jdk8-mips64-public/hotspot: src/share/vm/memory/referenceProcessor.hpp@01dcaba9b3f3 (annotated)

src/share/vm/memory/referenceProcessor.hpp@01dcaba9b3f3 (annotated)

src/share/vm/memory/referenceProcessor.hpp

Fri, 26 Sep 2014 17:48:10 -0400

author: jmasa
date: Fri, 26 Sep 2014 17:48:10 -0400
changeset 7469: 01dcaba9b3f3
parent 6719: 8e20ef014b08
child 7476: c2844108a708
permissions: -rw-r--r--

8047125: (ref) More phantom object references
Reviewed-by: mchung, dfuchs, ahgross, jmasa, brutisso, mgerdin
Contributed-by: kim.barrett@oracle.com

 /*
  * Copyright (c) 2001, 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.
  *
  */
 #ifndef SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP
 #define SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP
 #include "memory/referencePolicy.hpp"
 #include "memory/referenceProcessorStats.hpp"
 #include "memory/referenceType.hpp"
 #include "oops/instanceRefKlass.hpp"
 class GCTimer;
 // ReferenceProcessor class encapsulates the per-"collector" processing
 // of java.lang.Reference objects for GC. The interface is useful for supporting
 // a generational abstraction, in particular when there are multiple
 // generations that are being independently collected -- possibly
 // concurrently and/or incrementally.  Note, however, that the
 // ReferenceProcessor class abstracts away from a generational setting
 // by using only a heap interval (called "span" below), thus allowing
 // its use in a straightforward manner in a general, non-generational
 // setting.
 //
 // The basic idea is that each ReferenceProcessor object concerns
 // itself with ("weak") reference processing in a specific "span"
 // of the heap of interest to a specific collector. Currently,
 // the span is a convex interval of the heap, but, efficiency
 // apart, there seems to be no reason it couldn't be extended
 // (with appropriate modifications) to any "non-convex interval".
 // forward references
 class ReferencePolicy;
 class AbstractRefProcTaskExecutor;
 // List of discovered references.
 class DiscoveredList {
 public:
   DiscoveredList() : _len(0), _compressed_head(0), _oop_head(NULL) { }
   oop head() const     {
      return UseCompressedOops ?  oopDesc::decode_heap_oop(_compressed_head) :
                                 _oop_head;
   }
   HeapWord* adr_head() {
     return UseCompressedOops ? (HeapWord*)&_compressed_head :
                                (HeapWord*)&_oop_head;
   }
   void set_head(oop o) {
     if (UseCompressedOops) {
       // Must compress the head ptr.
       _compressed_head = oopDesc::encode_heap_oop(o);
     } else {
       _oop_head = o;
     }
   }
   bool   is_empty() const       { return head() == NULL; }
   size_t length()               { return _len; }
   void   set_length(size_t len) { _len = len;  }
   void   inc_length(size_t inc) { _len += inc; assert(_len > 0, "Error"); }
   void   dec_length(size_t dec) { _len -= dec; }
 private:
   // Set value depending on UseCompressedOops. This could be a template class
   // but then we have to fix all the instantiations and declarations that use this class.
   oop       _oop_head;
   narrowOop _compressed_head;
   size_t _len;
 };
 // Iterator for the list of discovered references.
 class DiscoveredListIterator {
 private:
   DiscoveredList&    _refs_list;
   HeapWord*          _prev_next;
   oop                _prev;
   oop                _ref;
   HeapWord*          _discovered_addr;
   oop                _next;
   HeapWord*          _referent_addr;
   oop                _referent;
   OopClosure*        _keep_alive;
   BoolObjectClosure* _is_alive;
   DEBUG_ONLY(
   oop                _first_seen; // cyclic linked list check
   )
   NOT_PRODUCT(
   size_t             _processed;
   size_t             _removed;
   )
 public:
   inline DiscoveredListIterator(DiscoveredList&    refs_list,
                                 OopClosure*        keep_alive,
                                 BoolObjectClosure* is_alive):
     _refs_list(refs_list),
     _prev_next(refs_list.adr_head()),
     _prev(NULL),
     _ref(refs_list.head()),
 #ifdef ASSERT
     _first_seen(refs_list.head()),
 #endif
 #ifndef PRODUCT
     _processed(0),
     _removed(0),
 #endif
     _next(NULL),
     _keep_alive(keep_alive),
     _is_alive(is_alive)
 { }
   // End Of List.
