/* * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved. * Copyright (c) 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 "gc/shenandoah/heuristics/shenandoahOldHeuristics.hpp" #include "gc/shenandoah/shenandoahAsserts.hpp" #include "gc/shenandoah/shenandoahCardTable.hpp" #include "gc/shenandoah/shenandoahClosures.inline.hpp" #include "gc/shenandoah/shenandoahCollectorPolicy.hpp" #include "gc/shenandoah/shenandoahFreeSet.hpp" #include "gc/shenandoah/shenandoahGenerationalHeap.hpp" #include "gc/shenandoah/shenandoahHeap.hpp" #include "gc/shenandoah/shenandoahHeap.inline.hpp" #include "gc/shenandoah/shenandoahHeapRegion.hpp" #include "gc/shenandoah/shenandoahHeapRegionClosures.hpp" #include "gc/shenandoah/shenandoahMonitoringSupport.hpp" #include "gc/shenandoah/shenandoahOldGeneration.hpp" #include "gc/shenandoah/shenandoahReferenceProcessor.hpp" #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp" #include "gc/shenandoah/shenandoahUtils.hpp" #include "gc/shenandoah/shenandoahWorkerPolicy.hpp" #include "gc/shenandoah/shenandoahYoungGeneration.hpp" #include "runtime/threads.hpp" #include "utilities/events.hpp" class ShenandoahFlushAllSATB : public ThreadClosure { private: SATBMarkQueueSet& _satb_qset; public: explicit ShenandoahFlushAllSATB(SATBMarkQueueSet& satb_qset) : _satb_qset(satb_qset) {} void do_thread(Thread* thread) override { // Transfer any partial buffer to the qset for completed buffer processing. _satb_qset.flush_queue(ShenandoahThreadLocalData::satb_mark_queue(thread)); } }; class ShenandoahProcessOldSATB : public SATBBufferClosure { private: ShenandoahObjToScanQueue* _queue; ShenandoahHeap* _heap; ShenandoahMarkingContext* const _mark_context; size_t _trashed_oops; public: explicit ShenandoahProcessOldSATB(ShenandoahObjToScanQueue* q) : _queue(q), _heap(ShenandoahHeap::heap()), _mark_context(_heap->marking_context()), _trashed_oops(0) {} void do_buffer(void** buffer, size_t size) override { assert(size == 0 || !_heap->has_forwarded_objects() || _heap->is_concurrent_old_mark_in_progress(), "Forwarded objects are not expected here"); for (size_t i = 0; i < size; ++i) { oop *p = (oop *) &buffer[i]; ShenandoahHeapRegion* region = _heap->heap_region_containing(*p); if (region->is_old() && region->is_active()) { ShenandoahMark::mark_through_ref(p, _queue, nullptr, _mark_context, false); } else { _trashed_oops++; } } } size_t trashed_oops() const { return _trashed_oops; } }; class ShenandoahPurgeSATBTask : public WorkerTask { private: ShenandoahObjToScanQueueSet* _mark_queues; // Keep track of the number of oops that are not transferred to mark queues. // This is volatile because workers update it, but the vm thread reads it. volatile size_t _trashed_oops; public: explicit ShenandoahPurgeSATBTask(ShenandoahObjToScanQueueSet* queues) : WorkerTask("Purge SATB"), _mark_queues(queues), _trashed_oops(0) { Threads::change_thread_claim_token(); } ~ShenandoahPurgeSATBTask() { if (_trashed_oops > 0) { log_debug(gc)("Purged %zu oops from old generation SATB buffers", _trashed_oops); } } void work(uint worker_id) override { ShenandoahParallelWorkerSession worker_session(worker_id); ShenandoahSATBMarkQueueSet &satb_queues = ShenandoahBarrierSet::satb_mark_queue_set(); ShenandoahFlushAllSATB flusher(satb_queues); Threads::possibly_parallel_threads_do(true /* is_par */, &flusher); ShenandoahObjToScanQueue* mark_queue = _mark_queues->queue(worker_id); ShenandoahProcessOldSATB processor(mark_queue); while (satb_queues.apply_closure_to_completed_buffer(&processor)) {} Atomic::add(&_trashed_oops, processor.trashed_oops()); } }; class ShenandoahTransferOldSATBTask : public WorkerTask { ShenandoahSATBMarkQueueSet& _satb_queues; ShenandoahObjToScanQueueSet* _mark_queues; // Keep track of the number of oops that are not transferred to mark queues. // This is volatile because workers update it, but the control thread reads it. volatile size_t _trashed_oops; public: explicit ShenandoahTransferOldSATBTask(ShenandoahSATBMarkQueueSet& satb_queues, ShenandoahObjToScanQueueSet* mark_queues) : WorkerTask("Transfer