| /* |
| * Copyright (c) 2001, 2018, 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 "precompiled.hpp" |
| #include "gc/g1/dirtyCardQueue.hpp" |
| #include "gc/g1/g1BarrierSet.hpp" |
| #include "gc/g1/g1BlockOffsetTable.inline.hpp" |
| #include "gc/g1/g1CardTable.inline.hpp" |
| #include "gc/g1/g1CollectedHeap.inline.hpp" |
| #include "gc/g1/g1ConcurrentRefine.hpp" |
| #include "gc/g1/g1FromCardCache.hpp" |
| #include "gc/g1/g1GCPhaseTimes.hpp" |
| #include "gc/g1/g1HotCardCache.hpp" |
| #include "gc/g1/g1OopClosures.inline.hpp" |
| #include "gc/g1/g1RootClosures.hpp" |
| #include "gc/g1/g1RemSet.hpp" |
| #include "gc/g1/heapRegion.inline.hpp" |
| #include "gc/g1/heapRegionManager.inline.hpp" |
| #include "gc/g1/heapRegionRemSet.hpp" |
| #include "gc/shared/gcTraceTime.inline.hpp" |
| #include "gc/shared/suspendibleThreadSet.hpp" |
| #include "memory/iterator.hpp" |
| #include "memory/resourceArea.hpp" |
| #include "oops/access.inline.hpp" |
| #include "oops/oop.inline.hpp" |
| #include "runtime/os.hpp" |
| #include "utilities/align.hpp" |
| #include "utilities/globalDefinitions.hpp" |
| #include "utilities/intHisto.hpp" |
| #include "utilities/stack.inline.hpp" |
| #include "utilities/ticks.hpp" |
| |
| // Collects information about the overall remembered set scan progress during an evacuation. |
| class G1RemSetScanState : public CHeapObj<mtGC> { |
| private: |
| class G1ClearCardTableTask : public AbstractGangTask { |
| G1CollectedHeap* _g1h; |
| uint* _dirty_region_list; |
| size_t _num_dirty_regions; |
| size_t _chunk_length; |
| |
| size_t volatile _cur_dirty_regions; |
| public: |
| G1ClearCardTableTask(G1CollectedHeap* g1h, |
| uint* dirty_region_list, |
| size_t num_dirty_regions, |
| size_t chunk_length) : |
| AbstractGangTask("G1 Clear Card Table Task"), |
| _g1h(g1h), |
| _dirty_region_list(dirty_region_list), |
| _num_dirty_regions(num_dirty_regions), |
| _chunk_length(chunk_length), |
| _cur_dirty_regions(0) { |
| |
| assert(chunk_length > 0, "must be"); |
| } |
| |
| static size_t chunk_size() { return M; } |
| |
| void work(uint worker_id) { |
| while (_cur_dirty_regions < _num_dirty_regions) { |
| size_t next = Atomic::add(_chunk_length, &_cur_dirty_regions) - _chunk_length; |
| size_t max = MIN2(next + _chunk_length, _num_dirty_regions); |
| |
| for (size_t i = next; i < max; i++) { |
| HeapRegion* r = _g1h->region_at(_dirty_region_list[i]); |
| if (!r->is_survivor()) { |
| r->clear_cardtable(); |
| } |
| } |
| } |
| } |
| }; |
| |
| size_t _max_regions; |
| |
| // Scan progress for the remembered set of a single region. Transitions from |
| // Unclaimed -> Claimed -> Complete. |
| // At each of the transitions the thread that does the transition needs to perform |
| // some special action once. This is the reason for the extra "Claimed" state. |
| typedef jint G1RemsetIterState; |
| |
| static const G1RemsetIterState Unclaimed = 0; // The remembered set has not been scanned yet. |
| static const G1RemsetIterState Claimed = 1; // The remembered set is currently being scanned. |
| static const G1RemsetIterState Complete = 2; // The remembered set has been completely scanned. |
| |
| G1RemsetIterState volatile* _iter_states; |
| // The current location where the next thread should continue scanning in a region's |
| // remembered set. |
| size_t volatile* _iter_claims; |
| |
| // Temporary buffer holding the regions we used to store remembered set scan duplicate |
| // information. These are also called "dirty". Valid entries are from [0.._cur_dirty_region) |
| uint* _dirty_region_buffer; |
| |
| typedef jbyte IsDirtyRegionState; |
| static const IsDirtyRegionState Clean = 0; |
| static const IsDirtyRegionState Dirty = 1; |
| // Holds a flag for every region whether it is in the _dirty_region_buffer already |
| // to avoid duplicates. Uses jbyte since there are no atomic instructions for bools. |
| IsDirtyRegionState* _in_dirty_region_buffer; |
| size_t _cur_dirty_region; |
| |
| // Creates a snapshot of the current _top values at the start of collection to |
| // filter out card marks that we do not want to scan. |
| class G1ResetScanTopClosure : public HeapRegionClosure { |
| private: |
| HeapWord** _scan_top; |
| public: |
| G1ResetScanTopClosure(HeapWord** scan_top) : _scan_top(scan_top) { } |
| |
| virtual bool do_heap_region(HeapRegion* r) { |
| uint hrm_index = r->hrm_index(); |
| if (!r->in_collection_set() && r->is_old_or_humongous()) { |
| _scan_top[hrm_index] = r->top(); |
| } else { |
| _scan_top[hrm_index] = r->bottom(); |
| } |
| return false; |
| } |
| }; |
| |
| // For each region, contains the maximum top() value to be used during this garbage |
| // collection. Subsumes common checks like filtering out everything but old and |
