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 /*

  * Copyright (c) 2001, 2009, 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

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  */

 class ChunkArray;

 class ParScanWithoutBarrierClosure;

 class ParScanWithBarrierClosure;

 class ParRootScanWithoutBarrierClosure;

 class ParRootScanWithBarrierTwoGensClosure;

 class ParEvacuateFollowersClosure;

 // It would be better if these types could be kept local to the .cpp file,

 // but they must be here to allow ParScanClosure::do_oop_work to be defined

 // in genOopClosures.inline.hpp.

 typedef OopTaskQueue       ObjToScanQueue;

 typedef OopTaskQueueSet    ObjToScanQueueSet;

 // Enable this to get push/pop/steal stats.

 const int PAR_STATS_ENABLED = 0;

 class ParKeepAliveClosure: public DefNewGeneration::KeepAliveClosure {

  private:

   ParScanWeakRefClosure* _par_cl;

  protected:

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

  public:

   ParKeepAliveClosure(ParScanWeakRefClosure* cl);

   virtual void do_oop(oop* p);

   virtual void do_oop(narrowOop* p);

 };

 // The state needed by thread performing parallel young-gen collection.

 class ParScanThreadState {

   friend class ParScanThreadStateSet;

  private:

   ObjToScanQueue *_work_queue;

   GrowableArray<oop>* _overflow_stack;

   ParGCAllocBuffer _to_space_alloc_buffer;

   ParScanWithoutBarrierClosure         _to_space_closure; // scan_without_gc_barrier

   ParScanWithBarrierClosure            _old_gen_closure; // scan_with_gc_barrier

   ParRootScanWithoutBarrierClosure     _to_space_root_closure; // scan_root_without_gc_barrier

   // One of these two will be passed to process_strong_roots, which will

   // set its generation.  The first is for two-gen configs where the

   // old gen collects the perm gen; the second is for arbitrary configs.

   // The second isn't used right now (it used to be used for the train, an

   // incremental collector) but the declaration has been left as a reminder.

   ParRootScanWithBarrierTwoGensClosure _older_gen_closure;

   // This closure will always be bound to the old gen; it will be used

   // in evacuate_followers.

   ParRootScanWithBarrierTwoGensClosure _old_gen_root_closure; // scan_old_root_with_gc_barrier

   ParEvacuateFollowersClosure          _evacuate_followers;

   DefNewGeneration::IsAliveClosure     _is_alive_closure;

   ParScanWeakRefClosure                _scan_weak_ref_closure;

   ParKeepAliveClosure                  _keep_alive_closure;

   Space* _to_space;

   Space* to_space() { return _to_space; }

   ParNewGeneration* _young_gen;

   ParNewGeneration* young_gen() const { return _young_gen; }

   Generation* _old_gen;

   Generation* old_gen() { return _old_gen; }

   HeapWord *_young_old_boundary;

   int _hash_seed;

   int _thread_num;

   ageTable _ageTable;

   bool _to_space_full;

   int _pushes, _pops, _steals, _steal_attempts, _term_attempts;

   int _overflow_pushes, _overflow_refills, _overflow_refill_objs;

   // Stats for promotion failure

   size_t _promotion_failure_size;

   // Timing numbers.

   double _start;

   double _start_strong_roots;

   double _strong_roots_time;

   double _start_term;

   double _term_time;

   // Helper for trim_queues. Scans subset of an array and makes

   // remainder available for work stealing.

   void scan_partial_array_and_push_remainder(oop obj);

   // In support of CMS' parallel rescan of survivor space.

   ChunkArray* _survivor_chunk_array;

   ChunkArray* survivor_chunk_array() { return _survivor_chunk_array; }

   void record_survivor_plab(HeapWord* plab_start, size_t plab_word_size);

   ParScanThreadState(Space* to_space_, ParNewGeneration* gen_,

                      Generation* old_gen_, int thread_num_,

                      ObjToScanQueueSet* work_queue_set_,

                      GrowableArray<oop>** overflow_stack_set_,

                      size_t desired_plab_sz_,

                      ParallelTaskTerminator& term_);

  public:

   ageTable* age_table() {return &_ageTable;}

   ObjToScanQueue* work_queue() { return _work_queue; }

   ParGCAllocBuffer* to_space_alloc_buffer() {

     return &_to_space_alloc_buffer;

   }

   ParEvacuateFollowersClosure&      evacuate_followers_closure() { return _evacuate_followers; }

   DefNewGeneration::IsAliveClosure& is_alive_closure() { return _is_alive_closure; }

   ParScanWeakRefClosure&            scan_weak_ref_closure() { return _scan_weak_ref_closure; }

   ParKeepAliveClosure&              keep_alive_closure() { return _keep_alive_closure; }

   ParScanClosure&                   older_gen_closure() { return _older_gen_closure; }

   ParRootScanWithoutBarrierClosure& to_space_root_closure() { return _to_space_root_closure; };

   // Decrease queue size below "max_size".

   void trim_queues(int max_size);

   // Private overflow stack usage

   GrowableArray<oop>* overflow_stack() { return _overflow_stack; }

   bool take_from_overflow_stack();

   void push_on_overflow_stack(oop p);

   // Is new_obj a candidate for scan_partial_array_and_push_remainder method.

   inline bool should_be_partially_scanned(oop new_obj, oop old_obj) const;

   int* hash_seed()  { return &_hash_seed; }

   int  thread_num() { return _thread_num; }

   // Allocate a to-space block of size "sz", or else return NULL.