SATB"), _satb_queues(satb_queues), _mark_queues(mark_queues), _trashed_oops(0) {} ~ShenandoahTransferOldSATBTask() { if (_trashed_oops > 0) { log_debug(gc)("Purged %zu oops from old generation SATB buffers", _trashed_oops); } } void work(uint worker_id) override { ShenandoahObjToScanQueue* mark_queue = _mark_queues->queue(worker_id); ShenandoahProcessOldSATB processor(mark_queue); while (_satb_queues.apply_closure_to_completed_buffer(&processor)) {} Atomic::add(&_trashed_oops, processor.trashed_oops()); } }; class ShenandoahConcurrentCoalesceAndFillTask : public WorkerTask { private: uint _nworkers; ShenandoahHeapRegion** _coalesce_and_fill_region_array; uint _coalesce_and_fill_region_count; volatile bool _is_preempted; public: ShenandoahConcurrentCoalesceAndFillTask(uint nworkers, ShenandoahHeapRegion** coalesce_and_fill_region_array, uint region_count) : WorkerTask("Shenandoah Concurrent Coalesce and Fill"), _nworkers(nworkers), _coalesce_and_fill_region_array(coalesce_and_fill_region_array), _coalesce_and_fill_region_count(region_count), _is_preempted(false) { } void work(uint worker_id) override { ShenandoahWorkerTimingsTracker timer(ShenandoahPhaseTimings::conc_coalesce_and_fill, ShenandoahPhaseTimings::ScanClusters, worker_id); for (uint region_idx = worker_id; region_idx < _coalesce_and_fill_region_count; region_idx += _nworkers) { ShenandoahHeapRegion* r = _coalesce_and_fill_region_array[region_idx]; if (r->is_humongous()) { // There is only one object in this region and it is not garbage, // so no need to coalesce or fill. continue; } if (!r->oop_coalesce_and_fill(true)) { // Coalesce and fill has been preempted Atomic::store(&_is_preempted, true); return; } } } // Value returned from is_completed() is only valid after all worker thread have terminated. bool is_completed() { return !Atomic::load(&_is_preempted); } }; ShenandoahOldGeneration::ShenandoahOldGeneration(uint max_queues, size_t max_capacity, size_t soft_max_capacity) : ShenandoahGeneration(OLD, max_queues, max_capacity, soft_max_capacity), _coalesce_and_fill_region_array(NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, ShenandoahHeap::heap()->num_regions(), mtGC)), _old_heuristics(nullptr), _region_balance(0), _promoted_reserve(0), _promoted_expended(0), _promotion_potential(0), _pad_for_promote_in_place(0), _promotable_humongous_regions(0), _promotable_regular_regions(0), _is_parsable(true), _card_scan(nullptr), _state(WAITING_FOR_BOOTSTRAP), _growth_before_compaction(INITIAL_GROWTH_BEFORE_COMPACTION), _min_growth_before_compaction ((ShenandoahMinOldGenGrowthPercent * FRACTIONAL_DENOMINATOR) / 100) { _live_bytes_after_last_mark = ShenandoahHeap::heap()->capacity() * INITIAL_LIVE_FRACTION / FRACTIONAL_DENOMINATOR; // Always clear references for old generation ref_processor()->set_soft_reference_policy(true); if (ShenandoahCardBarrier) { ShenandoahCardTable* card_table = ShenandoahBarrierSet::barrier_set()->card_table(); size_t card_count = card_table->cards_required(ShenandoahHeap::heap()->reserved_region().word_size()); auto rs = new ShenandoahDirectCardMarkRememberedSet(card_table, card_count); _card_scan = new ShenandoahScanRemembered(rs); } } void ShenandoahOldGeneration::set_promoted_reserve(size_t new_val) { shenandoah_assert_heaplocked_or_safepoint(); _promoted_reserve = new_val; } size_t ShenandoahOldGeneration::get_promoted_reserve() const { return _promoted_reserve; } void ShenandoahOldGeneration::augment_promoted_reserve(size_t increment) { shenandoah_assert_heaplocked_or_safepoint(); _promoted_reserve += increment; } void ShenandoahOldGeneration::reset_promoted_expended() { shenandoah_assert_heaplocked_or_safepoint(); Atomic::store(&_promoted_expended, (size_t) 0); } size_t ShenandoahOldGeneration::expend_promoted(size_t increment) { shenandoah_assert_heaplocked_or_safepoint(); assert(get_promoted_expended() + increment <= get_promoted_reserve(), "Do not expend more promotion than budgeted"); return Atomic::add(&_promoted_expended, increment); } size_t ShenandoahOldGeneration::unexpend_promoted(size_t decrement) { return