| // humongous regions outside the collection set. |
| // This is valid because we are not interested in scanning stray remembered set |
| // entries from free or archive regions. |
| HeapWord** _scan_top; |
| public: |
| G1RemSetScanState() : |
| _max_regions(0), |
| _iter_states(NULL), |
| _iter_claims(NULL), |
| _dirty_region_buffer(NULL), |
| _in_dirty_region_buffer(NULL), |
| _cur_dirty_region(0), |
| _scan_top(NULL) { |
| } |
| |
| ~G1RemSetScanState() { |
| if (_iter_states != NULL) { |
| FREE_C_HEAP_ARRAY(G1RemsetIterState, _iter_states); |
| } |
| if (_iter_claims != NULL) { |
| FREE_C_HEAP_ARRAY(size_t, _iter_claims); |
| } |
| if (_dirty_region_buffer != NULL) { |
| FREE_C_HEAP_ARRAY(uint, _dirty_region_buffer); |
| } |
| if (_in_dirty_region_buffer != NULL) { |
| FREE_C_HEAP_ARRAY(IsDirtyRegionState, _in_dirty_region_buffer); |
| } |
| if (_scan_top != NULL) { |
| FREE_C_HEAP_ARRAY(HeapWord*, _scan_top); |
| } |
| } |
| |
| void initialize(uint max_regions) { |
| assert(_iter_states == NULL, "Must not be initialized twice"); |
| assert(_iter_claims == NULL, "Must not be initialized twice"); |
| _max_regions = max_regions; |
| _iter_states = NEW_C_HEAP_ARRAY(G1RemsetIterState, max_regions, mtGC); |
| _iter_claims = NEW_C_HEAP_ARRAY(size_t, max_regions, mtGC); |
| _dirty_region_buffer = NEW_C_HEAP_ARRAY(uint, max_regions, mtGC); |
| _in_dirty_region_buffer = NEW_C_HEAP_ARRAY(IsDirtyRegionState, max_regions, mtGC); |
| _scan_top = NEW_C_HEAP_ARRAY(HeapWord*, max_regions, mtGC); |
| } |
| |
| void reset() { |
| for (uint i = 0; i < _max_regions; i++) { |
| _iter_states[i] = Unclaimed; |
| } |
| |
| G1ResetScanTopClosure cl(_scan_top); |
| G1CollectedHeap::heap()->heap_region_iterate(&cl); |
| |
| memset((void*)_iter_claims, 0, _max_regions * sizeof(size_t)); |
| memset(_in_dirty_region_buffer, Clean, _max_regions * sizeof(IsDirtyRegionState)); |
| _cur_dirty_region = 0; |
| } |
| |
| // Attempt to claim the remembered set of the region for iteration. Returns true |
| // if this call caused the transition from Unclaimed to Claimed. |
| inline bool claim_iter(uint region) { |
| assert(region < _max_regions, "Tried to access invalid region %u", region); |
| if (_iter_states[region] != Unclaimed) { |
| return false; |
| } |
| G1RemsetIterState res = Atomic::cmpxchg(Claimed, &_iter_states[region], Unclaimed); |
| return (res == Unclaimed); |
| } |
| |
| // Try to atomically sets the iteration state to "complete". Returns true for the |
| // thread that caused the transition. |
| inline bool set_iter_complete(uint region) { |
| if (iter_is_complete(region)) { |
| return false; |
| } |
| G1RemsetIterState res = Atomic::cmpxchg(Complete, &_iter_states[region], Claimed); |
| return (res == Claimed); |
| } |
| |
| // Returns true if the region's iteration is complete. |
| inline bool iter_is_complete(uint region) const { |
| assert(region < _max_regions, "Tried to access invalid region %u", region); |
| return _iter_states[region] == Complete; |
| } |
| |
| // The current position within the remembered set of the given region. |
| inline size_t iter_claimed(uint region) const { |
| assert(region < _max_regions, "Tried to access invalid region %u", region); |
| return _iter_claims[region]; |
| } |
| |
| // Claim the next block of cards within the remembered set of the region with |
| // step size. |
| inline size_t iter_claimed_next(uint region, size_t step) { |
| return Atomic::add(step, &_iter_claims[region]) - step; |
| } |
| |
| void add_dirty_region(uint region) { |
| if (_in_dirty_region_buffer[region] == Dirty) { |
| return; |
| } |
| |
| bool marked_as_dirty = Atomic::cmpxchg(Dirty, &_in_dirty_region_buffer[region], Clean) == Clean; |
| if (marked_as_dirty) { |
| size_t allocated = Atomic::add(1u, &_cur_dirty_region) - 1; |
| _dirty_region_buffer[allocated] = region; |
| } |
| } |
| |
| HeapWord* scan_top(uint region_idx) const { |
| return _scan_top[region_idx]; |
| } |
| |
| // Clear the card table of "dirty" regions. |
| void clear_card_table(WorkGang* workers) { |
| if (_cur_dirty_region == 0) { |
| return; |
| } |
| |
| size_t const num_chunks = align_up(_cur_dirty_region * HeapRegion::CardsPerRegion, G1ClearCardTableTask::chunk_size()) / G1ClearCardTableTask::chunk_size(); |
| uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers()); |
| size_t const chunk_length = G1ClearCardTableTask::chunk_size() / HeapRegion::CardsPerRegion; |
| |
| // Iterate over the dirty cards region list. |
| G1ClearCardTableTask cl(G1CollectedHeap::heap(), _dirty_region_buffer, _cur_dirty_region, chunk_length); |
| |
| log_debug(gc, ergo)("Running %s using %u workers for " SIZE_FORMAT " " |
