Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright (c) 2002, 2013, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  *

  */

 #include "precompiled.hpp"

 #include "classfile/symbolTable.hpp"

 #include "code/codeCache.hpp"

 #include "gc_implementation/parallelScavenge/cardTableExtension.hpp"

 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp"

 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp"

 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"

 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp"

 #include "gc_implementation/parallelScavenge/psParallelCompact.hpp"

 #include "gc_implementation/parallelScavenge/psScavenge.inline.hpp"

 #include "gc_implementation/parallelScavenge/psTasks.hpp"

 #include "gc_implementation/shared/gcHeapSummary.hpp"

 #include "gc_implementation/shared/gcTimer.hpp"

 #include "gc_implementation/shared/gcTrace.hpp"

 #include "gc_implementation/shared/gcTraceTime.hpp"

 #include "gc_implementation/shared/isGCActiveMark.hpp"

 #include "gc_implementation/shared/spaceDecorator.hpp"

 #include "gc_interface/gcCause.hpp"

 #include "memory/collectorPolicy.hpp"

 #include "memory/gcLocker.inline.hpp"

 #include "memory/referencePolicy.hpp"

 #include "memory/referenceProcessor.hpp"

 #include "memory/resourceArea.hpp"

 #include "oops/oop.inline.hpp"

 #include "oops/oop.psgc.inline.hpp"

 #include "runtime/biasedLocking.hpp"

 #include "runtime/fprofiler.hpp"

 #include "runtime/handles.inline.hpp"

 #include "runtime/threadCritical.hpp"

 #include "runtime/vmThread.hpp"

 #include "runtime/vm_operations.hpp"

 #include "services/memoryService.hpp"

 #include "utilities/stack.inline.hpp"

 HeapWord*                  PSScavenge::_to_space_top_before_gc = NULL;

 int                        PSScavenge::_consecutive_skipped_scavenges = 0;

 ReferenceProcessor*        PSScavenge::_ref_processor = NULL;

 CardTableExtension*        PSScavenge::_card_table = NULL;

 bool                       PSScavenge::_survivor_overflow = false;

 uint                       PSScavenge::_tenuring_threshold = 0;

 HeapWord*                  PSScavenge::_young_generation_boundary = NULL;

 uintptr_t                  PSScavenge::_young_generation_boundary_compressed = 0;

 elapsedTimer               PSScavenge::_accumulated_time;

 STWGCTimer                 PSScavenge::_gc_timer;

 ParallelScavengeTracer     PSScavenge::_gc_tracer;

 Stack<markOop, mtGC>       PSScavenge::_preserved_mark_stack;

 Stack<oop, mtGC>           PSScavenge::_preserved_oop_stack;

 CollectorCounters*         PSScavenge::_counters = NULL;

 // Define before use

 class PSIsAliveClosure: public BoolObjectClosure {

 public:

   bool do_object_b(oop p) {

     return (!PSScavenge::is_obj_in_young(p)) || p->is_forwarded();

   }

 };

 PSIsAliveClosure PSScavenge::_is_alive_closure;

 class PSKeepAliveClosure: public OopClosure {

 protected:

   MutableSpace* _to_space;

   PSPromotionManager* _promotion_manager;

 public:

   PSKeepAliveClosure(PSPromotionManager* pm) : _promotion_manager(pm) {

     ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

     assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

     _to_space = heap->young_gen()->to_space();

     assert(_promotion_manager != NULL, "Sanity");

   }

   template <class T> void do_oop_work(T* p) {

     assert (!oopDesc::is_null(*p), "expected non-null ref");

     assert ((oopDesc::load_decode_heap_oop_not_null(p))->is_oop(),

             "expected an oop while scanning weak refs");

     // Weak refs may be visited more than once.

     if (PSScavenge::should_scavenge(p, _to_space)) {

       PSScavenge::copy_and_push_safe_barrier<T, /*promote_immediately=*/false>(_promotion_manager, p);

     }

   }

   virtual void do_oop(oop* p)       { PSKeepAliveClosure::do_oop_work(p); }

   virtual void do_oop(narrowOop* p) { PSKeepAliveClosure::do_oop_work(p); }

 };

 class PSEvacuateFollowersClosure: public VoidClosure {

  private:

   PSPromotionManager* _promotion_manager;

  public:

