1 
   2 /*
   3  * Copyright (c) 2002, 2014, Oracle and/or its affiliates. All rights reserved.
   4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   5  *
   6  * This code is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License version 2 only, as
   8  * published by the Free Software Foundation.
   9  *
  10  * This code is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13  * version 2 for more details (a copy is included in the LICENSE file that
  14  * accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License version
  17  * 2 along with this work; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  19  *
  20  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  21  * or visit www.oracle.com if you need additional information or have any
  22  * questions.
  23  *
  24  */
  25 
  26 #include "precompiled.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "code/codeCache.hpp"
  29 #include "gc_implementation/parallelScavenge/cardTableExtension.hpp"
  30 #include "gc_implementation/parallelScavenge/gcTaskManager.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 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  61 
  62 HeapWord*                  PSScavenge::_to_space_top_before_gc = NULL;
  63 int                        PSScavenge::_consecutive_skipped_scavenges = 0;
  64 ReferenceProcessor*        PSScavenge::_ref_processor = NULL;
  65 CardTableExtension*        PSScavenge::_card_table = NULL;
  66 bool                       PSScavenge::_survivor_overflow = false;
  67 uint                       PSScavenge::_tenuring_threshold = 0;
  68 HeapWord*                  PSScavenge::_young_generation_boundary = NULL;
  69 uintptr_t                  PSScavenge::_young_generation_boundary_compressed = 0;
  70 elapsedTimer               PSScavenge::_accumulated_time;
  71 STWGCTimer                 PSScavenge::_gc_timer;
  72 ParallelScavengeTracer     PSScavenge::_gc_tracer;
  73 Stack<markOop, mtGC>       PSScavenge::_preserved_mark_stack;
  74 Stack<oop, mtGC>           PSScavenge::_preserved_oop_stack;
  75 CollectorCounters*         PSScavenge::_counters = NULL;
  76 
  77 // Define before use
  78 class PSIsAliveClosure: public BoolObjectClosure {
  79 public:
  80   bool do_object_b(oop p) {
  81     return (!PSScavenge::is_obj_in_young(p)) || p->is_forwarded();
  82   }
  83 };
  84 
  85 PSIsAliveClosure PSScavenge::_is_alive_closure;
  86 
  87 class PSKeepAliveClosure: public OopClosure {
  88 protected:
  89   MutableSpace* _to_space;
  90   PSPromotionManager* _promotion_manager;
  91 
  92 public:
  93   PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {
  94     ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  95     assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
  96     _to_space = heap->young_gen()->to_space();
  97 
  98     assert(_promotion_manager != NULL, "Sanity");
  99   }
 100 
 101   template <class T> void do_oop_work(T* p) {
 102     assert (!oopDesc::is_null(*p), "expected non-null ref");
 103     assert ((oopDesc::load_decode_heap_oop_not_null(p))->is_oop(),
 104             "expected an oop while scanning weak refs");
 105 
 106     // Weak refs may be visited more than once.
