| /* |
| * Copyright (c) 2001, 2025, 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. |
| * |
| */ |
| |
| #include "classfile/javaClasses.inline.hpp" |
| #include "compiler/compilerDefinitions.inline.hpp" |
| #include "gc/shared/collectedHeap.hpp" |
| #include "gc/shared/collectedHeap.inline.hpp" |
| #include "gc/shared/gc_globals.hpp" |
| #include "gc/shared/gcTimer.hpp" |
| #include "gc/shared/gcTraceTime.inline.hpp" |
| #include "gc/shared/referencePolicy.hpp" |
| #include "gc/shared/referenceProcessor.inline.hpp" |
| #include "gc/shared/referenceProcessorPhaseTimes.hpp" |
| #include "logging/log.hpp" |
| #include "memory/allocation.inline.hpp" |
| #include "memory/resourceArea.hpp" |
| #include "memory/universe.hpp" |
| #include "oops/access.inline.hpp" |
| #include "oops/oop.inline.hpp" |
| #include "runtime/java.hpp" |
| #include "runtime/nonJavaThread.hpp" |
| #include "utilities/globalDefinitions.hpp" |
| |
| ReferencePolicy* ReferenceProcessor::_always_clear_soft_ref_policy = nullptr; |
| ReferencePolicy* ReferenceProcessor::_default_soft_ref_policy = nullptr; |
| jlong ReferenceProcessor::_soft_ref_timestamp_clock = 0; |
| |
| void referenceProcessor_init() { |
| ReferenceProcessor::init_statics(); |
| } |
| |
| void ReferenceProcessor::init_statics() { |
| // We need a monotonically non-decreasing time in ms but |
| // os::javaTimeMillis() does not guarantee monotonicity. |
| jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; |
| |
| // Initialize the soft ref timestamp clock. |
| _soft_ref_timestamp_clock = now; |
| // Also update the soft ref clock in j.l.r.SoftReference |
| java_lang_ref_SoftReference::set_clock(_soft_ref_timestamp_clock); |
| |
| _always_clear_soft_ref_policy = new AlwaysClearPolicy(); |
| if (CompilerConfig::is_c2_or_jvmci_compiler_enabled()) { |
| _default_soft_ref_policy = new LRUMaxHeapPolicy(); |
| } else { |
| _default_soft_ref_policy = new LRUCurrentHeapPolicy(); |
| } |
| } |
| |
| void ReferenceProcessor::enable_discovery() { |
| #ifdef ASSERT |
| // Verify that we're not currently discovering refs |
| assert(!_discovering_refs, "nested call?"); |
| |
| // Verify that the discovered lists are empty |
| verify_no_references_recorded(); |
| #endif // ASSERT |
| |
| _discovering_refs = true; |
| } |
| |
| ReferenceProcessor::ReferenceProcessor(BoolObjectClosure* is_subject_to_discovery, |
| uint mt_processing_degree, |
| uint mt_discovery_degree, |
| bool concurrent_discovery, |
| BoolObjectClosure* is_alive_non_header) : |
| _is_subject_to_discovery(is_subject_to_discovery), |
| _discovering_refs(false), |
| _next_id(0), |
| _is_alive_non_header(is_alive_non_header) |
| { |
| assert(is_subject_to_discovery != nullptr, "must be set"); |
| |
| _discovery_is_concurrent = concurrent_discovery; |
| _discovery_is_mt = (mt_discovery_degree > 1); |
| _num_queues = MAX2(1U, mt_processing_degree); |
| _max_num_queues = MAX2(_num_queues, mt_discovery_degree); |
| _discovered_refs = NEW_C_HEAP_ARRAY(DiscoveredList, |
| _max_num_queues * number_of_subclasses_of_ref(), mtGC); |
| |
| _discoveredSoftRefs = &_discovered_refs[0]; |
| _discoveredWeakRefs = &_discoveredSoftRefs[_max_num_queues]; |
| _discoveredFinalRefs = &_discoveredWeakRefs[_max_num_queues]; |
| _discoveredPhantomRefs = &_discoveredFinalRefs[_max_num_queues]; |
| |
| // Initialize all entries to null |
| for (uint i = 0; i < _max_num_queues * number_of_subclasses_of_ref(); i++) { |
| _discovered_refs[i].clear(); |
| } |
| |
| setup_policy(false /* default soft ref policy */); |
| } |
| |
| #ifndef PRODUCT |
| void ReferenceProcessor::verify_no_references_recorded() { |
| guarantee(!_discovering_refs, "Discovering refs?"); |
| for (uint i = 0; i < _max_num_queues * number_of_subclasses_of_ref(); i++) { |
| guarantee(_discovered_refs[i].is_empty(), |
| "Found non-empty discovered list at %u", i); |
| } |
| } |
| #endif |
| |
| bool ReferenceProcessor::processing_is_mt() const { |
| return ParallelRefProcEnabled && _num_queues > 1; |
| } |
| |
| void ReferenceProcessor::weak_oops_do(OopClosure* f) { |
| for (uint i = 0; i < _max_num_queues * number_of_subclasses_of_ref(); i++) { |
| if (UseCompressedOops) { |
| f->do_oop((narrowOop*)_discovered_refs[i].adr_head()); |
| } else { |
| f->do_oop((oop*)_discovered_refs[i].adr_head()); |
| } |
| } |
| } |
| |
| 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. |
| |
| // We need a monotonically non-decreasing time in ms but |
| // os::javaTimeMillis() does not guarantee monotonicity. |
| jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC; |
| |
| NOT_PRODUCT( |
| if (now < _soft_ref_timestamp_clock) { |
| log_warning(gc)("time warp: " JLONG_FORMAT " to " JLONG_FORMAT, |
| _soft_ref_timestamp_clock, now); |
| } |
| ) |
| // The values of now and _soft_ref_timestamp_clock are set using |
| // javaTimeNanos(), which is guaranteed to be monotonically |
| // non-decreasing provided the underlying platform provides such |