Atomic::sub(&_promoted_expended, decrement); } size_t ShenandoahOldGeneration::get_promoted_expended() const { return Atomic::load(&_promoted_expended); } bool ShenandoahOldGeneration::can_allocate(const ShenandoahAllocRequest &req) const { assert(req.type() != ShenandoahAllocRequest::_alloc_gclab, "GCLAB pertains only to young-gen memory"); const size_t requested_bytes = req.size() * HeapWordSize; // The promotion reserve may also be used for evacuations. If we can promote this object, // then we can also evacuate it. if (can_promote(requested_bytes)) { // The promotion reserve should be able to accommodate this request. The request // might still fail if alignment with the card table increases the size. The request // may also fail if the heap is badly fragmented and the free set cannot find room for it. return true; } if (req.type() == ShenandoahAllocRequest::_alloc_plab) { // The promotion reserve cannot accommodate this plab request. Check if we still have room for // evacuations. Note that we cannot really know how much of the plab will be used for evacuations, // so here we only check that some evacuation reserve still exists. return get_evacuation_reserve() > 0; } // This is a shared allocation request. We've already checked that it can't be promoted, so if // it is a promotion, we return false. Otherwise, it is a shared evacuation request, and we allow // the allocation to proceed. return !req.is_promotion(); } void ShenandoahOldGeneration::configure_plab_for_current_thread(const ShenandoahAllocRequest &req) { // Note: Even when a mutator is performing a promotion outside a LAB, we use a 'shared_gc' request. if (req.is_gc_alloc()) { const size_t actual_size = req.actual_size() * HeapWordSize; if (req.type() == ShenandoahAllocRequest::_alloc_plab) { // We've created a new plab. Now we configure it whether it will be used for promotions // and evacuations - or just evacuations. Thread* thread = Thread::current(); ShenandoahThreadLocalData::reset_plab_promoted(thread); // The actual size of the allocation may be larger than the requested bytes (due to alignment on card boundaries). // If this puts us over our promotion budget, we need to disable future PLAB promotions for this thread. if (can_promote(actual_size)) { // Assume the entirety of this PLAB will be used for promotion. This prevents promotion from overreach. // When we retire this plab, we'll unexpend what we don't really use. expend_promoted(actual_size); ShenandoahThreadLocalData::enable_plab_promotions(thread); ShenandoahThreadLocalData::set_plab_actual_size(thread, actual_size); } else { // Disable promotions in this thread because entirety of this PLAB must be available to hold old-gen evacuations. ShenandoahThreadLocalData::disable_plab_promotions(thread); ShenandoahThreadLocalData::set_plab_actual_size(thread, 0); } } else if (req.is_promotion()) { // Shared promotion. expend_promoted(actual_size); } } } size_t ShenandoahOldGeneration::get_live_bytes_after_last_mark() const { return _live_bytes_after_last_mark; } void ShenandoahOldGeneration::set_live_bytes_after_last_mark(size_t bytes) { if (bytes == 0) { // Restart search for best old-gen size to the initial state _live_bytes_after_last_mark = ShenandoahHeap::heap()->capacity() * INITIAL_LIVE_FRACTION / FRACTIONAL_DENOMINATOR; _growth_before_compaction = INITIAL_GROWTH_BEFORE_COMPACTION; } else { _live_bytes_after_last_mark = bytes; _growth_before_compaction /= 2; if (_growth_before_compaction < _min_growth_before_compaction) { _growth_before_compaction = _min_growth_before_compaction; } } } void ShenandoahOldGeneration::handle_failed_transfer() { _old_heuristics->trigger_cannot_expand(); } size_t ShenandoahOldGeneration::usage_trigger_threshold() const { size_t result = _live_bytes_after_last_mark + (_live_bytes_after_last_mark * _growth_before_compaction) / FRACTIONAL_DENOMINATOR; return result; } bool ShenandoahOldGeneration::contains(ShenandoahAffiliation affiliation) const { return affiliation == OLD_GENERATION; } bool ShenandoahOldGeneration::contains(ShenandoahHeapRegion* region) const { return