jdk8-mips64-public/hotspot: src/share/vm/memory/referenceProcessor.hpp@a61af66fc99e (annotated)

src/share/vm/memory/referenceProcessor.hpp@a61af66fc99e (annotated)

src/share/vm/memory/referenceProcessor.hpp

Sat, 01 Dec 2007 00:00:00 +0000

author: duke
date: Sat, 01 Dec 2007 00:00:00 +0000
changeset 435: a61af66fc99e
child 548: ba764ed4b6f2
permissions: -rw-r--r--

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 /*
  * Copyright 2001-2007 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  * CA 95054 USA or visit www.sun.com if you need additional information or
  * have any questions.
  *
  */
 // ReferenceProcessor class encapsulates the per-"collector" processing
 // of "weak" references 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;
 class DiscoveredList;
 class ReferenceProcessor : public CHeapObj {
  friend class DiscoveredList;
  friend class DiscoveredListIterator;
  protected:
   // End of list marker
   static oop  _sentinelRef;
   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.
   int         _next_id;               // round-robin counter in
                                       // support of work distribution
   // For collectors that do not keep GC marking information
   // in the object header, this field holds a closure that
   // helps the reference processor determine the reachability
   // of an oop (the field is currently initialized to NULL for
   // all collectors but the CMS collector).
   BoolObjectClosure* _is_alive_non_header;
   // The discovered ref lists themselves
   int             _num_q;       // the MT'ness degree of the queues below
   DiscoveredList* _discoveredSoftRefs; // pointer to array of oops
   DiscoveredList* _discoveredWeakRefs;
   DiscoveredList* _discoveredFinalRefs;
   DiscoveredList* _discoveredPhantomRefs;
  public:
   int  num_q()                           { return _num_q; }
   DiscoveredList* discovered_soft_refs() { return _discoveredSoftRefs; }
   static oop* sentinel_ref()             { return &_sentinelRef; }
  public:
   // Process references with a certain reachability level.
   void 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_addr,
                       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_addr,
                              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_addr, is_alive, keep_alive);
     } else {
       assert(complete_gc != NULL, "Error");
       pp2_work_concurrent_discovery(refs_list_addr, is_alive,
                                     keep_alive, complete_gc);
     }
   }
   // Work methods in support of process_phase2
   void pp2_work(DiscoveredList&    refs_list_addr,
                 BoolObjectClosure* is_alive,
                 OopClosure*        keep_alive);
   void pp2_work_concurrent_discovery(
                 DiscoveredList&    refs_list_addr,
                 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_addr,
                       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, oop* 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);
   // 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(int i);
  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);
   void enqueue_discovered_reflists(oop* pending_list_addr, AbstractRefProcTaskExecutor* task_executor);
   int next_id() {
     int 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,
                                         oop* discovered_addr);
   void verify_ok_to_handle_reflists() PRODUCT_RETURN;
   void abandon_partial_discovered_list(DiscoveredList& refs_list);
   void abandon_partial_discovered_list_arr(DiscoveredList refs_lists[]);
   // 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:
   // constructor
   ReferenceProcessor():
     _span((HeapWord*)NULL, (HeapWord*)NULL),
     _discoveredSoftRefs(NULL),  _discoveredWeakRefs(NULL),
     _discoveredFinalRefs(NULL), _discoveredPhantomRefs(NULL),
     _discovering_refs(false),
     _discovery_is_atomic(true),
     _enqueuing_is_done(false),
     _discovery_is_mt(false),
     _is_alive_non_header(NULL),
     _num_q(0),
     _processing_is_mt(false),
     _next_id(0)
   {}
   ReferenceProcessor(MemRegion span, bool atomic_discovery,
                      bool mt_discovery, int mt_degree = 1,
                      bool mt_processing = false);
   // Allocates and initializes a reference processor.
   static ReferenceProcessor* create_ref_processor(
     MemRegion          span,
     bool               atomic_discovery,
     bool               mt_discovery,
     BoolObjectClosure* is_alive_non_header = NULL,
     int                parallel_gc_threads = 1,
     bool               mt_processing = false);
   // RefDiscoveryPolicy values
   enum {
     ReferenceBasedDiscovery = 0,
     ReferentBasedDiscovery  = 1
   };
   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()   { _discovering_refs = true;  }
   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 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
   static void oops_do(OopClosure* f);     // strong root(s)
   // 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)
   void process_discovered_references(ReferencePolicy*             policy,
                                      BoolObjectClosure*           is_alive,
                                      OopClosure*                  keep_alive,
                                      VoidClosure*                 complete_gc,
                                      AbstractRefProcTaskExecutor* task_executor);
  public:
   // Enqueue references at end of GC (called by the garbage collector)
   bool enqueue_discovered_references(AbstractRefProcTaskExecutor* task_executor = NULL);
   // debugging
   void verify_no_references_recorded() PRODUCT_RETURN;
   static void verify();
   // 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) {
     if (_was_discovering_refs = _rp->discovery_enabled()) {
       _rp->disable_discovery();
     }
   }
   ~NoRefDiscovery() {
     if (_was_discovering_refs) {
       _rp->enable_discovery();
     }
   }
 };
 // 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 ReferenceProcessorMTMutator: StackObj {
  private:
   ReferenceProcessor* _rp;
   bool                _saved_mt;
  public:
   ReferenceProcessorMTMutator(ReferenceProcessor* rp,
                               bool mt):
     _rp(rp) {
     _saved_mt = _rp->discovery_is_mt();
     _rp->set_mt_discovery(mt);
   }
   ~ReferenceProcessorMTMutator() {
     _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[],
               oop*                pending_list_addr,
               oop                 sentinel_ref,
               int                 n_queues)
     : _ref_processor(ref_processor),
       _refs_lists(refs_lists),
       _pending_list_addr(pending_list_addr),
       _sentinel_ref(sentinel_ref),
       _n_queues(n_queues)
   { }
 public:
   virtual void work(unsigned int work_id) = 0;
 protected:
   ReferenceProcessor& _ref_processor;
   DiscoveredList*     _refs_lists;
   oop*                _pending_list_addr;
   oop                 _sentinel_ref;
   int                 _n_queues;
 };

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/memory/referenceProcessor.hpp@a61af66fc99e (annotated)

src/share/vm/memory/referenceProcessor.hpp