984 lines
38 KiB
C++
984 lines
38 KiB
C++
/*
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* Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#include "precompiled.hpp"
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#include "gc/g1/dirtyCardQueue.hpp"
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#include "gc/g1/g1BarrierSet.hpp"
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#include "gc/g1/g1BlockOffsetTable.inline.hpp"
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#include "gc/g1/g1CardTable.inline.hpp"
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#include "gc/g1/g1CollectedHeap.inline.hpp"
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#include "gc/g1/g1ConcurrentRefine.hpp"
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#include "gc/g1/g1FromCardCache.hpp"
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#include "gc/g1/g1GCPhaseTimes.hpp"
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#include "gc/g1/g1HotCardCache.hpp"
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#include "gc/g1/g1OopClosures.inline.hpp"
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#include "gc/g1/g1RemSet.hpp"
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#include "gc/g1/heapRegion.inline.hpp"
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#include "gc/g1/heapRegionManager.inline.hpp"
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#include "gc/g1/heapRegionRemSet.hpp"
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#include "gc/shared/gcTraceTime.inline.hpp"
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#include "gc/shared/suspendibleThreadSet.hpp"
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#include "memory/iterator.hpp"
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#include "memory/resourceArea.hpp"
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#include "oops/access.inline.hpp"
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#include "oops/oop.inline.hpp"
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#include "utilities/align.hpp"
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#include "utilities/globalDefinitions.hpp"
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#include "utilities/intHisto.hpp"
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#include "utilities/stack.inline.hpp"
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#include "utilities/ticks.inline.hpp"
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// Collects information about the overall remembered set scan progress during an evacuation.
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class G1RemSetScanState : public CHeapObj<mtGC> {
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private:
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class G1ClearCardTableTask : public AbstractGangTask {
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G1CollectedHeap* _g1h;
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uint* _dirty_region_list;
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size_t _num_dirty_regions;
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size_t _chunk_length;
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size_t volatile _cur_dirty_regions;
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public:
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G1ClearCardTableTask(G1CollectedHeap* g1h,
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uint* dirty_region_list,
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size_t num_dirty_regions,
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size_t chunk_length) :
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AbstractGangTask("G1 Clear Card Table Task"),
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_g1h(g1h),
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_dirty_region_list(dirty_region_list),
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_num_dirty_regions(num_dirty_regions),
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_chunk_length(chunk_length),
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_cur_dirty_regions(0) {
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assert(chunk_length > 0, "must be");
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}
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static size_t chunk_size() { return M; }
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void work(uint worker_id) {
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while (_cur_dirty_regions < _num_dirty_regions) {
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size_t next = Atomic::add(_chunk_length, &_cur_dirty_regions) - _chunk_length;
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size_t max = MIN2(next + _chunk_length, _num_dirty_regions);
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for (size_t i = next; i < max; i++) {
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HeapRegion* r = _g1h->region_at(_dirty_region_list[i]);
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if (!r->is_survivor()) {
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r->clear_cardtable();
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}
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}
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}
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}
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};
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size_t _max_regions;
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// Scan progress for the remembered set of a single region. Transitions from
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// Unclaimed -> Claimed -> Complete.
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// At each of the transitions the thread that does the transition needs to perform
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// some special action once. This is the reason for the extra "Claimed" state.
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typedef jint G1RemsetIterState;
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static const G1RemsetIterState Unclaimed = 0; // The remembered set has not been scanned yet.
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static const G1RemsetIterState Claimed = 1; // The remembered set is currently being scanned.
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static const G1RemsetIterState Complete = 2; // The remembered set has been completely scanned.
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G1RemsetIterState volatile* _iter_states;
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// The current location where the next thread should continue scanning in a region's
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// remembered set.
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size_t volatile* _iter_claims;
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// Temporary buffer holding the regions we used to store remembered set scan duplicate
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// information. These are also called "dirty". Valid entries are from [0.._cur_dirty_region)
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uint* _dirty_region_buffer;
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typedef jbyte IsDirtyRegionState;
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static const IsDirtyRegionState Clean = 0;
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static const IsDirtyRegionState Dirty = 1;
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// Holds a flag for every region whether it is in the _dirty_region_buffer already
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// to avoid duplicates. Uses jbyte since there are no atomic instructions for bools.
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IsDirtyRegionState* _in_dirty_region_buffer;
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size_t _cur_dirty_region;
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// Creates a snapshot of the current _top values at the start of collection to
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// filter out card marks that we do not want to scan.