   PSEvacuateFollowersClosure(PSPromotionManager* pm) : _promotion_manager(pm) {}

   virtual void do_void() {

     assert(_promotion_manager != NULL, "Sanity");

     _promotion_manager->drain_stacks(true);

     guarantee(_promotion_manager->stacks_empty(),

               "stacks should be empty at this point");

   }

 };

 class PSPromotionFailedClosure : public ObjectClosure {

   virtual void do_object(oop obj) {

     if (obj->is_forwarded()) {

       obj->init_mark();

     }

   }

 };

 class PSRefProcTaskProxy: public GCTask {

   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;

   ProcessTask & _rp_task;

   uint          _work_id;

 public:

   PSRefProcTaskProxy(ProcessTask & rp_task, uint work_id)

     : _rp_task(rp_task),

       _work_id(work_id)

   { }

 private:

   virtual char* name() { return (char *)"Process referents by policy in parallel"; }

   virtual void do_it(GCTaskManager* manager, uint which);

 };

 void PSRefProcTaskProxy::do_it(GCTaskManager* manager, uint which)

 {

   PSPromotionManager* promotion_manager =

     PSPromotionManager::gc_thread_promotion_manager(which);

   assert(promotion_manager != NULL, "sanity check");

   PSKeepAliveClosure keep_alive(promotion_manager);

   PSEvacuateFollowersClosure evac_followers(promotion_manager);

   PSIsAliveClosure is_alive;

   _rp_task.work(_work_id, is_alive, keep_alive, evac_followers);

 }

 class PSRefEnqueueTaskProxy: public GCTask {

   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;

   EnqueueTask& _enq_task;

   uint         _work_id;

 public:

   PSRefEnqueueTaskProxy(EnqueueTask& enq_task, uint work_id)

     : _enq_task(enq_task),

       _work_id(work_id)

   { }

   virtual char* name() { return (char *)"Enqueue reference objects in parallel"; }

   virtual void do_it(GCTaskManager* manager, uint which)

   {

     _enq_task.work(_work_id);

   }

 };

 class PSRefProcTaskExecutor: public AbstractRefProcTaskExecutor {

   virtual void execute(ProcessTask& task);

   virtual void execute(EnqueueTask& task);

 };

 void PSRefProcTaskExecutor::execute(ProcessTask& task)

 {

   GCTaskQueue* q = GCTaskQueue::create();

   GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();

   for(uint i=0; i < manager->active_workers(); i++) {

     q->enqueue(new PSRefProcTaskProxy(task, i));

   }

   ParallelTaskTerminator terminator(manager->active_workers(),

                  (TaskQueueSetSuper*) PSPromotionManager::stack_array_depth());

   if (task.marks_oops_alive() && manager->active_workers() > 1) {

     for (uint j = 0; j < manager->active_workers(); j++) {

       q->enqueue(new StealTask(&terminator));

     }

   }

   manager->execute_and_wait(q);

 }

 void PSRefProcTaskExecutor::execute(EnqueueTask& task)

 {

   GCTaskQueue* q = GCTaskQueue::create();

   GCTaskManager* manager = ParallelScavengeHeap::gc_task_manager();

   for(uint i=0; i < manager->active_workers(); i++) {

     q->enqueue(new PSRefEnqueueTaskProxy(task, i));

   }

   manager->execute_and_wait(q);

 }

 // This method contains all heap specific policy for invoking scavenge.

 // PSScavenge::invoke_no_policy() will do nothing but attempt to

 // scavenge. It will not clean up after failed promotions, bail out if

 // we've exceeded policy time limits, or any other special behavior.

 // All such policy should be placed here.

 //

 // Note that this method should only be called from the vm_thread while

 // at a safepoint!

 bool PSScavenge::invoke() {

   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");

   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");

   assert(!Universe::heap()->is_gc_active(), "not reentrant");

   ParallelScavengeHeap* const heap = (ParallelScavengeHeap*)Universe::heap();

   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

   PSAdaptiveSizePolicy* policy = heap->size_policy();

   IsGCActiveMark mark;

   const bool scavenge_done = PSScavenge::invoke_no_policy();

   const bool need_full_gc = !scavenge_done ||

     policy->should_full_GC(heap->old_gen()->free_in_bytes());

   bool full_gc_done = false;

   if (UsePerfData) {

     PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();

     const int ffs_val = need_full_gc ? full_follows_scavenge : not_skipped;

     counters->update_full_follows_scavenge(ffs_val);

