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jdk/src/hotspot/share/gc/g1/g1RemSet.cpp
Thomas Schatzl 8d5c005642 8342382: Implement JEP 522: G1 GC: Improve Throughput by Reducing Synchronization 
Co-authored-by: Amit Kumar <amitkumar@openjdk.org>
Co-authored-by: Martin Doerr <mdoerr@openjdk.org>
Co-authored-by: Carlo Refice <carlo.refice@oracle.com>
Co-authored-by: Fei Yang <fyang@openjdk.org>
Reviewed-by: iwalulya, rcastanedalo, aph, ayang
2025-09-22 13:47:45 +00:00

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/*
* Copyright (c) 2001, 2025, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include "gc/g1/g1BarrierSet.hpp"
#include "gc/g1/g1BatchedTask.hpp"
#include "gc/g1/g1BlockOffsetTable.inline.hpp"
#include "gc/g1/g1CardSet.inline.hpp"
#include "gc/g1/g1CardTable.inline.hpp"
#include "gc/g1/g1CardTableClaimTable.inline.hpp"
#include "gc/g1/g1CardTableEntryClosure.hpp"
#include "gc/g1/g1CollectedHeap.inline.hpp"
#include "gc/g1/g1CollectionSet.inline.hpp"
#include "gc/g1/g1ConcurrentRefine.hpp"
#include "gc/g1/g1ConcurrentRefineSweepTask.hpp"
#include "gc/g1/g1FromCardCache.hpp"
#include "gc/g1/g1GCParPhaseTimesTracker.hpp"
#include "gc/g1/g1GCPhaseTimes.hpp"
#include "gc/g1/g1HeapRegion.inline.hpp"
#include "gc/g1/g1HeapRegionManager.inline.hpp"
#include "gc/g1/g1HeapRegionRemSet.inline.hpp"
#include "gc/g1/g1OopClosures.inline.hpp"
#include "gc/g1/g1Policy.hpp"
#include "gc/g1/g1RemSet.hpp"
#include "gc/g1/g1RootClosures.hpp"
#include "gc/shared/gc_globals.hpp"
#include "gc/shared/gcTraceTime.inline.hpp"
#include "jfr/jfrEvents.hpp"
#include "memory/iterator.hpp"
#include "memory/resourceArea.hpp"
#include "oops/access.inline.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/atomicAccess.hpp"
#include "runtime/os.hpp"
#include "utilities/align.hpp"
#include "utilities/globalDefinitions.hpp"
#include "utilities/powerOfTwo.hpp"
#include "utilities/stack.inline.hpp"
#include "utilities/ticks.hpp"
#include CPU_HEADER(gc/g1/g1Globals)
// Collects information about the overall heap root scan progress during an evacuation.
//
// Scanning the remembered sets works by first merging all sources of cards to be
// scanned (refinement table, remembered sets) into a single data structure to remove
// duplicates and simplify work distribution.
//
// During the following card scanning we not only scan this combined set of cards, but
// also remember that these were completely scanned. The following evacuation passes
// do not scan these cards again, and so need to be preserved across increments.
//
// The representation for all the cards to scan is the card table: cards can have
// one of three states during GC:
// - clean: these cards will not be scanned in this pass
// - dirty: these cards will be scanned in this pass
// - scanned: these cards have already been scanned in a previous pass
//
// After all evacuation is done, we reset the card table to clean.
//
// Work distribution occurs on "chunk" basis, i.e. contiguous ranges of cards. As an
// additional optimization, during card merging we remember which regions and which
// chunks actually contain cards to be scanned. Threads iterate only across these
// regions, and only compete for chunks containing any cards.
//
// Within these chunks, a worker scans the card table on "blocks" of cards, i.e.
// contiguous ranges of dirty cards to be scanned. These blocks are converted to actual
// memory ranges and then passed on to actual scanning.
class G1RemSetScanState : public CHeapObj<mtGC> {
class G1DirtyRegions;
G1CardTableClaimTable _card_claim_table;
// The complete set of regions which card table needs to be cleared at the end
// of GC because we scribbled over these card table entries.
//
// Regions may be added for two reasons:
// - they were part of the collection set: they may contain regular card marks
// that we never scan so we must always clear their card table.
// - or in case g1 does an optional evacuation pass, g1 marks the cards in there
// as g1_scanned_card_val. If G1 only did an initial evacuation pass, the
// scanning already cleared these cards. In that case they are not in this set
// at the end of the collection.
G1DirtyRegions* _all_dirty_regions;
// The set of regions which card table needs to be scanned for new dirty cards
// in the current evacuation pass.
G1DirtyRegions* _next_dirty_regions;
// Set of (unique) regions that can be added to concurrently.
class G1DirtyRegions : public CHeapObj<mtGC> {
uint* _buffer;
uint _cur_idx;
size_t _max_reserved_regions;
bool* _contains;
public:
G1DirtyRegions(size_t max_reserved_regions) :
_buffer(NEW_C_HEAP_ARRAY(uint, max_reserved_regions, mtGC)),
_cur_idx(0),
_max_reserved_regions(max_reserved_regions),
_contains(NEW_C_HEAP_ARRAY(bool, max_reserved_regions, mtGC)) {
reset();
}
~G1DirtyRegions() {
FREE_C_HEAP_ARRAY(uint, _buffer);
FREE_C_HEAP_ARRAY(bool, _contains);
}
void reset() {
_cur_idx = 0;
::memset(_contains, false, _max_reserved_regions * sizeof(bool));
}
uint size() const { return _cur_idx; }
uint at(uint idx) const {
assert(idx < _cur_idx, "Index %u beyond valid regions", idx);
return _buffer[idx];
}
void add_dirty_region(uint region) {
if (_contains[region]) {
return;
}
bool marked_as_dirty = AtomicAccess::cmpxchg(&_contains[region], false, true) == false;
if (marked_as_dirty) {
uint allocated = AtomicAccess::fetch_then_add(&_cur_idx, 1u);
_buffer[allocated] = region;
}
}
// Creates the union of this and the other G1DirtyRegions.
void merge(const G1DirtyRegions* other) {
for (uint i = 0; i < other->size(); i++) {
uint region = other->at(i);
if (!_contains[region]) {
_buffer[_cur_idx++] = region;
_contains[region] = true;
}
}
}
};
// 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 regions.