 107     if (PSScavenge::should_scavenge(p, _to_space)) {
 108       _promotion_manager->copy_and_push_safe_barrier<T, /*promote_immediately=*/false>(p);
 109     }
 110   }
 111   virtual void do_oop(oop* p)       { PSKeepAliveClosure::do_oop_work(p); }
 112   virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }
 113 };
 114 
 115 class PSEvacuateFollowersClosure: public VoidClosure {
 116  private:
 117   PSPromotionManager* _promotion_manager;
 118  public:
 119   PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}
 120 
 121   virtual void do_void() {
 122     assert(_promotion_manager != NULL, "Sanity");
 123     _promotion_manager->drain_stacks(true);
 124     guarantee(_promotion_manager->stacks_empty(),
 125               "stacks should be empty at this point");
 126   }
 127 };
 128 
 129 class PSPromotionFailedClosure : public ObjectClosure {
 130   virtual void do_object(oop obj) {
 131     if (obj->is_forwarded()) {
 132       obj->init_mark();
 133     }
 134   }
 135 };
 136 
 137 class PSRefProcTaskProxy: public GCTask {
 138   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
 139   ProcessTask & _rp_task;
 140   uint          _work_id;
 141 public:
 142   PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id)
 143     : _rp_task(rp_task),
 144       _work_id(work_id)
 145   { }
 146 
 147 private:
 148   virtual char* name() { return (char *)"Process referents by policy in parallel"; }
 149   virtual void do_it(GCTaskManager* manager, uint which);
 150 };
 151 
 152 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which)
 153 {
 154   PSPromotionManager* promotion_manager =
 155     PSPromotionManager::gc_thread_promotion_manager(which);
 156   assert(promotion_manager != NULL, "sanity check");
 157   PSKeepAliveClosure keep_alive(promotion_manager);
 158   PSEvacuateFollowersClosure evac_followers(promotion_manager);
 159   PSIsAliveClosure is_alive;
 160   _rp_task.work(_work_id, is_alive, keep_alive, evac_followers);
 161 }
 162 
 163 class PSRefEnqueueTaskProxy: public GCTask {
 164   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
 165   EnqueueTask& _enq_task;
 166   uint         _work_id;
 167 
 168 public:
 169   PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id)
 170     : _enq_task(enq_task),
 171       _work_id(work_id)
 172   { }
 173 
 174   virtual char* name() { return (char *)"Enqueue reference objects in parallel"; }
 175   virtual void do_it(GCTaskManager* manager, uint which)
 176   {
 177     _enq_task.work(_work_id);
 178   }
 179 };
 180 
 181 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
 182   virtual void execute(ProcessTask& task);
 183   virtual void execute(EnqueueTask& task);
 184 };
 185 
 186 void PSRefProcTaskExecutor::execute(ProcessTask& task)
 187 {
 188   GCTaskQueue* q = GCTaskQueue::create();
 189   GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
 190   for(uint i=0; i < manager->active_workers(); i++) {
 191     q->enqueue(new PSRefProcTaskProxy(task, i));
 192   }
 193   ParallelTaskTerminator terminator(manager->active_workers(),
 194                  (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth());
 195   if (task.marks_oops_alive() && manager->active_workers() > 1) {
 196     for (uint j = 0; j < manager->active_workers(); j++) {
 197       q->enqueue(new StealTask(&terminator));
 198     }
 199   }
 200   manager->execute_and_wait(q);
 201 }
 202 
 203 
 204 void PSRefProcTaskExecutor::execute(EnqueueTask& task)
 205 {
 206   GCTaskQueue* q = GCTaskQueue::create();
 207   GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();
 208   for(uint i=0; i < manager->active_workers(); i++) {
 209     q->enqueue(new PSRefEnqueueTaskProxy(task, i));
 210   }
 211   manager->execute_and_wait(q);
 212 }
 213 
 214 // This method contains all heap specific policy for invoking scavenge.
 215 // PSScavenge::invoke_no_policy() will do nothing but attempt to
 216 // scavenge. It will not clean up after failed promotions, bail out if
 217 // we've exceeded policy time limits, or any other special behavior.
 218 // All such policy should be placed here.
 219 //
 220 // Note that this method should only be called from the vm_thread while
 221 // at a safepoint!
 222 bool PSScavenge::invoke() {
 223   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 224   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
 225   assert(!Universe::heap()->is_gc_active(), "not reentrant");
 226 
 227   ParallelScavengeHeap* const heap = (ParallelScavengeHeap*)Universe::heap();
 228   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 229 
 230   PSAdaptiveSizePolicy* policy = heap->size_policy();
 231   IsGCActiveMark mark;
 232 
 233   const bool scavenge_done = PSScavenge::invoke_no_policy();
 234   const bool need_full_gc = !scavenge_done ||
 235     policy->should_full_GC(heap->old_gen()->free_in_bytes());
 236   bool full_gc_done = false;
 237 
 238   if (UsePerfData) {
 239     PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
 240     const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped;
 241     counters->update_full_follows_scavenge(ffs_val);
 242   }
 243 
 244   if (need_full_gc) {
 245     GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);
 246     CollectorPolicy* cp = heap->collector_policy();
 247     const bool clear_all_softrefs = cp->should_clear_all_soft_refs();
 248 
 249     if (UseParallelOldGC) {
 250       full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs);
 251     } else {
 252       full_gc_done = PSMarkSweep::invoke_no_policy(clear_all_softrefs);
 253     }
 254   }
 255 
 256   return full_gc_done;
 257 }
 258 
 259 // This method contains no policy. You should probably
 260 // be calling invoke() instead.
