--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/g1/g1RemSet.cpp Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,788 @@
+/*
+ * Copyright (c) 2001, 2017, 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/concurrentG1Refine.hpp"
+#include "gc/g1/dirtyCardQueue.hpp"
+#include "gc/g1/g1BlockOffsetTable.inline.hpp"
+#include "gc/g1/g1CollectedHeap.inline.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/g1RemSet.inline.hpp"
+#include "gc/g1/g1SATBCardTableModRefBS.inline.hpp"
+#include "gc/g1/heapRegion.inline.hpp"
+#include "gc/g1/heapRegionManager.inline.hpp"
+#include "gc/g1/heapRegionRemSet.hpp"
+#include "gc/g1/suspendibleThreadSet.hpp"
+#include "gc/shared/gcTraceTime.inline.hpp"
+#include "memory/iterator.hpp"
+#include "memory/resourceArea.hpp"
+#include "oops/oop.inline.hpp"
+#include "utilities/align.hpp"
+#include "utilities/globalDefinitions.hpp"
+#include "utilities/intHisto.hpp"
+#include "utilities/stack.inline.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) {
+ G1SATBCardTableModRefBS* ct_bs = _g1h->g1_barrier_set();
+
+ 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()) {
+ ct_bs->clear(MemRegion(r->bottom(), r->end()));
+ }
+ }
+ }
+ }
+ };
+
+ 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 doHeapRegion(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;
+ }
+ jint res = Atomic::cmpxchg(Claimed, (jint*)(&_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;
+ }
+ jint res = Atomic::cmpxchg(Complete, (jint*)(&_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
+ // Need to synchronize with concurrent cleanup since it needs to
+ // finish its card table clearing before we can verify.
+ G1CollectedHeap::heap()->wait_while_free_regions_coming();
+ G1CollectedHeap::heap()->verifier()->verify_card_table_cleanup();
+#endif
+ }
+};
+
+G1RemSet::G1RemSet(G1CollectedHeap* g1,
+ CardTableModRefBS* ct_bs,
+ G1HotCardCache* hot_card_cache) :
+ _g1(g1),
+ _scan_state(new G1RemSetScanState()),
+ _num_conc_refined_cards(0),
+ _ct_bs(ct_bs),
+ _g1p(_g1->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 MAX2(DirtyCardQueueSet::num_par_ids() + ConcurrentG1Refine::thread_num(), ParallelGCThreads);
+}
+
+void G1RemSet::initialize(size_t capacity, uint max_regions) {
+ G1FromCardCache::initialize(num_par_rem_sets(), max_regions);
+ _scan_state->initialize(max_regions);
+ {
+ GCTraceTime(Debug, gc, marking)("Initialize Card Live Data");
+ _card_live_data.initialize(capacity, max_regions);
+ }
+ if (G1PretouchAuxiliaryMemory) {
+ GCTraceTime(Debug, gc, marking)("Pre-Touch Card Live Data");
+ _card_live_data.pretouch();
+ }
+}
+
+G1ScanRSForRegionClosure::G1ScanRSForRegionClosure(G1RemSetScanState* scan_state,
+ G1ScanObjsDuringScanRSClosure* scan_obj_on_card,
+ CodeBlobClosure* code_root_cl,
+ uint worker_i) :
+ _scan_state(scan_state),
+ _scan_objs_on_card_cl(scan_obj_on_card),
+ _code_root_cl(code_root_cl),
+ _strong_code_root_scan_time_sec(0.0),
+ _cards_claimed(0),
+ _cards_scanned(0),
+ _cards_skipped(0),
+ _worker_i(worker_i) {
+ _g1h = G1CollectedHeap::heap();
+ _bot = _g1h->bot();
+ _ct_bs = _g1h->g1_barrier_set();
+}
+
+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);
+ _cards_scanned++;
+}
+
+void G1ScanRSForRegionClosure::scan_strong_code_roots(HeapRegion* r) {
+ double scan_start = os::elapsedTime();
+ r->strong_code_roots_do(_code_root_cl);
+ _strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start);
+}
+
+void G1ScanRSForRegionClosure::claim_card(size_t card_index, const uint region_idx_for_card){
+ _ct_bs->set_card_claimed(card_index);
+ _scan_state->add_dirty_region(region_idx_for_card);
+}
+
+bool G1ScanRSForRegionClosure::doHeapRegion(HeapRegion* r) {