HeapWord** _scan_top;
class G1ClearCardTableTask : public G1AbstractSubTask {
G1CollectedHeap* _g1h;
G1DirtyRegions* _regions;
uint volatile _cur_dirty_regions;
G1RemSetScanState* _scan_state;
static constexpr uint num_cards_per_worker = M;
public:
G1ClearCardTableTask(G1CollectedHeap* g1h,
G1DirtyRegions* regions,
G1RemSetScanState* scan_state) :
G1AbstractSubTask(G1GCPhaseTimes::ClearCardTable),
_g1h(g1h),
_regions(regions),
_cur_dirty_regions(0),
_scan_state(scan_state) {}
double worker_cost() const override {
uint num_regions = _regions->size();
if (num_regions == 0) {
// There is no card table clean work, only some cleanup of memory.
return AlmostNoWork;
}
double num_cards = num_regions << G1HeapRegion::LogCardsPerRegion;
return ceil(num_cards / num_cards_per_worker);
}
virtual ~G1ClearCardTableTask() {
_scan_state->cleanup();
if (VerifyDuringGC) {
G1CollectedHeap::heap()->verifier()->verify_card_table_cleanup();
}
}
void do_work(uint worker_id) override {
const uint num_regions_per_worker = num_cards_per_worker / (uint)G1HeapRegion::CardsPerRegion;
while (_cur_dirty_regions < _regions->size()) {
uint next = AtomicAccess::fetch_then_add(&_cur_dirty_regions, num_regions_per_worker);
uint max = MIN2(next + num_regions_per_worker, _regions->size());
for (uint i = next; i < max; i++) {
G1HeapRegion* r = _g1h->region_at(_regions->at(i));
// The card table contains "dirty" card marks. Clear unconditionally.
//
// Humongous reclaim candidates are not in the dirty set. This is fine because
// their card and refinement table should always be clear as they are typeArrays.
r->clear_card_table();
// There is no need to clear the refinement table here: at the start of the collection
// we had to clear the refinement card table for collection set regions already, and any
// old regions use it for old->collection set candidates, so they should not be cleared
// either.
}
}
}
};
public:
G1RemSetScanState() :
_card_claim_table(G1CollectedHeap::get_chunks_per_region_for_scan()),
_all_dirty_regions(nullptr),
_next_dirty_regions(nullptr),
_scan_top(nullptr) { }
~G1RemSetScanState() {
FREE_C_HEAP_ARRAY(HeapWord*, _scan_top);
}
void initialize(uint max_reserved_regions) {
_card_claim_table.initialize(max_reserved_regions);
_scan_top = NEW_C_HEAP_ARRAY(HeapWord*, max_reserved_regions, mtGC);
}
// Reset the claim and clear scan top for all regions, including
// regions currently not available or free. Since regions might
// become used during the collection these values must be valid
// for those regions as well.
void prepare() {
size_t max_reserved_regions = _card_claim_table.max_reserved_regions();
for (size_t i = 0; i < max_reserved_regions; i++) {
clear_scan_top((uint)i);
}
_all_dirty_regions = new G1DirtyRegions(max_reserved_regions);
_next_dirty_regions = new G1DirtyRegions(max_reserved_regions);
}
void prepare_for_merge_heap_roots() {
// We populate the next dirty regions at the start of GC with all old/humongous
// regions.
//assert(_next_dirty_regions->size() == 0, "next dirty regions must be empty");
_card_claim_table.reset_all_to_unclaimed();
}
void complete_evac_phase(bool merge_dirty_regions) {
if (merge_dirty_regions) {
_all_dirty_regions->merge(_next_dirty_regions);
}
_next_dirty_regions->reset();
}
// Returns whether the given region contains cards we need to scan. The remembered
// set and other sources may contain cards that
// - are in uncommitted regions
// - are located in the collection set
// - are located in free regions
// as we do not clean up remembered sets before merging heap roots.
bool contains_cards_to_process(uint const region_idx) const {
G1HeapRegion* hr = G1CollectedHeap::heap()->region_at_or_null(region_idx);
return (hr != nullptr && !hr->in_collection_set() && hr->is_old_or_humongous());
}
size_t num_cards_in_dirty_regions() const {
return _next_dirty_regions->size() * G1HeapRegion::CardsPerRegion;
}
G1AbstractSubTask* create_cleanup_after_scan_heap_roots_task() {
return new G1ClearCardTableTask(G1CollectedHeap::heap(), _all_dirty_regions, this);
}
void cleanup() {
delete _all_dirty_regions;
_all_dirty_regions = nullptr;
delete _next_dirty_regions;
_next_dirty_regions = nullptr;
}
void iterate_dirty_regions_from(G1HeapRegionClosure* cl, uint worker_id) {
uint num_regions = _next_dirty_regions->size();
if (num_regions == 0) {
return;
}
G1CollectedHeap* g1h = G1CollectedHeap::heap();
WorkerThreads* workers = g1h->workers();
uint const max_workers = workers->active_workers();
uint const start_pos = num_regions * worker_id / max_workers;
uint cur = start_pos;
do {
bool result = cl->do_heap_region(g1h->region_at(_next_dirty_regions->at(cur)));
guarantee(!result, "Not allowed to ask for early termination.");
cur++;
if (cur == _next_dirty_regions->size()) {
cur = 0;
}
} while (cur != start_pos);
}
bool has_cards_to_scan(uint region) {
return _card_claim_table.has_unclaimed_cards(region);
}
void add_dirty_region(uint const region) {
#ifdef ASSERT
G1HeapRegion* hr = G1CollectedHeap::heap()->region_at(region);
assert(!hr->in_collection_set() && hr->is_old_or_humongous(),
"Region %u is not suitable for scanning, is %sin collection set or %s",
hr->hrm_index(), hr->in_collection_set() ? "" : "not ", hr->get_short_type_str());
#endif
_next_dirty_regions->add_dirty_region(region);
}
void add_all_dirty_region(uint region) {
#ifdef ASSERT
G1HeapRegion* hr = G1CollectedHeap::heap()->region_at(region);
assert(hr->in_collection_set(),
"Only add collection set regions to all dirty regions directly but %u is %s",
hr->hrm_index(), hr->get_short_type_str());
#endif
_all_dirty_regions->add_dirty_region(region);
}
void set_scan_top(uint region_idx, HeapWord* value) {
_scan_top[region_idx] = value;
}
HeapWord* scan_top(uint region_idx) const {
return _scan_top[region_idx];
}
void clear_scan_top(uint region_idx) {
set_scan_top(region_idx, nullptr);
}
G1CardTableChunkClaimer claimer(uint region_idx) {
return G1CardTableChunkClaimer(&_card_claim_table, region_idx);
}
};
G1RemSet::G1RemSet(G1CollectedHeap* g1h) :
_scan_state(new G1RemSetScanState()),
_prev_period_summary(false),
_g1h(g1h),
_g1p(_g1h->policy()) {
}
G1RemSet::~G1RemSet() {
delete _scan_state;
}
void G1RemSet::initialize(uint max_reserved_regions) {
_scan_state->initialize(max_reserved_regions);
}
// Scans a heap region for dirty cards.