   inline bool has_next() const { return _ref != NULL; }
   // Get oop to the Reference object.
   inline oop obj() const { return _ref; }
   // Get oop to the referent object.
   inline oop referent() const { return _referent; }
   // Returns true if referent is alive.
   inline bool is_referent_alive() const {
     return _is_alive->do_object_b(_referent);
   }
   // Loads data for the current reference.
   // The "allow_null_referent" argument tells us to allow for the possibility
   // of a NULL referent in the discovered Reference object. This typically
   // happens in the case of concurrent collectors that may have done the
   // discovery concurrently, or interleaved, with mutator execution.
   void load_ptrs(DEBUG_ONLY(bool allow_null_referent));
   // Move to the next discovered reference.
   inline void next() {
     _prev_next = _discovered_addr;
     _prev = _ref;
     move_to_next();
   }
   // Remove the current reference from the list
   void remove();
   // Make the Reference object active again.
   void make_active();
   // Make the referent alive.
   inline void make_referent_alive() {
     if (UseCompressedOops) {
       _keep_alive->do_oop((narrowOop*)_referent_addr);
     } else {
       _keep_alive->do_oop((oop*)_referent_addr);
     }
   }
   // Update the discovered field.
   inline void update_discovered() {
     // First _prev_next ref actually points into DiscoveredList (gross).
     if (UseCompressedOops) {
       if (!oopDesc::is_null(*(narrowOop*)_prev_next)) {
         _keep_alive->do_oop((narrowOop*)_prev_next);
       }
     } else {
       if (!oopDesc::is_null(*(oop*)_prev_next)) {
         _keep_alive->do_oop((oop*)_prev_next);
       }
     }
   }
   // NULL out referent pointer.
   void clear_referent();
   // Statistics
   NOT_PRODUCT(
   inline size_t processed() const { return _processed; }
   inline size_t removed() const   { return _removed; }
   )
   inline void move_to_next() {
     if (_ref == _next) {
       // End of the list.
       _ref = NULL;
     } else {
       _ref = _next;
     }
     assert(_ref != _first_seen, "cyclic ref_list found");
     NOT_PRODUCT(_processed++);
   }
 };
 class ReferenceProcessor : public CHeapObj<mtGC> {
  private:
   size_t total_count(DiscoveredList lists[]);
  protected:
   // Compatibility with pre-4965777 JDK's
   static bool _pending_list_uses_discovered_field;
   // The SoftReference master timestamp clock
   static jlong _soft_ref_timestamp_clock;
   MemRegion   _span;                    // (right-open) interval of heap
                                         // subject to wkref discovery
   bool        _discovering_refs;        // true when discovery enabled
   bool        _discovery_is_atomic;     // if discovery is atomic wrt
                                         // other collectors in configuration
   bool        _discovery_is_mt;         // true if reference discovery is MT.
   bool        _enqueuing_is_done;       // true if all weak references enqueued
   bool        _processing_is_mt;        // true during phases when
                                         // reference processing is MT.
   uint        _next_id;                 // round-robin mod _num_q counter in
                                         // support of work distribution
   // For collectors that do not keep GC liveness information
   // in the object header, this field holds a closure that
   // helps the reference processor determine the reachability
   // of an oop. It is currently initialized to NULL for all
   // collectors except for CMS and G1.