 261 bool PSScavenge::invoke_no_policy() {
 262   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
 263   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
 264 
 265   assert(_preserved_mark_stack.is_empty(), "should be empty");
 266   assert(_preserved_oop_stack.is_empty(), "should be empty");
 267 
 268   _gc_timer.register_gc_start();
 269 
 270   TimeStamp scavenge_entry;
 271   TimeStamp scavenge_midpoint;
 272   TimeStamp scavenge_exit;
 273 
 274   scavenge_entry.update();
 275 
 276   if (GC_locker::check_active_before_gc()) {
 277     return false;
 278   }
 279 
 280   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 281   GCCause::Cause gc_cause = heap->gc_cause();
 282   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 283 
 284   // Check for potential problems.
 285   if (!should_attempt_scavenge()) {
 286     return false;
 287   }
 288 
 289   _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
 290 
 291   bool promotion_failure_occurred = false;
 292 
 293   PSYoungGen* young_gen = heap->young_gen();
 294   PSOldGen* old_gen = heap->old_gen();
 295   PSAdaptiveSizePolicy* size_policy = heap->size_policy();
 296 
 297   heap->increment_total_collections();
 298 
 299   AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
 300 
 301   if ((gc_cause != GCCause::_java_lang_system_gc) ||
 302        UseAdaptiveSizePolicyWithSystemGC) {
 303     // Gather the feedback data for eden occupancy.
 304     young_gen->eden_space()->accumulate_statistics();
 305   }
 306 
 307   if (ZapUnusedHeapArea) {
 308     // Save information needed to minimize mangling
 309     heap->record_gen_tops_before_GC();
 310   }
 311 
 312   heap->print_heap_before_gc();
 313   heap->trace_heap_before_gc(&_gc_tracer);
 314 
 315   assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");
 316   assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");
 317 
 318   size_t prev_used = heap->used();
 319 
 320   // Fill in TLABs
 321   heap->accumulate_statistics_all_tlabs();
 322   heap->ensure_parsability(true);  // retire TLABs
 323 
 324   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
 325     HandleMark hm;  // Discard invalid handles created during verification
 326     Universe::verify(" VerifyBeforeGC:");
 327   }
 328 
 329   {
 330     ResourceMark rm;
 331     HandleMark hm;
 332 
 333     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
 334     GCTraceTime t1(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, NULL, _gc_tracer.gc_id());
 335     TraceCollectorStats tcs(counters());
 336     TraceMemoryManagerStats tms(false /* not full GC */,gc_cause);
 337 
 338     if (TraceYoungGenTime) accumulated_time()->start();
 339 
 340     // Let the size policy know we're starting
 341     size_policy->minor_collection_begin();
 342 
 343     // Verify the object start arrays.
 344     if (VerifyObjectStartArray &&
 345         VerifyBeforeGC) {
 346       old_gen->verify_object_start_array();
 347     }
 348 
 349     // Verify no unmarked old->young roots
 350     if (VerifyRememberedSets) {
 351       CardTableExtension::verify_all_young_refs_imprecise();
 352     }
 353 
 354     if (!ScavengeWithObjectsInToSpace) {
 355       assert(young_gen->to_space()->is_empty(),
 356              "Attempt to scavenge with live objects in to_space");
 357       young_gen->to_space()->clear(SpaceDecorator::Mangle);
 358     } else if (ZapUnusedHeapArea) {
 359       young_gen->to_space()->mangle_unused_area();
 360     }
 361     save_to_space_top_before_gc();
 362 
 363     COMPILER2_PRESENT(DerivedPointerTable::clear());
 364 
 365     reference_processor()->enable_discovery();
 366     reference_processor()->setup_policy(false);
 367 
 368     // We track how much was promoted to the next generation for
 369     // the AdaptiveSizePolicy.