region->is_old(); } void ShenandoahOldGeneration::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* cl) { ShenandoahIncludeRegionClosure old_regions_cl(cl); ShenandoahHeap::heap()->parallel_heap_region_iterate(&old_regions_cl); } void ShenandoahOldGeneration::heap_region_iterate(ShenandoahHeapRegionClosure* cl) { ShenandoahIncludeRegionClosure old_regions_cl(cl); ShenandoahHeap::heap()->heap_region_iterate(&old_regions_cl); } void ShenandoahOldGeneration::set_concurrent_mark_in_progress(bool in_progress) { ShenandoahHeap::heap()->set_concurrent_old_mark_in_progress(in_progress); } bool ShenandoahOldGeneration::is_concurrent_mark_in_progress() { return ShenandoahHeap::heap()->is_concurrent_old_mark_in_progress(); } void ShenandoahOldGeneration::cancel_marking() { if (is_concurrent_mark_in_progress()) { log_debug(gc)("Abandon SATB buffers"); ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking(); } ShenandoahGeneration::cancel_marking(); } void ShenandoahOldGeneration::cancel_gc() { shenandoah_assert_safepoint(); if (is_idle()) { #ifdef ASSERT validate_waiting_for_bootstrap(); #endif } else { log_info(gc)("Terminating old gc cycle."); // Stop marking cancel_marking(); // Stop tracking old regions abandon_collection_candidates(); // Remove old generation access to young generation mark queues ShenandoahHeap::heap()->young_generation()->set_old_gen_task_queues(nullptr); // Transition to IDLE now. transition_to(ShenandoahOldGeneration::WAITING_FOR_BOOTSTRAP); } } void ShenandoahOldGeneration::prepare_gc() { // Now that we have made the old generation parsable, it is safe to reset the mark bitmap. assert(state() != FILLING, "Cannot reset old without making it parsable"); ShenandoahGeneration::prepare_gc(); } bool ShenandoahOldGeneration::entry_coalesce_and_fill() { ShenandoahHeap* const heap = ShenandoahHeap::heap(); static const char* msg = "Coalescing and filling (Old)"; ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_coalesce_and_fill); TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters()); EventMark em("%s", msg); ShenandoahWorkerScope scope(heap->workers(), ShenandoahWorkerPolicy::calc_workers_for_conc_marking(), msg); return coalesce_and_fill(); } // Make the old generation regions parsable, so they can be safely // scanned when looking for objects in memory indicated by dirty cards. bool ShenandoahOldGeneration::coalesce_and_fill() { transition_to(FILLING); // This code will see the same set of regions to fill on each resumption as it did // on the initial run. That's okay because each region keeps track of its own coalesce // and fill state. Regions that were filled on a prior attempt will not try to fill again. uint coalesce_and_fill_regions_count = _old_heuristics->get_coalesce_and_fill_candidates(_coalesce_and_fill_region_array); assert(coalesce_and_fill_regions_count <= ShenandoahHeap::heap()->num_regions(), "Sanity"); if (coalesce_and_fill_regions_count == 0) { // No regions need to be filled. abandon_collection_candidates(); return true; } ShenandoahHeap* const heap = ShenandoahHeap::heap(); WorkerThreads* workers = heap->workers(); uint nworkers = workers->active_workers(); ShenandoahConcurrentCoalesceAndFillTask task(nworkers, _coalesce_and_fill_region_array, coalesce_and_fill_regions_count); log_debug(gc)("Starting (or resuming) coalesce-and-fill of " UINT32_FORMAT " old heap regions", coalesce_and_fill_regions_count); workers->run_task(&task); if (task.is_completed()) { // We no longer need to track regions that need to be coalesced and filled. abandon_collection_candidates(); return true; } else { // Coalesce-and-fill has been preempted. We'll finish that effort in the future. Do not invoke // ShenandoahGeneration::prepare_gc() until coalesce-and-fill is done because it resets the mark bitmap // and invokes set_mark_incomplete(). Coalesce-and-fill depends on the mark bitmap. log_debug(gc)("Suspending coalesce-and-fill of old heap regions"); return false; } } void ShenandoahOldGeneration::concurrent_transfer_pointers_from_satb() const { const ShenandoahHeap* heap = ShenandoahHeap::heap(); assert(heap->is_concurrent_old_mark_in_progress(), "Only necessary during old marking."); log_debug(gc)("Transfer SATB buffers"); // Step 1. All threads need to 'complete' partially filled, thread local SATB buffers. This // is accomplished in ShenandoahConcurrentGC::complete_abbreviated_cycle using a Handshake // operation. // Step 2. Use worker threads to transfer oops from old, active regions in the completed // SATB buffers to old generation mark queues. ShenandoahSATBMarkQueueSet& satb_queues = ShenandoahBarrierSet::satb_mark_queue_set(); ShenandoahTransferOldSATBTask transfer_task(satb_queues, task_queues()); heap->workers()->run_task(&transfer_task); } void ShenandoahOldGeneration::transfer_pointers_from_satb() const { const ShenandoahHeap* heap = ShenandoahHeap::heap(); assert(heap->is_concurrent_old_mark_in_progress(), "Only necessary during old marking."); log_debug(gc)("Transfer SATB buffers"); ShenandoahPurgeSATBTask purge_satb_task(task_queues()); heap->workers()->run_task(&purge_satb_task); } bool ShenandoahOldGeneration::contains(oop obj) const { return ShenandoahHeap::heap()->is_in_old(obj); } void ShenandoahOldGeneration::prepare_regions_and_collection_set(bool concurrent) { ShenandoahHeap* heap = ShenandoahHeap::heap(); assert(!heap->is_full_gc_in_progress(), "Only for concurrent and degenerated GC"); { ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_update_region_states : ShenandoahPhaseTimings::degen_gc_final_update_region_states); ShenandoahFinalMarkUpdateRegionStateClosure cl(complete_marking_context()); parallel_heap_region_iterate(&cl); heap->assert_pinned_region_status(); } { // This doesn't actually choose a collection set, but prepares a list of // regions as 'candidates' for inclusion in a mixed collection. ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::choose_cset : ShenandoahPhaseTimings::degen_gc_choose_cset); ShenandoahHeapLocker locker(heap->lock()); _old_heuristics->prepare_for_old_collections(); } { // Though we did not choose a collection set above, we still may have // freed up immediate garbage regions so proceed with rebuilding the free set. ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_rebuild_freeset : ShenandoahPhaseTimings::degen_gc_final_rebuild_freeset); ShenandoahHeapLocker locker(heap->lock()); size_t cset_young_regions, cset_old_regions; size_t first_old, last_old, num_old; heap->free_set()->prepare_to_rebuild(cset_young_regions, cset_old_regions, first_old, last_old, num_old); // This is just old-gen completion. No future budgeting required here. The only reason to rebuild the freeset here // is in case there was any immediate old garbage identified. heap->free_set()->finish_rebuild(cset_young_regions, cset_old_regions, num_old); } } const char* ShenandoahOldGeneration::state_name(State state) { switch (state) { case WAITING_FOR_BOOTSTRAP: return "Waiting for Bootstrap"; case FILLING: return "Coalescing"; case BOOTSTRAPPING: return "Bootstrapping"; case MARKING: return "Marking"; case EVACUATING: return "Evacuating"; case EVACUATING_AFTER_GLOBAL: return "Evacuating (G)"; default: ShouldNotReachHere(); return "Unknown"; } } void ShenandoahOldGeneration::transition_to(State new_state) { if (_state != new_state) { log_debug(gc, thread)("Old generation transition from %s to %s", state_name(_state), state_name(new_state)); EventMark event("Old was %s, now is %s", state_name(_state), state_name(new_state)); validate_transition(new_state); _state = new_state; } } #ifdef ASSERT // This diagram depicts the expected state transitions for marking the old generation // and preparing for old collections. When a young generation cycle executes, the // remembered set scan must visit objects in old regions. Visiting an object which // has become dead on previous old cycles will result in crashes. To avoid visiting // such objects, the remembered set scan will use the old generation mark bitmap when // possible. It is _not_ possible to use the old generation bitmap when old marking // is active (bitmap is not complete). For this reason, the old