| // a time source (and it is bug free). |
| // In product mode, however, protect ourselves from non-monotonicity. |
| if (now > _soft_ref_timestamp_clock) { |
| _soft_ref_timestamp_clock = now; |
| java_lang_ref_SoftReference::set_clock(now); |
| } |
| // Else leave clock stalled at its old value until time progresses |
| // past clock value. |
| } |
| |
| size_t ReferenceProcessor::total_count(DiscoveredList lists[]) const { |
| size_t total = 0; |
| for (uint i = 0; i < _max_num_queues; ++i) { |
| total += lists[i].length(); |
| } |
| return total; |
| } |
| |
| #ifdef ASSERT |
| void ReferenceProcessor::verify_total_count_zero(DiscoveredList lists[], const char* type) { |
| size_t count = total_count(lists); |
| assert(count == 0, "%ss must be empty but has %zu elements", type, count); |
| } |
| #endif |
| |
| ReferenceProcessorStats ReferenceProcessor::process_discovered_references(RefProcProxyTask& proxy_task, |
| ReferenceProcessorPhaseTimes& phase_times) { |
| |
| double start_time = os::elapsedTime(); |
| |
| // Stop treating discovered references specially. |
| disable_discovery(); |
| |
| phase_times.set_ref_discovered(REF_SOFT, total_count(_discoveredSoftRefs)); |
| phase_times.set_ref_discovered(REF_WEAK, total_count(_discoveredWeakRefs)); |
| phase_times.set_ref_discovered(REF_FINAL, total_count(_discoveredFinalRefs)); |
| phase_times.set_ref_discovered(REF_PHANTOM, total_count(_discoveredPhantomRefs)); |
| |
| update_soft_ref_master_clock(); |
| |
| phase_times.set_processing_is_mt(processing_is_mt()); |
| |
| { |
| RefProcTotalPhaseTimesTracker tt(SoftWeakFinalRefsPhase, &phase_times); |
| process_soft_weak_final_refs(proxy_task, phase_times); |
| } |
| |
| { |
| RefProcTotalPhaseTimesTracker tt(KeepAliveFinalRefsPhase, &phase_times); |
| process_final_keep_alive(proxy_task, phase_times); |
| } |
| |
| { |
| RefProcTotalPhaseTimesTracker tt(PhantomRefsPhase, &phase_times); |
| process_phantom_refs(proxy_task, phase_times); |
| } |
| |
| phase_times.set_total_time_ms((os::elapsedTime() - start_time) * 1000); |
| |
| // Elements on discovered lists were pushed to the pending list. |
| verify_no_references_recorded(); |
| |
| ReferenceProcessorStats stats(phase_times.ref_discovered(REF_SOFT), |
| phase_times.ref_discovered(REF_WEAK), |
| phase_times.ref_discovered(REF_FINAL), |
| phase_times.ref_discovered(REF_PHANTOM)); |
| return stats; |
| } |
| |
| void BarrierEnqueueDiscoveredFieldClosure::enqueue(HeapWord* discovered_field_addr, oop value) { |
| assert(Universe::heap()->is_in(discovered_field_addr), PTR_FORMAT " not in heap", p2i(discovered_field_addr)); |
| HeapAccess<AS_NO_KEEPALIVE>::oop_store(discovered_field_addr, |
| value); |
| } |
| |
| void DiscoveredListIterator::load_ptrs(DEBUG_ONLY(bool allow_null_referent)) { |
| _current_discovered_addr = java_lang_ref_Reference::discovered_addr_raw(_current_discovered); |
| oop discovered = java_lang_ref_Reference::discovered(_current_discovered); |
| assert(_current_discovered_addr && oopDesc::is_oop_or_null(discovered), |
| "Expected an oop or null for discovered field at " PTR_FORMAT, p2i(discovered)); |
| _next_discovered = discovered; |
| _referent = java_lang_ref_Reference::unknown_referent_no_keepalive(_current_discovered); |
| assert(Universe::heap()->is_in_or_null(_referent), |
| "Wrong oop found in java.lang.Reference object"); |
| assert(allow_null_referent ? |
| oopDesc::is_oop_or_null(_referent) |
| : oopDesc::is_oop(_referent), |
| "Expected an oop%s for referent field at " PTR_FORMAT, |
| (allow_null_referent ? " or null" : ""), |
| p2i(_referent)); |
| } |
| |
| void DiscoveredListIterator::remove() { |
| assert(oopDesc::is_oop(_current_discovered), "Dropping a bad reference"); |
| RawAccess<>::oop_store(_current_discovered_addr, oop(nullptr)); |
| |
| // First _prev_next ref actually points into DiscoveredList (gross). |
| oop new_next; |
| if (_next_discovered == _current_discovered) { |
| // At the end of the list, we should make _prev point to itself. |
| // If _ref is the first ref, then _prev_next will be in the DiscoveredList, |
| // and _prev will be null. |
| new_next = _prev_discovered; |
| } else { |
| new_next = _next_discovered; |
| } |
| // Remove Reference object from discovered list. We do not need barriers here, |
| // as we only remove. We will do the barrier when we actually advance the cursor. |
| RawAccess<>::oop_store(_prev_discovered_addr, new_next); |
| _removed++; |
| _refs_list.dec_length(1); |
| } |
| |
| void DiscoveredListIterator::make_referent_alive() { |
| HeapWord* addr = java_lang_ref_Reference::referent_addr_raw(_current_discovered); |
| if (UseCompressedOops) { |
| _keep_alive->do_oop((narrowOop*)addr); |
| } else { |
| _keep_alive->do_oop((oop*)addr); |
| } |
| } |
| |
| void DiscoveredListIterator::clear_referent() { |
| java_lang_ref_Reference::clear_referent_raw(_current_discovered); |
| } |
| |
| void DiscoveredListIterator::enqueue() { |
