| /* |
| * Copyright 2001-2008 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. |
| * |
| */ |
| |
| # include "incls/_precompiled.incl" |
| # include "incls/_referenceProcessor.cpp.incl" |
| |
| ReferencePolicy* ReferenceProcessor::_always_clear_soft_ref_policy = NULL; |
| ReferencePolicy* ReferenceProcessor::_default_soft_ref_policy = NULL; |
| oop ReferenceProcessor::_sentinelRef = NULL; |
| const int subclasses_of_ref = REF_PHANTOM - REF_OTHER; |
| |
| // 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_not_null(_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_not_null(o); |
| } else { |
| _oop_head = o; |
| } |
| } |
| bool empty() const { return head() == ReferenceProcessor::sentinel_ref(); } |
| 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; |
| }; |
| |
| void referenceProcessor_init() { |
| ReferenceProcessor::init_statics(); |
| } |
| |
| void ReferenceProcessor::init_statics() { |
| assert(_sentinelRef == NULL, "should be initialized precisely once"); |
| EXCEPTION_MARK; |
| _sentinelRef = instanceKlass::cast( |
| SystemDictionary::reference_klass())-> |
| allocate_permanent_instance(THREAD); |
| |
| // Initialize the master soft ref clock. |
| java_lang_ref_SoftReference::set_clock(os::javaTimeMillis()); |
| |
| if (HAS_PENDING_EXCEPTION) { |
| Handle ex(THREAD, PENDING_EXCEPTION); |
| vm_exit_during_initialization(ex); |
| } |
| assert(_sentinelRef != NULL && _sentinelRef->is_oop(), |
| "Just constructed it!"); |
| _always_clear_soft_ref_policy = new AlwaysClearPolicy(); |
| _default_soft_ref_policy = new COMPILER2_PRESENT(LRUMaxHeapPolicy()) |
| NOT_COMPILER2(LRUCurrentHeapPolicy()); |
| if (_always_clear_soft_ref_policy == NULL || _default_soft_ref_policy == NULL) { |
| vm_exit_during_initialization("Could not allocate reference policy object"); |
| } |
| guarantee(RefDiscoveryPolicy == ReferenceBasedDiscovery || |
| RefDiscoveryPolicy == ReferentBasedDiscovery, |
| "Unrecongnized RefDiscoveryPolicy"); |
| } |
| |
| ReferenceProcessor* |
| ReferenceProcessor::create_ref_processor(MemRegion span, |
| bool atomic_discovery, |
| bool mt_discovery, |
| BoolObjectClosure* is_alive_non_header, |
| int parallel_gc_threads, |
| bool mt_processing, |
| bool dl_needs_barrier) { |
| int mt_degree = 1; |
| if (parallel_gc_threads > 1) { |
| mt_degree = parallel_gc_threads; |
| } |
| ReferenceProcessor* rp = |
| new ReferenceProcessor(span, atomic_discovery, |
| mt_discovery, mt_degree, |
| mt_processing && (parallel_gc_threads > 0), |
| dl_needs_barrier); |
| if (rp == NULL) { |
| vm_exit_during_initialization("Could not allocate ReferenceProcessor object"); |
| } |
| rp->set_is_alive_non_header(is_alive_non_header); |
| rp->setup_policy(false /* default soft ref policy */); |
| return rp; |
| } |
| |
| ReferenceProcessor::ReferenceProcessor(MemRegion span, |
| bool atomic_discovery, |
| bool mt_discovery, |
| int mt_degree, |
| bool mt_processing, |
| bool discovered_list_needs_barrier) : |
| _discovering_refs(false), |
| _enqueuing_is_done(false), |
| _is_alive_non_header(NULL), |
| _discovered_list_needs_barrier(discovered_list_needs_barrier), |
| _bs(NULL), |
| _processing_is_mt(mt_processing), |
| _next_id(0) |
| { |
| _span = span; |
| _discovery_is_atomic = atomic_discovery; |
| _discovery_is_mt = mt_discovery; |
| _num_q = mt_degree; |
| _discoveredSoftRefs = NEW_C_HEAP_ARRAY(DiscoveredList, _num_q * subclasses_of_ref); |
| if (_discoveredSoftRefs == NULL) { |
| vm_exit_during_initialization("Could not allocated RefProc Array"); |
| } |
| _discoveredWeakRefs = &_discoveredSoftRefs[_num_q]; |
| _discoveredFinalRefs = &_discoveredWeakRefs[_num_q]; |
| _discoveredPhantomRefs = &_discoveredFinalRefs[_num_q]; |
| assert(sentinel_ref() != NULL, "_sentinelRef is NULL"); |
| // Initialized all entries to _sentinelRef |
| for (int i = 0; i < _num_q * subclasses_of_ref; i++) { |
| _discoveredSoftRefs[i].set_head(sentinel_ref()); |
| _discoveredSoftRefs[i].set_length(0); |
| } |
| // If we do barreirs, cache a copy of the barrier set. |
| if (discovered_list_needs_barrier) { |
| _bs = Universe::heap()->barrier_set(); |
| } |
| } |
| |
| #ifndef PRODUCT |
| void ReferenceProcessor::verify_no_references_recorded() { |
| guarantee(!_discovering_refs, "Discovering refs?"); |
| for (int i = 0; i < _num_q * subclasses_of_ref; i++) { |
| guarantee(_discoveredSoftRefs[i].empty(), |
| "Found non-empty discovered list"); |
| } |
| } |
| #endif |
| |
| void ReferenceProcessor::weak_oops_do(OopClosure* f) { |
| for (int i = 0; i < _num_q * subclasses_of_ref; i++) { |
| if (UseCompressedOops) { |
| f->do_oop((narrowOop*)_discoveredSoftRefs[i].adr_head()); |
| } else { |
| f->do_oop((oop*)_discoveredSoftRefs[i].adr_head()); |
| } |
| } |
| } |
| |
| void ReferenceProcessor::oops_do(OopClosure* f) { |
| f->do_oop(adr_sentinel_ref()); |
| } |
| |
| void ReferenceProcessor::update_soft_ref_master_clock() { |
| // Update (advance) the soft ref master clock field. This must be done |
| // after processing the soft ref list. |
| jlong now = os::javaTimeMillis(); |
| jlong clock = java_lang_ref_SoftReference::clock(); |
| NOT_PRODUCT( |
| if (now < clock) { |
| warning("time warp: %d to %d", clock, now); |
| } |
| ) |
| // In product mode, protect ourselves from system time being adjusted |
| // externally and going backward; see note in the implementation of |
| // GenCollectedHeap::time_since_last_gc() for the right way to fix |
| // this uniformly throughout the VM; see bug-id 4741166. XXX |
| if (now > clock) { |
| java_lang_ref_SoftReference::set_clock(now); |
| } |
| // Else leave clock stalled at its old value until time progresses |
| // past clock value. |
| } |
| |
| void ReferenceProcessor::process_discovered_references( |
| BoolObjectClosure* is_alive, |
| OopClosure* keep_alive, |
| VoidClosure* complete_gc, |