   }

   if (need_full_gc) {

     GCCauseSetter gccs(heap, GCCause::_adaptive_size_policy);

     CollectorPolicy* cp = heap->collector_policy();

     const bool clear_all_softrefs = cp->should_clear_all_soft_refs();

     if (UseParallelOldGC) {

       full_gc_done = PSParallelCompact::invoke_no_policy(clear_all_softrefs);

     } else {

       full_gc_done = PSMarkSweep::invoke_no_policy(clear_all_softrefs);

     }

   }

   return full_gc_done;

 }

 // This method contains no policy. You should probably

 // be calling invoke() instead.

 bool PSScavenge::invoke_no_policy() {

   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");

   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");

   assert(_preserved_mark_stack.is_empty(), "should be empty");

   assert(_preserved_oop_stack.is_empty(), "should be empty");

   _gc_timer.register_gc_start();

   TimeStamp scavenge_entry;

   TimeStamp scavenge_midpoint;

   TimeStamp scavenge_exit;

   scavenge_entry.update();

   if (GC_locker::check_active_before_gc()) {

     return false;

   }

   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

   GCCause::Cause gc_cause = heap->gc_cause();

   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

   // Check for potential problems.

   if (!should_attempt_scavenge()) {

     return false;

   }

   _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());

   bool promotion_failure_occurred = false;

   PSYoungGen* young_gen = heap->young_gen();

   PSOldGen* old_gen = heap->old_gen();

   PSAdaptiveSizePolicy* size_policy = heap->size_policy();

   heap->increment_total_collections();

   AdaptiveSizePolicyOutput(size_policy, heap->total_collections());

   if ((gc_cause != GCCause::_java_lang_system_gc) ||

        UseAdaptiveSizePolicyWithSystemGC) {

     // Gather the feedback data for eden occupancy.

     young_gen->eden_space()->accumulate_statistics();

   }

   if (ZapUnusedHeapArea) {

     // Save information needed to minimize mangling

     heap->record_gen_tops_before_GC();

   }

   heap->print_heap_before_gc();

   heap->trace_heap_before_gc(&_gc_tracer);

   assert(!NeverTenure || _tenuring_threshold == markOopDesc::max_age + 1, "Sanity");

   assert(!AlwaysTenure || _tenuring_threshold == 0, "Sanity");

   size_t prev_used = heap->used();

   // Fill in TLABs

   heap->accumulate_statistics_all_tlabs();

   heap->ensure_parsability(true);  // retire TLABs

   if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {

     HandleMark hm;  // Discard invalid handles created during verification

     Universe::verify(" VerifyBeforeGC:");

   }

   {

     ResourceMark rm;

     HandleMark hm;

     gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);

     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);

     GCTraceTime t1(GCCauseString("GC", gc_cause), PrintGC, !PrintGCDetails, NULL);

     TraceCollectorStats tcs(counters());

     TraceMemoryManagerStats tms(false /* not full GC */,gc_cause);

     if (TraceGen0Time) accumulated_time()->start();

     // Let the size policy know we're starting

     size_policy->minor_collection_begin();

     // Verify the object start arrays.

     if (VerifyObjectStartArray &&

         VerifyBeforeGC) {

       old_gen->verify_object_start_array();

     }

     // Verify no unmarked old->young roots

     if (VerifyRememberedSets) {

       CardTableExtension::verify_all_young_refs_imprecise();

     }

     if (!ScavengeWithObjectsInToSpace) {

       assert(young_gen->to_space()->is_empty(),

              "Attempt to scavenge with live objects in to_space");

       young_gen->to_space()->clear(SpaceDecorator::Mangle);

     } else if (ZapUnusedHeapArea) {

       young_gen->to_space()->mangle_unused_area();

     }

     save_to_space_top_before_gc();

     COMPILER2_PRESENT(DerivedPointerTable::clear());

     reference_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);

     reference_processor()->setup_policy(false);

     // We track how much was promoted to the next generation for

     // the AdaptiveSizePolicy.

     size_t old_gen_used_before = old_gen->used_in_bytes();

     // For PrintGCDetails

     size_t young_gen_used_before = young_gen->used_in_bytes();

     // Reset our survivor overflow.

     set_survivor_overflow(false);

     // We need to save the old top values before

     // creating the promotion_manager. We pass the top

     // values to the card_table, to prevent it from

     // straying into the promotion labs.