| if (_prev_discovered_addr != _refs_list.adr_head()) { |
| _enqueue->enqueue(_prev_discovered_addr, _current_discovered); |
| } else { |
| RawAccess<>::oop_store(_prev_discovered_addr, _current_discovered); |
| } |
| } |
| |
| void DiscoveredListIterator::complete_enqueue() { |
| if (_prev_discovered != nullptr) { |
| // This is the last object. |
| // Swap refs_list into pending list and set obj's |
| // discovered to what we read from the pending list. |
| oop old = Universe::swap_reference_pending_list(_refs_list.head()); |
| _enqueue->enqueue(java_lang_ref_Reference::discovered_addr_raw(_prev_discovered), old); |
| } |
| } |
| |
| inline void log_preclean_ref(const DiscoveredListIterator& iter, const char* reason) { |
| if (log_develop_is_enabled(Trace, gc, ref)) { |
| ResourceMark rm; |
| log_develop_trace(gc, ref)("Precleaning %s reference " PTR_FORMAT ": %s", |
| reason, p2i(iter.obj()), |
| iter.obj()->klass()->internal_name()); |
| } |
| } |
| |
| inline void log_dropped_ref(const DiscoveredListIterator& iter, const char* reason) { |
| if (log_develop_is_enabled(Trace, gc, ref)) { |
| ResourceMark rm; |
| log_develop_trace(gc, ref)("Dropping %s reference " PTR_FORMAT ": %s", |
| reason, p2i(iter.obj()), |
| iter.obj()->klass()->internal_name()); |
| } |
| } |
| |
| inline void log_enqueued_ref(const DiscoveredListIterator& iter, const char* reason) { |
| if (log_develop_is_enabled(Trace, gc, ref)) { |
| ResourceMark rm; |
| log_develop_trace(gc, ref)("Enqueue %s reference (" PTR_FORMAT ": %s)", |
| reason, p2i(iter.obj()), iter.obj()->klass()->internal_name()); |
| } |
| assert(oopDesc::is_oop(iter.obj()), "Adding a bad reference"); |
| } |
| |
| size_t ReferenceProcessor::process_discovered_list_work(DiscoveredList& refs_list, |
| BoolObjectClosure* is_alive, |
| OopClosure* keep_alive, |
| EnqueueDiscoveredFieldClosure* enqueue, |
| bool do_enqueue_and_clear) { |
| DiscoveredListIterator iter(refs_list, keep_alive, is_alive, enqueue); |
| while (iter.has_next()) { |
| iter.load_ptrs(DEBUG_ONLY(discovery_is_concurrent() /* allow_null_referent */)); |
| if (iter.referent() == nullptr) { |
| // Reference has been cleared since discovery; only possible if |
| // discovery is concurrent (checked by load_ptrs). Remove |
| // reference from list. |
| log_dropped_ref(iter, "cleared"); |
| iter.remove(); |
| iter.move_to_next(); |
| } else if (iter.is_referent_alive()) { |
| // The referent is reachable after all. |
| // Remove reference from list. |
| log_dropped_ref(iter, "reachable"); |
| 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 { |
| if (do_enqueue_and_clear) { |
| iter.clear_referent(); |
| iter.enqueue(); |
| log_enqueued_ref(iter, "cleared"); |
| } |
| // Keep in discovered list |
| iter.next(); |
| } |
| } |
| if (do_enqueue_and_clear) { |
| iter.complete_enqueue(); |
| refs_list.clear(); |
| } |
| |
| log_develop_trace(gc, ref)(" Dropped %zu active Refs out of %zu" |
| " Refs in discovered list " PTR_FORMAT, |
| iter.removed(), iter.processed(), p2i(&refs_list)); |
| return iter.removed(); |
| } |
| |
| size_t ReferenceProcessor::process_final_keep_alive_work(DiscoveredList& refs_list, |
| OopClosure* keep_alive, |
| EnqueueDiscoveredFieldClosure* enqueue) { |
| DiscoveredListIterator iter(refs_list, keep_alive, nullptr, enqueue); |
| while (iter.has_next()) { |
| iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */)); |
| // keep the referent and followers around |
| iter.make_referent_alive(); |
| |
| // Self-loop next, to mark the FinalReference not active. |
| assert(java_lang_ref_Reference::next(iter.obj()) == nullptr, "enqueued FinalReference"); |
| java_lang_ref_Reference::set_next_raw(iter.obj(), iter.obj()); |
| |
| iter.enqueue(); |
| log_enqueued_ref(iter, "Final"); |
| iter.next(); |
| } |
| iter.complete_enqueue(); |
| refs_list.clear(); |
| |
| assert(iter.removed() == 0, "This phase does not remove anything."); |
| return iter.removed(); |
| } |
| |
| void |
| ReferenceProcessor::clear_discovered_references(DiscoveredList& refs_list) { |
| oop obj = nullptr; |
| oop next = refs_list.head(); |
| while (next != obj) { |
| obj = next; |
| next = java_lang_ref_Reference::discovered(obj); |
| java_lang_ref_Reference::set_discovered_raw(obj, nullptr); |
| } |
| refs_list.clear(); |
| } |
| |
| void ReferenceProcessor::abandon_partial_discovery() { |
| // loop over the lists |
| for (uint i = 0; i < _max_num_queues * number_of_subclasses_of_ref(); i++) { |
| if ((i % _max_num_queues) == 0) { |
| log_develop_trace(gc, ref)("Abandoning %s discovered list", list_name(i)); |
| } |
| clear_discovered_references(_discovered_refs[i]); |
| } |
| } |
| |
| size_t ReferenceProcessor::total_reference_count(ReferenceType type) const { |
| DiscoveredList* list = nullptr; |
| |
| switch (type) { |
| case REF_SOFT: |
| list = _discoveredSoftRefs; |
| break; |
| case REF_WEAK: |
| list = _discoveredWeakRefs; |