| AbstractRefProcTaskExecutor* task_executor) { |
| NOT_PRODUCT(verify_ok_to_handle_reflists()); |
| |
| assert(!enqueuing_is_done(), "If here enqueuing should not be complete"); |
| // Stop treating discovered references specially. |
| disable_discovery(); |
| |
| bool trace_time = PrintGCDetails && PrintReferenceGC; |
| // Soft references |
| { |
| TraceTime tt("SoftReference", trace_time, false, gclog_or_tty); |
| process_discovered_reflist(_discoveredSoftRefs, _current_soft_ref_policy, true, |
| is_alive, keep_alive, complete_gc, task_executor); |
| } |
| |
| update_soft_ref_master_clock(); |
| |
| // Weak references |
| { |
| TraceTime tt("WeakReference", trace_time, false, gclog_or_tty); |
| process_discovered_reflist(_discoveredWeakRefs, NULL, true, |
| is_alive, keep_alive, complete_gc, task_executor); |
| } |
| |
| // Final references |
| { |
| TraceTime tt("FinalReference", trace_time, false, gclog_or_tty); |
| process_discovered_reflist(_discoveredFinalRefs, NULL, false, |
| is_alive, keep_alive, complete_gc, task_executor); |
| } |
| |
| // Phantom references |
| { |
| TraceTime tt("PhantomReference", trace_time, false, gclog_or_tty); |
| process_discovered_reflist(_discoveredPhantomRefs, NULL, false, |
| is_alive, keep_alive, complete_gc, task_executor); |
| } |
| |
| // Weak global JNI references. It would make more sense (semantically) to |
| // traverse these simultaneously with the regular weak references above, but |
| // that is not how the JDK1.2 specification is. See #4126360. Native code can |
| // thus use JNI weak references to circumvent the phantom references and |
| // resurrect a "post-mortem" object. |
| { |
| TraceTime tt("JNI Weak Reference", trace_time, false, gclog_or_tty); |
| if (task_executor != NULL) { |
| task_executor->set_single_threaded_mode(); |
| } |
| process_phaseJNI(is_alive, keep_alive, complete_gc); |
| } |
| } |
| |
| #ifndef PRODUCT |
| // Calculate the number of jni handles. |
| uint ReferenceProcessor::count_jni_refs() { |
| class AlwaysAliveClosure: public BoolObjectClosure { |
| public: |
| virtual bool do_object_b(oop obj) { return true; } |
| virtual void do_object(oop obj) { assert(false, "Don't call"); } |
| }; |
| |
| class CountHandleClosure: public OopClosure { |
| private: |
| int _count; |
| public: |
| CountHandleClosure(): _count(0) {} |
| void do_oop(oop* unused) { _count++; } |
| void do_oop(narrowOop* unused) { ShouldNotReachHere(); } |
| int count() { return _count; } |
| }; |
| CountHandleClosure global_handle_count; |
| AlwaysAliveClosure always_alive; |
| JNIHandles::weak_oops_do(&always_alive, &global_handle_count); |
| return global_handle_count.count(); |
| } |
| #endif |
| |
| void ReferenceProcessor::process_phaseJNI(BoolObjectClosure* is_alive, |
| OopClosure* keep_alive, |
| VoidClosure* complete_gc) { |
| #ifndef PRODUCT |
| if (PrintGCDetails && PrintReferenceGC) { |
| unsigned int count = count_jni_refs(); |
| gclog_or_tty->print(", %u refs", count); |
| } |
| #endif |
| JNIHandles::weak_oops_do(is_alive, keep_alive); |
| // Finally remember to keep sentinel around |
| keep_alive->do_oop(adr_sentinel_ref()); |
| complete_gc->do_void(); |
| } |
| |
| |
| template <class T> |
| static bool enqueue_discovered_ref_helper(ReferenceProcessor* ref, |
| AbstractRefProcTaskExecutor* task_executor) { |
| |
| // Remember old value of pending references list |
| T* pending_list_addr = (T*)java_lang_ref_Reference::pending_list_addr(); |
| T old_pending_list_value = *pending_list_addr; |
| |
| // Enqueue references that are not made active again, and |
| // clear the decks for the next collection (cycle). |
| ref->enqueue_discovered_reflists((HeapWord*)pending_list_addr, task_executor); |
| // Do the oop-check on pending_list_addr missed in |
| // enqueue_discovered_reflist. We should probably |
| // do a raw oop_check so that future such idempotent |
| // oop_stores relying on the oop-check side-effect |
| // may be elided automatically and safely without |
| // affecting correctness. |
| oop_store(pending_list_addr, oopDesc::load_decode_heap_oop(pending_list_addr)); |
| |
| // Stop treating discovered references specially. |
| ref->disable_discovery(); |
| |
| // Return true if new pending references were added |
| return old_pending_list_value != *pending_list_addr; |
| } |
| |
| bool ReferenceProcessor::enqueue_discovered_references(AbstractRefProcTaskExecutor* task_executor) { |
| NOT_PRODUCT(verify_ok_to_handle_reflists()); |
| if (UseCompressedOops) { |
| return enqueue_discovered_ref_helper<narrowOop>(this, task_executor); |
| } else { |
| return enqueue_discovered_ref_helper<oop>(this, task_executor); |
| } |
| } |
| |
| void ReferenceProcessor::enqueue_discovered_reflist(DiscoveredList& refs_list, |
| HeapWord* pending_list_addr) { |
| // Given a list of refs linked through the "discovered" field |
| // (java.lang.ref.Reference.discovered) chain them through the |
| // "next" field (java.lang.ref.Reference.next) and prepend |
| // to the pending list. |
| if (TraceReferenceGC && PrintGCDetails) { |
| gclog_or_tty->print_cr("ReferenceProcessor::enqueue_discovered_reflist list " |
| INTPTR_FORMAT, (address)refs_list.head()); |
| } |
| oop obj = refs_list.head(); |
| // Walk down the list, copying the discovered field into |
| // the next field and clearing it (except for the last |
| // non-sentinel object which is treated specially to avoid |
| // confusion with an active reference). |
| while (obj != sentinel_ref()) { |
| assert(obj->is_instanceRef(), "should be reference object"); |
| oop next = java_lang_ref_Reference::discovered(obj); |
| if (TraceReferenceGC && PrintGCDetails) { |
| gclog_or_tty->print_cr(" obj " INTPTR_FORMAT "/next " INTPTR_FORMAT, |
| obj, next); |
| } |
| assert(java_lang_ref_Reference::next(obj) == NULL, |
| "The reference should not be enqueued"); |
