promoted(promoted);
 537           counters->update_survivor_overflowed(_survivor_overflow);
 538         }
 539 
 540         size_t survivor_limit =
 541           size_policy->max_survivor_size(young_gen->max_size());
 542         _tenuring_threshold =
 543           size_policy->compute_survivor_space_size_and_threshold(
 544                                                            _survivor_overflow,
 545                                                            _tenuring_threshold,
 546                                                            survivor_limit);
 547 
 548        if (PrintTenuringDistribution) {
 549          gclog_or_tty->cr();
 550          gclog_or_tty->print_cr("Desired survivor size %ld bytes, new threshold %d (max %d)",
 551                                 size_policy->calculated_survivor_size_in_bytes(),
 552                                 _tenuring_threshold, MaxTenuringThreshold);
 553        }
 554 
 555         if (UsePerfData) {
 556           PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 557           counters->update_tenuring_threshold(_tenuring_threshold);
 558           counters->update_survivor_size_counters();
 559         }
 560 
 561         // Do call at minor collections?
 562         // Don't check if the size_policy is ready at this
 563         // level.  Let the size_policy check that internally.
 564         if (UseAdaptiveSizePolicy &&
 565             UseAdaptiveGenerationSizePolicyAtMinorCollection &&
 566             ((gc_cause != GCCause::_java_lang_system_gc) ||
 567               UseAdaptiveSizePolicyWithSystemGC)) {
 568 
 569           // Calculate optimial free space amounts
 570           assert(young_gen->max_size() >
 571             young_gen->from_space()->capacity_in_bytes() +
 572             young_gen->to_space()->capacity_in_bytes(),
 573             "Sizes of space in young gen are out-of-bounds");
 574           size_t max_eden_size = young_gen->max_size() -
 575             young_gen->from_space()->capacity_in_bytes() -
 576             young_gen->to_space()->capacity_in_bytes();
 577           size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
 578                                    young_gen->eden_space()->used_in_bytes(),
 579                                    old_gen->used_in_bytes(),
 580                                    perm_gen->used_in_bytes(),
 581                                    young_gen->eden_space()->capacity_in_bytes(),
 582                                    old_gen->max_gen_size(),
 583                                    max_eden_size,
 584                                    false  /* full gc*/,
 585                                    gc_cause,
 586                                    heap->collector_policy());
 587 
 588         }
 589         // Resize the young generation at every collection
 590         // even if new sizes have not been calculated.  This is
 591         // to allow resizes that may have been inhibited by the
 592         // relative location of the "to" and "from" spaces.
 593 
 594         // Resizing the old gen at minor collects can cause increases
 595         // that don't feed back to the generation sizing policy until
 596         // a major collection.  Don't resize the old gen here.
 597 
 598         heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
 599                         size_policy->calculated_survivor_size_in_bytes());
 600 
 601         if (PrintAdaptiveSizePolicy) {
 602           gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
 603                          heap->total_collections());
 604         }
 605       }
 606 
 607       // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
 608       // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
 609       // Also update() will case adaptive NUMA chunk resizing.
 610       assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
 611       young_gen->eden_space()->update();
 612 
 613       heap->gc_policy_counters()->update_counters();
 614 
 615       heap->resize_all_tlabs();
 616 
 617       assert(young_gen->to_space()->is_empty(), "to space should be empty now");
 618     }
 619 
 620     COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
 621 
 622     NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
 623 
 624     {
 625       GCTraceTime tm("Prune Scavenge Root Methods", false, false, &_gc_timer);
 626 
 627       CodeCache::prune_scavenge_root_nmethods();
 628     }
 629 
 630     // Re-verify object start arrays
 631     if (VerifyObjectStartArray &&
 632         VerifyAfterGC) {
 633       old_gen->verify_object_start_array();
 634       perm_gen->verify_object_start_array();
 635     }
 636 
 637     // Verify all old -> young cards are now precise
 638     if (VerifyRememberedSets) {
 639       // Precise verification will give false positives. Until this is fixed,
 640       // use imprecise verification.