| break; |
| case REF_FINAL: |
| list = _discoveredFinalRefs; |
| break; |
| case REF_PHANTOM: |
| list = _discoveredPhantomRefs; |
| break; |
| case REF_NONE: |
| default: |
| ShouldNotReachHere(); |
| } |
| return total_count(list); |
| } |
| |
| void RefProcTask::process_discovered_list(uint worker_id, |
| ReferenceType ref_type, |
| BoolObjectClosure* is_alive, |
| OopClosure* keep_alive, |
| EnqueueDiscoveredFieldClosure* enqueue) { |
| ReferenceProcessor::RefProcSubPhases subphase; |
| DiscoveredList* dl; |
| switch (ref_type) { |
| case ReferenceType::REF_SOFT: |
| subphase = ReferenceProcessor::ProcessSoftRefSubPhase; |
| dl = _ref_processor._discoveredSoftRefs; |
| break; |
| case ReferenceType::REF_WEAK: |
| subphase = ReferenceProcessor::ProcessWeakRefSubPhase; |
| dl = _ref_processor._discoveredWeakRefs; |
| break; |
| case ReferenceType::REF_FINAL: |
| subphase = ReferenceProcessor::ProcessFinalRefSubPhase; |
| dl = _ref_processor._discoveredFinalRefs; |
| break; |
| case ReferenceType::REF_PHANTOM: |
| subphase = ReferenceProcessor::ProcessPhantomRefsSubPhase; |
| dl = _ref_processor._discoveredPhantomRefs; |
| break; |
| default: |
| ShouldNotReachHere(); |
| } |
| |
| // Only Final refs are not enqueued and cleared here. |
| bool do_enqueue_and_clear = (ref_type != REF_FINAL); |
| |
| { |
| RefProcSubPhasesWorkerTimeTracker tt(subphase, _phase_times, tracker_id(worker_id)); |
| size_t const removed = _ref_processor.process_discovered_list_work(dl[worker_id], |
| is_alive, |
| keep_alive, |
| enqueue, |
| do_enqueue_and_clear); |
| _phase_times->add_ref_dropped(ref_type, removed); |
| } |
| } |
| |
| class RefProcSoftWeakFinalPhaseTask: public RefProcTask { |
| public: |
| RefProcSoftWeakFinalPhaseTask(ReferenceProcessor& ref_processor, |
| ReferenceProcessorPhaseTimes* phase_times) |
| : RefProcTask(ref_processor, |
| phase_times) {} |
| |
| void rp_work(uint worker_id, |
| BoolObjectClosure* is_alive, |
| OopClosure* keep_alive, |
| EnqueueDiscoveredFieldClosure* enqueue, |
| VoidClosure* complete_gc) override { |
| RefProcWorkerTimeTracker t(_phase_times->soft_weak_final_refs_phase_worker_time_sec(), tracker_id(worker_id)); |
| |
| process_discovered_list(worker_id, REF_SOFT, is_alive, keep_alive, enqueue); |
| |
| process_discovered_list(worker_id, REF_WEAK, is_alive, keep_alive, enqueue); |
| |
| process_discovered_list(worker_id, REF_FINAL, is_alive, keep_alive, enqueue); |
| |
| // Close the reachable set; needed for collectors which keep_alive_closure do |
| // not immediately complete their work. |
| complete_gc->do_void(); |
| } |
| }; |
| |
| class RefProcKeepAliveFinalPhaseTask: public RefProcTask { |
| public: |
| RefProcKeepAliveFinalPhaseTask(ReferenceProcessor& ref_processor, |
| ReferenceProcessorPhaseTimes* phase_times) |
| : RefProcTask(ref_processor, |
| phase_times) {} |
| |
| void rp_work(uint worker_id, |
| BoolObjectClosure* is_alive, |
| OopClosure* keep_alive, |
| EnqueueDiscoveredFieldClosure* enqueue, |
| VoidClosure* complete_gc) override { |
| RefProcSubPhasesWorkerTimeTracker tt(ReferenceProcessor::KeepAliveFinalRefsSubPhase, _phase_times, tracker_id(worker_id)); |
| _ref_processor.process_final_keep_alive_work(_ref_processor._discoveredFinalRefs[worker_id], keep_alive, enqueue); |
| // Close the reachable set |
| complete_gc->do_void(); |
| } |
| }; |
| |
| class RefProcPhantomPhaseTask: public RefProcTask { |
| public: |
| RefProcPhantomPhaseTask(ReferenceProcessor& ref_processor, |
| ReferenceProcessorPhaseTimes* phase_times) |
| : RefProcTask(ref_processor, |
| phase_times) {} |
| |
| void rp_work(uint worker_id, |
| BoolObjectClosure* is_alive, |
| OopClosure* keep_alive, |
| EnqueueDiscoveredFieldClosure* enqueue, |
| VoidClosure* complete_gc) override { |
| process_discovered_list(worker_id, REF_PHANTOM, is_alive, keep_alive, enqueue); |
| |
| // Close the reachable set; needed for collectors which keep_alive_closure do |
| // not immediately complete their work. |
| complete_gc->do_void(); |
| } |
| }; |
| |
| void ReferenceProcessor::log_reflist(const char* prefix, DiscoveredList list[], uint num_active_queues) { |
| LogTarget(Trace, gc, ref) lt; |
| |
| if (!lt.is_enabled()) { |
| return; |
| } |
| |
| size_t total = 0; |
| |
| LogStream ls(lt); |
| ls.print("%s", prefix); |
| for (uint i = 0; i < num_active_queues; i++) { |
| ls.print("%zu ", list[i].length()); |
| total += list[i].length(); |
| } |
| ls.print_cr("(%zu)", total); |
| } |
| |
| #ifndef PRODUCT |
| void ReferenceProcessor::log_reflist_counts(DiscoveredList ref_lists[], uint num_active_queues) { |
| if (!log_is_enabled(Trace, gc, ref)) { |
| return; |
| } |
| |
| log_reflist("", ref_lists, num_active_queues); |
| #ifdef ASSERT |
| for (uint i = num_active_queues; i < _max_num_queues; i++) { |
| assert(ref_lists[i].length() == 0, "%zu unexpected References in %u", |
| ref_lists[i].length(), i); |
| } |
| #endif |
| } |
| #endif |
| |