| if (next == sentinel_ref()) { // obj is last |
| // Swap refs_list into pendling_list_addr and |
| // set obj's next to what we read from pending_list_addr. |
| oop old = oopDesc::atomic_exchange_oop(refs_list.head(), pending_list_addr); |
| // Need oop_check on pending_list_addr above; |
| // see special oop-check code at the end of |
| // enqueue_discovered_reflists() further below. |
| if (old == NULL) { |
| // obj should be made to point to itself, since |
| // pending list was empty. |
| java_lang_ref_Reference::set_next(obj, obj); |
| } else { |
| java_lang_ref_Reference::set_next(obj, old); |
| } |
| } else { |
| java_lang_ref_Reference::set_next(obj, next); |
| } |
| java_lang_ref_Reference::set_discovered(obj, (oop) NULL); |
| obj = next; |
| } |
| } |
| |
| // Parallel enqueue task |
| class RefProcEnqueueTask: public AbstractRefProcTaskExecutor::EnqueueTask { |
| public: |
| RefProcEnqueueTask(ReferenceProcessor& ref_processor, |
| DiscoveredList discovered_refs[], |
| HeapWord* pending_list_addr, |
| oop sentinel_ref, |
| int n_queues) |
| : EnqueueTask(ref_processor, discovered_refs, |
| pending_list_addr, sentinel_ref, n_queues) |
| { } |
| |
| virtual void work(unsigned int work_id) { |
| assert(work_id < (unsigned int)_ref_processor.num_q(), "Index out-of-bounds"); |
| // Simplest first cut: static partitioning. |
| int index = work_id; |
| for (int j = 0; j < subclasses_of_ref; j++, index += _n_queues) { |
| _ref_processor.enqueue_discovered_reflist( |
| _refs_lists[index], _pending_list_addr); |
| _refs_lists[index].set_head(_sentinel_ref); |
| _refs_lists[index].set_length(0); |
| } |
| } |
| }; |
| |
| // Enqueue references that are not made active again |
| void ReferenceProcessor::enqueue_discovered_reflists(HeapWord* pending_list_addr, |
| AbstractRefProcTaskExecutor* task_executor) { |
| if (_processing_is_mt && task_executor != NULL) { |
| // Parallel code |
| RefProcEnqueueTask tsk(*this, _discoveredSoftRefs, |
| pending_list_addr, sentinel_ref(), _num_q); |
| task_executor->execute(tsk); |
| } else { |
| // Serial code: call the parent class's implementation |
| for (int i = 0; i < _num_q * subclasses_of_ref; i++) { |
| enqueue_discovered_reflist(_discoveredSoftRefs[i], pending_list_addr); |
| _discoveredSoftRefs[i].set_head(sentinel_ref()); |
| _discoveredSoftRefs[i].set_length(0); |
| } |
| } |
| } |
| |
| // Iterator for the list of discovered references. |
| class DiscoveredListIterator { |
| public: |
| inline DiscoveredListIterator(DiscoveredList& refs_list, |
| OopClosure* keep_alive, |
| BoolObjectClosure* is_alive); |
| |
| // End Of List. |
| inline bool has_next() const { return _next != ReferenceProcessor::sentinel_ref(); } |
| |
| // 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; |
| |
| // 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. |
| inline void load_ptrs(DEBUG_ONLY(bool allow_null_referent)); |
| |
| // Move to the next discovered reference. |
| inline void next(); |
| |
| // Remove the current reference from the list |
| inline void remove(); |
| |
| // Make the Reference object active again. |
| inline void make_active() { java_lang_ref_Reference::set_next(_ref, NULL); } |
| |
| // 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) { |
| _keep_alive->do_oop((narrowOop*)_prev_next); |
| } else { |
| _keep_alive->do_oop((oop*)_prev_next); |
| } |
| } |
| |
| // NULL out referent pointer. |
| inline void clear_referent() { oop_store_raw(_referent_addr, NULL); } |
| |
| // Statistics |
| NOT_PRODUCT( |
| inline size_t processed() const { return _processed; } |
| inline size_t removed() const { return _removed; } |
| ) |
| |
| inline void move_to_next(); |
| |
| private: |
| DiscoveredList& _refs_list; |
| HeapWord* _prev_next; |
| 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; |
| ) |
| }; |
| |
| inline DiscoveredListIterator::DiscoveredListIterator(DiscoveredList& refs_list, |
| OopClosure* keep_alive, |
| BoolObjectClosure* is_alive) |
| : _refs_list(refs_list), |
| _prev_next(refs_list.adr_head()), |
| _ref(refs_list.head()), |
| #ifdef ASSERT |
| _first_seen(refs_list.head()), |
| #endif |
| #ifndef PRODUCT |
| _processed(0), |
| _removed(0), |
| #endif |
| _next(refs_list.head()), |
| _keep_alive(keep_alive), |
| _is_alive(is_alive) |
| { } |
| |
| inline bool DiscoveredListIterator::is_referent_alive() const { |
| return _is_alive->do_object_b(_referent); |
| } |
| |
| inline void DiscoveredListIterator::load_ptrs(DEBUG_ONLY(bool allow_null_referent)) { |
| _discovered_addr = java_lang_ref_Reference::discovered_addr(_ref); |
| oop discovered = java_lang_ref_Reference::discovered(_ref); |
| assert(_discovered_addr && discovered->is_oop_or_null(), |
| "discovered field is bad"); |
| _next = discovered; |
| _referent_addr = java_lang_ref_Reference::referent_addr(_ref); |
| _referent = java_lang_ref_Reference::referent(_ref); |
| assert(Universe::heap()->is_in_reserved_or_null(_referent), |
| "Wrong oop found in java.lang.Reference object"); |
| assert(allow_null_referent ? |
| _referent->is_oop_or_null() |
| : _referent->is_oop(), |
| "bad referent"); |
| } |
| |
| inline void DiscoveredListIterator::next() { |
| _prev_next = _discovered_addr; |
| move_to_next(); |
| } |
| |
| inline void DiscoveredListIterator::remove() { |
| assert(_ref->is_oop(), "Dropping a bad reference"); |
| oop_store_raw(_discovered_addr, NULL); |
| // First _prev_next ref actually points into DiscoveredList (gross). |
| if (UseCompressedOops) { |
| // Remove Reference object from list. |
| oopDesc::encode_store_heap_oop_not_null((narrowOop*)_prev_next, _next); |
| } else { |
| // Remove Reference object from list. |
| oopDesc::store_heap_oop((oop*)_prev_next, _next); |
| } |
| NOT_PRODUCT(_removed++); |
| _refs_list.dec_length(1); |
| } |
| |
| inline void DiscoveredListIterator::move_to_next() { |