regions are made // parsable _before_ the old generation bitmap is reset. The diagram does not depict // cancellation of old collections by global or full collections. // // When a global collection supersedes an old collection, the global mark still // "completes" the old mark bitmap. Subsequent remembered set scans may use the // old generation mark bitmap, but any uncollected old regions must still be made parsable // before the next old generation cycle begins. For this reason, a global collection may // create mixed collection candidates and coalesce and fill candidates and will put // the old generation in the respective states (EVACUATING or FILLING). After a Full GC, // the mark bitmaps are all reset, all regions are parsable and the mark context will // not be "complete". After a Full GC, remembered set scans will _not_ use the mark bitmap // and we expect the old generation to be waiting for bootstrap. // // +-----------------+ // +------------> | FILLING | <---+ // | +--------> | | | // | | +-----------------+ | // | | | | // | | | Filling Complete | <-> A global collection may // | | v | move the old generation // | | +-----------------+ | directly from waiting for // +-- |-- |--------> | WAITING | | bootstrap to filling or // | | | +---- | FOR BOOTSTRAP | ----+ evacuating. It may also // | | | | +-----------------+ move from filling to waiting // | | | | | for bootstrap. // | | | | | Reset Bitmap // | | | | v // | | | | +-----------------+ +----------------------+ // | | | | | BOOTSTRAP | <-> | YOUNG GC | // | | | | | | | (RSet Parses Region) | // | | | | +-----------------+ +----------------------+ // | | | | | // | | | | | Old Marking // | | | | v // | | | | +-----------------+ +----------------------+ // | | | | | MARKING | <-> | YOUNG GC | // | | +--------- | | | (RSet Parses Region) | // | | | +-----------------+ +----------------------+ // | | | | // | | | | Has Evacuation Candidates // | | | v // | | | +-----------------+ +--------------------+ // | | +---> | EVACUATING | <-> | YOUNG GC | // | +------------- | | | (RSet Uses Bitmap) | // | +-----------------+ +--------------------+ // | | // | | Global Cycle Coalesces and Fills Old Regions // | v // | +-----------------+ +--------------------+ // +----------------- | EVACUATING | <-> | YOUNG GC | // | AFTER GLOBAL | | (RSet Uses Bitmap) | // +-----------------+ +--------------------+ // // void ShenandoahOldGeneration::validate_transition(State new_state) { ShenandoahGenerationalHeap* heap = ShenandoahGenerationalHeap::heap(); switch (new_state) { case FILLING: assert(_state != BOOTSTRAPPING, "Cannot begin making old regions parsable after bootstrapping"); assert(is_mark_complete(), "Cannot begin filling without first completing marking, state is '%s'", state_name(_state)); assert(_old_heuristics->has_coalesce_and_fill_candidates(), "Cannot begin filling without something to fill."); break; case WAITING_FOR_BOOTSTRAP: // GC cancellation can send us back here from any state. validate_waiting_for_bootstrap(); break; case BOOTSTRAPPING: assert(_state == WAITING_FOR_BOOTSTRAP, "Cannot reset bitmap without making old regions parsable, state is '%s'", state_name(_state)); assert(_old_heuristics->unprocessed_old_collection_candidates() == 0, "Cannot bootstrap with mixed collection candidates"); assert(!heap->is_prepare_for_old_mark_in_progress(), "Cannot still be making old regions parsable."); break; case MARKING: assert(_state == BOOTSTRAPPING, "Must have finished bootstrapping before marking, state is '%s'", state_name(_state)); assert(heap->young_generation()->old_gen_task_queues() != nullptr, "Young generation needs old mark queues."); assert(heap->is_concurrent_old_mark_in_progress(), "Should be marking old now."); break; case EVACUATING_AFTER_GLOBAL: assert(_state == EVACUATING, "Must have been evacuating, state is '%s'", state_name(_state)); break; case EVACUATING: assert(_state == WAITING_FOR_BOOTSTRAP || _state == MARKING, "Cannot have old collection candidates without first marking, state is '%s'", state_name(_state)); assert(_old_heuristics->unprocessed_old_collection_candidates() > 