| "units of work for " SIZE_FORMAT " regions.", |
| cl.name(), num_workers, num_chunks, _cur_dirty_region); |
| workers->run_task(&cl, num_workers); |
| |
| #ifndef PRODUCT |
| G1CollectedHeap::heap()->verifier()->verify_card_table_cleanup(); |
| #endif |
| } |
| }; |
| |
| G1RemSet::G1RemSet(G1CollectedHeap* g1h, |
| G1CardTable* ct, |
| G1HotCardCache* hot_card_cache) : |
| _g1h(g1h), |
| _scan_state(new G1RemSetScanState()), |
| _num_conc_refined_cards(0), |
| _ct(ct), |
| _g1p(_g1h->g1_policy()), |
| _hot_card_cache(hot_card_cache), |
| _prev_period_summary() { |
| } |
| |
| G1RemSet::~G1RemSet() { |
| if (_scan_state != NULL) { |
| delete _scan_state; |
| } |
| } |
| |
| uint G1RemSet::num_par_rem_sets() { |
| return DirtyCardQueueSet::num_par_ids() + G1ConcurrentRefine::max_num_threads() + MAX2(ConcGCThreads, ParallelGCThreads); |
| } |
| |
| void G1RemSet::initialize(size_t capacity, uint max_regions) { |
| G1FromCardCache::initialize(num_par_rem_sets(), max_regions); |
| _scan_state->initialize(max_regions); |
| } |
| |
| G1ScanRSForRegionClosure::G1ScanRSForRegionClosure(G1RemSetScanState* scan_state, |
| G1ScanObjsDuringScanRSClosure* scan_obj_on_card, |
| G1ParScanThreadState* pss, |
| uint worker_i) : |
| _g1h(G1CollectedHeap::heap()), |
| _ct(_g1h->card_table()), |
| _pss(pss), |
| _scan_objs_on_card_cl(scan_obj_on_card), |
| _scan_state(scan_state), |
| _worker_i(worker_i), |
| _cards_claimed(0), |
| _cards_scanned(0), |
| _cards_skipped(0), |
| _rem_set_root_scan_time(), |
| _rem_set_trim_partially_time(), |
| _strong_code_root_scan_time(), |
| _strong_code_trim_partially_time() { |
| } |
| |
| void G1ScanRSForRegionClosure::claim_card(size_t card_index, const uint region_idx_for_card){ |
| _ct->set_card_claimed(card_index); |
| _scan_state->add_dirty_region(region_idx_for_card); |
| } |
| |
| void G1ScanRSForRegionClosure::scan_card(MemRegion mr, uint region_idx_for_card) { |
| HeapRegion* const card_region = _g1h->region_at(region_idx_for_card); |
| _scan_objs_on_card_cl->set_region(card_region); |
| card_region->oops_on_card_seq_iterate_careful<true>(mr, _scan_objs_on_card_cl); |
| _scan_objs_on_card_cl->trim_queue_partially(); |
| _cards_scanned++; |
| } |
| |
| void G1ScanRSForRegionClosure::scan_rem_set_roots(HeapRegion* r) { |
| uint const region_idx = r->hrm_index(); |
| |
| if (_scan_state->claim_iter(region_idx)) { |
| // If we ever free the collection set concurrently, we should also |
| // clear the card table concurrently therefore we won't need to |
| // add regions of the collection set to the dirty cards region. |
| _scan_state->add_dirty_region(region_idx); |
| } |
| |
| // We claim cards in blocks so as to reduce the contention. |
| size_t const block_size = G1RSetScanBlockSize; |
| |
| HeapRegionRemSetIterator iter(r->rem_set()); |
| size_t card_index; |
| |
| size_t claimed_card_block = _scan_state->iter_claimed_next(region_idx, block_size); |
| for (size_t current_card = 0; iter.has_next(card_index); current_card++) { |
| if (current_card >= claimed_card_block + block_size) { |
| claimed_card_block = _scan_state->iter_claimed_next(region_idx, block_size); |
| } |
| if (current_card < claimed_card_block) { |
| _cards_skipped++; |
| continue; |
| } |
| _cards_claimed++; |
| |
| // If the card is dirty, then G1 will scan it during Update RS. |
| if (_ct->is_card_claimed(card_index) || _ct->is_card_dirty(card_index)) { |
| continue; |
| } |
| |
| HeapWord* const card_start = _g1h->bot()->address_for_index(card_index); |
| uint const region_idx_for_card = _g1h->addr_to_region(card_start); |
| |
| assert(_g1h->region_at(region_idx_for_card)->is_in_reserved(card_start), |
| "Card start " PTR_FORMAT " to scan outside of region %u", p2i(card_start), _g1h->region_at(region_idx_for_card)->hrm_index()); |
| HeapWord* const top = _scan_state->scan_top(region_idx_for_card); |
| if (card_start >= top) { |
| continue; |
| } |
| |
| // We claim lazily (so races are possible but they're benign), which reduces the |
| // number of duplicate scans (the rsets of the regions in the cset can intersect). |
| // Claim the card after checking bounds above: the remembered set may contain |
| // random cards into current survivor, and we would then have an incorrectly |
| // claimed card in survivor space. Card table clear does not reset the card table |
| // of survivor space regions. |
| claim_card(card_index, region_idx_for_card); |
| |
| MemRegion const mr(card_start, MIN2(card_start + BOTConstants::N_words, top)); |
| |
| scan_card(mr, region_idx_for_card); |
| } |
| } |
| |
| void G1ScanRSForRegionClosure::scan_strong_code_roots(HeapRegion* r) { |
| r->strong_code_roots_do(_pss->closures()->weak_codeblobs()); |
| } |
| |