class G1ScanHRForRegionClosure : public G1HeapRegionClosure {
using CardValue = CardTable::CardValue;
G1CollectedHeap* _g1h;
G1CardTable* _ct;
G1ParScanThreadState* _pss;
G1RemSetScanState* _scan_state;
G1GCPhaseTimes::GCParPhases _phase;
uint _worker_id;
size_t _cards_pending;
size_t _cards_empty;
size_t _cards_scanned;
size_t _blocks_scanned;
size_t _chunks_claimed;
size_t _heap_roots_found;
Tickspan _rem_set_root_scan_time;
Tickspan _rem_set_trim_partially_time;
// The address to which this thread already scanned (walked the heap) up to during
// card scanning (exclusive).
HeapWord* _scanned_to;
CardValue _scanned_card_value;
HeapWord* scan_memregion(uint region_idx_for_card, MemRegion mr, size_t &roots_found) {
G1HeapRegion* const card_region = _g1h->region_at(region_idx_for_card);
G1ScanCardClosure card_cl(_g1h, _pss, roots_found);
HeapWord* const scanned_to = card_region->oops_on_memregion_seq_iterate_careful<true>(mr, &card_cl);
assert(scanned_to != nullptr, "Should be able to scan range");
assert(scanned_to >= mr.end(), "Scanned to " PTR_FORMAT " less than range " PTR_FORMAT, p2i(scanned_to), p2i(mr.end()));
_pss->trim_queue_partially();
return scanned_to;
}
void do_claimed_block(uint const region_idx, CardValue* const dirty_l, CardValue* const dirty_r, size_t& pending_cards) {
pending_cards += _ct->change_dirty_cards_to(dirty_l, dirty_r, _scanned_card_value);
size_t num_cards = pointer_delta(dirty_r, dirty_l, sizeof(CardValue));
_blocks_scanned++;
HeapWord* const card_start = _ct->addr_for(dirty_l);
HeapWord* const top = _scan_state->scan_top(region_idx);
if (card_start >= top) {
return;
}
HeapWord* scan_end = MIN2(card_start + (num_cards << (CardTable::card_shift() - LogHeapWordSize)), top);
if (_scanned_to >= scan_end) {
return;
}
MemRegion mr(MAX2(card_start, _scanned_to), scan_end);
size_t roots_found = 0;
_scanned_to = scan_memregion(region_idx, mr, roots_found);
if (roots_found == 0) {
_cards_empty += num_cards;
}
_cards_scanned += num_cards;
_heap_roots_found += roots_found;
}
void scan_heap_roots(G1HeapRegion* r) {
uint const region_idx = r->hrm_index();
ResourceMark rm;
G1CardTableChunkClaimer claim = _scan_state->claimer(region_idx);
// Set the current scan "finger" to null for every heap region to scan. Since
// the claim value is monotonically increasing, the check to not scan below this
// will filter out objects spanning chunks within the region too then, as opposed
// to resetting this value for every claim.
_scanned_to = nullptr;
size_t pending_cards = 0;
while (claim.has_next()) {
_chunks_claimed++;
size_t const region_card_base_idx = ((size_t)region_idx << G1HeapRegion::LogCardsPerRegion) + claim.value();
CardValue* const start_card = _ct->byte_for_index(region_card_base_idx);
CardValue* const end_card = start_card + claim.size();
G1ChunkScanner chunk_scanner{start_card, end_card};
chunk_scanner.on_dirty_cards([&] (CardValue* dirty_l, CardValue* dirty_r) {
do_claimed_block(region_idx, dirty_l, dirty_r, pending_cards);
});
}
_cards_pending += pending_cards;
}
public:
G1ScanHRForRegionClosure(G1RemSetScanState* scan_state,
G1ParScanThreadState* pss,
uint worker_id,
G1GCPhaseTimes::GCParPhases phase,
bool remember_already_scanned_cards) :
_g1h(G1CollectedHeap::heap()),
_ct(_g1h->card_table()),
_pss(pss),
_scan_state(scan_state),
_phase(phase),
_worker_id(worker_id),
_cards_pending(0),
_cards_empty(0),
_cards_scanned(0),
_blocks_scanned(0),
_chunks_claimed(0),
_heap_roots_found(0),
_rem_set_root_scan_time(),
_rem_set_trim_partially_time(),
_scanned_to(nullptr),
_scanned_card_value(remember_already_scanned_cards ? G1CardTable::g1_scanned_card_val()
: G1CardTable::clean_card_val()) {
}
bool do_heap_region(G1HeapRegion* r) {
assert(!r->in_collection_set() && r->is_old_or_humongous(),
"Should only be called on old gen non-collection set regions but region %u is not.",
r->hrm_index());
uint const region_idx = r->hrm_index();
if (_scan_state->has_cards_to_scan(region_idx)) {
G1EvacPhaseWithTrimTimeTracker timer(_pss, _rem_set_root_scan_time, _rem_set_trim_partially_time);
scan_heap_roots(r);
}
return false;
}
Tickspan rem_set_root_scan_time() const { return _rem_set_root_scan_time; }
Tickspan rem_set_trim_partially_time() const { return _rem_set_trim_partially_time; }
size_t cards_pending() const { return _cards_pending; }
size_t cards_scanned_empty() const { return _cards_empty; }
size_t cards_scanned() const { return _cards_scanned; }
size_t blocks_scanned() const { return _blocks_scanned; }
size_t chunks_claimed() const { return _chunks_claimed; }
size_t heap_roots_found() const { return _heap_roots_found; }
};
void G1RemSet::scan_heap_roots(G1ParScanThreadState* pss,
uint worker_id,
G1GCPhaseTimes::GCParPhases scan_phase,
G1GCPhaseTimes::GCParPhases objcopy_phase,
bool remember_already_scanned_cards) {
EventGCPhaseParallel event;
G1ScanHRForRegionClosure cl(_scan_state, pss, worker_id, scan_phase, remember_already_scanned_cards);
_scan_state->iterate_dirty_regions_from(&cl, worker_id);
event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(scan_phase));