   HeapWord* alloc_in_to_space_slow(size_t word_sz);

   HeapWord* alloc_in_to_space(size_t word_sz) {

     HeapWord* obj = to_space_alloc_buffer()->allocate(word_sz);

     if (obj != NULL) return obj;

     else return alloc_in_to_space_slow(word_sz);

   }

   HeapWord* young_old_boundary() { return _young_old_boundary; }

   void set_young_old_boundary(HeapWord *boundary) {

     _young_old_boundary = boundary;

   }

   // Undo the most recent allocation ("obj", of "word_sz").

   void undo_alloc_in_to_space(HeapWord* obj, size_t word_sz);

   // Promotion failure stats

   size_t promotion_failure_size() { return promotion_failure_size(); }

   void log_promotion_failure(size_t sz) {

     if (_promotion_failure_size == 0) {

       _promotion_failure_size = sz;

     }

   }

   void print_and_clear_promotion_failure_size();

   int pushes() { return _pushes; }

   int pops()   { return _pops; }

   int steals() { return _steals; }

   int steal_attempts() { return _steal_attempts; }

   int term_attempts()  { return _term_attempts; }

   int overflow_pushes() { return _overflow_pushes; }

   int overflow_refills() { return _overflow_refills; }

   int overflow_refill_objs() { return _overflow_refill_objs; }

   void note_push()  { if (PAR_STATS_ENABLED) _pushes++; }

   void note_pop()   { if (PAR_STATS_ENABLED) _pops++; }

   void note_steal() { if (PAR_STATS_ENABLED) _steals++; }

   void note_steal_attempt() { if (PAR_STATS_ENABLED) _steal_attempts++; }

   void note_term_attempt()  { if (PAR_STATS_ENABLED) _term_attempts++; }

   void note_overflow_push() { if (PAR_STATS_ENABLED) _overflow_pushes++; }

   void note_overflow_refill(int objs) {

     if (PAR_STATS_ENABLED) {

       _overflow_refills++;

       _overflow_refill_objs += objs;

     }

   }

   void start_strong_roots() {

     _start_strong_roots = os::elapsedTime();

   }

   void end_strong_roots() {

     _strong_roots_time += (os::elapsedTime() - _start_strong_roots);

   }

   double strong_roots_time() { return _strong_roots_time; }

   void start_term_time() {

     note_term_attempt();

     _start_term = os::elapsedTime();

   }

   void end_term_time() {

     _term_time += (os::elapsedTime() - _start_term);

   }

   double term_time() { return _term_time; }

   double elapsed() {

     return os::elapsedTime() - _start;

   }

 };

 class ParNewGenTask: public AbstractGangTask {

  private:

   ParNewGeneration*            _gen;

   Generation*                  _next_gen;

   HeapWord*                    _young_old_boundary;

   class ParScanThreadStateSet* _state_set;

 public:

   ParNewGenTask(ParNewGeneration*      gen,

                 Generation*            next_gen,

                 HeapWord*              young_old_boundary,

                 ParScanThreadStateSet* state_set);

   HeapWord* young_old_boundary() { return _young_old_boundary; }

   void work(int i);

 };

 class KeepAliveClosure: public DefNewGeneration::KeepAliveClosure {

  protected:

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

  public:

   KeepAliveClosure(ScanWeakRefClosure* cl);

   virtual void do_oop(oop* p);

   virtual void do_oop(narrowOop* p);

 };

 class EvacuateFollowersClosureGeneral: public VoidClosure {

  private:

   GenCollectedHeap* _gch;

   int               _level;

   OopsInGenClosure* _scan_cur_or_nonheap;

   OopsInGenClosure* _scan_older;

  public:

   EvacuateFollowersClosureGeneral(GenCollectedHeap* gch, int level,

                                   OopsInGenClosure* cur,

                                   OopsInGenClosure* older);

   virtual void do_void();

 };

 // Closure for scanning ParNewGeneration.

 // Same as ScanClosure, except does parallel GC barrier.

 class ScanClosureWithParBarrier: public ScanClosure {

  protected:

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

  public:

   ScanClosureWithParBarrier(ParNewGeneration* g, bool gc_barrier);

   virtual void do_oop(oop* p);

   virtual void do_oop(narrowOop* p);

 };

 // Implements AbstractRefProcTaskExecutor for ParNew.

 class ParNewRefProcTaskExecutor: public AbstractRefProcTaskExecutor {

  private:

   ParNewGeneration&      _generation;

   ParScanThreadStateSet& _state_set;

  public:

   ParNewRefProcTaskExecutor(ParNewGeneration& generation,

                             ParScanThreadStateSet& state_set)

     : _generation(generation), _state_set(state_set)