     HeapWord* old_top = old_gen->object_space()->top();

     // Release all previously held resources

     gc_task_manager()->release_all_resources();

     // Set the number of GC threads to be used in this collection

     gc_task_manager()->set_active_gang();

     gc_task_manager()->task_idle_workers();

     // Get the active number of workers here and use that value

     // throughout the methods.

     uint active_workers = gc_task_manager()->active_workers();

     heap->set_par_threads(active_workers);

     PSPromotionManager::pre_scavenge();

     // We'll use the promotion manager again later.

     PSPromotionManager* promotion_manager = PSPromotionManager::vm_thread_promotion_manager();

     {

       GCTraceTime tm("Scavenge", false, false, &_gc_timer);

       ParallelScavengeHeap::ParStrongRootsScope psrs;

       GCTaskQueue* q = GCTaskQueue::create();

       if (!old_gen->object_space()->is_empty()) {

         // There are only old-to-young pointers if there are objects

         // in the old gen.

         uint stripe_total = active_workers;

         for(uint i=0; i < stripe_total; i++) {

           q->enqueue(new OldToYoungRootsTask(old_gen, old_top, i, stripe_total));

         }

       }

       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::universe));

       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jni_handles));

       // We scan the thread roots in parallel

       Threads::create_thread_roots_tasks(q);

       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::object_synchronizer));

       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::flat_profiler));

       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::management));

       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::system_dictionary));

       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::class_loader_data));

       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::jvmti));

       q->enqueue(new ScavengeRootsTask(ScavengeRootsTask::code_cache));

       ParallelTaskTerminator terminator(

         active_workers,

                   (TaskQueueSetSuper*) promotion_manager->stack_array_depth());

       if (active_workers > 1) {

         for (uint j = 0; j < active_workers; j++) {

           q->enqueue(new StealTask(&terminator));

         }

       }

       gc_task_manager()->execute_and_wait(q);

     }

     scavenge_midpoint.update();

     // Process reference objects discovered during scavenge

     {

       GCTraceTime tm("References", false, false, &_gc_timer);

       reference_processor()->setup_policy(false); // not always_clear

       reference_processor()->set_active_mt_degree(active_workers);

       PSKeepAliveClosure keep_alive(promotion_manager);

       PSEvacuateFollowersClosure evac_followers(promotion_manager);

       ReferenceProcessorStats stats;

       if (reference_processor()->processing_is_mt()) {

         PSRefProcTaskExecutor task_executor;

         stats = reference_processor()->process_discovered_references(

           &_is_alive_closure, &keep_alive, &evac_followers, &task_executor,

           &_gc_timer);

       } else {

         stats = reference_processor()->process_discovered_references(

           &_is_alive_closure, &keep_alive, &evac_followers, NULL, &_gc_timer);

       }

       _gc_tracer.report_gc_reference_stats(stats);

       // Enqueue reference objects discovered during scavenge.

       if (reference_processor()->processing_is_mt()) {

         PSRefProcTaskExecutor task_executor;

         reference_processor()->enqueue_discovered_references(&task_executor);

       } else {

         reference_processor()->enqueue_discovered_references(NULL);

       }

     }

     GCTraceTime tm("StringTable", false, false, &_gc_timer);

     // Unlink any dead interned Strings and process the remaining live ones.

     PSScavengeRootsClosure root_closure(promotion_manager);

     StringTable::unlink_or_oops_do(&_is_alive_closure, &root_closure);

     // Finally, flush the promotion_manager's labs, and deallocate its stacks.

     promotion_failure_occurred = PSPromotionManager::post_scavenge(_gc_tracer);

     if (promotion_failure_occurred) {

       clean_up_failed_promotion();

       if (PrintGC) {

         gclog_or_tty->print("--");

       }

     }

     // Let the size policy know we're done.  Note that we count promotion

     // failure cleanup time as part of the collection (otherwise, we're

     // implicitly saying it's mutator time).

     size_policy->minor_collection_end(gc_cause);

     if (!promotion_failure_occurred) {

       // Swap the survivor spaces.