G1GCPhaseTimes* p = _g1p->phase_times();
p->record_or_add_time_secs(objcopy_phase, worker_id, cl.rem_set_trim_partially_time().seconds());
p->record_or_add_time_secs(scan_phase, worker_id, cl.rem_set_root_scan_time().seconds());
p->record_or_add_thread_work_item(scan_phase, worker_id, cl.cards_pending(), G1GCPhaseTimes::ScanHRPendingCards);
p->record_or_add_thread_work_item(scan_phase, worker_id, cl.cards_scanned_empty(), G1GCPhaseTimes::ScanHRScannedEmptyCards);
p->record_or_add_thread_work_item(scan_phase, worker_id, cl.cards_scanned(), G1GCPhaseTimes::ScanHRScannedCards);
p->record_or_add_thread_work_item(scan_phase, worker_id, cl.blocks_scanned(), G1GCPhaseTimes::ScanHRScannedBlocks);
p->record_or_add_thread_work_item(scan_phase, worker_id, cl.chunks_claimed(), G1GCPhaseTimes::ScanHRClaimedChunks);
p->record_or_add_thread_work_item(scan_phase, worker_id, cl.heap_roots_found(), G1GCPhaseTimes::ScanHRFoundRoots);
}
// Wrapper around a NMethodClosure to count the number of nmethods scanned.
class G1ScanAndCountNMethodClosure : public NMethodClosure {
NMethodClosure* _cl;
size_t _count;
public:
G1ScanAndCountNMethodClosure(NMethodClosure* cl) : _cl(cl), _count(0) {
}
void do_nmethod(nmethod* nm) override {
_cl->do_nmethod(nm);
_count++;
}
size_t count() const {
return _count;
}
};
// Heap region closure to be applied to all regions in the current collection set
// increment to fix up non-card related roots.
class G1ScanCodeRootsClosure : public G1HeapRegionClosure {
G1ParScanThreadState* _pss;
G1RemSetScanState* _scan_state;
uint _worker_id;
size_t _code_roots_scanned;
public:
G1ScanCodeRootsClosure(G1RemSetScanState* scan_state,
G1ParScanThreadState* pss,
uint worker_id) :
_pss(pss),
_scan_state(scan_state),
_worker_id(worker_id),
_code_roots_scanned(0) { }
bool do_heap_region(G1HeapRegion* r) {
// Scan the code root list attached to the current region
G1ScanAndCountNMethodClosure cl(_pss->closures()->weak_nmethods());
r->code_roots_do(&cl);
_code_roots_scanned += cl.count();
return false;
}
size_t code_roots_scanned() const { return _code_roots_scanned; }
};
void G1RemSet::scan_collection_set_code_roots(G1ParScanThreadState* pss,
uint worker_id,
G1GCPhaseTimes::GCParPhases coderoots_phase,
G1GCPhaseTimes::GCParPhases objcopy_phase) {
EventGCPhaseParallel event;
Tickspan code_root_scan_time;
Tickspan code_root_trim_partially_time;
G1EvacPhaseWithTrimTimeTracker timer(pss, code_root_scan_time, code_root_trim_partially_time);
G1GCPhaseTimes* p = _g1h->phase_times();
G1ScanCodeRootsClosure cl(_scan_state, pss, worker_id);
// Code roots work distribution occurs inside the iteration method. So scan all collection
// set regions for all threads.
_g1h->collection_set_iterate_increment_from(&cl, worker_id);
p->record_or_add_time_secs(coderoots_phase, worker_id, code_root_scan_time.seconds());
p->add_time_secs(objcopy_phase, worker_id, code_root_trim_partially_time.seconds());
p->record_or_add_thread_work_item(coderoots_phase, worker_id, cl.code_roots_scanned(), G1GCPhaseTimes::CodeRootsScannedNMethods);
event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(coderoots_phase));
}
class G1ScanOptionalRemSetRootsClosure : public G1HeapRegionClosure {
G1ParScanThreadState* _pss;
uint _worker_id;
G1GCPhaseTimes::GCParPhases _scan_phase;
size_t _opt_roots_scanned;
size_t _opt_refs_scanned;
size_t _opt_refs_memory_used;
void scan_opt_rem_set_roots(G1HeapRegion* r) {
G1OopStarChunkedList* opt_rem_set_list = _pss->oops_into_optional_region(r);
G1ScanCardClosure scan_cl(G1CollectedHeap::heap(), _pss, _opt_roots_scanned);
G1ScanRSForOptionalClosure cl(G1CollectedHeap::heap(), &scan_cl);
_opt_refs_scanned += opt_rem_set_list->oops_do(&cl, _pss->closures()->strong_oops());
_opt_refs_memory_used += opt_rem_set_list->used_memory();
}
public:
G1ScanOptionalRemSetRootsClosure(G1ParScanThreadState* pss,
uint worker_id,
G1GCPhaseTimes::GCParPhases scan_phase) :
_pss(pss),
_worker_id(worker_id),
_scan_phase(scan_phase),
_opt_roots_scanned(0),
_opt_refs_scanned(0),
_opt_refs_memory_used(0) { }
bool do_heap_region(G1HeapRegion* r) override {
if (r->has_index_in_opt_cset()) {
scan_opt_rem_set_roots(r);
}
return false;
}
size_t opt_roots_scanned() const { return _opt_roots_scanned; }
size_t opt_refs_scanned() const { return _opt_refs_scanned; }
size_t opt_refs_memory_used() const { return _opt_refs_memory_used; }
};
void G1RemSet::scan_collection_set_optional_roots(G1ParScanThreadState* pss,
uint worker_id,
G1GCPhaseTimes::GCParPhases scan_phase,
G1GCPhaseTimes::GCParPhases objcopy_phase) {
assert(scan_phase == G1GCPhaseTimes::OptScanHR, "must be");
EventGCPhaseParallel event;
Tickspan rem_set_opt_root_scan_time;
Tickspan rem_set_opt_trim_partially_time;
G1EvacPhaseWithTrimTimeTracker timer(pss, rem_set_opt_root_scan_time, rem_set_opt_trim_partially_time);
G1GCPhaseTimes* p = _g1h->phase_times();
G1ScanOptionalRemSetRootsClosure cl(pss, worker_id, scan_phase);
// The individual references for the optional remembered set are per-worker, so every worker
// always need to scan all regions (no claimer).