 370     size_t old_gen_used_before = old_gen->used_in_bytes();
 371 
 372     // For PrintGCDetails
 373     size_t young_gen_used_before = young_gen->used_in_bytes();
 374 
 375     // Reset our survivor overflow.
 376     set_survivor_overflow(false);
 377 
 378     // We need to save the old top values before
 379     // creating the promotion_manager. We pass the top
 380     // values to the card_table, to prevent it from
 381     // straying into the promotion labs.
 382     HeapWord* old_top = old_gen->object_space()->top();
 383 
 384     // Release all previously held resources
 385     gc_task_manager()->release_all_resources();
 386 
 387     // Set the number of GC threads to be used in this collection
 388     gc_task_manager()->set_active_gang();
 389     gc_task_manager()->task_idle_workers();
 390     // Get the active number of workers here and use that value
 391     // throughout the methods.
 392     uint active_workers = gc_task_manager()->active_workers();
 393     heap->set_par_threads(active_workers);
 394 
 395     PSPromotionManager::pre_scavenge();
 396 
 397     // We'll use the promotion manager again later.
 398     PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();
 399     {
 400       GCTraceTime tm("Scavenge", false, false, &_gc_timer, _gc_tracer.gc_id());
 401       ParallelScavengeHeap::ParStrongRootsScope psrs;
 402 
 403       GCTaskQueue* q = GCTaskQueue::create();
 404 
 405       if (!old_gen->object_space()->is_empty()) {
 406         // There are only old-to-young pointers if there are objects
 407         // in the old gen.
 408         uint stripe_total = active_workers;
 409         for(uint i=0; i < stripe_total; i++) {
 410           q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));
 411         }
 412       }
 413 
 414       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));
 415       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));
 416       // We scan the thread roots in parallel
 417       Threads::create_thread_roots_tasks(q);
 418       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));
 419       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));
 420       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));
 421       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));
 422       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::class_loader_data));
 423       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));
 424       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));
 425 
 426       ParallelTaskTerminator terminator(
 427         active_workers,
 428                   (TaskQueueSetSuper*) promotion_manager->stack_array_depth());
 429       if (active_workers > 1) {
 430         for (uint j = 0; j < active_workers; j++) {
 431           q->enqueue(new StealTask(&terminator));
 432         }
 433       }
 434 
 435       gc_task_manager()->execute_and_wait(q);
 436     }
 437 
 438     scavenge_midpoint.update();
 439 
 440     // Process reference objects discovered during scavenge
 441     {
 442       GCTraceTime tm("References", false, false, &_gc_timer, _gc_tracer.gc_id());
 443 
 444       reference_processor()->setup_policy(false); // not always_clear
 445       reference_processor()->set_active_mt_degree(active_workers);
 446       PSKeepAliveClosure keep_alive(promotion_manager);
 447       PSEvacuateFollowersClosure evac_followers(promotion_manager);
 448       ReferenceProcessorStats stats;
 449       if (reference_processor()->processing_is_mt()) {
 450         PSRefProcTaskExecutor task_executor;
 451         stats = reference_processor()->process_discovered_references(
 452           &_is_alive_closure, &keep_alive, &evac_followers, &task_executor,
 453           &_gc_timer, _gc_tracer.gc_id());
 454       } else {
 455         stats = reference_processor()->process_discovered_references(
 456           &_is_alive_closure, &keep_alive, &evac_followers, NULL, &_gc_timer, _gc_tracer.gc_id());
 457       }
 458 
 459       _gc_tracer.report_gc_reference_stats(stats);
 460 
 461       // Enqueue reference objects discovered during scavenge.