0, "Must have collection candidates here."); break; default: fatal("Unknown new state"); } } bool ShenandoahOldGeneration::validate_waiting_for_bootstrap() { ShenandoahHeap* heap = ShenandoahHeap::heap(); assert(!heap->is_concurrent_old_mark_in_progress(), "Cannot become ready for bootstrap during old mark."); assert(heap->young_generation()->old_gen_task_queues() == nullptr, "Cannot become ready for bootstrap when still setup for bootstrapping."); assert(!is_concurrent_mark_in_progress(), "Cannot be marking in IDLE"); assert(!heap->young_generation()->is_bootstrap_cycle(), "Cannot have old mark queues if IDLE"); assert(!_old_heuristics->has_coalesce_and_fill_candidates(), "Cannot have coalesce and fill candidates in IDLE"); assert(_old_heuristics->unprocessed_old_collection_candidates() == 0, "Cannot have mixed collection candidates in IDLE"); return true; } #endif ShenandoahHeuristics* ShenandoahOldGeneration::initialize_heuristics(ShenandoahMode* gc_mode) { _old_heuristics = new ShenandoahOldHeuristics(this, ShenandoahGenerationalHeap::heap()); _old_heuristics->set_guaranteed_gc_interval(ShenandoahGuaranteedOldGCInterval); _heuristics = _old_heuristics; return _heuristics; } void ShenandoahOldGeneration::record_success_concurrent(bool abbreviated) { heuristics()->record_success_concurrent(); ShenandoahHeap::heap()->shenandoah_policy()->record_success_old(); } void ShenandoahOldGeneration::handle_failed_evacuation() { if (_failed_evacuation.try_set()) { log_debug(gc)("Old gen evac failure."); } } void ShenandoahOldGeneration::handle_failed_promotion(Thread* thread, size_t size) { // We squelch excessive reports to reduce noise in logs. const size_t MaxReportsPerEpoch = 4; static size_t last_report_epoch = 0; static size_t epoch_report_count = 0; auto heap = ShenandoahGenerationalHeap::heap(); size_t promotion_reserve; size_t promotion_expended; const size_t gc_id = heap->control_thread()->get_gc_id(); if ((gc_id != last_report_epoch) || (epoch_report_count++ < MaxReportsPerEpoch)) { { // Promotion failures should be very rare. Invest in providing useful diagnostic info. ShenandoahHeapLocker locker(heap->lock()); promotion_reserve = get_promoted_reserve(); promotion_expended = get_promoted_expended(); } PLAB* const plab = ShenandoahThreadLocalData::plab(thread); const size_t words_remaining = (plab == nullptr)? 0: plab->words_remaining(); const char* promote_enabled = ShenandoahThreadLocalData::allow_plab_promotions(thread)? "enabled": "disabled"; log_info(gc, ergo)("Promotion failed, size %zu, has plab? %s, PLAB remaining: %zu" ", plab promotions %s, promotion reserve: %zu, promotion expended: %zu" ", old capacity: %zu, old_used: %zu, old unaffiliated regions: %zu", size * HeapWordSize, plab == nullptr? "no": "yes", words_remaining * HeapWordSize, promote_enabled, promotion_reserve, promotion_expended, max_capacity(), used(), free_unaffiliated_regions()); if ((gc_id == last_report_epoch) && (epoch_report_count >= MaxReportsPerEpoch)) { log_debug(gc, ergo)("Squelching additional promotion failure reports for current epoch"); } else if (gc_id != last_report_epoch) { last_report_epoch = gc_id; epoch_report_count = 1; } } } void ShenandoahOldGeneration::handle_evacuation(HeapWord* obj, size_t words, bool promotion) { // Only register the copy of the object that won the evacuation race. _card_scan->register_object_without_lock(obj); // Mark the entire range of the evacuated object as dirty. At next remembered set scan, // we will clear dirty bits that do not hold interesting pointers. It's more efficient to // do this in batch, in a background GC thread than to try to carefully dirty only cards // that hold interesting pointers right now. _card_scan->mark_range_as_dirty(obj, words); if (promotion) { // This evacuation was a promotion, track this as allocation against old gen increase_allocated(words * HeapWordSize); } } bool ShenandoahOldGeneration::has_unprocessed_collection_candidates() { return _old_heuristics->unprocessed_old_collection_candidates() > 0; } size_t