| void ReferenceProcessor::set_active_mt_degree(uint v) { |
| assert(v <= max_num_queues(), "Mt degree %u too high, maximum %u", v, max_num_queues()); |
| _num_queues = v; |
| _next_id = 0; |
| } |
| |
| bool ReferenceProcessor::need_balance_queues(DiscoveredList refs_lists[]) { |
| assert(processing_is_mt(), "why balance non-mt processing?"); |
| // _num_queues is the processing degree. Only list entries up to |
| // _num_queues will be processed, so any non-empty lists beyond |
| // that must be redistributed to lists in that range. Even if not |
| // needed for that, balancing may be desirable to eliminate poor |
| // distribution of references among the lists. |
| if (ParallelRefProcBalancingEnabled) { |
| return true; // Configuration says do it. |
| } else { |
| // Configuration says don't balance, but if there are non-empty |
| // lists beyond the processing degree, then must ignore the |
| // configuration and balance anyway. |
| for (uint i = _num_queues; i < _max_num_queues; ++i) { |
| if (!refs_lists[i].is_empty()) { |
| return true; // Must balance despite configuration. |
| } |
| } |
| return false; // Safe to obey configuration and not balance. |
| } |
| } |
| |
| void ReferenceProcessor::maybe_balance_queues(DiscoveredList refs_lists[]) { |
| assert(processing_is_mt(), "Should not call this otherwise"); |
| if (need_balance_queues(refs_lists)) { |
| balance_queues(refs_lists); |
| } |
| } |
| |
| // Balances reference queues. |
| // Move entries from all queues[0, 1, ..., _max_num_q-1] to |
| // queues[0, 1, ..., _num_q-1] because only the first _num_q |
| // corresponding to the active workers will be processed. |
| void ReferenceProcessor::balance_queues(DiscoveredList ref_lists[]) |
| { |
| // calculate total length |
| size_t total_refs = 0; |
| log_develop_trace(gc, ref)("Balance ref_lists "); |
| |
| log_reflist_counts(ref_lists, _max_num_queues); |
| |
| for (uint i = 0; i < _max_num_queues; ++i) { |
| total_refs += ref_lists[i].length(); |
| } |
| size_t avg_refs = total_refs / _num_queues + 1; |
| uint to_idx = 0; |
| for (uint from_idx = 0; from_idx < _max_num_queues; from_idx++) { |
| bool move_all = false; |
| if (from_idx >= _num_queues) { |
| move_all = ref_lists[from_idx].length() > 0; |
| } |
| while ((ref_lists[from_idx].length() > avg_refs) || |
| move_all) { |
| assert(to_idx < _num_queues, "Sanity Check!"); |
| if (ref_lists[to_idx].length() < avg_refs) { |
| // move superfluous refs |
| size_t refs_to_move; |
| // Move all the Ref's if the from queue will not be processed. |
| if (move_all) { |
| refs_to_move = MIN2(ref_lists[from_idx].length(), |
| avg_refs - ref_lists[to_idx].length()); |
| } else { |
| refs_to_move = MIN2(ref_lists[from_idx].length() - avg_refs, |
| avg_refs - ref_lists[to_idx].length()); |
| } |
| |
| assert(refs_to_move > 0, "otherwise the code below will fail"); |
| |
| 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); |
| } |
| |
| // Add the chain to the to list. |
| if (ref_lists[to_idx].head() == nullptr) { |
| // to list is empty. Make a loop at the end. |
| java_lang_ref_Reference::set_discovered_raw(move_tail, move_tail); |
| } else { |
| java_lang_ref_Reference::set_discovered_raw(move_tail, ref_lists[to_idx].head()); |
| } |
| ref_lists[to_idx].set_head(move_head); |
| ref_lists[to_idx].inc_length(refs_to_move); |
| |
| // Remove the chain from the from list. |
| if (move_tail == new_head) { |
| // We found the end of the from list. |
| ref_lists[from_idx].set_head(nullptr); |
| } else { |
| ref_lists[from_idx].set_head(new_head); |
| } |
| ref_lists[from_idx].dec_length(refs_to_move); |
| if (ref_lists[from_idx].length() == 0) { |
| break; |
| } |
| } else { |
| to_idx = (to_idx + 1) % _num_queues; |
| } |
| } |
| } |
| #ifdef ASSERT |
| log_reflist_counts(ref_lists, _num_queues); |
| size_t balanced_total_refs = 0; |
| for (uint i = 0; i < _num_queues; ++i) { |
| balanced_total_refs += ref_lists[i].length(); |
| } |
| assert(total_refs == balanced_total_refs, "Balancing was incomplete"); |
| #endif |
| } |
| |
| void ReferenceProcessor::run_task(RefProcTask& task, RefProcProxyTask& proxy_task, bool marks_oops_alive) { |
| log_debug(gc, ref)("ReferenceProcessor::execute queues: %d, %s, marks_oops_alive: %s", |
| num_queues(), |
| processing_is_mt() ? "RefProcThreadModel::Multi" : "RefProcThreadModel::Single", |
| marks_oops_alive ? "true" : "false"); |
| |
| proxy_task.prepare_run_task(task, num_queues(), processing_is_mt() ? RefProcThreadModel::Multi : RefProcThreadModel::Single, marks_oops_alive); |
| if (processing_is_mt()) { |
| WorkerThreads* workers = Universe::heap()->safepoint_workers(); |
| assert(workers != nullptr, "can not dispatch multi threaded without workers"); |
| assert(workers->active_workers() >= num_queues(), |
| "Ergonomically chosen workers(%u) should be less than or equal to active workers(%u)", |
| num_queues(), workers->active_workers()); |