 462       if (reference_processor()->processing_is_mt()) {
 463         PSRefProcTaskExecutor task_executor;
 464         reference_processor()->enqueue_discovered_references(&task_executor);
 465       } else {
 466         reference_processor()->enqueue_discovered_references(NULL);
 467       }
 468     }
 469 
 470     {
 471       GCTraceTime tm("StringTable", false, false, &_gc_timer, _gc_tracer.gc_id());
 472       // Unlink any dead interned Strings and process the remaining live ones.
 473       PSScavengeRootsClosure root_closure(promotion_manager);
 474       StringTable::unlink_or_oops_do(&_is_alive_closure, &root_closure);
 475     }
 476 
 477     // Finally, flush the promotion_manager's labs, and deallocate its stacks.
 478     promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer);
 479     if (promotion_failure_occurred) {
 480       clean_up_failed_promotion();
 481       if (PrintGC) {
 482         gclog_or_tty->print("--");
 483       }
 484     }
 485 
 486     // Let the size policy know we're done.  Note that we count promotion
 487     // failure cleanup time as part of the collection (otherwise, we're
 488     // implicitly saying it's mutator time).
 489     size_policy->minor_collection_end(gc_cause);
 490 
 491     if (!promotion_failure_occurred) {
 492       // Swap the survivor spaces.
 493       young_gen->eden_space()->clear(SpaceDecorator::Mangle);
 494       young_gen->from_space()->clear(SpaceDecorator::Mangle);
 495       young_gen->swap_spaces();
 496 
 497       size_t survived = young_gen->from_space()->used_in_bytes();
 498       size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;
 499       size_policy->update_averages(_survivor_overflow, survived, promoted);
 500 
 501       // A successful scavenge should restart the GC time limit count which is
 502       // for full GC's.
 503       size_policy->reset_gc_overhead_limit_count();
 504       if (UseAdaptiveSizePolicy) {
 505         // Calculate the new survivor size and tenuring threshold
 506 
 507         if (PrintAdaptiveSizePolicy) {
 508           gclog_or_tty->print("AdaptiveSizeStart: ");
 509           gclog_or_tty->stamp();
 510           gclog_or_tty->print_cr(" collection: %d ",
 511                          heap->total_collections());
 512 
 513           if (Verbose) {
 514             gclog_or_tty->print("old_gen_capacity: " SIZE_FORMAT
 515               " young_gen_capacity: " SIZE_FORMAT,
 516               old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
 517           }
 518         }
 519 
 520 
 521         if (UsePerfData) {
 522           PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 523           counters->update_old_eden_size(
 524             size_policy->calculated_eden_size_in_bytes());
 525           counters->update_old_promo_size(
 526             size_policy->calculated_promo_size_in_bytes());
 527           counters->update_old_capacity(old_gen->capacity_in_bytes());
 528           counters->update_young_capacity(young_gen->capacity_in_bytes());
 529           counters->update_survived(survived);
 530           counters->update_promoted(promoted);
 531           counters->update_survivor_overflowed(_survivor_overflow);
 532         }
 533 
 534         size_t max_young_size = young_gen->max_size();
 535 
 536         // Deciding a free ratio in the young generation is tricky, so if
 537         // MinHeapFreeRatio or MaxHeapFreeRatio are in use (implicating
 538         // that the old generation size may have been limited because of them) we
 539         // should then limit our young generation size using NewRatio to have it
 540         // follow the old generation size.
 541         if (MinHeapFreeRatio != 0 || MaxHeapFreeRatio != 100) {
 542           max_young_size = MIN2(old_gen->capacity_in_bytes() / NewRatio, young_gen->max_size());
 543         }
 544 
 545         size_t survivor_limit =
 546           size_policy->max_survivor_size(max_young_size);
 547         _tenuring_threshold =
 548           size_policy->compute_survivor_space_size_and_threshold(
 549                                                            _survivor_overflow,
 550                                                            _tenuring_threshold,
 551                                                            survivor_limit);
 552 
 553        if (PrintTenuringDistribution) {
 554          gclog_or_tty->cr();
 555          gclog_or_tty->print_cr("Desired survivor size " SIZE_FORMAT " bytes, new threshold "
 556                                 UINTX_FORMAT " (max threshold " UINTX_FORMAT ")",
 557                                 size_policy->calculated_survivor_size_in_bytes(),
 558                                 _tenuring_threshold, MaxTenuringThreshold);
 559        }
 560 
 561         if (UsePerfData) {
 562           PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 563           counters->update_tenuring_threshold(_tenuring_threshold);
 564           counters->update_survivor_size_counters();
 565         }
 566 
 567         // Do call at minor collections?