| _ref = _next; |
| assert(_ref != _first_seen, "cyclic ref_list found"); |
| NOT_PRODUCT(_processed++); |
| } |
| |
| // NOTE: process_phase*() are largely similar, and at a high level |
| // merely iterate over the extant list applying a predicate to |
| // each of its elements and possibly removing that element from the |
| // list and applying some further closures to that element. |
| // We should consider the possibility of replacing these |
| // process_phase*() methods by abstracting them into |
| // a single general iterator invocation that receives appropriate |
| // closures that accomplish this work. |
| |
| // (SoftReferences only) Traverse the list and remove any SoftReferences whose |
| // referents are not alive, but that should be kept alive for policy reasons. |
| // Keep alive the transitive closure of all such referents. |
| void |
| ReferenceProcessor::process_phase1(DiscoveredList& refs_list, |
| ReferencePolicy* policy, |
| BoolObjectClosure* is_alive, |
| OopClosure* keep_alive, |
| VoidClosure* complete_gc) { |
| assert(policy != NULL, "Must have a non-NULL policy"); |
| DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
| // Decide which softly reachable refs should be kept alive. |
| while (iter.has_next()) { |
| iter.load_ptrs(DEBUG_ONLY(!discovery_is_atomic() /* allow_null_referent */)); |
| bool referent_is_dead = (iter.referent() != NULL) && !iter.is_referent_alive(); |
| if (referent_is_dead && !policy->should_clear_reference(iter.obj())) { |
| if (TraceReferenceGC) { |
| gclog_or_tty->print_cr("Dropping reference (" INTPTR_FORMAT ": %s" ") by policy", |
| iter.obj(), iter.obj()->blueprint()->internal_name()); |
| } |
| // Remove Reference object from list |
| iter.remove(); |
| // Make the Reference object active again |
| iter.make_active(); |
| // keep the referent around |
| iter.make_referent_alive(); |
| iter.move_to_next(); |
| } else { |
| iter.next(); |
| } |
| } |
| // Close the reachable set |
| complete_gc->do_void(); |
| NOT_PRODUCT( |
| if (PrintGCDetails && TraceReferenceGC) { |
| gclog_or_tty->print(" Dropped %d dead Refs out of %d " |
| "discovered Refs by policy ", iter.removed(), iter.processed()); |
| } |
| ) |
| } |
| |
| // Traverse the list and remove any Refs that are not active, or |
| // whose referents are either alive or NULL. |
| void |
| ReferenceProcessor::pp2_work(DiscoveredList& refs_list, |
| BoolObjectClosure* is_alive, |
| OopClosure* keep_alive) { |
| assert(discovery_is_atomic(), "Error"); |
| DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
| while (iter.has_next()) { |
| iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */)); |
| DEBUG_ONLY(oop next = java_lang_ref_Reference::next(iter.obj());) |
| assert(next == NULL, "Should not discover inactive Reference"); |
| if (iter.is_referent_alive()) { |
| if (TraceReferenceGC) { |
| gclog_or_tty->print_cr("Dropping strongly reachable reference (" INTPTR_FORMAT ": %s)", |
| iter.obj(), iter.obj()->blueprint()->internal_name()); |
| } |
| // The referent is reachable after all. |
| // Remove Reference object from list. |
| iter.remove(); |
| // Update the referent pointer as necessary: Note that this |
| // should not entail any recursive marking because the |
| // referent must already have been traversed. |
| iter.make_referent_alive(); |
| iter.move_to_next(); |
| } else { |
| iter.next(); |
| } |
| } |
| NOT_PRODUCT( |
| if (PrintGCDetails && TraceReferenceGC) { |
| gclog_or_tty->print(" Dropped %d active Refs out of %d " |
| "Refs in discovered list ", iter.removed(), iter.processed()); |
| } |
| ) |
| } |
| |
| void |
| ReferenceProcessor::pp2_work_concurrent_discovery(DiscoveredList& refs_list, |
| BoolObjectClosure* is_alive, |
| OopClosure* keep_alive, |
| VoidClosure* complete_gc) { |
| assert(!discovery_is_atomic(), "Error"); |
| DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
| while (iter.has_next()) { |
| iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); |
| HeapWord* next_addr = java_lang_ref_Reference::next_addr(iter.obj()); |
| oop next = java_lang_ref_Reference::next(iter.obj()); |
| if ((iter.referent() == NULL || iter.is_referent_alive() || |
| next != NULL)) { |
| assert(next->is_oop_or_null(), "bad next field"); |
| // Remove Reference object from list |
| iter.remove(); |
| // Trace the cohorts |
| iter.make_referent_alive(); |
| if (UseCompressedOops) { |
| keep_alive->do_oop((narrowOop*)next_addr); |
| } else { |
| keep_alive->do_oop((oop*)next_addr); |
| } |
| iter.move_to_next(); |
| } else { |
| iter.next(); |
| } |
| } |
| // Now close the newly reachable set |
| complete_gc->do_void(); |
| NOT_PRODUCT( |
| if (PrintGCDetails && TraceReferenceGC) { |
| gclog_or_tty->print(" Dropped %d active Refs out of %d " |
| "Refs in discovered list ", iter.removed(), iter.processed()); |
| } |
| ) |
| } |
| |
| // Traverse the list and process the referents, by either |
| // clearing them or keeping them (and their reachable |
| // closure) alive. |
| void |
| ReferenceProcessor::process_phase3(DiscoveredList& refs_list, |
| bool clear_referent, |
| BoolObjectClosure* is_alive, |
| OopClosure* keep_alive, |
| VoidClosure* complete_gc) { |
| DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
| while (iter.has_next()) { |
| iter.update_discovered(); |
| iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */)); |
| if (clear_referent) { |
| // NULL out referent pointer |
| iter.clear_referent(); |
| } else { |
| // keep the referent around |
| iter.make_referent_alive(); |
| } |
| if (TraceReferenceGC) { |
| gclog_or_tty->print_cr("Adding %sreference (" INTPTR_FORMAT ": %s) as pending", |
| clear_referent ? "cleared " : "", |
| iter.obj(), iter.obj()->blueprint()->internal_name()); |
| } |
| assert(iter.obj()->is_oop(UseConcMarkSweepGC), "Adding a bad reference"); |