| bool G1ScanRSForRegionClosure::do_heap_region(HeapRegion* r) { |
| assert(r->in_collection_set(), |
| "Should only be called on elements of the collection set but region %u is not.", |
| r->hrm_index()); |
| uint const region_idx = r->hrm_index(); |
| |
| // Do an early out if we know we are complete. |
| if (_scan_state->iter_is_complete(region_idx)) { |
| return false; |
| } |
| |
| { |
| G1EvacPhaseWithTrimTimeTracker timer(_pss, _rem_set_root_scan_time, _rem_set_trim_partially_time); |
| scan_rem_set_roots(r); |
| } |
| |
| if (_scan_state->set_iter_complete(region_idx)) { |
| G1EvacPhaseWithTrimTimeTracker timer(_pss, _strong_code_root_scan_time, _strong_code_trim_partially_time); |
| // Scan the strong code root list attached to the current region |
| scan_strong_code_roots(r); |
| } |
| return false; |
| } |
| |
| void G1RemSet::scan_rem_set(G1ParScanThreadState* pss, uint worker_i) { |
| G1ScanObjsDuringScanRSClosure scan_cl(_g1h, pss); |
| G1ScanRSForRegionClosure cl(_scan_state, &scan_cl, pss, worker_i); |
| _g1h->collection_set_iterate_from(&cl, worker_i); |
| |
| G1GCPhaseTimes* p = _g1p->phase_times(); |
| |
| p->record_time_secs(G1GCPhaseTimes::ScanRS, worker_i, cl.rem_set_root_scan_time().seconds()); |
| p->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_i, cl.rem_set_trim_partially_time().seconds()); |
| |
| p->record_thread_work_item(G1GCPhaseTimes::ScanRS, worker_i, cl.cards_scanned(), G1GCPhaseTimes::ScanRSScannedCards); |
| p->record_thread_work_item(G1GCPhaseTimes::ScanRS, worker_i, cl.cards_claimed(), G1GCPhaseTimes::ScanRSClaimedCards); |
| p->record_thread_work_item(G1GCPhaseTimes::ScanRS, worker_i, cl.cards_skipped(), G1GCPhaseTimes::ScanRSSkippedCards); |
| |
| p->record_time_secs(G1GCPhaseTimes::CodeRoots, worker_i, cl.strong_code_root_scan_time().seconds()); |
| p->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_i, cl.strong_code_root_trim_partially_time().seconds()); |
| } |
| |
| // Closure used for updating rem sets. Only called during an evacuation pause. |
| class G1RefineCardClosure: public CardTableEntryClosure { |
| G1RemSet* _g1rs; |
| G1ScanObjsDuringUpdateRSClosure* _update_rs_cl; |
| |
| size_t _cards_scanned; |
| size_t _cards_skipped; |
| public: |
| G1RefineCardClosure(G1CollectedHeap* g1h, G1ScanObjsDuringUpdateRSClosure* update_rs_cl) : |
| _g1rs(g1h->g1_rem_set()), _update_rs_cl(update_rs_cl), _cards_scanned(0), _cards_skipped(0) |
| {} |
| |
| bool do_card_ptr(jbyte* card_ptr, uint worker_i) { |
| // The only time we care about recording cards that |
| // contain references that point into the collection set |
| // is during RSet updating within an evacuation pause. |
| // In this case worker_i should be the id of a GC worker thread. |
| assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause"); |
| |
| bool card_scanned = _g1rs->refine_card_during_gc(card_ptr, _update_rs_cl); |
| |
| if (card_scanned) { |
| _update_rs_cl->trim_queue_partially(); |
| _cards_scanned++; |
| } else { |
| _cards_skipped++; |
| } |
| return true; |
| } |
| |
| size_t cards_scanned() const { return _cards_scanned; } |
| size_t cards_skipped() const { return _cards_skipped; } |
| }; |
| |
| void G1RemSet::update_rem_set(G1ParScanThreadState* pss, uint worker_i) { |
| G1GCPhaseTimes* p = _g1p->phase_times(); |
| |
| // Apply closure to log entries in the HCC. |
| if (G1HotCardCache::default_use_cache()) { |
| G1EvacPhaseTimesTracker x(p, pss, G1GCPhaseTimes::ScanHCC, worker_i); |
| |
| G1ScanObjsDuringUpdateRSClosure scan_hcc_cl(_g1h, pss, worker_i); |
| G1RefineCardClosure refine_card_cl(_g1h, &scan_hcc_cl); |
| _g1h->iterate_hcc_closure(&refine_card_cl, worker_i); |
| } |
| |
| // Now apply the closure to all remaining log entries. |
| { |
| G1EvacPhaseTimesTracker x(p, pss, G1GCPhaseTimes::UpdateRS, worker_i); |
| |
| G1ScanObjsDuringUpdateRSClosure update_rs_cl(_g1h, pss, worker_i); |
| G1RefineCardClosure refine_card_cl(_g1h, &update_rs_cl); |
| _g1h->iterate_dirty_card_closure(&refine_card_cl, worker_i); |
| |
| p->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, refine_card_cl.cards_scanned(), G1GCPhaseTimes::UpdateRSScannedCards); |
| p->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, refine_card_cl.cards_skipped(), G1GCPhaseTimes::UpdateRSSkippedCards); |
| } |
| } |
| |
| void G1RemSet::cleanupHRRS() { |
| HeapRegionRemSet::cleanup(); |
| } |
| |
| void G1RemSet::oops_into_collection_set_do(G1ParScanThreadState* pss, uint worker_i) { |
| update_rem_set(pss, worker_i); |
| scan_rem_set(pss, worker_i);; |
| } |
| |
| void G1RemSet::prepare_for_oops_into_collection_set_do() { |
| DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set(); |
| dcqs.concatenate_logs(); |
| |
| _scan_state->reset(); |