 568         // Don't check if the size_policy is ready at this
 569         // level.  Let the size_policy check that internally.
 570         if (UseAdaptiveGenerationSizePolicyAtMinorCollection &&
 571             ((gc_cause != GCCause::_java_lang_system_gc) ||
 572               UseAdaptiveSizePolicyWithSystemGC)) {
 573 
 574           // Calculate optimal free space amounts
 575           assert(young_gen->max_size() >
 576             young_gen->from_space()->capacity_in_bytes() +
 577             young_gen->to_space()->capacity_in_bytes(),
 578             "Sizes of space in young gen are out-of-bounds");
 579 
 580           size_t young_live = young_gen->used_in_bytes();
 581           size_t eden_live = young_gen->eden_space()->used_in_bytes();
 582           size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
 583           size_t max_old_gen_size = old_gen->max_gen_size();
 584           size_t max_eden_size = max_young_size -
 585             young_gen->from_space()->capacity_in_bytes() -
 586             young_gen->to_space()->capacity_in_bytes();
 587 
 588           // Used for diagnostics
 589           size_policy->clear_generation_free_space_flags();
 590 
 591           size_policy->compute_eden_space_size(young_live,
 592                                                eden_live,
 593                                                cur_eden,
 594                                                max_eden_size,
 595                                                false /* not full gc*/);
 596 
 597           size_policy->check_gc_overhead_limit(young_live,
 598                                                eden_live,
 599                                                max_old_gen_size,
 600                                                max_eden_size,
 601                                                false /* not full gc*/,
 602                                                gc_cause,
 603                                                heap->collector_policy());
 604 
 605           size_policy->decay_supplemental_growth(false /* not full gc*/);
 606         }
 607         // Resize the young generation at every collection
 608         // even if new sizes have not been calculated.  This is
 609         // to allow resizes that may have been inhibited by the
 610         // relative location of the "to" and "from" spaces.
 611 
 612         // Resizing the old gen at minor collects can cause increases
 613         // that don't feed back to the generation sizing policy until
 614         // a major collection.  Don't resize the old gen here.
 615 
 616         heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
 617                         size_policy->calculated_survivor_size_in_bytes());
 618 
 619         if (PrintAdaptiveSizePolicy) {
 620           gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
 621                          heap->total_collections());
 622         }
 623       }
 624 
 625       // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can
 626       // cause the change of the heap layout. Make sure eden is reshaped if that's the case.
 627       // Also update() will case adaptive NUMA chunk resizing.
 628       assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");
 629       young_gen->eden_space()->update();
 630 
 631       heap->gc_policy_counters()->update_counters();
 632 
 633       heap->resize_all_tlabs();
 634 
 635       assert(young_gen->to_space()->is_empty(), "to space should be empty now");
 636     }
 637 
 638     COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
 639 
 640     NOT_PRODUCT(reference_processor()->verify_no_references_recorded());
 641 
 642     {
 643       GCTraceTime tm("Prune Scavenge Root Methods", false, false, &_gc_timer, _gc_tracer.gc_id());
 644 
 645       CodeCache::prune_scavenge_root_nmethods();
 646     }
 647 
 648     // Re-verify object start arrays
 649     if (VerifyObjectStartArray &&
 650         VerifyAfterGC) {
 651       old_gen->verify_object_start_array();
 652     }
 653 
 654     // Verify all old -> young cards are now precise
 655     if (VerifyRememberedSets) {
 656       // Precise verification will give false positives. Until this is fixed,
 657       // use imprecise verification.