+ assert(r->in_collection_set(), "should only be called on elements of CS.");
+ uint region_idx = r->hrm_index();
+
+ if (_scan_state->iter_is_complete(region_idx)) {
+ return false;
+ }
+ 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_bs->is_card_claimed(card_index) || _ct_bs->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);
+ }
+ if (_scan_state->set_iter_complete(region_idx)) {
+ // 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,
+ CodeBlobClosure* heap_region_codeblobs,
+ uint worker_i) {
+ double rs_time_start = os::elapsedTime();
+
+ G1ScanObjsDuringScanRSClosure scan_cl(_g1, pss);
+ G1ScanRSForRegionClosure cl(_scan_state, &scan_cl, heap_region_codeblobs, worker_i);
+ _g1->collection_set_iterate_from(&cl, worker_i);
+
+ double scan_rs_time_sec = (os::elapsedTime() - rs_time_start) -
+ cl.strong_code_root_scan_time_sec();
+
+ G1GCPhaseTimes* p = _g1p->phase_times();
+
+ p->record_time_secs(G1GCPhaseTimes::ScanRS, worker_i, scan_rs_time_sec);
+ 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_sec());
+}
+
+// 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) {
+ _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) {
+ G1ScanObjsDuringUpdateRSClosure update_rs_cl(_g1, pss, worker_i);
+ G1RefineCardClosure refine_card_cl(_g1, &update_rs_cl);
+
+ G1GCParPhaseTimesTracker x(_g1p->phase_times(), G1GCPhaseTimes::UpdateRS, worker_i);
+ if (G1HotCardCache::default_use_cache()) {
+ // Apply the closure to the entries of the hot card cache.
+ G1GCParPhaseTimesTracker y(_g1p->phase_times(), G1GCPhaseTimes::ScanHCC, worker_i);
+ _g1->iterate_hcc_closure(&refine_card_cl, worker_i);
+ }
+ // Apply the closure to all remaining log entries.
+ _g1->iterate_dirty_card_closure(&refine_card_cl, worker_i);
+
+ G1GCPhaseTimes* p = _g1p->phase_times();
+ 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,
+ CodeBlobClosure* heap_region_codeblobs,
+ uint worker_i) {
+ update_rem_set(pss, worker_i);
+ scan_rem_set(pss, heap_region_codeblobs, worker_i);;
+}
+
+void G1RemSet::prepare_for_oops_into_collection_set_do() {
+ DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
+ dcqs.concatenate_logs();
+
+ _scan_state->reset();
+}
+
+void G1RemSet::cleanup_after_oops_into_collection_set_do() {
+ G1GCPhaseTimes* phase_times = _g1->g1_policy()->phase_times();
+
+ // Set all cards back to clean.
+ double start = os::elapsedTime();
+ _scan_state->clear_card_table(_g1->workers());
+ phase_times->record_clear_ct_time((os::elapsedTime() - start) * 1000.0);
+}
+
+class G1ScrubRSClosure: public HeapRegionClosure {
+ G1CollectedHeap* _g1h;
+ G1CardLiveData* _live_data;
+public:
+ G1ScrubRSClosure(G1CardLiveData* live_data) :
+ _g1h(G1CollectedHeap::heap()),
+ _live_data(live_data) { }
+
+ bool doHeapRegion(HeapRegion* r) {
+ if (!r->is_continues_humongous()) {
+ r->rem_set()->scrub(_live_data);
+ }
+ return false;
+ }
+};
+
+void G1RemSet::scrub(uint worker_num, HeapRegionClaimer *hrclaimer) {
+ G1ScrubRSClosure scrub_cl(&_card_live_data);
+ _g1->heap_region_par_iterate(&scrub_cl, worker_num, hrclaimer);
+}
+
+inline void check_card_ptr(jbyte* card_ptr, CardTableModRefBS* ct_bs) {
+#ifdef ASSERT
+ G1CollectedHeap* g1 = G1CollectedHeap::heap();
+ assert(g1->is_in_exact(ct_bs->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_bs->index_for(ct_bs->addr_for(card_ptr)),
+ p2i(ct_bs->addr_for(card_ptr)),
+ g1->addr_to_region(ct_bs->addr_for(card_ptr)));
+#endif
+}
+
+void G1RemSet::refine_card_concurrently(jbyte* card_ptr,
+ uint worker_i) {
+ assert(!_g1->is_gc_active(), "Only call concurrently");
+
+ check_card_ptr(card_ptr, _ct_bs);
+
+ // If the card is no longer dirty, nothing to do.