       young_gen->eden_space()->clear(SpaceDecorator::Mangle);

       young_gen->from_space()->clear(SpaceDecorator::Mangle);

       young_gen->swap_spaces();

       size_t survived = young_gen->from_space()->used_in_bytes();

       size_t promoted = old_gen->used_in_bytes() - old_gen_used_before;

       size_policy->update_averages(_survivor_overflow, survived, promoted);

       // A successful scavenge should restart the GC time limit count which is

       // for full GC's.

       size_policy->reset_gc_overhead_limit_count();

       if (UseAdaptiveSizePolicy) {

         // Calculate the new survivor size and tenuring threshold

         if (PrintAdaptiveSizePolicy) {

           gclog_or_tty->print("AdaptiveSizeStart: ");

           gclog_or_tty->stamp();

           gclog_or_tty->print_cr(" collection: %d ",

                          heap->total_collections());

           if (Verbose) {

             gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d",

               old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());

           }

         }

         if (UsePerfData) {

           PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();

           counters->update_old_eden_size(

             size_policy->calculated_eden_size_in_bytes());

           counters->update_old_promo_size(

             size_policy->calculated_promo_size_in_bytes());

           counters->update_old_capacity(old_gen->capacity_in_bytes());

           counters->update_young_capacity(young_gen->capacity_in_bytes());

           counters->update_survived(survived);

           counters->update_promoted(promoted);

           counters->update_survivor_overflowed(_survivor_overflow);

         }

         size_t survivor_limit =

           size_policy->max_survivor_size(young_gen->max_size());

         _tenuring_threshold =

           size_policy->compute_survivor_space_size_and_threshold(

                                                            _survivor_overflow,

                                                            _tenuring_threshold,

                                                            survivor_limit);

        if (PrintTenuringDistribution) {

          gclog_or_tty->cr();

          gclog_or_tty->print_cr("Desired survivor size " SIZE_FORMAT " bytes, new threshold %u (max %u)",

                                 size_policy->calculated_survivor_size_in_bytes(),

                                 _tenuring_threshold, MaxTenuringThreshold);

        }

         if (UsePerfData) {

           PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();

           counters->update_tenuring_threshold(_tenuring_threshold);

           counters->update_survivor_size_counters();

         }

         // Do call at minor collections?

         // Don't check if the size_policy is ready at this

         // level.  Let the size_policy check that internally.

         if (UseAdaptiveSizePolicy &&

             UseAdaptiveGenerationSizePolicyAtMinorCollection &&

             ((gc_cause != GCCause::_java_lang_system_gc) ||

               UseAdaptiveSizePolicyWithSystemGC)) {

           // Calculate optimial free space amounts

           assert(young_gen->max_size() >

             young_gen->from_space()->capacity_in_bytes() +

             young_gen->to_space()->capacity_in_bytes(),

             "Sizes of space in young gen are out-of-bounds");

           size_t young_live = young_gen->used_in_bytes();

           size_t eden_live = young_gen->eden_space()->used_in_bytes();

           size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();

           size_t max_old_gen_size = old_gen->max_gen_size();

           size_t max_eden_size = young_gen->max_size() -

             young_gen->from_space()->capacity_in_bytes() -

             young_gen->to_space()->capacity_in_bytes();

           // Used for diagnostics

           size_policy->clear_generation_free_space_flags();

           size_policy->compute_eden_space_size(young_live,

                                                eden_live,

                                                cur_eden,

                                                max_eden_size,

                                                false /* not full gc*/);

           size_policy->check_gc_overhead_limit(young_live,

                                                eden_live,

                                                max_old_gen_size,

                                                max_eden_size,

                                                false /* not full gc*/,

                                                gc_cause,

                                                heap->collector_policy());

           size_policy->decay_supplemental_growth(false /* not full gc*/);

         }

         // Resize the young generation at every collection

         // even if new sizes have not been calculated.  This is

         // to allow resizes that may have been inhibited by the

         // relative location of the "to" and "from" spaces.

         // Resizing the old gen at minor collects can cause increases

         // that don't feed back to the generation sizing policy until

         // a major collection.  Don't resize the old gen here.

         heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),

                         size_policy->calculated_survivor_size_in_bytes());

         if (PrintAdaptiveSizePolicy) {

           gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",

                          heap->total_collections());

         }

       }

       // Update the structure of the eden. With NUMA-eden CPU hotplugging or offlining can

       // cause the change of the heap layout. Make sure eden is reshaped if that's the case.