| workers->run_task(&proxy_task, num_queues()); |
| } else { |
| for (unsigned i = 0; i < _max_num_queues; ++i) { |
| proxy_task.work(i); |
| } |
| } |
| } |
| |
| void ReferenceProcessor::process_soft_weak_final_refs(RefProcProxyTask& proxy_task, |
| ReferenceProcessorPhaseTimes& phase_times) { |
| |
| size_t const num_soft_refs = phase_times.ref_discovered(REF_SOFT); |
| size_t const num_weak_refs = phase_times.ref_discovered(REF_WEAK); |
| size_t const num_final_refs = phase_times.ref_discovered(REF_FINAL); |
| size_t const num_total_refs = num_soft_refs + num_weak_refs + num_final_refs; |
| |
| if (num_total_refs == 0) { |
| log_debug(gc, ref)("Skipped SoftWeakFinalRefsPhase of Reference Processing: no references"); |
| return; |
| } |
| |
| RefProcMTDegreeAdjuster a(this, SoftWeakFinalRefsPhase, num_total_refs); |
| |
| if (processing_is_mt()) { |
| RefProcBalanceQueuesTimeTracker tt(SoftWeakFinalRefsPhase, &phase_times); |
| maybe_balance_queues(_discoveredSoftRefs); |
| maybe_balance_queues(_discoveredWeakRefs); |
| maybe_balance_queues(_discoveredFinalRefs); |
| } |
| |
| log_reflist("SoftWeakFinalRefsPhase Soft before", _discoveredSoftRefs, _max_num_queues); |
| log_reflist("SoftWeakFinalRefsPhase Weak before", _discoveredWeakRefs, _max_num_queues); |
| log_reflist("SoftWeakFinalRefsPhase Final before", _discoveredFinalRefs, _max_num_queues); |
| |
| RefProcSoftWeakFinalPhaseTask phase_task(*this, &phase_times); |
| run_task(phase_task, proxy_task, false); |
| |
| verify_total_count_zero(_discoveredSoftRefs, "SoftReference"); |
| verify_total_count_zero(_discoveredWeakRefs, "WeakReference"); |
| log_reflist("SoftWeakFinalRefsPhase Final after", _discoveredFinalRefs, _max_num_queues); |
| } |
| |
| void ReferenceProcessor::process_final_keep_alive(RefProcProxyTask& proxy_task, |
| ReferenceProcessorPhaseTimes& phase_times) { |
| |
| size_t const num_final_refs = phase_times.ref_discovered(REF_FINAL); |
| |
| if (num_final_refs == 0) { |
| log_debug(gc, ref)("Skipped KeepAliveFinalRefsPhase of Reference Processing: no references"); |
| return; |
| } |
| |
| RefProcMTDegreeAdjuster a(this, KeepAliveFinalRefsPhase, num_final_refs); |
| |
| if (processing_is_mt()) { |
| RefProcBalanceQueuesTimeTracker tt(KeepAliveFinalRefsPhase, &phase_times); |
| maybe_balance_queues(_discoveredFinalRefs); |
| } |
| |
| // Traverse referents of final references and keep them and followers alive. |
| RefProcKeepAliveFinalPhaseTask phase_task(*this, &phase_times); |
| run_task(phase_task, proxy_task, true); |
| |
| verify_total_count_zero(_discoveredFinalRefs, "FinalReference"); |
| } |
| |
| void ReferenceProcessor::process_phantom_refs(RefProcProxyTask& proxy_task, |
| ReferenceProcessorPhaseTimes& phase_times) { |
| |
| size_t const num_phantom_refs = phase_times.ref_discovered(REF_PHANTOM); |
| |
| if (num_phantom_refs == 0) { |
| log_debug(gc, ref)("Skipped PhantomRefsPhase of Reference Processing: no references"); |
| return; |
| } |
| |
| RefProcMTDegreeAdjuster a(this, PhantomRefsPhase, num_phantom_refs); |
| |
| if (processing_is_mt()) { |
| RefProcBalanceQueuesTimeTracker tt(PhantomRefsPhase, &phase_times); |
| maybe_balance_queues(_discoveredPhantomRefs); |
| } |
| |
| log_reflist("PhantomRefsPhase Phantom before", _discoveredPhantomRefs, _max_num_queues); |
| |
| RefProcPhantomPhaseTask phase_task(*this, &phase_times); |
| run_task(phase_task, proxy_task, false); |
| |
| verify_total_count_zero(_discoveredPhantomRefs, "PhantomReference"); |
| } |
| |
| inline DiscoveredList* ReferenceProcessor::get_discovered_list(ReferenceType rt) { |
| uint 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. |
| id = WorkerThread::worker_id(); |
| } else { |
| // single-threaded discovery, we save in round-robin |
| // fashion to each of the lists. |
| if (processing_is_mt()) { |
| id = next_id(); |
| } |
| } |
| assert(id < _max_num_queues, "Id is out of bounds id %u and max id %u)", id, _max_num_queues); |
| |
| // Get the discovered queue to which we will add |
| DiscoveredList* list = nullptr; |
| switch (rt) { |
| 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(); |
| } |
| log_develop_trace(gc, ref)("Thread %d gets list " PTR_FORMAT, id, p2i(list)); |
| return list; |
| } |
| |
| inline bool ReferenceProcessor::set_discovered_link(HeapWord* discovered_addr, oop next_discovered) { |
| return discovery_is_mt() ? set_discovered_link_mt(discovered_addr, next_discovered) |
| : set_discovered_link_st(discovered_addr, next_discovered); |
| } |
| |
| inline void ReferenceProcessor::add_to_discovered_list(DiscoveredList& refs_list, |
| oop obj, |
| HeapWord* discovered_addr) { |
| oop current_head = refs_list.head(); |
| // Prepare value to put into the discovered field. The last ref must have its |
| // discovered field pointing to itself. |
| oop next_discovered = (current_head != nullptr) ? current_head : obj; |
| |
| bool added = set_discovered_link(discovered_addr, next_discovered); |