   BoolObjectClosure* _is_alive_non_header;
   // Soft ref clearing policies
   // . the default policy
   static ReferencePolicy*   _default_soft_ref_policy;
   // . the "clear all" policy
   static ReferencePolicy*   _always_clear_soft_ref_policy;
   // . the current policy below is either one of the above
   ReferencePolicy*          _current_soft_ref_policy;
   // The discovered ref lists themselves
   // The active MT'ness degree of the queues below
   uint             _num_q;
   // The maximum MT'ness degree of the queues below
   uint             _max_num_q;
   // Master array of discovered oops
   DiscoveredList* _discovered_refs;
   // Arrays of lists of oops, one per thread (pointers into master array above)
   DiscoveredList* _discoveredSoftRefs;
   DiscoveredList* _discoveredWeakRefs;
   DiscoveredList* _discoveredFinalRefs;
   DiscoveredList* _discoveredPhantomRefs;
   DiscoveredList* _discoveredCleanerRefs;
  public:
   static int number_of_subclasses_of_ref() { return (REF_CLEANER - REF_OTHER); }
   uint num_q()                             { return _num_q; }
   uint max_num_q()                         { return _max_num_q; }
   void set_active_mt_degree(uint v)        { _num_q = v; }
   DiscoveredList* discovered_refs()        { return _discovered_refs; }
   ReferencePolicy* setup_policy(bool always_clear) {
     _current_soft_ref_policy = always_clear ?
       _always_clear_soft_ref_policy : _default_soft_ref_policy;
     _current_soft_ref_policy->setup();   // snapshot the policy threshold
     return _current_soft_ref_policy;
   }
   // Process references with a certain reachability level.
   size_t process_discovered_reflist(DiscoveredList               refs_lists[],
                                     ReferencePolicy*             policy,
                                     bool                         clear_referent,
                                     BoolObjectClosure*           is_alive,
                                     OopClosure*                  keep_alive,
                                     VoidClosure*                 complete_gc,
                                     AbstractRefProcTaskExecutor* task_executor);
   void process_phaseJNI(BoolObjectClosure* is_alive,
                         OopClosure*        keep_alive,
                         VoidClosure*       complete_gc);
   // Work methods used by the method process_discovered_reflist
   // Phase1: keep alive all those referents that are otherwise
   // dead but which must be kept alive by policy (and their closure).
   void process_phase1(DiscoveredList&     refs_list,
                       ReferencePolicy*    policy,
                       BoolObjectClosure*  is_alive,
                       OopClosure*         keep_alive,
                       VoidClosure*        complete_gc);
   // Phase2: remove all those references whose referents are
   // reachable.
   inline void process_phase2(DiscoveredList&    refs_list,
                              BoolObjectClosure* is_alive,
                              OopClosure*        keep_alive,
                              VoidClosure*       complete_gc) {
     if (discovery_is_atomic()) {
       // complete_gc is ignored in this case for this phase
       pp2_work(refs_list, is_alive, keep_alive);
     } else {
       assert(complete_gc != NULL, "Error");
       pp2_work_concurrent_discovery(refs_list, is_alive,
                                     keep_alive, complete_gc);
     }
   }
   // Work methods in support of process_phase2
   void pp2_work(DiscoveredList&    refs_list,
                 BoolObjectClosure* is_alive,
                 OopClosure*        keep_alive);
   void pp2_work_concurrent_discovery(
                 DiscoveredList&    refs_list,
                 BoolObjectClosure* is_alive,
                 OopClosure*        keep_alive,
                 VoidClosure*       complete_gc);
   // Phase3: process the referents by either clearing them
   // or keeping them alive (and their closure)
   void process_phase3(DiscoveredList&    refs_list,
                       bool               clear_referent,
                       BoolObjectClosure* is_alive,
                       OopClosure*        keep_alive,
                       VoidClosure*       complete_gc);
   // Enqueue references with a certain reachability level
   void enqueue_discovered_reflist(DiscoveredList& refs_list, HeapWord* pending_list_addr);
   // "Preclean" all the discovered reference lists
   // by removing references with strongly reachable referents.
   // The first argument is a predicate on an oop that indicates
   // its (strong) reachability and the second is a closure that
   // may be used to incrementalize or abort the precleaning process.