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class G1ResetScanTopClosure : public HeapRegionClosure {
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private:
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HeapWord** _scan_top;
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public:
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G1ResetScanTopClosure(HeapWord** scan_top) : _scan_top(scan_top) { }
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virtual bool do_heap_region(HeapRegion* r) {
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uint hrm_index = r->hrm_index();
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if (!r->in_collection_set() && r->is_old_or_humongous()) {
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_scan_top[hrm_index] = r->top();
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} else {
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_scan_top[hrm_index] = r->bottom();
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}
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return false;
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}
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};
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// For each region, contains the maximum top() value to be used during this garbage
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// collection. Subsumes common checks like filtering out everything but old and
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// humongous regions outside the collection set.
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// This is valid because we are not interested in scanning stray remembered set
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// entries from free or archive regions.
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HeapWord** _scan_top;
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public:
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G1RemSetScanState() :
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_max_regions(0),
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_iter_states(NULL),
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_iter_claims(NULL),
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_dirty_region_buffer(NULL),
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_in_dirty_region_buffer(NULL),
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_cur_dirty_region(0),
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_scan_top(NULL) {
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}
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~G1RemSetScanState() {
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if (_iter_states != NULL) {
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FREE_C_HEAP_ARRAY(G1RemsetIterState, _iter_states);
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}
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if (_iter_claims != NULL) {
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FREE_C_HEAP_ARRAY(size_t, _iter_claims);
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}
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if (_dirty_region_buffer != NULL) {
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FREE_C_HEAP_ARRAY(uint, _dirty_region_buffer);
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}
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if (_in_dirty_region_buffer != NULL) {
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FREE_C_HEAP_ARRAY(IsDirtyRegionState, _in_dirty_region_buffer);
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}
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if (_scan_top != NULL) {
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FREE_C_HEAP_ARRAY(HeapWord*, _scan_top);
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}
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}
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void initialize(uint max_regions) {
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assert(_iter_states == NULL, "Must not be initialized twice");
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assert(_iter_claims == NULL, "Must not be initialized twice");
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_max_regions = max_regions;
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_iter_states = NEW_C_HEAP_ARRAY(G1RemsetIterState, max_regions, mtGC);
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_iter_claims = NEW_C_HEAP_ARRAY(size_t, max_regions, mtGC);
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_dirty_region_buffer = NEW_C_HEAP_ARRAY(uint, max_regions, mtGC);
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_in_dirty_region_buffer = NEW_C_HEAP_ARRAY(IsDirtyRegionState, max_regions, mtGC);
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_scan_top = NEW_C_HEAP_ARRAY(HeapWord*, max_regions, mtGC);
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}
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void reset() {
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for (uint i = 0; i < _max_regions; i++) {
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_iter_states[i] = Unclaimed;
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}
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G1ResetScanTopClosure cl(_scan_top);
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G1CollectedHeap::heap()->heap_region_iterate(&cl);
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memset((void*)_iter_claims, 0, _max_regions * sizeof(size_t));
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memset(_in_dirty_region_buffer, Clean, _max_regions * sizeof(IsDirtyRegionState));
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_cur_dirty_region = 0;
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}
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// Attempt to claim the remembered set of the region for iteration. Returns true
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// if this call caused the transition from Unclaimed to Claimed.
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inline bool claim_iter(uint region) {
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assert(region < _max_regions, "Tried to access invalid region %u", region);
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if (_iter_states[region] != Unclaimed) {
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return false;
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}
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G1RemsetIterState res = Atomic::cmpxchg(Claimed, &_iter_states[region], Unclaimed);
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return (res == Unclaimed);
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}
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// Try to atomically sets the iteration state to "complete". Returns true for the
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// thread that caused the transition.
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inline bool set_iter_complete(uint region) {
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if (iter_is_complete(region)) {
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return false;
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}
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G1RemsetIterState res = Atomic::cmpxchg(Complete, &_iter_states[region], Claimed);
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return (res == Claimed);
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}
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// Returns true if the region's iteration is complete.
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inline bool iter_is_complete(uint region) const {
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assert(region < _max_regions, "Tried to access invalid region %u", region);
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return _iter_states[region] == Complete;
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}
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// The current position within the remembered set of the given region.
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inline size_t iter_claimed(uint region) const {
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assert(region < _max_regions, "Tried to access invalid region %u", region);
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return _iter_claims[region];
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}
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// Claim the next block of cards within the remembered set of the region with
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// step size.