| if (added) { |
| // We can always add the object without synchronization: every thread has its |
| // own list head. |
| refs_list.add_as_head(obj); |
| log_develop_trace(gc, ref)("Discovered reference (%s) (" PTR_FORMAT ": %s)", |
| discovery_is_mt() ? "mt" : "st", p2i(obj), obj->klass()->internal_name()); |
| } else { |
| log_develop_trace(gc, ref)("Already discovered reference (mt) (" PTR_FORMAT ": %s)", |
| p2i(obj), obj->klass()->internal_name()); |
| } |
| } |
| |
| inline bool ReferenceProcessor::set_discovered_link_st(HeapWord* discovered_addr, |
| oop next_discovered) { |
| assert(!discovery_is_mt(), "must be"); |
| |
| if (discovery_is_stw()) { |
| // Do a raw store here: the field will be visited later when processing |
| // the discovered references. |
| RawAccess<>::oop_store(discovered_addr, next_discovered); |
| } else { |
| HeapAccess<AS_NO_KEEPALIVE>::oop_store(discovered_addr, next_discovered); |
| } |
| // Always successful. |
| return true; |
| } |
| |
| inline bool ReferenceProcessor::set_discovered_link_mt(HeapWord* discovered_addr, |
| oop next_discovered) { |
| assert(discovery_is_mt(), "must be"); |
| |
| // We must make sure this object is only enqueued once. Try to CAS into the discovered_addr. |
| oop retest; |
| if (discovery_is_stw()) { |
| // Try a raw store here, still making sure that we enqueue only once: the field |
| // will be visited later when processing the discovered references. |
| retest = RawAccess<>::oop_atomic_cmpxchg(discovered_addr, oop(nullptr), next_discovered); |
| } else { |
| retest = HeapAccess<AS_NO_KEEPALIVE>::oop_atomic_cmpxchg(discovered_addr, oop(nullptr), next_discovered); |
| } |
| return retest == nullptr; |
| } |
| |
| #ifndef PRODUCT |
| // Concurrent discovery might allow us to observe j.l.References with null |
| // referents, being those cleared concurrently by mutators during (or after) discovery. |
| void ReferenceProcessor::verify_referent(oop obj) { |
| bool concurrent = discovery_is_concurrent(); |
| oop referent = java_lang_ref_Reference::unknown_referent_no_keepalive(obj); |
| assert(concurrent ? oopDesc::is_oop_or_null(referent) : oopDesc::is_oop(referent), |
| "Bad referent " PTR_FORMAT " found in Reference " |
| PTR_FORMAT " during %sconcurrent discovery ", |
| p2i(referent), p2i(obj), concurrent ? "" : "non-"); |
| } |
| #endif |
| |
| bool ReferenceProcessor::is_subject_to_discovery(oop const obj) const { |
| return _is_subject_to_discovery->do_object_b(obj); |
| } |
| |
| // Reference discovery policy: |
| // 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 discovered 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. |
| bool ReferenceProcessor::discover_reference(oop obj, ReferenceType rt) { |
| // Make sure we are discovering refs (rather than processing discovered refs). |
| if (!_discovering_refs || !RegisterReferences) { |
| return false; |
| } |
| |
| if ((rt == REF_FINAL) && (java_lang_ref_Reference::next(obj) != nullptr)) { |
| // Don't rediscover non-active FinalReferences. |
| return false; |
| } |
| |
| if (!is_subject_to_discovery(obj)) { |
| // 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 discover references whose referents are not (yet) |
| // known to be strongly reachable. |
| if (is_alive_non_header() != nullptr) { |
| verify_referent(obj); |
| oop referent = java_lang_ref_Reference::unknown_referent_no_keepalive(obj); |
| 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 full collection cycle, this is always currently |
| // accurate. |
| if (!_current_soft_ref_policy->should_clear_reference(obj, _soft_ref_timestamp_clock)) { |
| return false; |
| } |
| } |
| |
| ResourceMark rm; // Needed for tracing. |
| |
| HeapWord* const discovered_addr = java_lang_ref_Reference::discovered_addr_raw(obj); |
| const oop discovered = java_lang_ref_Reference::discovered(obj); |
| assert(oopDesc::is_oop_or_null(discovered), "Expected an oop or null for discovered field at " PTR_FORMAT, p2i(discovered)); |
| if (discovered != nullptr) { |
| // The reference has already been discovered... |
| log_develop_trace(gc, ref)("Already discovered reference (" PTR_FORMAT ": %s)", |
| p2i(obj), obj->klass()->internal_name()); |
| |
| // Encountering an already-discovered non-strong ref because G1 can restart |
| // concurrent marking on marking-stack overflow. Must continue to treat |
| // this non-strong ref as discovered to avoid keeping the referent |
| // unnecessarily alive. |
| assert(UseG1GC, "inv"); |
| assert(_discovery_is_concurrent, "inv"); |
| return true; |
| } |
| |
| // Get the right type of discovered queue head. |
| DiscoveredList* list = get_discovered_list(rt); |
| add_to_discovered_list(*list, obj, discovered_addr); |
| |
| assert(oopDesc::is_oop(obj), "Discovered a bad reference"); |
| verify_referent(obj); |
| return true; |
| } |
| |
| void ReferenceProcessor::preclean_discovered_references(BoolObjectClosure* is_alive, |