_g1h->collection_set_iterate_increment_from(&cl, worker_id);
p->record_or_add_time_secs(scan_phase, worker_id, rem_set_opt_root_scan_time.seconds());
p->record_or_add_time_secs(objcopy_phase, worker_id, rem_set_opt_trim_partially_time.seconds());
p->record_or_add_thread_work_item(scan_phase, worker_id, cl.opt_roots_scanned(), G1GCPhaseTimes::ScanHRFoundRoots);
p->record_or_add_thread_work_item(scan_phase, worker_id, cl.opt_refs_scanned(), G1GCPhaseTimes::ScanHRScannedOptRefs);
p->record_or_add_thread_work_item(scan_phase, worker_id, cl.opt_refs_memory_used(), G1GCPhaseTimes::ScanHRUsedMemory);
event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(scan_phase));
}
#ifdef ASSERT
void G1RemSet::assert_scan_top_is_null(uint hrm_index) {
assert(_scan_state->scan_top(hrm_index) == nullptr,
"scan_top of region %u is unexpectedly " PTR_FORMAT,
hrm_index, p2i(_scan_state->scan_top(hrm_index)));
}
#endif
void G1RemSet::prepare_region_for_scan(G1HeapRegion* r) {
uint hrm_index = r->hrm_index();
r->prepare_remset_for_scan();
// Only update non-collection set old regions, others must have already been set
// to null (don't scan) in the initialization.
if (r->in_collection_set()) {
assert_scan_top_is_null(hrm_index);
} else if (r->is_old_or_humongous()) {
_scan_state->set_scan_top(hrm_index, r->top());
_scan_state->add_dirty_region(hrm_index);
} else {
assert_scan_top_is_null(hrm_index);
assert(r->is_free(),
"Region %u should be free region but is %s", hrm_index, r->get_type_str());
}
}
void G1RemSet::prepare_for_scan_heap_roots() {
_scan_state->prepare();
}
// Small ring buffer used for prefetching cards for write from the card
// table during GC.
template <class T>
class G1MergeHeapRootsPrefetchCache {
public:
static const uint CacheSize = G1MergeHeapRootsPrefetchCacheSize;
static_assert(is_power_of_2(CacheSize), "Cache size must be power of 2");
private:
T* _cache[CacheSize];
uint _cur_cache_idx;
NONCOPYABLE(G1MergeHeapRootsPrefetchCache);
protected:
// Initial content of all elements in the cache. It's value should be
// "neutral", i.e. no work done on it when processing it.
G1CardTable::CardValue _dummy_card;
~G1MergeHeapRootsPrefetchCache() = default;
public:
G1MergeHeapRootsPrefetchCache(G1CardTable::CardValue dummy_card_value) :
_cur_cache_idx(0),
_dummy_card(dummy_card_value) {
for (uint i = 0; i < CacheSize; i++) {
push(&_dummy_card);
}
}
T* push(T* elem) {
Prefetch::write(elem, 0);
T* result = _cache[_cur_cache_idx];
_cache[_cur_cache_idx++] = elem;
_cur_cache_idx &= (CacheSize - 1);
return result;
}
};
// Task to merge a non-dirty refinement table into the (primary) card table.
class MergeRefinementTableTask : public WorkerTask {
G1CardTableClaimTable* _scan_state;
uint _max_workers;
class G1MergeRefinementTableRegionClosure : public G1HeapRegionClosure {
G1CardTableClaimTable* _scan_state;
bool do_heap_region(G1HeapRegion* r) override {
if (!_scan_state->has_unclaimed_cards(r->hrm_index())) {
return false;
}
// We can blindly clear all collection set region's refinement tables: these
// regions will be evacuated and need their refinement table reset in case
// of evacuation failure.
// Young regions contain random marks, which are obvious to just clear. The
// card marks of other collection set region's refinement tables are also
// uninteresting.
if (r->in_collection_set()) {
uint claim = _scan_state->claim_all_cards(r->hrm_index());
// Concurrent refinement may have started merging this region (we also
// get here for non-young regions), the claim may be non-zero for those.
// We could get away here with just clearing the area from the current
// claim to the last card in the region, but for now just do it all.
if (claim < G1HeapRegion::CardsPerRegion) {
r->clear_refinement_table();
}
return false;
}
assert(r->is_old_or_humongous(), "must be");
G1CollectedHeap* g1h = G1CollectedHeap::heap();
G1CardTable* card_table = g1h->card_table();
G1CardTable* refinement_table = g1h->refinement_table();
size_t const region_card_base_idx = (size_t)r->hrm_index() << G1HeapRegion::LogCardsPerRegion;
G1CardTableChunkClaimer claim(_scan_state, r->hrm_index());
while (claim.has_next()) {
size_t const start_idx = region_card_base_idx + claim.value();
size_t* card_cur_word = (size_t*)card_table->byte_for_index(start_idx);
size_t* refinement_cur_word = (size_t*)refinement_table->byte_for_index(start_idx);
size_t* const refinement_end_word = refinement_cur_word + claim.size() / (sizeof(size_t) / sizeof(G1CardTable::CardValue));
for (; refinement_cur_word < refinement_end_word; ++refinement_cur_word, ++card_cur_word) {
size_t value = *refinement_cur_word;
*refinement_cur_word = G1CardTable::WordAllClean;
// Dirty is "0", so we need to logically-and here. This is also safe
// for all other possible values in the card table; at this point this
// can be either g1_dirty_card or g1_to_cset_card which will both be
// scanned.