| // If discovery is concurrent, we may have objects with null referents, |
| // being those that were concurrently cleared after they were discovered |
| // (and not subsequently precleaned). |
| assert( (discovery_is_atomic() && iter.referent()->is_oop()) |
| || (!discovery_is_atomic() && iter.referent()->is_oop_or_null(UseConcMarkSweepGC)), |
| "Adding a bad referent"); |
| iter.next(); |
| } |
| // Remember to keep sentinel pointer around |
| iter.update_discovered(); |
| // Close the reachable set |
| complete_gc->do_void(); |
| } |
| |
| void |
| ReferenceProcessor::abandon_partial_discovered_list(DiscoveredList& refs_list) { |
| oop obj = refs_list.head(); |
| while (obj != sentinel_ref()) { |
| oop discovered = java_lang_ref_Reference::discovered(obj); |
| java_lang_ref_Reference::set_discovered_raw(obj, NULL); |
| obj = discovered; |
| } |
| refs_list.set_head(sentinel_ref()); |
| refs_list.set_length(0); |
| } |
| |
| void ReferenceProcessor::abandon_partial_discovery() { |
| // loop over the lists |
| for (int i = 0; i < _num_q * subclasses_of_ref; i++) { |
| if (TraceReferenceGC && PrintGCDetails && ((i % _num_q) == 0)) { |
| gclog_or_tty->print_cr( |
| "\nAbandoning %s discovered list", |
| list_name(i)); |
| } |
| abandon_partial_discovered_list(_discoveredSoftRefs[i]); |
| } |
| } |
| |
| class RefProcPhase1Task: public AbstractRefProcTaskExecutor::ProcessTask { |
| public: |
| RefProcPhase1Task(ReferenceProcessor& ref_processor, |
| DiscoveredList refs_lists[], |
| ReferencePolicy* policy, |
| bool marks_oops_alive) |
| : ProcessTask(ref_processor, refs_lists, marks_oops_alive), |
| _policy(policy) |
| { } |
| virtual void work(unsigned int i, BoolObjectClosure& is_alive, |
| OopClosure& keep_alive, |
| VoidClosure& complete_gc) |
| { |
| _ref_processor.process_phase1(_refs_lists[i], _policy, |
| &is_alive, &keep_alive, &complete_gc); |
| } |
| private: |
| ReferencePolicy* _policy; |
| }; |
| |
| class RefProcPhase2Task: public AbstractRefProcTaskExecutor::ProcessTask { |
| public: |
| RefProcPhase2Task(ReferenceProcessor& ref_processor, |
| DiscoveredList refs_lists[], |
| bool marks_oops_alive) |
| : ProcessTask(ref_processor, refs_lists, marks_oops_alive) |
| { } |
| virtual void work(unsigned int i, BoolObjectClosure& is_alive, |
| OopClosure& keep_alive, |
| VoidClosure& complete_gc) |
| { |
| _ref_processor.process_phase2(_refs_lists[i], |
| &is_alive, &keep_alive, &complete_gc); |
| } |
| }; |
| |
| class RefProcPhase3Task: public AbstractRefProcTaskExecutor::ProcessTask { |
| public: |
| RefProcPhase3Task(ReferenceProcessor& ref_processor, |
| DiscoveredList refs_lists[], |
| bool clear_referent, |
| bool marks_oops_alive) |
| : ProcessTask(ref_processor, refs_lists, marks_oops_alive), |
| _clear_referent(clear_referent) |
| { } |
| virtual void work(unsigned int i, BoolObjectClosure& is_alive, |
| OopClosure& keep_alive, |
| VoidClosure& complete_gc) |
| { |
| _ref_processor.process_phase3(_refs_lists[i], _clear_referent, |
| &is_alive, &keep_alive, &complete_gc); |
| } |
| private: |
| bool _clear_referent; |
| }; |
| |
| // Balances reference queues. |
| void ReferenceProcessor::balance_queues(DiscoveredList ref_lists[]) |
| { |
| // calculate total length |
| size_t total_refs = 0; |
| for (int i = 0; i < _num_q; ++i) { |
| total_refs += ref_lists[i].length(); |
| } |
| size_t avg_refs = total_refs / _num_q + 1; |
| int to_idx = 0; |
| for (int from_idx = 0; from_idx < _num_q; from_idx++) { |
| while (ref_lists[from_idx].length() > avg_refs) { |
| assert(to_idx < _num_q, "Sanity Check!"); |
| if (ref_lists[to_idx].length() < avg_refs) { |
| // move superfluous refs |
| size_t refs_to_move = |
| MIN2(ref_lists[from_idx].length() - avg_refs, |
| avg_refs - ref_lists[to_idx].length()); |
| oop move_head = ref_lists[from_idx].head(); |
| oop move_tail = move_head; |
| oop new_head = move_head; |
| // find an element to split the list on |
| for (size_t j = 0; j < refs_to_move; ++j) { |
| move_tail = new_head; |
| new_head = java_lang_ref_Reference::discovered(new_head); |
| } |
| java_lang_ref_Reference::set_discovered(move_tail, ref_lists[to_idx].head()); |
| ref_lists[to_idx].set_head(move_head); |
| ref_lists[to_idx].inc_length(refs_to_move); |
| ref_lists[from_idx].set_head(new_head); |
| ref_lists[from_idx].dec_length(refs_to_move); |
| } else { |
| ++to_idx; |
| } |
| } |
| } |
| } |
| |
| void |
| ReferenceProcessor::process_discovered_reflist( |
| DiscoveredList refs_lists[], |
| ReferencePolicy* policy, |
| bool clear_referent, |
| BoolObjectClosure* is_alive, |
| OopClosure* keep_alive, |
| VoidClosure* complete_gc, |
| AbstractRefProcTaskExecutor* task_executor) |
| { |
| bool mt = task_executor != NULL && _processing_is_mt; |
| if (mt && ParallelRefProcBalancingEnabled) { |
| balance_queues(refs_lists); |
| } |
| if (PrintReferenceGC && PrintGCDetails) { |
| size_t total = 0; |
| for (int i = 0; i < _num_q; ++i) { |
| total += refs_lists[i].length(); |
| } |
| gclog_or_tty->print(", %u refs", total); |
| } |
| |
| // Phase 1 (soft refs only): |
| // . Traverse the list and remove any SoftReferences whose |
| // referents are not alive, but that should be kept alive for |
| // policy reasons. Keep alive the transitive closure of all |
| // such referents. |
| if (policy != NULL) { |
| if (mt) { |
| RefProcPhase1Task phase1(*this, refs_lists, policy, true /*marks_oops_alive*/); |
| task_executor->execute(phase1); |
| } else { |
| for (int i = 0; i < _num_q; i++) { |
| process_phase1(refs_lists[i], policy, |
| is_alive, keep_alive, complete_gc); |
| } |
| } |
| } else { // policy == NULL |
| assert(refs_lists != _discoveredSoftRefs, |
| "Policy must be specified for soft references."); |
| } |
| |
| // Phase 2: |
| // . Traverse the list and remove any refs whose referents are alive. |
| if (mt) { |