| EnqueueDiscoveredFieldClosure* enqueue, |
| YieldClosure* yield, |
| GCTimer* gc_timer) { |
| // These lists can be handled here in any order and, indeed, concurrently. |
| |
| // Soft references |
| { |
| GCTraceTime(Debug, gc, ref) tm("Preclean SoftReferences", gc_timer); |
| log_reflist("SoftRef before: ", _discoveredSoftRefs, _max_num_queues); |
| for (uint i = 0; i < _max_num_queues; i++) { |
| if (yield->should_return()) { |
| return; |
| } |
| if (preclean_discovered_reflist(_discoveredSoftRefs[i], is_alive, |
| enqueue, yield)) { |
| log_reflist("SoftRef abort: ", _discoveredSoftRefs, _max_num_queues); |
| return; |
| } |
| } |
| log_reflist("SoftRef after: ", _discoveredSoftRefs, _max_num_queues); |
| } |
| |
| // Weak references |
| { |
| GCTraceTime(Debug, gc, ref) tm("Preclean WeakReferences", gc_timer); |
| log_reflist("WeakRef before: ", _discoveredWeakRefs, _max_num_queues); |
| for (uint i = 0; i < _max_num_queues; i++) { |
| if (yield->should_return()) { |
| return; |
| } |
| if (preclean_discovered_reflist(_discoveredWeakRefs[i], is_alive, |
| enqueue, yield)) { |
| log_reflist("WeakRef abort: ", _discoveredWeakRefs, _max_num_queues); |
| return; |
| } |
| } |
| log_reflist("WeakRef after: ", _discoveredWeakRefs, _max_num_queues); |
| } |
| |
| // Final references |
| { |
| GCTraceTime(Debug, gc, ref) tm("Preclean FinalReferences", gc_timer); |
| log_reflist("FinalRef before: ", _discoveredFinalRefs, _max_num_queues); |
| for (uint i = 0; i < _max_num_queues; i++) { |
| if (yield->should_return()) { |
| return; |
| } |
| if (preclean_discovered_reflist(_discoveredFinalRefs[i], is_alive, |
| enqueue, yield)) { |
| log_reflist("FinalRef abort: ", _discoveredFinalRefs, _max_num_queues); |
| return; |
| } |
| } |
| log_reflist("FinalRef after: ", _discoveredFinalRefs, _max_num_queues); |
| } |
| |
| // Phantom references |
| { |
| GCTraceTime(Debug, gc, ref) tm("Preclean PhantomReferences", gc_timer); |
| log_reflist("PhantomRef before: ", _discoveredPhantomRefs, _max_num_queues); |
| for (uint i = 0; i < _max_num_queues; i++) { |
| if (yield->should_return()) { |
| return; |
| } |
| if (preclean_discovered_reflist(_discoveredPhantomRefs[i], is_alive, |
| enqueue, yield)) { |
| log_reflist("PhantomRef abort: ", _discoveredPhantomRefs, _max_num_queues); |
| return; |
| } |
| } |
| log_reflist("PhantomRef after: ", _discoveredPhantomRefs, _max_num_queues); |
| } |
| } |
| |
| bool ReferenceProcessor::preclean_discovered_reflist(DiscoveredList& refs_list, |
| BoolObjectClosure* is_alive, |
| EnqueueDiscoveredFieldClosure* enqueue, |
| YieldClosure* yield) { |
| DiscoveredListIterator iter(refs_list, nullptr /* keep_alive */, is_alive, enqueue); |
| while (iter.has_next()) { |
| if (yield->should_return_fine_grain()) { |
| return true; |
| } |
| iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); |
| if (iter.referent() == nullptr) { |
| log_preclean_ref(iter, "cleared"); |
| iter.remove(); |
| iter.move_to_next(); |
| } else if (iter.is_referent_alive()) { |
| log_preclean_ref(iter, "reachable"); |
| iter.remove(); |
| iter.move_to_next(); |
| } else { |
| iter.next(); |
| } |
| } |
| |
| if (iter.processed() > 0) { |
| log_develop_trace(gc, ref)(" Dropped %zu Refs out of %zu Refs in discovered list " PTR_FORMAT, |
| iter.removed(), iter.processed(), p2i(&refs_list)); |
| } |
| return false; |
| } |
| |
| const char* ReferenceProcessor::list_name(uint i) { |
| assert(i <= _max_num_queues * number_of_subclasses_of_ref(), |
| "Out of bounds index"); |
| |
| int j = i / _max_num_queues; |
| switch (j) { |
| case 0: return "SoftRef"; |
| case 1: return "WeakRef"; |
| case 2: return "FinalRef"; |
| case 3: return "PhantomRef"; |
| } |
| ShouldNotReachHere(); |
| return nullptr; |
| } |
| |
| uint RefProcMTDegreeAdjuster::ergo_proc_thread_count(size_t ref_count, |
| uint max_threads, |
| RefProcPhases phase) const { |
| assert(0 < max_threads, "must allow at least one thread"); |
| |
| if (use_max_threads(phase) || (ReferencesPerThread == 0)) { |
| return max_threads; |
| } |
| |
| size_t thread_count = 1 + (ref_count / ReferencesPerThread); |
| return (uint)MIN3(thread_count, |
| static_cast<size_t>(max_threads), |
| (size_t)os::active_processor_count()); |
| } |
| |
| bool RefProcMTDegreeAdjuster::use_max_threads(RefProcPhases phase) const { |
| // Even a small number of references in this phase could produce large amounts of work. |
| return phase == ReferenceProcessor::KeepAliveFinalRefsPhase; |
| } |
| |
| RefProcMTDegreeAdjuster::RefProcMTDegreeAdjuster(ReferenceProcessor* rp, |
| RefProcPhases phase, |
| size_t ref_count): |
| _rp(rp), |
| _saved_num_queues(_rp->num_queues()) { |
| uint workers = ergo_proc_thread_count(ref_count, _rp->num_queues(), phase); |
| _rp->set_active_mt_degree(workers); |
| } |
| |
| RefProcMTDegreeAdjuster::~RefProcMTDegreeAdjuster() { |
| // Revert to previous status. |
| _rp->set_active_mt_degree(_saved_num_queues); |
| } |