   // The caller is responsible for taking care of potential
   // interference with concurrent operations on these lists
   // (or predicates involved) by other threads. Currently
   // only used by the CMS collector.
   void preclean_discovered_references(BoolObjectClosure* is_alive,
                                       OopClosure*        keep_alive,
                                       VoidClosure*       complete_gc,
                                       YieldClosure*      yield,
                                       GCTimer*           gc_timer);
   // Delete entries in the discovered lists that have
   // either a null referent or are not active. Such
   // Reference objects can result from the clearing
   // or enqueueing of Reference objects concurrent
   // with their discovery by a (concurrent) collector.
   // For a definition of "active" see java.lang.ref.Reference;
   // Refs are born active, become inactive when enqueued,
   // and never become active again. The state of being
   // active is encoded as follows: A Ref is active
   // if and only if its "next" field is NULL.
   void clean_up_discovered_references();
   void clean_up_discovered_reflist(DiscoveredList& refs_list);
   // Returns the name of the discovered reference list
   // occupying the i / _num_q slot.
   const char* list_name(uint i);
   void enqueue_discovered_reflists(HeapWord* pending_list_addr, AbstractRefProcTaskExecutor* task_executor);
  protected:
   // "Preclean" the given discovered reference list
   // by removing references with strongly reachable referents.
   // Currently used in support of CMS only.
   void preclean_discovered_reflist(DiscoveredList&    refs_list,
                                    BoolObjectClosure* is_alive,
                                    OopClosure*        keep_alive,
                                    VoidClosure*       complete_gc,
                                    YieldClosure*      yield);
   // round-robin mod _num_q (not: _not_ mode _max_num_q)
   uint next_id() {
     uint id = _next_id;
     if (++_next_id == _num_q) {
       _next_id = 0;
     }
     return id;
   }
   DiscoveredList* get_discovered_list(ReferenceType rt);
   inline void add_to_discovered_list_mt(DiscoveredList& refs_list, oop obj,
                                         HeapWord* discovered_addr);
   void verify_ok_to_handle_reflists() PRODUCT_RETURN;
   void clear_discovered_references(DiscoveredList& refs_list);
   void abandon_partial_discovered_list(DiscoveredList& refs_list);
   // Calculate the number of jni handles.
   unsigned int count_jni_refs();
   // Balances reference queues.
   void balance_queues(DiscoveredList ref_lists[]);
   // Update (advance) the soft ref master clock field.
   void update_soft_ref_master_clock();
  public:
   // Default parameters give you a vanilla reference processor.
   ReferenceProcessor(MemRegion span,
                      bool mt_processing = false, uint mt_processing_degree = 1,
                      bool mt_discovery  = false, uint mt_discovery_degree  = 1,
                      bool atomic_discovery = true,
                      BoolObjectClosure* is_alive_non_header = NULL);
   // RefDiscoveryPolicy values
   enum DiscoveryPolicy {
     ReferenceBasedDiscovery = 0,
     ReferentBasedDiscovery  = 1,
     DiscoveryPolicyMin      = ReferenceBasedDiscovery,
     DiscoveryPolicyMax      = ReferentBasedDiscovery
   };
   static void init_statics();
  public:
   // get and set "is_alive_non_header" field
   BoolObjectClosure* is_alive_non_header() {
     return _is_alive_non_header;
   }
   void set_is_alive_non_header(BoolObjectClosure* is_alive_non_header) {
     _is_alive_non_header = is_alive_non_header;
   }
   // get and set span
   MemRegion span()                   { return _span; }
   void      set_span(MemRegion span) { _span = span; }
   // start and stop weak ref discovery
   void enable_discovery(bool verify_disabled, bool check_no_refs);
   void disable_discovery()  { _discovering_refs = false; }
   bool discovery_enabled()  { return _discovering_refs;  }
   // whether discovery is atomic wrt other collectors
   bool discovery_is_atomic() const { return _discovery_is_atomic; }
   void set_atomic_discovery(bool atomic) { _discovery_is_atomic = atomic; }
   // whether the JDK in which we are embedded is a pre-4965777 JDK,
   // and thus whether or not it uses the discovered field to chain
   // the entries in the pending list.