size_t new_value = *card_cur_word & value;
*card_cur_word = new_value;
}
}
return false;
}
public:
G1MergeRefinementTableRegionClosure(G1CardTableClaimTable* scan_state) : G1HeapRegionClosure(), _scan_state(scan_state) {
}
};
public:
MergeRefinementTableTask(G1CardTableClaimTable* scan_state, uint max_workers) :
WorkerTask("Merge Refinement Table"), _scan_state(scan_state), _max_workers(max_workers) { guarantee(_scan_state != nullptr, "must be"); }
void work(uint worker_id) override {
G1CollectedHeap* g1h = G1CollectedHeap::heap();
G1GCParPhaseTimesTracker x(g1h->phase_times(), G1GCPhaseTimes::SweepRT, worker_id, false /* allow multiple invocation */);
G1MergeRefinementTableRegionClosure cl(_scan_state);
_scan_state->heap_region_iterate_from_worker_offset(&cl, worker_id, _max_workers);
}
};
class G1MergeHeapRootsTask : public WorkerTask {
class G1MergeCardSetStats {
size_t _merged[G1GCPhaseTimes::MergeRSContainersSentinel];
public:
G1MergeCardSetStats() {
for (uint i = 0; i < ARRAY_SIZE(_merged); i++) {
_merged[i] = 0;
}
}
void inc_card_set_merged(uint tag) {
assert(tag < ARRAY_SIZE(_merged), "tag out of bounds %u", tag);
_merged[tag]++;
}
void inc_merged_cards(size_t increment = 1) {
_merged[G1GCPhaseTimes::MergeRSFromRemSetCards] += increment;
}
void inc_total_cards(size_t increment = 1) {
_merged[G1GCPhaseTimes::MergeRSTotalCards] += increment;
}
void dec_remset_cards(size_t decrement) {
_merged[G1GCPhaseTimes::MergeRSTotalCards] -= decrement;
}
size_t merged(uint i) const { return _merged[i]; }
};
// Visitor for remembered sets. Several methods of it are called by a region's
// card set iterator to drop card set remembered set entries onto the card.
// table.
//
// We add a small prefetching cache in front of the actual work as dropping
// onto the card table is basically random memory access. This improves
// performance of this operation significantly.
class G1MergeCardSetClosure {
friend class G1MergeCardSetCache;
G1RemSetScanState* _scan_state;
G1CardTable* _ct;
G1MergeCardSetStats _stats;
// Cached card table index of the currently processed region to avoid constant
// recalculation as our remembered set containers are per region.
size_t _region_base_idx;
class G1MergeCardSetCache : public G1MergeHeapRootsPrefetchCache<G1CardTable::CardValue> {
G1MergeCardSetClosure* const _merge_card_cl;
public:
G1MergeCardSetCache(G1MergeCardSetClosure* const merge_card_cl) :
// Initially set dummy card value to Dirty to avoid any actual mark work if we
// try to process it.
G1MergeHeapRootsPrefetchCache<G1CardTable::CardValue>(G1CardTable::dirty_card_val()),
_merge_card_cl(merge_card_cl) { }
void flush() {
for (uint i = 0; i < CacheSize; i++) {
_merge_card_cl->mark_card(push(&_dummy_card));
}
}
} _merge_card_set_cache;
// Returns whether the region contains cards we need to scan. If so, remember that
// region in the current set of dirty regions.
bool remember_if_interesting(uint const region_idx) {
if (!_scan_state->contains_cards_to_process(region_idx)) {
return false;
}
_scan_state->add_dirty_region(region_idx);
return true;
}
void mark_card(G1CardTable::CardValue* value) {
if (_ct->mark_clean_as_from_remset(value)) {
_stats.inc_merged_cards();
}
_stats.inc_total_cards();
}
public:
G1MergeCardSetClosure(G1RemSetScanState* scan_state) :
_scan_state(scan_state),
_ct(G1CollectedHeap::heap()->card_table()),
_stats(),
_region_base_idx(0),
_merge_card_set_cache(this) { }
void do_card(uint const card_idx) {
G1CardTable::CardValue* to_prefetch = _ct->byte_for_index(_region_base_idx + card_idx);
G1CardTable::CardValue* to_process = _merge_card_set_cache.push(to_prefetch);
mark_card(to_process);
}
// Returns whether the given region actually needs iteration.
bool start_iterate(uint const tag, uint const region_idx) {
assert(tag < G1GCPhaseTimes::MergeRSFromRemSetCards, "invalid tag %u", tag);
if (remember_if_interesting(region_idx)) {
_region_base_idx = (size_t)region_idx << G1HeapRegion::LogCardsPerRegion;
_stats.inc_card_set_merged(tag);
return true;
}
return false;
}
void do_card_range(uint const start_card_idx, uint const length) {
size_t cards_changed = _ct->mark_clean_range_as_from_remset(_region_base_idx + start_card_idx, length);
_stats.inc_merged_cards(cards_changed);
_stats.inc_total_cards(length);
}
G1MergeCardSetStats stats() {
_merge_card_set_cache.flush();
// Compensation for the dummy cards that were initially pushed into the
// card cache.
// We do not need to compensate for the other counters because the dummy
// card mark will never update another counter because it is initally "dirty".
_stats.dec_remset_cards(G1MergeCardSetCache::CacheSize);
return _stats;
}
};
// Closure to make sure that the marking bitmap is clear for any old region in
// the collection set.
// This is needed to be able to use the bitmap for evacuation failure handling.
class G1ClearBitmapClosure : public G1HeapRegionClosure {
G1CollectedHeap* _g1h;
G1RemSetScanState* _scan_state;
bool _initial_evacuation;
void assert_bitmap_clear(G1HeapRegion* hr, const G1CMBitMap* bitmap) {
assert(bitmap->get_next_marked_addr(hr->bottom(), hr->end()) == hr->end(),
"Bitmap should have no mark for region %u (%s)", hr->hrm_index(), hr->get_short_type_str());
}
void assert_refinement_table_clear(G1HeapRegion* hr) {
#ifdef ASSERT
_g1h->refinement_table()->verify_region(MemRegion(hr->bottom(), hr->end()), G1CardTable::clean_card_val(), true);
#endif
}
bool should_clear_region(G1HeapRegion* hr) const {
// The bitmap for young regions must obviously be clear as we never mark through them;
// old regions that are currently being marked through are only in the collection set
// after the concurrent cycle completed, so their bitmaps must also be clear except when
// the pause occurs during the Concurrent Cleanup for Next Mark phase.