 658       // CardTableExtension::verify_all_young_refs_precise();
 659       CardTableExtension::verify_all_young_refs_imprecise();
 660     }
 661 
 662     if (TraceYoungGenTime) accumulated_time()->stop();
 663 
 664     if (PrintGC) {
 665       if (PrintGCDetails) {
 666         // Don't print a GC timestamp here.  This is after the GC so
 667         // would be confusing.
 668         young_gen->print_used_change(young_gen_used_before);
 669       }
 670       heap->print_heap_change(prev_used);
 671     }
 672 
 673     // Track memory usage and detect low memory
 674     MemoryService::track_memory_usage();
 675     heap->update_counters();
 676 
 677     gc_task_manager()->release_idle_workers();
 678   }
 679 
 680   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
 681     HandleMark hm;  // Discard invalid handles created during verification
 682     Universe::verify(" VerifyAfterGC:");
 683   }
 684 
 685   heap->print_heap_after_gc();
 686   heap->trace_heap_after_gc(&_gc_tracer);
 687   _gc_tracer.report_tenuring_threshold(tenuring_threshold());
 688 
 689   if (ZapUnusedHeapArea) {
 690     young_gen->eden_space()->check_mangled_unused_area_complete();
 691     young_gen->from_space()->check_mangled_unused_area_complete();
 692     young_gen->to_space()->check_mangled_unused_area_complete();
 693   }
 694 
 695   scavenge_exit.update();
 696 
 697   if (PrintGCTaskTimeStamps) {
 698     tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,
 699                   scavenge_entry.ticks(), scavenge_midpoint.ticks(),
 700                   scavenge_exit.ticks());
 701     gc_task_manager()->print_task_time_stamps();
 702   }
 703 
 704 #ifdef TRACESPINNING
 705   ParallelTaskTerminator::print_termination_counts();
 706 #endif
 707 
 708 
 709   _gc_timer.register_gc_end();
 710 
 711   _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
 712 
 713   return !promotion_failure_occurred;
 714 }
 715 
 716 // This method iterates over all objects in the young generation,
 717 // unforwarding markOops. It then restores any preserved mark oops,
 718 // and clears the _preserved_mark_stack.
 719 void PSScavenge::clean_up_failed_promotion() {
 720   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 721   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 722 
 723   PSYoungGen* young_gen = heap->young_gen();
 724 
 725   {
 726     ResourceMark rm;
 727 
 728     // Unforward all pointers in the young gen.
 729     PSPromotionFailedClosure unforward_closure;
 730     young_gen->object_iterate(&unforward_closure);
 731 
 732     if (PrintGC && Verbose) {
 733       gclog_or_tty->print_cr("Restoring " SIZE_FORMAT " marks", _preserved_oop_stack.size());
 734     }
 735 
 736     // Restore any saved marks.
 737     while (!_preserved_oop_stack.is_empty()) {
 738       oop obj      = _preserved_oop_stack.pop();
 739       markOop mark = _preserved_mark_stack.pop();
 740       obj->set_mark(mark);
 741     }
 742 
 743     // Clear the preserved mark and oop stack caches.
 744     _preserved_mark_stack.clear(true);
 745     _preserved_oop_stack.clear(true);
 746   }
 747 
 748   // Reset the PromotionFailureALot counters.
 749   NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
 750 }
 751 
 752 // This method is called whenever an attempt to promote an object
 753 // fails. Some markOops will need preservation, some will not. Note
 754 // that the entire eden is traversed after a failed promotion, with
 755 // all forwarded headers replaced by the default markOop. This means
 756 // it is not necessary to preserve most markOops.
 757 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {
 758   if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {
 759     // Should use per-worker private stacks here rather than
 760     // locking a common pair of stacks.