| RefProcPhase2Task phase2(*this, refs_lists, !discovery_is_atomic() /*marks_oops_alive*/); |
| task_executor->execute(phase2); |
| } else { |
| for (int i = 0; i < _num_q; i++) { |
| process_phase2(refs_lists[i], is_alive, keep_alive, complete_gc); |
| } |
| } |
| |
| // Phase 3: |
| // . Traverse the list and process referents as appropriate. |
| if (mt) { |
| RefProcPhase3Task phase3(*this, refs_lists, clear_referent, true /*marks_oops_alive*/); |
| task_executor->execute(phase3); |
| } else { |
| for (int i = 0; i < _num_q; i++) { |
| process_phase3(refs_lists[i], clear_referent, |
| is_alive, keep_alive, complete_gc); |
| } |
| } |
| } |
| |
| void ReferenceProcessor::clean_up_discovered_references() { |
| // loop over the lists |
| for (int i = 0; i < _num_q * subclasses_of_ref; i++) { |
| if (TraceReferenceGC && PrintGCDetails && ((i % _num_q) == 0)) { |
| gclog_or_tty->print_cr( |
| "\nScrubbing %s discovered list of Null referents", |
| list_name(i)); |
| } |
| clean_up_discovered_reflist(_discoveredSoftRefs[i]); |
| } |
| } |
| |
| void ReferenceProcessor::clean_up_discovered_reflist(DiscoveredList& refs_list) { |
| assert(!discovery_is_atomic(), "Else why call this method?"); |
| DiscoveredListIterator iter(refs_list, NULL, NULL); |
| while (iter.has_next()) { |
| iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); |
| oop next = java_lang_ref_Reference::next(iter.obj()); |
| assert(next->is_oop_or_null(), "bad next field"); |
| // If referent has been cleared or Reference is not active, |
| // drop it. |
| if (iter.referent() == NULL || next != NULL) { |
| debug_only( |
| if (PrintGCDetails && TraceReferenceGC) { |
| gclog_or_tty->print_cr("clean_up_discovered_list: Dropping Reference: " |
| INTPTR_FORMAT " with next field: " INTPTR_FORMAT |
| " and referent: " INTPTR_FORMAT, |
| iter.obj(), next, iter.referent()); |
| } |
| ) |
| // Remove Reference object from list |
| iter.remove(); |
| iter.move_to_next(); |
| } else { |
| iter.next(); |
| } |
| } |
| NOT_PRODUCT( |
| if (PrintGCDetails && TraceReferenceGC) { |
| gclog_or_tty->print( |
| " Removed %d Refs with NULL referents out of %d discovered Refs", |
| iter.removed(), iter.processed()); |
| } |
| ) |
| } |
| |
| inline DiscoveredList* ReferenceProcessor::get_discovered_list(ReferenceType rt) { |
| int id = 0; |
| // Determine the queue index to use for this object. |
| if (_discovery_is_mt) { |
| // During a multi-threaded discovery phase, |
| // each thread saves to its "own" list. |
| Thread* thr = Thread::current(); |
| assert(thr->is_GC_task_thread(), |
| "Dubious cast from Thread* to WorkerThread*?"); |
| id = ((WorkerThread*)thr)->id(); |
| } else { |
| // single-threaded discovery, we save in round-robin |
| // fashion to each of the lists. |
| if (_processing_is_mt) { |
| id = next_id(); |
| } |
| } |
| assert(0 <= id && id < _num_q, "Id is out-of-bounds (call Freud?)"); |
| |
| // Get the discovered queue to which we will add |
| DiscoveredList* list = NULL; |
| switch (rt) { |
| case REF_OTHER: |
| // Unknown reference type, no special treatment |
| break; |
| case REF_SOFT: |
| list = &_discoveredSoftRefs[id]; |
| break; |
| case REF_WEAK: |
| list = &_discoveredWeakRefs[id]; |
| break; |
| case REF_FINAL: |
| list = &_discoveredFinalRefs[id]; |
| break; |
| case REF_PHANTOM: |
| list = &_discoveredPhantomRefs[id]; |
| break; |
| case REF_NONE: |
| // we should not reach here if we are an instanceRefKlass |
| default: |
| ShouldNotReachHere(); |
| } |
| return list; |
| } |
| |
| inline void |
| ReferenceProcessor::add_to_discovered_list_mt(DiscoveredList& refs_list, |
| oop obj, |
| HeapWord* discovered_addr) { |
| assert(_discovery_is_mt, "!_discovery_is_mt should have been handled by caller"); |
| // First we must make sure this object is only enqueued once. CAS in a non null |
| // discovered_addr. |
| oop current_head = refs_list.head(); |
| |
| // Note: In the case of G1, this pre-barrier is strictly |
| // not necessary because the only case we are interested in |
| // here is when *discovered_addr is NULL, so this will expand to |
| // nothing. As a result, I am just manually eliding this out for G1. |
| if (_discovered_list_needs_barrier && !UseG1GC) { |
| _bs->write_ref_field_pre((void*)discovered_addr, current_head); guarantee(false, "Needs to be fixed: YSR"); |
| } |
| oop retest = oopDesc::atomic_compare_exchange_oop(current_head, discovered_addr, |
| NULL); |
| if (retest == NULL) { |
| // This thread just won the right to enqueue the object. |
| // We have separate lists for enqueueing so no synchronization |
| // is necessary. |
| refs_list.set_head(obj); |
| refs_list.inc_length(1); |
| if (_discovered_list_needs_barrier) { |
| _bs->write_ref_field((void*)discovered_addr, current_head); guarantee(false, "Needs to be fixed: YSR"); |
| } |
| |
| } else { |
| // If retest was non NULL, another thread beat us to it: |
| // The reference has already been discovered... |
| if (TraceReferenceGC) { |
| gclog_or_tty->print_cr("Already enqueued reference (" INTPTR_FORMAT ": %s)", |
| obj, obj->blueprint()->internal_name()); |
| } |
| } |
| } |
| |
| // We mention two of several possible choices here: |
| // #0: if the reference object is not in the "originating generation" |
| // (or part of the heap being collected, indicated by our "span" |
| // we don't treat it specially (i.e. we scan it as we would |
| // a normal oop, treating its references as strong references). |
| // This means that references can't be enqueued unless their |
| // referent is also in the same span. This is the simplest, |
| // most "local" and most conservative approach, albeit one |
| // that may cause weak references to be enqueued least promptly. |
| // We call this choice the "ReferenceBasedDiscovery" policy. |
| // #1: the reference object may be in any generation (span), but if |