 641       // CardTableExtension::verify_all_young_refs_precise();
 642       CardTableExtension::verify_all_young_refs_imprecise();
 643     }
 644 
 645     if (TraceGen0Time) accumulated_time()->stop();
 646 
 647     if (PrintGC) {
 648       if (PrintGCDetails) {
 649         // Don't print a GC timestamp here.  This is after the GC so
 650         // would be confusing.
 651         young_gen->print_used_change(young_gen_used_before);
 652       }
 653       heap->print_heap_change(prev_used);
 654     }
 655 
 656     // Track memory usage and detect low memory
 657     MemoryService::track_memory_usage();
 658     heap->update_counters();
 659 
 660     gc_task_manager()->release_idle_workers();
 661   }
 662 
 663   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
 664     HandleMark hm;  // Discard invalid handles created during verification
 665     gclog_or_tty->print(" VerifyAfterGC:");
 666     Universe::verify();
 667   }
 668 
 669   heap->print_heap_after_gc();
 670   heap->trace_heap_after_gc(&_gc_tracer);
 671   _gc_tracer.report_tenuring_threshold(tenuring_threshold());
 672 
 673   if (ZapUnusedHeapArea) {
 674     young_gen->eden_space()->check_mangled_unused_area_complete();
 675     young_gen->from_space()->check_mangled_unused_area_complete();
 676     young_gen->to_space()->check_mangled_unused_area_complete();
 677   }
 678 
 679   scavenge_exit.update();
 680 
 681   if (PrintGCTaskTimeStamps) {
 682     tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,
 683                   scavenge_entry.ticks(), scavenge_midpoint.ticks(),
 684                   scavenge_exit.ticks());
 685     gc_task_manager()->print_task_time_stamps();
 686   }
 687 
 688 #ifdef TRACESPINNING
 689   ParallelTaskTerminator::print_termination_counts();
 690 #endif
 691 
 692 
 693   _gc_timer.register_gc_end(os::elapsed_counter());
 694 
 695   _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
 696 
 697   return !promotion_failure_occurred;
 698 }
 699 
 700 // This method iterates over all objects in the young generation,
 701 // unforwarding markOops. It then restores any preserved mark oops,
 702 // and clears the _preserved_mark_stack.
 703 void PSScavenge::clean_up_failed_promotion() {
 704   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 705   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 706 
 707   PSYoungGen* young_gen = heap->young_gen();
 708 
 709   {
 710     ResourceMark rm;
 711 
 712     // Unforward all pointers in the young gen.
 713     PSPromotionFailedClosure unforward_closure;
 714     young_gen->object_iterate(&unforward_closure);
 715 
 716     if (PrintGC && Verbose) {
 717       gclog_or_tty->print_cr("Restoring %d marks", _preserved_oop_stack.size());
 718     }
 719 
 720     // Restore any saved marks.
 721     while (!_preserved_oop_stack.is_empty()) {
 722       oop obj      = _preserved_oop_stack.pop();
 723       markOop mark = _preserved_mark_stack.pop();
 724       obj->set_mark(mark);
 725     }
 726 
 727     // Clear the preserved mark and oop stack caches.
 728     _preserved_mark_stack.clear(true);
 729     _preserved_oop_stack.clear(true);
 730   }
 731 
 732   // Reset the PromotionFailureALot counters.
 733   NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
 734 }
 735 
 736 // This method is called whenever an attempt to promote an object
 737 // fails. Some markOops will need preservation, some will not. Note
 738 // that the entire eden is traversed after a failed promotion, with
 739 // all forwarded headers replaced by the default markOop. This means
 740 // it is not necessary to preserve most markOops.
 741 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
 742   if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
 743     // Should use per-worker private stacks here rather than
 744     // locking a common pair of stacks.