| } |
| |
| void G1RemSet::cleanup_after_oops_into_collection_set_do() { |
| G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times(); |
| |
| // Set all cards back to clean. |
| double start = os::elapsedTime(); |
| _scan_state->clear_card_table(_g1h->workers()); |
| phase_times->record_clear_ct_time((os::elapsedTime() - start) * 1000.0); |
| } |
| |
| inline void check_card_ptr(jbyte* card_ptr, G1CardTable* ct) { |
| #ifdef ASSERT |
| G1CollectedHeap* g1h = G1CollectedHeap::heap(); |
| assert(g1h->is_in_exact(ct->addr_for(card_ptr)), |
| "Card at " PTR_FORMAT " index " SIZE_FORMAT " representing heap at " PTR_FORMAT " (%u) must be in committed heap", |
| p2i(card_ptr), |
| ct->index_for(ct->addr_for(card_ptr)), |
| p2i(ct->addr_for(card_ptr)), |
| g1h->addr_to_region(ct->addr_for(card_ptr))); |
| #endif |
| } |
| |
| void G1RemSet::refine_card_concurrently(jbyte* card_ptr, |
| uint worker_i) { |
| assert(!_g1h->is_gc_active(), "Only call concurrently"); |
| |
| check_card_ptr(card_ptr, _ct); |
| |
| // If the card is no longer dirty, nothing to do. |
| if (*card_ptr != G1CardTable::dirty_card_val()) { |
| return; |
| } |
| |
| // Construct the region representing the card. |
| HeapWord* start = _ct->addr_for(card_ptr); |
| // And find the region containing it. |
| HeapRegion* r = _g1h->heap_region_containing(start); |
| |
| // This check is needed for some uncommon cases where we should |
| // ignore the card. |
| // |
| // The region could be young. Cards for young regions are |
| // distinctly marked (set to g1_young_gen), so the post-barrier will |
| // filter them out. However, that marking is performed |
| // concurrently. A write to a young object could occur before the |
| // card has been marked young, slipping past the filter. |
| // |
| // The card could be stale, because the region has been freed since |
| // the card was recorded. In this case the region type could be |
| // anything. If (still) free or (reallocated) young, just ignore |
| // it. If (reallocated) old or humongous, the later card trimming |
| // and additional checks in iteration may detect staleness. At |
| // worst, we end up processing a stale card unnecessarily. |
| // |
| // In the normal (non-stale) case, the synchronization between the |
| // enqueueing of the card and processing it here will have ensured |
| // we see the up-to-date region type here. |
| if (!r->is_old_or_humongous()) { |
| return; |
| } |
| |
| // The result from the hot card cache insert call is either: |
| // * pointer to the current card |
| // (implying that the current card is not 'hot'), |
| // * null |
| // (meaning we had inserted the card ptr into the "hot" card cache, |
| // which had some headroom), |
| // * a pointer to a "hot" card that was evicted from the "hot" cache. |
| // |
| |
| if (_hot_card_cache->use_cache()) { |
| assert(!SafepointSynchronize::is_at_safepoint(), "sanity"); |
| |
| const jbyte* orig_card_ptr = card_ptr; |
| card_ptr = _hot_card_cache->insert(card_ptr); |
| if (card_ptr == NULL) { |
| // There was no eviction. Nothing to do. |
| return; |
| } else if (card_ptr != orig_card_ptr) { |
| // Original card was inserted and an old card was evicted. |
| start = _ct->addr_for(card_ptr); |
| r = _g1h->heap_region_containing(start); |
| |
| // Check whether the region formerly in the cache should be |
| // ignored, as discussed earlier for the original card. The |
| // region could have been freed while in the cache. |
| if (!r->is_old_or_humongous()) { |
| return; |
| } |
| } // Else we still have the original card. |
| } |
| |
| // Trim the region designated by the card to what's been allocated |
| // in the region. The card could be stale, or the card could cover |
| // (part of) an object at the end of the allocated space and extend |
| // beyond the end of allocation. |
| |
| // Non-humongous objects are only allocated in the old-gen during |
| // GC, so if region is old then top is stable. Humongous object |
| // allocation sets top last; if top has not yet been set, this is |
| // a stale card and we'll end up with an empty intersection. If |
| // this is not a stale card, the synchronization between the |
| // enqueuing of the card and processing it here will have ensured |
| // we see the up-to-date top here. |
| HeapWord* scan_limit = r->top(); |
| |
| if (scan_limit <= start) { |
| // If the trimmed region is empty, the card must be stale. |
| return; |
| } |
| |
| // Okay to clean and process the card now. There are still some |
| // stale card cases that may be detected by iteration and dealt with |
| // as iteration failure. |
| *const_cast<volatile jbyte*>(card_ptr) = G1CardTable::clean_card_val(); |
| |