       // Also update() will case adaptive NUMA chunk resizing.

       assert(young_gen->eden_space()->is_empty(), "eden space should be empty now");

       young_gen->eden_space()->update();

       heap->gc_policy_counters()->update_counters();

       heap->resize_all_tlabs();

       assert(young_gen->to_space()->is_empty(), "to space should be empty now");

     }

     COMPILER2_PRESENT(DerivedPointerTable::update_pointers());

     NOT_PRODUCT(reference_processor()->verify_no_references_recorded());

     {

       GCTraceTime tm("Prune Scavenge Root Methods", false, false, &_gc_timer);

       CodeCache::prune_scavenge_root_nmethods();

     }

     // Re-verify object start arrays

     if (VerifyObjectStartArray &&

         VerifyAfterGC) {

       old_gen->verify_object_start_array();

     }

     // Verify all old -> young cards are now precise

     if (VerifyRememberedSets) {

       // Precise verification will give false positives. Until this is fixed,

       // use imprecise verification.

       // CardTableExtension::verify_all_young_refs_precise();

       CardTableExtension::verify_all_young_refs_imprecise();

     }

     if (TraceGen0Time) accumulated_time()->stop();

     if (PrintGC) {

       if (PrintGCDetails) {

         // Don't print a GC timestamp here.  This is after the GC so

         // would be confusing.

         young_gen->print_used_change(young_gen_used_before);

       }

       heap->print_heap_change(prev_used);

     }

     // Track memory usage and detect low memory

     MemoryService::track_memory_usage();

     heap->update_counters();

     gc_task_manager()->release_idle_workers();

   }

   if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {

     HandleMark hm;  // Discard invalid handles created during verification

     Universe::verify(" VerifyAfterGC:");

   }

   heap->print_heap_after_gc();

   heap->trace_heap_after_gc(&_gc_tracer);

   _gc_tracer.report_tenuring_threshold(tenuring_threshold());

   if (ZapUnusedHeapArea) {

     young_gen->eden_space()->check_mangled_unused_area_complete();

     young_gen->from_space()->check_mangled_unused_area_complete();

     young_gen->to_space()->check_mangled_unused_area_complete();

   }

   scavenge_exit.update();

   if (PrintGCTaskTimeStamps) {

     tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " " INT64_FORMAT,

                   scavenge_entry.ticks(), scavenge_midpoint.ticks(),

                   scavenge_exit.ticks());

     gc_task_manager()->print_task_time_stamps();

   }

 #ifdef TRACESPINNING

   ParallelTaskTerminator::print_termination_counts();

 #endif

   _gc_timer.register_gc_end();

   _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());

   return !promotion_failure_occurred;

 }

 // This method iterates over all objects in the young generation,

 // unforwarding markOops. It then restores any preserved mark oops,

 // and clears the _preserved_mark_stack.

 void PSScavenge::clean_up_failed_promotion() {

   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

   PSYoungGen* young_gen = heap->young_gen();

   {

     ResourceMark rm;

     // Unforward all pointers in the young gen.

     PSPromotionFailedClosure unforward_closure;

     young_gen->object_iterate(&unforward_closure);

     if (PrintGC && Verbose) {

       gclog_or_tty->print_cr("Restoring %d marks", _preserved_oop_stack.size());

     }

     // Restore any saved marks.

     while (!_preserved_oop_stack.is_empty()) {

       oop obj      = _preserved_oop_stack.pop();

       markOop mark = _preserved_mark_stack.pop();

       obj->set_mark(mark);

     }

     // Clear the preserved mark and oop stack caches.

     _preserved_mark_stack.clear(true);

     _preserved_oop_stack.clear(true);

   }

   // Reset the PromotionFailureALot counters.

   NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)

 }

 // This method is called whenever an attempt to promote an object

 // fails. Some markOops will need preservation, some will not. Note

 // that the entire eden is traversed after a failed promotion, with

 // all forwarded headers replaced by the default markOop. This means

 // it is not necessary to preserve most markOops.

 void PSScavenge::oop_promotion_failed(oop obj, markOop obj_mark) {

   if (obj_mark->must_be_preserved_for_promotion_failure(obj)) {

     // Should use per-worker private stacks here rather than

     // locking a common pair of stacks.