 761     ThreadCritical tc;
 762     _preserved_oop_stack.push(obj);
 763     _preserved_mark_stack.push(obj_mark);
 764   }
 765 }
 766 
 767 bool PSScavenge::should_attempt_scavenge() {
 768   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 769   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 770   PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();
 771 
 772   if (UsePerfData) {
 773     counters->update_scavenge_skipped(not_skipped);
 774   }
 775 
 776   PSYoungGen* young_gen = heap->young_gen();
 777   PSOldGen* old_gen = heap->old_gen();
 778 
 779   if (!ScavengeWithObjectsInToSpace) {
 780     // Do not attempt to promote unless to_space is empty
 781     if (!young_gen->to_space()->is_empty()) {
 782       _consecutive_skipped_scavenges++;
 783       if (UsePerfData) {
 784         counters->update_scavenge_skipped(to_space_not_empty);
 785       }
 786       return false;
 787     }
 788   }
 789 
 790   // Test to see if the scavenge will likely fail.
 791   PSAdaptiveSizePolicy* policy = heap->size_policy();
 792 
 793   // A similar test is done in the policy's should_full_GC().  If this is
 794   // changed, decide if that test should also be changed.
 795   size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();
 796   size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());
 797   bool result = promotion_estimate < old_gen->free_in_bytes();
 798 
 799   if (PrintGCDetails && Verbose) {
 800     gclog_or_tty->print(result ? "  do scavenge: " : "  skip scavenge: ");
 801     gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT
 802       " padded_average_promoted " SIZE_FORMAT
 803       " free in old gen " SIZE_FORMAT,
 804       (size_t) policy->average_promoted_in_bytes(),
 805       (size_t) policy->padded_average_promoted_in_bytes(),
 806       old_gen->free_in_bytes());
 807     if (young_gen->used_in_bytes() <
 808         (size_t) policy->padded_average_promoted_in_bytes()) {
 809       gclog_or_tty->print_cr(" padded_promoted_average is greater"
 810         " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());
 811     }
 812   }
 813 
 814   if (result) {
 815     _consecutive_skipped_scavenges = 0;
 816   } else {
 817     _consecutive_skipped_scavenges++;
 818     if (UsePerfData) {
 819       counters->update_scavenge_skipped(promoted_too_large);
 820     }
 821   }
 822   return result;
 823 }
 824 
 825   // Used to add tasks
 826 GCTaskManager* const PSScavenge::gc_task_manager() {
 827   assert(ParallelScavengeHeap::gc_task_manager() != NULL,
 828    "shouldn't return NULL");
 829   return ParallelScavengeHeap::gc_task_manager();
 830 }
 831 
 832 void PSScavenge::initialize() {
 833   // Arguments must have been parsed
 834 
 835   if (AlwaysTenure || NeverTenure) {
 836     assert(MaxTenuringThreshold == 0 || MaxTenuringThreshold == markOopDesc::max_age + 1,
 837         err_msg("MaxTenuringThreshold should be 0 or markOopDesc::max_age + 1, but is %d", (int) MaxTenuringThreshold));
 838     _tenuring_threshold = MaxTenuringThreshold;
 839   } else {
 840     // We want to smooth out our startup times for the AdaptiveSizePolicy
 841     _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :
 842                                                     MaxTenuringThreshold;
 843   }
 844 
 845   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
 846   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
 847 
 848   PSYoungGen* young_gen = heap->young_gen();
 849   PSOldGen* old_gen = heap->old_gen();
 850 
 851   // Set boundary between young_gen and old_gen
 852   assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),
 853          "old above young");
 854   set_young_generation_boundary(young_gen->eden_space()->bottom());
 855 
 856   // Initialize ref handling object for scavenging.
 857   MemRegion mr = young_gen->reserved();
 858 
 859   _ref_processor =
 860     new ReferenceProcessor(mr,                         // span
 861                            ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
 862                            (int) ParallelGCThreads,    // mt processing degree
 863                            true,                       // mt discovery
 864                            (int) ParallelGCThreads,    // mt discovery degree
 865                            true,                       // atomic_discovery
 866                            NULL);                      // header provides liveness info
 867 
 868   // Cache the cardtable
 869   BarrierSet* bs = Universe::heap()->barrier_set();
 870   assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");
 871   _card_table = (CardTableExtension*)bs;
 872 
 873   _counters = new CollectorCounters("PSScavenge", 0);
 874 }