| // This fence serves two purposes. First, the card must be cleaned |
| // before processing the contents. Second, we can't proceed with |
| // processing until after the read of top, for synchronization with |
| // possibly concurrent humongous object allocation. It's okay that |
| // reading top and reading type were racy wrto each other. We need |
| // both set, in any order, to proceed. |
| OrderAccess::fence(); |
| |
| // Don't use addr_for(card_ptr + 1) which can ask for |
| // a card beyond the heap. |
| HeapWord* end = start + G1CardTable::card_size_in_words; |
| MemRegion dirty_region(start, MIN2(scan_limit, end)); |
| assert(!dirty_region.is_empty(), "sanity"); |
| |
| G1ConcurrentRefineOopClosure conc_refine_cl(_g1h, worker_i); |
| |
| bool card_processed = |
| r->oops_on_card_seq_iterate_careful<false>(dirty_region, &conc_refine_cl); |
| |
| // If unable to process the card then we encountered an unparsable |
| // part of the heap (e.g. a partially allocated object) while |
| // processing a stale card. Despite the card being stale, redirty |
| // and re-enqueue, because we've already cleaned the card. Without |
| // this we could incorrectly discard a non-stale card. |
| if (!card_processed) { |
| // The card might have gotten re-dirtied and re-enqueued while we |
| // worked. (In fact, it's pretty likely.) |
| if (*card_ptr != G1CardTable::dirty_card_val()) { |
| *card_ptr = G1CardTable::dirty_card_val(); |
| MutexLockerEx x(Shared_DirtyCardQ_lock, |
| Mutex::_no_safepoint_check_flag); |
| DirtyCardQueue* sdcq = |
| G1BarrierSet::dirty_card_queue_set().shared_dirty_card_queue(); |
| sdcq->enqueue(card_ptr); |
| } |
| } else { |
| _num_conc_refined_cards++; // Unsynchronized update, only used for logging. |
| } |
| } |
| |
| bool G1RemSet::refine_card_during_gc(jbyte* card_ptr, |
| G1ScanObjsDuringUpdateRSClosure* update_rs_cl) { |
| assert(_g1h->is_gc_active(), "Only call during GC"); |
| |
| check_card_ptr(card_ptr, _ct); |
| |
| // If the card is no longer dirty, nothing to do. This covers cards that were already |
| // scanned as parts of the remembered sets. |
| if (*card_ptr != G1CardTable::dirty_card_val()) { |
| return false; |
| } |
| |
| // We claim lazily (so races are possible but they're benign), which reduces the |
| // number of potential duplicate scans (multiple threads may enqueue the same card twice). |
| *card_ptr = G1CardTable::clean_card_val() | G1CardTable::claimed_card_val(); |
| |
| // Construct the region representing the card. |
| HeapWord* card_start = _ct->addr_for(card_ptr); |
| // And find the region containing it. |
| uint const card_region_idx = _g1h->addr_to_region(card_start); |
| |
| _scan_state->add_dirty_region(card_region_idx); |
| HeapWord* scan_limit = _scan_state->scan_top(card_region_idx); |
| if (scan_limit <= card_start) { |
| // If the card starts above the area in the region containing objects to scan, skip it. |
| return false; |
| } |
| |
| // Don't use addr_for(card_ptr + 1) which can ask for |
| // a card beyond the heap. |
| HeapWord* card_end = card_start + G1CardTable::card_size_in_words; |
| MemRegion dirty_region(card_start, MIN2(scan_limit, card_end)); |
| assert(!dirty_region.is_empty(), "sanity"); |
| |
| HeapRegion* const card_region = _g1h->region_at(card_region_idx); |
| update_rs_cl->set_region(card_region); |
| bool card_processed = card_region->oops_on_card_seq_iterate_careful<true>(dirty_region, update_rs_cl); |
| assert(card_processed, "must be"); |
| return true; |
| } |
| |
| void G1RemSet::print_periodic_summary_info(const char* header, uint period_count) { |
| if ((G1SummarizeRSetStatsPeriod > 0) && log_is_enabled(Trace, gc, remset) && |
| (period_count % G1SummarizeRSetStatsPeriod == 0)) { |
| |
| G1RemSetSummary current(this); |
| _prev_period_summary.subtract_from(¤t); |
| |
| Log(gc, remset) log; |
| log.trace("%s", header); |
| ResourceMark rm; |
| LogStream ls(log.trace()); |
| _prev_period_summary.print_on(&ls); |
| |
| _prev_period_summary.set(¤t); |
| } |
| } |
| |
| void G1RemSet::print_summary_info() { |
| Log(gc, remset, exit) log; |
| if (log.is_trace()) { |
| log.trace(" Cumulative RS summary"); |
| G1RemSetSummary current(this); |
| ResourceMark rm; |
| LogStream ls(log.trace()); |
| current.print_on(&ls); |
| } |
| } |
| |
| class G1RebuildRemSetTask: public AbstractGangTask { |
| // Aggregate the counting data that was constructed concurrently |
| // with marking. |
| class G1RebuildRemSetHeapRegionClosure : public HeapRegionClosure { |
| G1ConcurrentMark* _cm; |
| G1RebuildRemSetClosure _update_cl; |
| |
| // Applies _update_cl to the references of the given object, limiting objArrays |
| // to the given MemRegion. Returns the amount of words actually scanned. |