// Only at that point the region's bitmap may contain marks while being in the collection
// set at the same time.
//
// There is one exception: shutdown might have aborted the Concurrent Cleanup for Next
// Mark phase midway, which might have also left stale marks in old generation regions.
// There might actually have been scheduled multiple collections, but at that point we do
// not care that much about performance and just do the work multiple times if needed.
return (_g1h->collector_state()->clear_bitmap_in_progress() ||
_g1h->concurrent_mark_is_terminating()) &&
hr->is_old();
}
public:
G1ClearBitmapClosure(G1CollectedHeap* g1h, G1RemSetScanState* scan_state, bool initial_evacuation) :
_g1h(g1h),
_scan_state(scan_state),
_initial_evacuation(initial_evacuation)
{ }
bool do_heap_region(G1HeapRegion* hr) {
assert(_g1h->is_in_cset(hr), "Should only be used iterating the collection set");
// Collection set regions after the initial evacuation need their refinement
// table cleared because
// * we use the refinement table for recording references to other regions
// during evacuation failure handling
// * during previous passes we used the refinement table to contain marks for
// cross-region references. Now that we evacuate the region, they need to be
// cleared.
//
// We do not need to do this extra work for initial evacuation because we
// make sure the refinement table is clean for all regions either in
// concurrent refinement or in the merge refinement table phase earlier.
if (!_initial_evacuation) {
hr->clear_refinement_table();
} else {
assert_refinement_table_clear(hr);
}
// Evacuation failure uses the bitmap to record evacuation failed objects,
// so the bitmap for the regions in the collection set must be cleared if not already.
if (should_clear_region(hr)) {
_g1h->clear_bitmap_for_region(hr);
_g1h->concurrent_mark()->reset_top_at_mark_start(hr);
} else {
assert_bitmap_clear(hr, _g1h->concurrent_mark()->mark_bitmap());
}
_g1h->concurrent_mark()->clear_statistics(hr);
_scan_state->add_all_dirty_region(hr->hrm_index());
return false;
}
};
// Visitor for the remembered sets of humongous candidate regions to merge their
// remembered set into the card table.
class G1FlushHumongousCandidateRemSets : public G1HeapRegionIndexClosure {
G1MergeCardSetClosure _cl;
public:
G1FlushHumongousCandidateRemSets(G1RemSetScanState* scan_state) : _cl(scan_state) { }
bool do_heap_region_index(uint region_index) override {
G1CollectedHeap* g1h = G1CollectedHeap::heap();
if (!g1h->region_attr(region_index).is_humongous_candidate()) {
return false;
}
G1HeapRegion* r = g1h->region_at(region_index);
assert(r->rem_set()->is_complete(), "humongous candidates must have complete remset");
guarantee(r->rem_set()->occupancy_less_or_equal_than(G1EagerReclaimRemSetThreshold),
"Found a not-small remembered set here. This is inconsistent with previous assumptions.");
if (!r->rem_set()->is_empty()) {
r->rem_set()->iterate_for_merge(_cl);
// We should only clear the card based remembered set here as we will not
// implicitly rebuild anything else during eager reclaim. Note that at the moment
// (and probably never) we do not enter this path if there are other kind of
// remembered sets for this region.
// We want to continue collecting remembered set entries for humongous regions
// that were not reclaimed.
r->rem_set()->clear(true /* only_cardset */, true /* keep_tracked */);
}
// Postcondition
assert(r->rem_set()->is_empty(), "must be empty after flushing");
assert(r->rem_set()->is_complete(), "should still be after flushing");
return false;
}
G1MergeCardSetStats stats() {
return _cl.stats();
}
};
uint _num_workers;
G1HeapRegionClaimer _hr_claimer;
G1RemSetScanState* _scan_state;
bool _initial_evacuation;
volatile bool _fast_reclaim_handled;
public:
G1MergeHeapRootsTask(G1RemSetScanState* scan_state, uint num_workers, bool initial_evacuation) :
WorkerTask("G1 Merge Heap Roots"),
_num_workers(num_workers),
_hr_claimer(num_workers),
_scan_state(scan_state),
_initial_evacuation(initial_evacuation),
_fast_reclaim_handled(false)
{ }
virtual void work(uint worker_id) {
G1CollectedHeap* g1h = G1CollectedHeap::heap();
G1GCPhaseTimes* p = g1h->phase_times();
G1GCPhaseTimes::GCParPhases merge_remset_phase = _initial_evacuation ?
G1GCPhaseTimes::MergeRS :
G1GCPhaseTimes::OptMergeRS;
{
// Merge remset of ...
G1GCParPhaseTimesTracker x(p, merge_remset_phase, worker_id, !_initial_evacuation /* allow_multiple_record */);
{
// 1. eager-reclaim candidates
if (_initial_evacuation &&
g1h->has_humongous_reclaim_candidates() &&
!_fast_reclaim_handled &&
!AtomicAccess::cmpxchg(&_fast_reclaim_handled, false, true)) {
G1GCParPhaseTimesTracker subphase_x(p, G1GCPhaseTimes::MergeER, worker_id);
G1FlushHumongousCandidateRemSets cl(_scan_state);
g1h->heap_region_iterate(&cl);
G1MergeCardSetStats stats = cl.stats();
for (uint i = 0; i < G1GCPhaseTimes::MergeRSContainersSentinel; i++) {
p->record_or_add_thread_work_item(merge_remset_phase, worker_id, stats.merged(i), i);
}
}
}
{
// 2. collection set
G1MergeCardSetClosure merge(_scan_state);
if (_initial_evacuation) {
G1HeapRegionRemSet::iterate_for_merge(g1h->young_regions_cardset(), merge);
}
g1h->collection_set()->merge_cardsets_for_collection_groups(merge, worker_id, _num_workers);
G1MergeCardSetStats stats = merge.stats();
for (uint i = 0; i < G1GCPhaseTimes::MergeRSContainersSentinel; i++) {
p->record_or_add_thread_work_item(merge_remset_phase, worker_id, stats.merged(i), i);
}
}
}
// Preparation for evacuation failure handling.