 745     ThreadCritical tc;
 746     _preserved_oop_stack.push(obj);
 747     _preserved_mark_stack.push(obj_mark);
 748   }
 749 }
 750 
 751 bool PSScavenge::should_attempt_scavenge() {
 752   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 753   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 754   PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 755 
 756   if (UsePerfData) {
 757     counters->update_scavenge_skipped(not_skipped);
 758   }
 759 
 760   PSYoungGen* young_gen = heap->young_gen();
 761   PSOldGen* old_gen = heap->old_gen();
 762 
 763   if (!ScavengeWithObjectsInToSpace) {
 764     // Do not attempt to promote unless to_space is empty
 765     if (!young_gen->to_space()->is_empty()) {
 766       _consecutive_skipped_scavenges++;
 767       if (UsePerfData) {
 768         counters->update_scavenge_skipped(to_space_not_empty);
 769       }
 770       return false;
 771     }
 772   }
 773 
 774   // Test to see if the scavenge will likely fail.
 775   PSAdaptiveSizePolicy* policy = heap->size_policy();
 776 
 777   // A similar test is done in the policy's should_full_GC().  If this is
 778   // changed, decide if that test should also be changed.
 779   size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
 780   size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
 781   bool result = promotion_estimate < old_gen->free_in_bytes();
 782 
 783   if (PrintGCDetails && Verbose) {
 784     gclog_or_tty->print(result ? "  do scavenge: " : "  skip scavenge: ");
 785     gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
 786       " padded_average_promoted " SIZE_FORMAT
 787       " free in old gen " SIZE_FORMAT,
 788       (size_t) policy->average_promoted_in_bytes(),
 789       (size_t) policy->padded_average_promoted_in_bytes(),
 790       old_gen->free_in_bytes());
 791     if (young_gen->used_in_bytes() <
 792         (size_t) policy->padded_average_promoted_in_bytes()) {
 793       gclog_or_tty->print_cr(" padded_promoted_average is greater"
 794         " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
 795     }
 796   }
 797 
 798   if (result) {
 799     _consecutive_skipped_scavenges = 0;
 800   } else {
 801     _consecutive_skipped_scavenges++;
 802     if (UsePerfData) {
 803       counters->update_scavenge_skipped(promoted_too_large);
 804     }
 805   }
 806   return result;
 807 }
 808 
 809   // Used to add tasks
 810 GCTaskManager* const PSScavenge::gc_task_manager() {
 811   assert(ParallelScavengeHeap::gc_task_manager() != NULL,
 812    "shouldn't return NULL");
 813   return ParallelScavengeHeap::gc_task_manager();
 814 }
 815 
 816 void PSScavenge::initialize() {
 817   // Arguments must have been parsed
 818 
 819   if (AlwaysTenure) {
 820     _tenuring_threshold = 0;
 821   } else if (NeverTenure) {
 822     _tenuring_threshold = markOopDesc::max_age + 1;
 823   } else {
 824     // We want to smooth out our startup times for the AdaptiveSizePolicy
 825     _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
 826                                                     MaxTenuringThreshold;
 827   }
 828 
 829   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 830   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 831 
 832   PSYoungGen* young_gen = heap->young_gen();
 833   PSOldGen* old_gen = heap->old_gen();
 834   PSPermGen* perm_gen = heap->perm_gen();
 835 
 836   // Set boundary between young_gen and old_gen
 837   assert(perm_gen->reserved().end() <= old_gen->object_space()->bottom(),
 838          "perm above old");
 839   assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
 840          "old above young");
 841   _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                            (int) ParallelGCThreads,    // mt processing degree
 850                            true,                       // mt discovery
 851                            (int) ParallelGCThreads,    // mt discovery degree
 852                            true,                       // atomic_discovery
 853                            NULL,                       // header provides liveness info
 854                            false);                     // next field updates do not need write barrier
 855 
 856   // Cache the cardtable
 857   BarrierSet* bs = Universe::heap()->barrier_set();
 858   assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
 859   _card_table = (CardTableExtension*)bs;
 860 
 861   _counters = new CollectorCounters("PSScavenge", 0);
 862 }