| // the referent is in the generation (span) being currently collected |
| // then we can discover the reference object, provided |
| // the object has not already been discovered by |
| // a different concurrently running collector (as may be the |
| // case, for instance, if the reference object is in CMS and |
| // the referent in DefNewGeneration), and provided the processing |
| // of this reference object by the current collector will |
| // appear atomic to every other collector in the system. |
| // (Thus, for instance, a concurrent collector may not |
| // discover references in other generations even if the |
| // referent is in its own generation). This policy may, |
| // in certain cases, enqueue references somewhat sooner than |
| // might Policy #0 above, but at marginally increased cost |
| // and complexity in processing these references. |
| // We call this choice the "RefeferentBasedDiscovery" policy. |
| bool ReferenceProcessor::discover_reference(oop obj, ReferenceType rt) { |
| // We enqueue references only if we are discovering refs |
| // (rather than processing discovered refs). |
| if (!_discovering_refs || !RegisterReferences) { |
| return false; |
| } |
| // We only enqueue active references. |
| oop next = java_lang_ref_Reference::next(obj); |
| if (next != NULL) { |
| return false; |
| } |
| |
| HeapWord* obj_addr = (HeapWord*)obj; |
| if (RefDiscoveryPolicy == ReferenceBasedDiscovery && |
| !_span.contains(obj_addr)) { |
| // Reference is not in the originating generation; |
| // don't treat it specially (i.e. we want to scan it as a normal |
| // object with strong references). |
| return false; |
| } |
| |
| // We only enqueue references whose referents are not (yet) strongly |
| // reachable. |
| if (is_alive_non_header() != NULL) { |
| oop referent = java_lang_ref_Reference::referent(obj); |
| // In the case of non-concurrent discovery, the last |
| // disjunct below should hold. It may not hold in the |
| // case of concurrent discovery because mutators may |
| // concurrently clear() a Reference. |
| assert(UseConcMarkSweepGC || UseG1GC || referent != NULL, |
| "Refs with null referents already filtered"); |
| if (is_alive_non_header()->do_object_b(referent)) { |
| return false; // referent is reachable |
| } |
| } |
| if (rt == REF_SOFT) { |
| // For soft refs we can decide now if these are not |
| // current candidates for clearing, in which case we |
| // can mark through them now, rather than delaying that |
| // to the reference-processing phase. Since all current |
| // time-stamp policies advance the soft-ref clock only |
| // at a major collection cycle, this is always currently |
| // accurate. |
| if (!_current_soft_ref_policy->should_clear_reference(obj)) { |
| return false; |
| } |
| } |
| |
| HeapWord* const discovered_addr = java_lang_ref_Reference::discovered_addr(obj); |
| const oop discovered = java_lang_ref_Reference::discovered(obj); |
| assert(discovered->is_oop_or_null(), "bad discovered field"); |
| if (discovered != NULL) { |
| // The reference has already been discovered... |
| if (TraceReferenceGC) { |
| gclog_or_tty->print_cr("Already enqueued reference (" INTPTR_FORMAT ": %s)", |
| obj, obj->blueprint()->internal_name()); |
| } |
| if (RefDiscoveryPolicy == ReferentBasedDiscovery) { |
| // assumes that an object is not processed twice; |
| // if it's been already discovered it must be on another |
| // generation's discovered list; so we won't discover it. |
| return false; |
| } else { |
| assert(RefDiscoveryPolicy == ReferenceBasedDiscovery, |
| "Unrecognized policy"); |
| // Check assumption that an object is not potentially |
| // discovered twice except by concurrent collectors that potentially |
| // trace the same Reference object twice. |
| assert(UseConcMarkSweepGC, |
| "Only possible with an incremental-update concurrent collector"); |
| return true; |
| } |
| } |
| |
| if (RefDiscoveryPolicy == ReferentBasedDiscovery) { |
| oop referent = java_lang_ref_Reference::referent(obj); |
| assert(referent->is_oop(), "bad referent"); |
| // enqueue if and only if either: |
| // reference is in our span or |
| // we are an atomic collector and referent is in our span |
| if (_span.contains(obj_addr) || |
| (discovery_is_atomic() && _span.contains(referent))) { |
| // should_enqueue = true; |
| } else { |
| return false; |
| } |
| } else { |
| assert(RefDiscoveryPolicy == ReferenceBasedDiscovery && |
| _span.contains(obj_addr), "code inconsistency"); |
| } |
| |
| // Get the right type of discovered queue head. |
| DiscoveredList* list = get_discovered_list(rt); |
| if (list == NULL) { |
| return false; // nothing special needs to be done |
| } |
| |
| if (_discovery_is_mt) { |
| add_to_discovered_list_mt(*list, obj, discovered_addr); |
| } else { |
| // If "_discovered_list_needs_barrier", we do write barriers when |
| // updating the discovered reference list. Otherwise, we do a raw store |
| // here: the field will be visited later when processing the discovered |
| // references. |
| oop current_head = list->head(); |
| // As in the case further above, since we are over-writing a NULL |
| // pre-value, we can safely elide the pre-barrier here for the case of G1. |
| assert(discovered == NULL, "control point invariant"); |
| if (_discovered_list_needs_barrier && !UseG1GC) { // safe to elide for G1 |
| _bs->write_ref_field_pre((oop*)discovered_addr, current_head); |
| } |
| oop_store_raw(discovered_addr, current_head); |
| if (_discovered_list_needs_barrier) { |
| _bs->write_ref_field((oop*)discovered_addr, current_head); |
| } |
| list->set_head(obj); |
| list->inc_length(1); |
| } |
| |
| // In the MT discovery case, it is currently possible to see |
| // the following message multiple times if several threads |
| // discover a reference about the same time. Only one will |