ShenandoahOldGeneration::unprocessed_collection_candidates_live_memory() { return _old_heuristics->unprocessed_old_collection_candidates_live_memory(); } void ShenandoahOldGeneration::abandon_collection_candidates() { _old_heuristics->abandon_collection_candidates(); } void ShenandoahOldGeneration::prepare_for_mixed_collections_after_global_gc() { assert(is_mark_complete(), "Expected old generation mark to be complete after global cycle."); _old_heuristics->prepare_for_old_collections(); log_info(gc, ergo)("After choosing global collection set, mixed candidates: " UINT32_FORMAT ", coalescing candidates: %zu", _old_heuristics->unprocessed_old_collection_candidates(), _old_heuristics->coalesce_and_fill_candidates_count()); } void ShenandoahOldGeneration::parallel_heap_region_iterate_free(ShenandoahHeapRegionClosure* cl) { // Iterate over old and free regions (exclude young). ShenandoahExcludeRegionClosure exclude_cl(cl); ShenandoahGeneration::parallel_heap_region_iterate_free(&exclude_cl); } void ShenandoahOldGeneration::set_parsable(bool parsable) { _is_parsable = parsable; if (_is_parsable) { // The current state would have been chosen during final mark of the global // collection, _before_ any decisions about class unloading have been made. // // After unloading classes, we have made the old generation regions parsable. // We can skip filling or transition to a state that knows everything has // already been filled. switch (state()) { case ShenandoahOldGeneration::EVACUATING: transition_to(ShenandoahOldGeneration::EVACUATING_AFTER_GLOBAL); break; case ShenandoahOldGeneration::FILLING: assert(_old_heuristics->unprocessed_old_collection_candidates() == 0, "Expected no mixed collection candidates"); assert(_old_heuristics->coalesce_and_fill_candidates_count() > 0, "Expected coalesce and fill candidates"); // When the heuristic put the old generation in this state, it didn't know // that we would unload classes and make everything parsable. But, we know // that now so we can override this state. abandon_collection_candidates(); transition_to(ShenandoahOldGeneration::WAITING_FOR_BOOTSTRAP); break; default: // We can get here during a full GC. The full GC will cancel anything // happening in the old generation and return it to the waiting for bootstrap // state. The full GC will then record that the old regions are parsable // after rebuilding the remembered set. assert(is_idle(), "Unexpected state %s at end of global GC", state_name()); break; } } } void ShenandoahOldGeneration::complete_mixed_evacuations() { assert(is_doing_mixed_evacuations(), "Mixed evacuations should be in progress"); if (!_old_heuristics->has_coalesce_and_fill_candidates()) { // No candidate regions to coalesce and fill transition_to(ShenandoahOldGeneration::WAITING_FOR_BOOTSTRAP); return; } if (state() == ShenandoahOldGeneration::EVACUATING) { transition_to(ShenandoahOldGeneration::FILLING); return; } // Here, we have no more candidates for mixed collections. The candidates for coalescing // and filling have already been processed during the global cycle, so there is nothing // more to do. assert(state() == ShenandoahOldGeneration::EVACUATING_AFTER_GLOBAL, "Should be evacuating after a global cycle"); abandon_collection_candidates(); transition_to(ShenandoahOldGeneration::WAITING_FOR_BOOTSTRAP); } void ShenandoahOldGeneration::abandon_mixed_evacuations() { switch(state()) { case ShenandoahOldGeneration::EVACUATING: transition_to(ShenandoahOldGeneration::FILLING); break; case ShenandoahOldGeneration::EVACUATING_AFTER_GLOBAL: abandon_collection_candidates(); transition_to(ShenandoahOldGeneration::WAITING_FOR_BOOTSTRAP); break; default: log_warning(gc)("Abandon mixed evacuations in unexpected state: %s", state_name(state())); ShouldNotReachHere(); break; } } void ShenandoahOldGeneration::clear_cards_for(ShenandoahHeapRegion* region) { _card_scan->mark_range_as_empty(region->bottom(), pointer_delta(region->end(), region->bottom())); } void ShenandoahOldGeneration::mark_card_as_dirty(void* location) { _card_scan->mark_card_as_dirty((HeapWord*)location); }