   { }

   // Executes a task using worker threads.

   virtual void execute(ProcessTask& task);

   virtual void execute(EnqueueTask& task);

   // Switch to single threaded mode.

   virtual void set_single_threaded_mode();

 };

 // A Generation that does parallel young-gen collection.

 class ParNewGeneration: public DefNewGeneration {

   friend class ParNewGenTask;

   friend class ParNewRefProcTask;

   friend class ParNewRefProcTaskExecutor;

   friend class ParScanThreadStateSet;

   friend class ParEvacuateFollowersClosure;

  private:

   // XXX use a global constant instead of 64!

   struct ObjToScanQueuePadded {

         ObjToScanQueue work_queue;

         char pad[64 - sizeof(ObjToScanQueue)];  // prevent false sharing

   };

   // The per-worker-thread work queues

   ObjToScanQueueSet* _task_queues;

   // Per-worker-thread local overflow stacks

   GrowableArray<oop>** _overflow_stacks;

   // Desired size of survivor space plab's

   PLABStats _plab_stats;

   // A list of from-space images of to-be-scanned objects, threaded through

   // klass-pointers (klass information already copied to the forwarded

   // image.)  Manipulated with CAS.

   oop _overflow_list;

   NOT_PRODUCT(ssize_t _num_par_pushes;)

   // If true, older generation does not support promotion undo, so avoid.

   static bool _avoid_promotion_undo;

   // This closure is used by the reference processor to filter out

   // references to live referent.

   DefNewGeneration::IsAliveClosure _is_alive_closure;

   static oop real_forwardee_slow(oop obj);

   static void waste_some_time();

   // Preserve the mark of "obj", if necessary, in preparation for its mark

   // word being overwritten with a self-forwarding-pointer.

   void preserve_mark_if_necessary(oop obj, markOop m);

  protected:

   bool _survivor_overflow;

   bool avoid_promotion_undo() { return _avoid_promotion_undo; }

   void set_avoid_promotion_undo(bool v) { _avoid_promotion_undo = v; }

   bool survivor_overflow() { return _survivor_overflow; }

   void set_survivor_overflow(bool v) { _survivor_overflow = v; }

   // Adjust the tenuring threshold.  See the implementation for

   // the details of the policy.

   virtual void adjust_desired_tenuring_threshold();

  public:

   ParNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level);

   ~ParNewGeneration() {

     for (uint i = 0; i < ParallelGCThreads; i++)

         delete _task_queues->queue(i);

     delete _task_queues;

   }

   virtual void ref_processor_init();

   virtual Generation::Name kind()        { return Generation::ParNew; }

   virtual const char* name() const;

   virtual const char* short_name() const { return "ParNew"; }

   // override

   virtual bool refs_discovery_is_mt()     const {

     assert(UseParNewGC, "ParNewGeneration only when UseParNewGC");

     return ParallelGCThreads > 1;

   }

   // Make the collection virtual.

   virtual void collect(bool   full,

                        bool   clear_all_soft_refs,

                        size_t size,

                        bool   is_tlab);

   // This needs to be visible to the closure function.

   // "obj" is the object to be copied, "m" is a recent value of its mark

   // that must not contain a forwarding pointer (though one might be

   // inserted in "obj"s mark word by a parallel thread).

   inline oop copy_to_survivor_space(ParScanThreadState* par_scan_state,

                              oop obj, size_t obj_sz, markOop m) {

     if (_avoid_promotion_undo) {

        return copy_to_survivor_space_avoiding_promotion_undo(par_scan_state,

                                                              obj, obj_sz, m);

     }

     return copy_to_survivor_space_with_undo(par_scan_state, obj, obj_sz, m);

   }

   oop copy_to_survivor_space_avoiding_promotion_undo(ParScanThreadState* par_scan_state,

                              oop obj, size_t obj_sz, markOop m);

   oop copy_to_survivor_space_with_undo(ParScanThreadState* par_scan_state,

                              oop obj, size_t obj_sz, markOop m);

   // in support of testing overflow code

   NOT_PRODUCT(int _overflow_counter;)

   NOT_PRODUCT(bool should_simulate_overflow();)

   // Accessor for overflow list

   oop overflow_list() { return _overflow_list; }

   // Push the given (from-space) object on the global overflow list.

   void push_on_overflow_list(oop from_space_obj, ParScanThreadState* par_scan_state);

   // If the global overflow list is non-empty, move some tasks from it

   // onto "work_q" (which need not be empty).  No more than 1/4 of the

   // available space on "work_q" is used.

   bool take_from_overflow_list(ParScanThreadState* par_scan_state);

   bool take_from_overflow_list_work(ParScanThreadState* par_scan_state);

   // The task queues to be used by parallel GC threads.

   ObjToScanQueueSet* task_queues() {

     return _task_queues;

   }

   PLABStats* plab_stats() {

     return &_plab_stats;

   }

   size_t desired_plab_sz() {

     return _plab_stats.desired_plab_sz();

   }

   static oop real_forwardee(oop obj);

   DEBUG_ONLY(static bool is_legal_forward_ptr(oop p);)

 };