| // however have actually added it to the disocvered queue. |
| // One could let add_to_discovered_list_mt() return an |
| // indication for success in queueing (by 1 thread) or |
| // failure (by all other threads), but I decided the extra |
| // code was not worth the effort for something that is |
| // only used for debugging support. |
| if (TraceReferenceGC) { |
| oop referent = java_lang_ref_Reference::referent(obj); |
| if (PrintGCDetails) { |
| gclog_or_tty->print_cr("Enqueued reference (" INTPTR_FORMAT ": %s)", |
| obj, obj->blueprint()->internal_name()); |
| } |
| assert(referent->is_oop(), "Enqueued a bad referent"); |
| } |
| assert(obj->is_oop(), "Enqueued a bad reference"); |
| return true; |
| } |
| |
| // Preclean the discovered references by removing those |
| // whose referents are alive, and by marking from those that |
| // are not active. These lists can be handled here |
| // in any order and, indeed, concurrently. |
| void ReferenceProcessor::preclean_discovered_references( |
| BoolObjectClosure* is_alive, |
| OopClosure* keep_alive, |
| VoidClosure* complete_gc, |
| YieldClosure* yield) { |
| |
| NOT_PRODUCT(verify_ok_to_handle_reflists()); |
| |
| // Soft references |
| { |
| TraceTime tt("Preclean SoftReferences", PrintGCDetails && PrintReferenceGC, |
| false, gclog_or_tty); |
| for (int i = 0; i < _num_q; i++) { |
| if (yield->should_return()) { |
| return; |
| } |
| preclean_discovered_reflist(_discoveredSoftRefs[i], is_alive, |
| keep_alive, complete_gc, yield); |
| } |
| } |
| |
| // Weak references |
| { |
| TraceTime tt("Preclean WeakReferences", PrintGCDetails && PrintReferenceGC, |
| false, gclog_or_tty); |
| for (int i = 0; i < _num_q; i++) { |
| if (yield->should_return()) { |
| return; |
| } |
| preclean_discovered_reflist(_discoveredWeakRefs[i], is_alive, |
| keep_alive, complete_gc, yield); |
| } |
| } |
| |
| // Final references |
| { |
| TraceTime tt("Preclean FinalReferences", PrintGCDetails && PrintReferenceGC, |
| false, gclog_or_tty); |
| for (int i = 0; i < _num_q; i++) { |
| if (yield->should_return()) { |
| return; |
| } |
| preclean_discovered_reflist(_discoveredFinalRefs[i], is_alive, |
| keep_alive, complete_gc, yield); |
| } |
| } |
| |
| // Phantom references |
| { |
| TraceTime tt("Preclean PhantomReferences", PrintGCDetails && PrintReferenceGC, |
| false, gclog_or_tty); |
| for (int i = 0; i < _num_q; i++) { |
| if (yield->should_return()) { |
| return; |
| } |
| preclean_discovered_reflist(_discoveredPhantomRefs[i], is_alive, |
| keep_alive, complete_gc, yield); |
| } |
| } |
| } |
| |
| // Walk the given discovered ref list, and remove all reference objects |
| // whose referents are still alive, whose referents are NULL or which |
| // are not active (have a non-NULL next field). NOTE: When we are |
| // thus precleaning the ref lists (which happens single-threaded today), |
| // we do not disable refs discovery to honour the correct semantics of |
| // java.lang.Reference. As a result, we need to be careful below |
| // that ref removal steps interleave safely with ref discovery steps |
| // (in this thread). |
| void |
| ReferenceProcessor::preclean_discovered_reflist(DiscoveredList& refs_list, |
| BoolObjectClosure* is_alive, |
| OopClosure* keep_alive, |
| VoidClosure* complete_gc, |
| YieldClosure* yield) { |
| DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
| while (iter.has_next()) { |
| iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); |
| oop obj = iter.obj(); |
| oop next = java_lang_ref_Reference::next(obj); |
| if (iter.referent() == NULL || iter.is_referent_alive() || |
| next != NULL) { |
| // The referent has been cleared, or is alive, or the Reference is not |
| // active; we need to trace and mark its cohort. |
| if (TraceReferenceGC) { |
| gclog_or_tty->print_cr("Precleaning Reference (" INTPTR_FORMAT ": %s)", |
| iter.obj(), iter.obj()->blueprint()->internal_name()); |
| } |
| // Remove Reference object from list |
| iter.remove(); |
| // Keep alive its cohort. |
| iter.make_referent_alive(); |
| if (UseCompressedOops) { |
| narrowOop* next_addr = (narrowOop*)java_lang_ref_Reference::next_addr(obj); |
| keep_alive->do_oop(next_addr); |
| } else { |
| oop* next_addr = (oop*)java_lang_ref_Reference::next_addr(obj); |
| keep_alive->do_oop(next_addr); |
| } |
| iter.move_to_next(); |
| } else { |
| iter.next(); |
| } |
| } |
| // Close the reachable set |
| complete_gc->do_void(); |
| |
| NOT_PRODUCT( |
| if (PrintGCDetails && PrintReferenceGC) { |
| gclog_or_tty->print(" Dropped %d Refs out of %d " |
| "Refs in discovered list ", iter.removed(), iter.processed()); |
| } |
| ) |
| } |
| |
| const char* ReferenceProcessor::list_name(int i) { |
| assert(i >= 0 && i <= _num_q * subclasses_of_ref, "Out of bounds index"); |
| int j = i / _num_q; |
| switch (j) { |
| case 0: return "SoftRef"; |
| case 1: return "WeakRef"; |
| case 2: return "FinalRef"; |
| case 3: return "PhantomRef"; |
| } |
| ShouldNotReachHere(); |
| return NULL; |
| } |
| |
| #ifndef PRODUCT |
| void ReferenceProcessor::verify_ok_to_handle_reflists() { |
| // empty for now |
| } |
| #endif |
| |
| void ReferenceProcessor::verify() { |
| guarantee(sentinel_ref() != NULL && sentinel_ref()->is_oop(), "Lost _sentinelRef"); |
| } |
| |
| #ifndef PRODUCT |
| void ReferenceProcessor::clear_discovered_references() { |
| guarantee(!_discovering_refs, "Discovering refs?"); |
| for (int i = 0; i < _num_q * subclasses_of_ref; i++) { |
| oop obj = _discoveredSoftRefs[i].head(); |
| while (obj != sentinel_ref()) { |
| oop next = java_lang_ref_Reference::discovered(obj); |
| java_lang_ref_Reference::set_discovered(obj, (oop) NULL); |
| obj = next; |
| } |
| _discoveredSoftRefs[i].set_head(sentinel_ref()); |
| _discoveredSoftRefs[i].set_length(0); |
| } |
| } |
| #endif // PRODUCT |