| size_t scan_for_references(oop const obj, MemRegion mr) { |
| size_t const obj_size = obj->size(); |
| // All non-objArrays and objArrays completely within the mr |
| // can be scanned without passing the mr. |
| if (!obj->is_objArray() || mr.contains(MemRegion((HeapWord*)obj, obj_size))) { |
| obj->oop_iterate(&_update_cl); |
| return obj_size; |
| } |
| // This path is for objArrays crossing the given MemRegion. Only scan the |
| // area within the MemRegion. |
| obj->oop_iterate(&_update_cl, mr); |
| return mr.intersection(MemRegion((HeapWord*)obj, obj_size)).word_size(); |
| } |
| |
| // A humongous object is live (with respect to the scanning) either |
| // a) it is marked on the bitmap as such |
| // b) its TARS is larger than TAMS, i.e. has been allocated during marking. |
| bool is_humongous_live(oop const humongous_obj, const G1CMBitMap* const bitmap, HeapWord* tams, HeapWord* tars) const { |
| return bitmap->is_marked(humongous_obj) || (tars > tams); |
| } |
| |
| // Iterator over the live objects within the given MemRegion. |
| class LiveObjIterator : public StackObj { |
| const G1CMBitMap* const _bitmap; |
| const HeapWord* _tams; |
| const MemRegion _mr; |
| HeapWord* _current; |
| |
| bool is_below_tams() const { |
| return _current < _tams; |
| } |
| |
| bool is_live(HeapWord* obj) const { |
| return !is_below_tams() || _bitmap->is_marked(obj); |
| } |
| |
| HeapWord* bitmap_limit() const { |
| return MIN2(const_cast<HeapWord*>(_tams), _mr.end()); |
| } |
| |
| void move_if_below_tams() { |
| if (is_below_tams() && has_next()) { |
| _current = _bitmap->get_next_marked_addr(_current, bitmap_limit()); |
| } |
| } |
| public: |
| LiveObjIterator(const G1CMBitMap* const bitmap, const HeapWord* tams, const MemRegion mr, HeapWord* first_oop_into_mr) : |
| _bitmap(bitmap), |
| _tams(tams), |
| _mr(mr), |
| _current(first_oop_into_mr) { |
| |
| assert(_current <= _mr.start(), |
| "First oop " PTR_FORMAT " should extend into mr [" PTR_FORMAT ", " PTR_FORMAT ")", |
| p2i(first_oop_into_mr), p2i(mr.start()), p2i(mr.end())); |
| |
| // Step to the next live object within the MemRegion if needed. |
| if (is_live(_current)) { |
| // Non-objArrays were scanned by the previous part of that region. |
| if (_current < mr.start() && !oop(_current)->is_objArray()) { |
| _current += oop(_current)->size(); |
| // We might have positioned _current on a non-live object. Reposition to the next |
| // live one if needed. |
| move_if_below_tams(); |
| } |
| } else { |
| // The object at _current can only be dead if below TAMS, so we can use the bitmap. |
| // immediately. |
| _current = _bitmap->get_next_marked_addr(_current, bitmap_limit()); |
| assert(_current == _mr.end() || is_live(_current), |
| "Current " PTR_FORMAT " should be live (%s) or beyond the end of the MemRegion (" PTR_FORMAT ")", |
| p2i(_current), BOOL_TO_STR(is_live(_current)), p2i(_mr.end())); |
| } |
| } |
| |
| void move_to_next() { |
| _current += next()->size(); |
| move_if_below_tams(); |
| } |
| |
| oop next() const { |
| oop result = oop(_current); |
| assert(is_live(_current), |
| "Object " PTR_FORMAT " must be live TAMS " PTR_FORMAT " below %d mr " PTR_FORMAT " " PTR_FORMAT " outside %d", |
| p2i(_current), p2i(_tams), _tams > _current, p2i(_mr.start()), p2i(_mr.end()), _mr.contains(result)); |
| return result; |
| } |
| |
| bool has_next() const { |
| return _current < _mr.end(); |
| } |
| }; |
| |
| // Rebuild remembered sets in the part of the region specified by mr and hr. |
| // Objects between the bottom of the region and the TAMS are checked for liveness |
| // using the given bitmap. Objects between TAMS and TARS are assumed to be live. |
| // Returns the number of live words between bottom and TAMS. |
| size_t rebuild_rem_set_in_region(const G1CMBitMap* const bitmap, |
| HeapWord* const top_at_mark_start, |
| HeapWord* const top_at_rebuild_start, |
| HeapRegion* hr, |
| MemRegion mr) { |
| size_t marked_words = 0; |
| |
| if (hr->is_humongous()) { |
| oop const humongous_obj = oop(hr->humongous_start_region()->bottom()); |
| if (is_humongous_live(humongous_obj, bitmap, top_at_mark_start, top_at_rebuild_start)) { |
| // We need to scan both [bottom, TAMS) and [TAMS, top_at_rebuild_start); |
| // however in case of humongous objects it is sufficient to scan the encompassing |
| // area (top_at_rebuild_start is always larger or equal to TAMS) as one of the |
| // two areas will be zero sized. I.e. TAMS is either |
| // the same as bottom or top(_at_rebuild_start). There is no way TAMS has a different |
| // value: this would mean that TAMS points somewhere into the object. |
| assert(hr->top() == top_at_mark_start || hr->top() == top_at_rebuild_start, |