   static bool pending_list_uses_discovered_field() {
     return _pending_list_uses_discovered_field;
   }
   // whether discovery is done by multiple threads same-old-timeously
   bool discovery_is_mt() const { return _discovery_is_mt; }
   void set_mt_discovery(bool mt) { _discovery_is_mt = mt; }
   // Whether we are in a phase when _processing_ is MT.
   bool processing_is_mt() const { return _processing_is_mt; }
   void set_mt_processing(bool mt) { _processing_is_mt = mt; }
   // whether all enqueuing of weak references is complete
   bool enqueuing_is_done()  { return _enqueuing_is_done; }
   void set_enqueuing_is_done(bool v) { _enqueuing_is_done = v; }
   // iterate over oops
   void weak_oops_do(OopClosure* f);       // weak roots
   // Balance each of the discovered lists.
   void balance_all_queues();
   void verify_list(DiscoveredList& ref_list);
   // Discover a Reference object, using appropriate discovery criteria
   bool discover_reference(oop obj, ReferenceType rt);
   // Process references found during GC (called by the garbage collector)
   ReferenceProcessorStats
   process_discovered_references(BoolObjectClosure*           is_alive,
                                 OopClosure*                  keep_alive,
                                 VoidClosure*                 complete_gc,
                                 AbstractRefProcTaskExecutor* task_executor,
                                 GCTimer *gc_timer);
   // Enqueue references at end of GC (called by the garbage collector)
   bool enqueue_discovered_references(AbstractRefProcTaskExecutor* task_executor = NULL);
   // If a discovery is in process that is being superceded, abandon it: all
   // the discovered lists will be empty, and all the objects on them will
   // have NULL discovered fields.  Must be called only at a safepoint.
   void abandon_partial_discovery();
   // debugging
   void verify_no_references_recorded() PRODUCT_RETURN;
   void verify_referent(oop obj)        PRODUCT_RETURN;
   // clear the discovered lists (unlinking each entry).
   void clear_discovered_references() PRODUCT_RETURN;
 };
 // A utility class to disable reference discovery in
 // the scope which contains it, for given ReferenceProcessor.
 class NoRefDiscovery: StackObj {
  private:
   ReferenceProcessor* _rp;
   bool _was_discovering_refs;
  public:
   NoRefDiscovery(ReferenceProcessor* rp) : _rp(rp) {
     _was_discovering_refs = _rp->discovery_enabled();
     if (_was_discovering_refs) {
       _rp->disable_discovery();
     }
   }
   ~NoRefDiscovery() {
     if (_was_discovering_refs) {
       _rp->enable_discovery(true /*verify_disabled*/, false /*check_no_refs*/);
     }
   }
 };
 // A utility class to temporarily mutate the span of the
 // given ReferenceProcessor in the scope that contains it.
 class ReferenceProcessorSpanMutator: StackObj {
  private:
   ReferenceProcessor* _rp;
   MemRegion           _saved_span;
  public:
   ReferenceProcessorSpanMutator(ReferenceProcessor* rp,
                                 MemRegion span):
     _rp(rp) {
     _saved_span = _rp->span();
     _rp->set_span(span);
   }
   ~ReferenceProcessorSpanMutator() {
     _rp->set_span(_saved_span);
   }
 };
 // A utility class to temporarily change the MT'ness of
 // reference discovery for the given ReferenceProcessor
 // in the scope that contains it.
 class ReferenceProcessorMTDiscoveryMutator: StackObj {
  private:
   ReferenceProcessor* _rp;
   bool                _saved_mt;
  public:
   ReferenceProcessorMTDiscoveryMutator(ReferenceProcessor* rp,
                                        bool mt):
     _rp(rp) {
     _saved_mt = _rp->discovery_is_mt();
     _rp->set_mt_discovery(mt);
   }
   ~ReferenceProcessorMTDiscoveryMutator() {
     _rp->set_mt_discovery(_saved_mt);
   }
 };
 // A utility class to temporarily change the disposition
 // of the "is_alive_non_header" closure field of the
 // given ReferenceProcessor in the scope that contains it.