+ if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
+ return;
+ }
+
+ // Construct the region representing the card.
+ HeapWord* start = _ct_bs->addr_for(card_ptr);
+ // And find the region containing it.
+ HeapRegion* r = _g1->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;
+ }
+
+ // While we are processing RSet buffers during the collection, we
+ // actually don't want to scan any cards on the collection set,
+ // since we don't want to update remembered sets with entries that
+ // point into the collection set, given that live objects from the
+ // collection set are about to move and such entries will be stale
+ // very soon. This change also deals with a reliability issue which
+ // involves scanning a card in the collection set and coming across
+ // an array that was being chunked and looking malformed. Note,
+ // however, that if evacuation fails, we have to scan any objects
+ // that were not moved and create any missing entries.
+ if (r->in_collection_set()) {
+ 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_bs->addr_for(card_ptr);
+ r = _g1->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. The cset is
+ // not relevant here, since we're in concurrent phase.
+ 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) = CardTableModRefBS::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 + CardTableModRefBS::card_size_in_words;
+ MemRegion dirty_region(start, MIN2(scan_limit, end));
+ assert(!dirty_region.is_empty(), "sanity");
+
+ G1ConcurrentRefineOopClosure conc_refine_cl(_g1, 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 != CardTableModRefBS::dirty_card_val()) {
+ *card_ptr = CardTableModRefBS::dirty_card_val();
+ MutexLockerEx x(Shared_DirtyCardQ_lock,
+ Mutex::_no_safepoint_check_flag);
+ DirtyCardQueue* sdcq =
+ JavaThread::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(_g1->is_gc_active(), "Only call during GC");
+
+ check_card_ptr(card_ptr, _ct_bs);
+
+ // 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 != CardTableModRefBS::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 = CardTableModRefBS::clean_card_val() | CardTableModRefBS::claimed_card_val();
+
+ // Construct the region representing the card.
+ HeapWord* card_start = _ct_bs->addr_for(card_ptr);
+ // And find the region containing it.
+ uint const card_region_idx = _g1->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 + CardTableModRefBS::card_size_in_words;
+ MemRegion dirty_region(card_start, MIN2(scan_limit, card_end));
+ assert(!dirty_region.is_empty(), "sanity");
+
+ HeapRegion* const card_region = _g1->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);
+ }
+}
+
+void G1RemSet::create_card_live_data(WorkGang* workers, G1CMBitMap* mark_bitmap) {
+ _card_live_data.create(workers, mark_bitmap);
+}
+
+void G1RemSet::finalize_card_live_data(WorkGang* workers, G1CMBitMap* mark_bitmap) {
+ _card_live_data.finalize(workers, mark_bitmap);
+}
+
+void G1RemSet::verify_card_live_data(WorkGang* workers, G1CMBitMap* bitmap) {
+ _card_live_data.verify(workers, bitmap);
+}
+
+void G1RemSet::clear_card_live_data(WorkGang* workers) {
+ _card_live_data.clear(workers);
+}
+
+#ifdef ASSERT
+void G1RemSet::verify_card_live_data_is_clear() {
+ _card_live_data.verify_is_clear();
+}
+#endif