{
G1ClearBitmapClosure clear(g1h, _scan_state, _initial_evacuation);
g1h->collection_set_iterate_increment_from(&clear, &_hr_claimer, worker_id);
}
}
};
static void merge_refinement_table() {
G1CollectedHeap* g1h = G1CollectedHeap::heap();
G1ConcurrentRefineSweepState& state = g1h->concurrent_refine()->sweep_state_for_merge();
WorkerThreads* workers = g1h->workers();
MergeRefinementTableTask cl(state.sweep_table(), workers->active_workers());
log_debug(gc, ergo)("Running %s using %u workers", cl.name(), workers->active_workers());
workers->run_task(&cl);
}
void G1RemSet::merge_heap_roots(bool initial_evacuation) {
G1CollectedHeap* g1h = G1CollectedHeap::heap();
G1GCPhaseTimes* pt = g1h->phase_times();
// 1. Prepare the merging process
{
Ticks start = Ticks::now();
_scan_state->prepare_for_merge_heap_roots();
Tickspan total = Ticks::now() - start;
if (initial_evacuation) {
pt->record_prepare_merge_heap_roots_time(total.seconds() * 1000.0);
} else {
pt->record_or_add_optional_prepare_merge_heap_roots_time(total.seconds() * 1000.0);
}
}
// 2. (Optionally) Merge the refinement table into the card table (if needed).
G1ConcurrentRefineSweepState& state = g1h->concurrent_refine()->sweep_state();
if (initial_evacuation && state.is_in_progress()) {
Ticks start = Ticks::now();
merge_refinement_table();
g1h->phase_times()->record_merge_refinement_table_time((Ticks::now() - start).seconds() * MILLIUNITS);
}
// 3. Merge other heap roots.
Ticks start = Ticks::now();
{
WorkerThreads* workers = g1h->workers();
size_t const increment_length = g1h->collection_set()->groups_increment_length();
uint const num_workers = initial_evacuation ? workers->active_workers() :
MIN2(workers->active_workers(), (uint)increment_length);
G1MergeHeapRootsTask cl(_scan_state, num_workers, initial_evacuation);
log_debug(gc, ergo)("Running %s using %u workers for %zu regions",
cl.name(), num_workers, increment_length);
workers->run_task(&cl, num_workers);
}
if (initial_evacuation) {
pt->record_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
} else {
pt->record_or_add_optional_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
}
if (VerifyDuringGC && initial_evacuation) {
g1h->verifier()->verify_card_tables_clean(false /* both_card_tables */);
}
}
void G1RemSet::complete_evac_phase(bool has_more_than_one_evacuation_phase) {
_scan_state->complete_evac_phase(has_more_than_one_evacuation_phase);
}
void G1RemSet::exclude_region_from_scan(uint region_idx) {
_scan_state->clear_scan_top(region_idx);
}
G1AbstractSubTask* G1RemSet::create_cleanup_after_scan_heap_roots_task() {
return _scan_state->create_cleanup_after_scan_heap_roots_task();
}
void G1RemSet::print_coarsen_stats() {
LogTarget(Debug, gc, remset) lt;
if (lt.is_enabled()) {
LogStream ls(lt);
G1CardSet::print_coarsen_stats(&ls);
}
}
inline void check_card_ptr(CardTable::CardValue* card_ptr, G1CardTable* ct) {
#ifdef ASSERT
G1CollectedHeap* g1h = G1CollectedHeap::heap();
assert(g1h->is_in(ct->addr_for(card_ptr)),
"Card at " PTR_FORMAT " index %zu 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
}
G1RemSet::RefineResult G1RemSet::refine_card_concurrently(CardValue* const card_ptr,
const uint worker_id) {
assert(!_g1h->is_stw_gc_active(), "Only call concurrently");
G1CardTable* ct = _g1h->refinement_table();
check_card_ptr(card_ptr, ct);
// That card is already known to contain a reference to the collection set. Skip
// further processing.
if (*card_ptr == G1CardTable::g1_to_cset_card) {
return AlreadyToCSet;
}
// Construct the MemRegion representing the card.
HeapWord* start = ct->addr_for(card_ptr);
// And find the region containing it.
G1HeapRegion* r = _g1h->heap_region_containing(start);
// This reload of the top is safe even though it happens after the full
// fence, because top is stable for old and unfiltered humongous
// regions, so it must return the same value as the previous load when
// cleaning the card. Also cleaning the card and refinement of the card
// cannot span across safepoint, so we don't need to worry about top being
// changed during safepoint.
HeapWord* scan_limit = r->top();
assert(scan_limit > start, "sanity region %u (%s) scan_limit " PTR_FORMAT " start " PTR_FORMAT, r->hrm_index(), r->get_short_type_str(), p2i(scan_limit), p2i(start));
// 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_id);
if (r->oops_on_memregion_seq_iterate_careful<false>(dirty_region, &conc_refine_cl) != nullptr) {
if (conc_refine_cl.has_ref_to_cset()) {
return HasRefToCSet;
} else if (conc_refine_cl.has_ref_to_old()) {
return HasRefToOld;
} else {
return NoCrossRegion;
}
}
// If unable to process the card then we encountered an unparsable
// part of the heap (e.g. a partially allocated object, so only
// temporarily a problem) while processing a stale card. Despite
// the card being stale, we can't simply ignore it, because we've
// already marked the card as cleaned, so taken responsibility for
// ensuring the card gets scanned.
return CouldNotParse;
}
void G1RemSet::print_periodic_summary_info(const char* header, uint period_count, bool show_thread_times) {
if ((G1SummarizeRSetStatsPeriod > 0) && log_is_enabled(Trace, gc, remset) &&
(period_count % G1SummarizeRSetStatsPeriod == 0)) {
G1RemSetSummary current;
_prev_period_summary.subtract_from(&current);
Log(gc, remset) log;
log.trace("%s", header);
LogStream ls(log.trace());
_prev_period_summary.print_on(&ls, show_thread_times);
_prev_period_summary.set(&current);
}
}
void G1RemSet::print_summary_info() {
Log(gc, remset, exit) log;
if (log.is_trace()) {
log.trace(" Cumulative RS summary");
G1RemSetSummary current;
LogStream ls(log.trace());
current.print_on(&ls, true /* show_thread_times*/);
}
}
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