 class ReferenceProcessorIsAliveMutator: StackObj {
  private:
   ReferenceProcessor* _rp;
   BoolObjectClosure*  _saved_cl;
  public:
   ReferenceProcessorIsAliveMutator(ReferenceProcessor* rp,
                                    BoolObjectClosure*  cl):
     _rp(rp) {
     _saved_cl = _rp->is_alive_non_header();
     _rp->set_is_alive_non_header(cl);
   }
   ~ReferenceProcessorIsAliveMutator() {
     _rp->set_is_alive_non_header(_saved_cl);
   }
 };
 // A utility class to temporarily change the disposition
 // of the "discovery_is_atomic" field of the
 // given ReferenceProcessor in the scope that contains it.
 class ReferenceProcessorAtomicMutator: StackObj {
  private:
   ReferenceProcessor* _rp;
   bool                _saved_atomic_discovery;
  public:
   ReferenceProcessorAtomicMutator(ReferenceProcessor* rp,
                                   bool atomic):
     _rp(rp) {
     _saved_atomic_discovery = _rp->discovery_is_atomic();
     _rp->set_atomic_discovery(atomic);
   }
   ~ReferenceProcessorAtomicMutator() {
     _rp->set_atomic_discovery(_saved_atomic_discovery);
   }
 };
 // A utility class to temporarily change the MT processing
 // disposition of the given ReferenceProcessor instance
 // in the scope that contains it.
 class ReferenceProcessorMTProcMutator: StackObj {
  private:
   ReferenceProcessor* _rp;
   bool  _saved_mt;
  public:
   ReferenceProcessorMTProcMutator(ReferenceProcessor* rp,
                                   bool mt):
     _rp(rp) {
     _saved_mt = _rp->processing_is_mt();
     _rp->set_mt_processing(mt);
   }
   ~ReferenceProcessorMTProcMutator() {
     _rp->set_mt_processing(_saved_mt);
   }
 };
 // This class is an interface used to implement task execution for the
 // reference processing.
 class AbstractRefProcTaskExecutor {
 public:
   // Abstract tasks to execute.
   class ProcessTask;
   class EnqueueTask;
   // Executes a task using worker threads.
   virtual void execute(ProcessTask& task) = 0;
   virtual void execute(EnqueueTask& task) = 0;
   // Switch to single threaded mode.
   virtual void set_single_threaded_mode() { };
 };
 // Abstract reference processing task to execute.
 class AbstractRefProcTaskExecutor::ProcessTask {
 protected:
   ProcessTask(ReferenceProcessor& ref_processor,
               DiscoveredList      refs_lists[],
               bool                marks_oops_alive)
     : _ref_processor(ref_processor),
       _refs_lists(refs_lists),
       _marks_oops_alive(marks_oops_alive)
   { }
 public:
   virtual void work(unsigned int work_id, BoolObjectClosure& is_alive,
                     OopClosure& keep_alive,
                     VoidClosure& complete_gc) = 0;
   // Returns true if a task marks some oops as alive.
   bool marks_oops_alive() const
   { return _marks_oops_alive; }
 protected:
   ReferenceProcessor& _ref_processor;
   DiscoveredList*     _refs_lists;
   const bool          _marks_oops_alive;
 };
 // Abstract reference processing task to execute.
 class AbstractRefProcTaskExecutor::EnqueueTask {
 protected:
   EnqueueTask(ReferenceProcessor& ref_processor,
               DiscoveredList      refs_lists[],
               HeapWord*           pending_list_addr,
               int                 n_queues)
     : _ref_processor(ref_processor),
       _refs_lists(refs_lists),
       _pending_list_addr(pending_list_addr),
       _n_queues(n_queues)
   { }
 public:
   virtual void work(unsigned int work_id) = 0;
 protected:
   ReferenceProcessor& _ref_processor;
   DiscoveredList*     _refs_lists;
   HeapWord*           _pending_list_addr;
   int                 _n_queues;
 };
 #endif // SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/memory/referenceProcessor.hpp@01dcaba9b3f3 (annotated)

src/share/vm/memory/referenceProcessor.hpp