| "More than one object in the humongous region?"); |
| humongous_obj->oop_iterate(&_update_cl, mr); |
| return top_at_mark_start != hr->bottom() ? mr.intersection(MemRegion((HeapWord*)humongous_obj, humongous_obj->size())).byte_size() : 0; |
| } else { |
| return 0; |
| } |
| } |
| |
| for (LiveObjIterator it(bitmap, top_at_mark_start, mr, hr->block_start(mr.start())); it.has_next(); it.move_to_next()) { |
| oop obj = it.next(); |
| size_t scanned_size = scan_for_references(obj, mr); |
| if ((HeapWord*)obj < top_at_mark_start) { |
| marked_words += scanned_size; |
| } |
| } |
| |
| return marked_words * HeapWordSize; |
| } |
| public: |
| G1RebuildRemSetHeapRegionClosure(G1CollectedHeap* g1h, |
| G1ConcurrentMark* cm, |
| uint worker_id) : |
| HeapRegionClosure(), |
| _cm(cm), |
| _update_cl(g1h, worker_id) { } |
| |
| bool do_heap_region(HeapRegion* hr) { |
| if (_cm->has_aborted()) { |
| return true; |
| } |
| |
| uint const region_idx = hr->hrm_index(); |
| DEBUG_ONLY(HeapWord* const top_at_rebuild_start_check = _cm->top_at_rebuild_start(region_idx);) |
| assert(top_at_rebuild_start_check == NULL || |
| top_at_rebuild_start_check > hr->bottom(), |
| "A TARS (" PTR_FORMAT ") == bottom() (" PTR_FORMAT ") indicates the old region %u is empty (%s)", |
| p2i(top_at_rebuild_start_check), p2i(hr->bottom()), region_idx, hr->get_type_str()); |
| |
| size_t total_marked_bytes = 0; |
| size_t const chunk_size_in_words = G1RebuildRemSetChunkSize / HeapWordSize; |
| |
| HeapWord* const top_at_mark_start = hr->prev_top_at_mark_start(); |
| |
| HeapWord* cur = hr->bottom(); |
| while (cur < hr->end()) { |
| // After every iteration (yield point) we need to check whether the region's |
| // TARS changed due to e.g. eager reclaim. |
| HeapWord* const top_at_rebuild_start = _cm->top_at_rebuild_start(region_idx); |
| if (top_at_rebuild_start == NULL) { |
| return false; |
| } |
| |
| MemRegion next_chunk = MemRegion(hr->bottom(), top_at_rebuild_start).intersection(MemRegion(cur, chunk_size_in_words)); |
| if (next_chunk.is_empty()) { |
| break; |
| } |
| |
| const Ticks start = Ticks::now(); |
| size_t marked_bytes = rebuild_rem_set_in_region(_cm->prev_mark_bitmap(), |
| top_at_mark_start, |
| top_at_rebuild_start, |
| hr, |
| next_chunk); |
| Tickspan time = Ticks::now() - start; |
| |
| log_trace(gc, remset, tracking)("Rebuilt region %u " |
| "live " SIZE_FORMAT " " |
| "time %.3fms " |
| "marked bytes " SIZE_FORMAT " " |
| "bot " PTR_FORMAT " " |
| "TAMS " PTR_FORMAT " " |
| "TARS " PTR_FORMAT, |
| region_idx, |
| _cm->liveness(region_idx) * HeapWordSize, |
| time.seconds() * 1000.0, |
| marked_bytes, |
| p2i(hr->bottom()), |
| p2i(top_at_mark_start), |
| p2i(top_at_rebuild_start)); |
| |
| if (marked_bytes > 0) { |
| total_marked_bytes += marked_bytes; |
| } |
| cur += chunk_size_in_words; |
| |
| _cm->do_yield_check(); |
| if (_cm->has_aborted()) { |
| return true; |
| } |
| } |
| // In the final iteration of the loop the region might have been eagerly reclaimed. |
| // Simply filter out those regions. We can not just use region type because there |
| // might have already been new allocations into these regions. |
| DEBUG_ONLY(HeapWord* const top_at_rebuild_start = _cm->top_at_rebuild_start(region_idx);) |
| assert(top_at_rebuild_start == NULL || |
| total_marked_bytes == hr->marked_bytes(), |
| "Marked bytes " SIZE_FORMAT " for region %u (%s) in [bottom, TAMS) do not match calculated marked bytes " SIZE_FORMAT " " |
| "(" PTR_FORMAT " " PTR_FORMAT " " PTR_FORMAT ")", |
| total_marked_bytes, hr->hrm_index(), hr->get_type_str(), hr->marked_bytes(), |
| p2i(hr->bottom()), p2i(top_at_mark_start), p2i(top_at_rebuild_start)); |
| // Abort state may have changed after the yield check. |
| return _cm->has_aborted(); |
| } |
| }; |
| |
| HeapRegionClaimer _hr_claimer; |
| G1ConcurrentMark* _cm; |
| |
| uint _worker_id_offset; |
| public: |
| G1RebuildRemSetTask(G1ConcurrentMark* cm, |
| uint n_workers, |
| uint worker_id_offset) : |
| AbstractGangTask("G1 Rebuild Remembered Set"), |
| _cm(cm), |
| _hr_claimer(n_workers), |
| _worker_id_offset(worker_id_offset) { |
| } |
| |
| void work(uint worker_id) { |
| SuspendibleThreadSetJoiner sts_join; |
| |
| G1CollectedHeap* g1h = G1CollectedHeap::heap(); |
| |
| G1RebuildRemSetHeapRegionClosure cl(g1h, _cm, _worker_id_offset + worker_id); |
| g1h->heap_region_par_iterate_from_worker_offset(&cl, &_hr_claimer, worker_id); |
| } |
| }; |
| |
| void G1RemSet::rebuild_rem_set(G1ConcurrentMark* cm, |
| WorkGang* workers, |
| uint worker_id_offset) { |
| uint num_workers = workers->active_workers(); |
| |
| G1RebuildRemSetTask cl(cm, |
| num_workers, |
| worker_id_offset); |
| workers->run_task(&cl, num_workers); |
| } |
