| /* |
| * 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; |
| }; |
