jdk8-mips64-public/hotspot: comparison src/share/vm/memory/referenceProcessor.hpp

--1:000000000000
+:f90c822e73f8
+/*
+* 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;
+public:
+static int number_of_subclasses_of_ref() { return (REF_PHANTOM - 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 / file comparison

comparison: src/share/vm/memory/referenceProcessor.hpp

src/share/vm/memory/referenceProcessor.hpp