     ThreadCritical tc;

     _preserved_oop_stack.push(obj);

     _preserved_mark_stack.push(obj_mark);

   }

 }

 bool PSScavenge::should_attempt_scavenge() {

   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

   PSGCAdaptivePolicyCounters* counters = heap->gc_policy_counters();

   if (UsePerfData) {

     counters->update_scavenge_skipped(not_skipped);

   }

   PSYoungGen* young_gen = heap->young_gen();

   PSOldGen* old_gen = heap->old_gen();

   if (!ScavengeWithObjectsInToSpace) {

     // Do not attempt to promote unless to_space is empty

     if (!young_gen->to_space()->is_empty()) {

       _consecutive_skipped_scavenges++;

       if (UsePerfData) {

         counters->update_scavenge_skipped(to_space_not_empty);

       }

       return false;

     }

   }

   // Test to see if the scavenge will likely fail.

   PSAdaptiveSizePolicy* policy = heap->size_policy();

   // A similar test is done in the policy's should_full_GC().  If this is

   // changed, decide if that test should also be changed.

   size_t avg_promoted = (size_t) policy->padded_average_promoted_in_bytes();

   size_t promotion_estimate = MIN2(avg_promoted, young_gen->used_in_bytes());

   bool result = promotion_estimate < old_gen->free_in_bytes();

   if (PrintGCDetails && Verbose) {

     gclog_or_tty->print(result ? "  do scavenge: " : "  skip scavenge: ");

     gclog_or_tty->print_cr(" average_promoted " SIZE_FORMAT

       " padded_average_promoted " SIZE_FORMAT

       " free in old gen " SIZE_FORMAT,

       (size_t) policy->average_promoted_in_bytes(),

       (size_t) policy->padded_average_promoted_in_bytes(),

       old_gen->free_in_bytes());

     if (young_gen->used_in_bytes() <

         (size_t) policy->padded_average_promoted_in_bytes()) {

       gclog_or_tty->print_cr(" padded_promoted_average is greater"

         " than maximum promotion = " SIZE_FORMAT, young_gen->used_in_bytes());

     }

   }

   if (result) {

     _consecutive_skipped_scavenges = 0;

   } else {

     _consecutive_skipped_scavenges++;

     if (UsePerfData) {

       counters->update_scavenge_skipped(promoted_too_large);

     }

   }

   return result;

 }

   // Used to add tasks

 GCTaskManager* const PSScavenge::gc_task_manager() {

   assert(ParallelScavengeHeap::gc_task_manager() != NULL,

    "shouldn't return NULL");

   return ParallelScavengeHeap::gc_task_manager();

 }

 void PSScavenge::initialize() {

   // Arguments must have been parsed

   if (AlwaysTenure) {

     _tenuring_threshold = 0;

   } else if (NeverTenure) {

     _tenuring_threshold = markOopDesc::max_age + 1;

   } else {

     // We want to smooth out our startup times for the AdaptiveSizePolicy

     _tenuring_threshold = (UseAdaptiveSizePolicy) ? InitialTenuringThreshold :

                                                     MaxTenuringThreshold;

   }

   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

   PSYoungGen* young_gen = heap->young_gen();

   PSOldGen* old_gen = heap->old_gen();

   // Set boundary between young_gen and old_gen

   assert(old_gen->reserved().end() <= young_gen->eden_space()->bottom(),

          "old above young");

   set_young_generation_boundary(young_gen->eden_space()->bottom());

   // Initialize ref handling object for scavenging.

   MemRegion mr = young_gen->reserved();

   _ref_processor =

     new ReferenceProcessor(mr,                         // span

                            ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing

                            (int) ParallelGCThreads,    // mt processing degree

                            true,                       // mt discovery

                            (int) ParallelGCThreads,    // mt discovery degree

                            true,                       // atomic_discovery

                            NULL,                       // header provides liveness info

                            false);                     // next field updates do not need write barrier

   // Cache the cardtable

   BarrierSet* bs = Universe::heap()->barrier_set();

   assert(bs->kind() == BarrierSet::CardTableModRef, "Wrong barrier set kind");

   _card_table = (CardTableExtension*)bs;

   _counters = new CollectorCounters("PSScavenge", 0);

 }