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inline size_t iter_claimed_next(uint region, size_t step) {
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return Atomic::add(step, &_iter_claims[region]) - step;
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}
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void add_dirty_region(uint region) {
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if (_in_dirty_region_buffer[region] == Dirty) {
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return;
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}
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bool marked_as_dirty = Atomic::cmpxchg(Dirty, &_in_dirty_region_buffer[region], Clean) == Clean;
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if (marked_as_dirty) {
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size_t allocated = Atomic::add(1u, &_cur_dirty_region) - 1;
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_dirty_region_buffer[allocated] = region;
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}
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}
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HeapWord* scan_top(uint region_idx) const {
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return _scan_top[region_idx];
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}
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// Clear the card table of "dirty" regions.
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void clear_card_table(WorkGang* workers) {
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if (_cur_dirty_region == 0) {
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return;
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}
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size_t const num_chunks = align_up(_cur_dirty_region * HeapRegion::CardsPerRegion, G1ClearCardTableTask::chunk_size()) / G1ClearCardTableTask::chunk_size();
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uint const num_workers = (uint)MIN2(num_chunks, (size_t)workers->active_workers());
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size_t const chunk_length = G1ClearCardTableTask::chunk_size() / HeapRegion::CardsPerRegion;
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// Iterate over the dirty cards region list.
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G1ClearCardTableTask cl(G1CollectedHeap::heap(), _dirty_region_buffer, _cur_dirty_region, chunk_length);
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log_debug(gc, ergo)("Running %s using %u workers for " SIZE_FORMAT " "
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"units of work for " SIZE_FORMAT " regions.",
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cl.name(), num_workers, num_chunks, _cur_dirty_region);
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workers->run_task(&cl, num_workers);
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#ifndef PRODUCT
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G1CollectedHeap::heap()->verifier()->verify_card_table_cleanup();
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#endif
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}
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};
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G1RemSet::G1RemSet(G1CollectedHeap* g1,
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G1CardTable* ct,
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G1HotCardCache* hot_card_cache) :
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_g1(g1),
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_scan_state(new G1RemSetScanState()),
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_num_conc_refined_cards(0),
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_ct(ct),
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_g1p(_g1->g1_policy()),
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_hot_card_cache(hot_card_cache),
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_prev_period_summary() {
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}
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G1RemSet::~G1RemSet() {
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if (_scan_state != NULL) {
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delete _scan_state;
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}
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}
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uint G1RemSet::num_par_rem_sets() {
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return DirtyCardQueueSet::num_par_ids() + G1ConcurrentRefine::max_num_threads() + MAX2(ConcGCThreads, ParallelGCThreads);
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}
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void G1RemSet::initialize(size_t capacity, uint max_regions) {
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G1FromCardCache::initialize(num_par_rem_sets(), max_regions);
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_scan_state->initialize(max_regions);
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}
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G1ScanRSForRegionClosure::G1ScanRSForRegionClosure(G1RemSetScanState* scan_state,
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G1ScanObjsDuringScanRSClosure* scan_obj_on_card,
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CodeBlobClosure* code_root_cl,
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uint worker_i) :
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_scan_state(scan_state),
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_scan_objs_on_card_cl(scan_obj_on_card),
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_code_root_cl(code_root_cl),
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_strong_code_root_scan_time_sec(0.0),
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_cards_claimed(0),
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_cards_scanned(0),
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_cards_skipped(0),
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_worker_i(worker_i) {
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_g1h = G1CollectedHeap::heap();
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_bot = _g1h->bot();
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_ct = _g1h->card_table();
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}
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void G1ScanRSForRegionClosure::scan_card(MemRegion mr, uint region_idx_for_card) {
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HeapRegion* const card_region = _g1h->region_at(region_idx_for_card);
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_scan_objs_on_card_cl->set_region(card_region);
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card_region->oops_on_card_seq_iterate_careful<true>(mr, _scan_objs_on_card_cl);
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_cards_scanned++;
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}
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void G1ScanRSForRegionClosure::scan_strong_code_roots(HeapRegion* r) {
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double scan_start = os::elapsedTime();
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r->strong_code_roots_do(_code_root_cl);
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_strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start);
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}
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void G1ScanRSForRegionClosure::claim_card(size_t card_index, const uint region_idx_for_card){
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_ct->set_card_claimed(card_index);
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_scan_state->add_dirty_region(region_idx_for_card);
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}
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bool G1ScanRSForRegionClosure::do_heap_region(HeapRegion* r) {
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assert(r->in_collection_set(), "should only be called on elements of CS.");
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uint region_idx = r->hrm_index();
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if (_scan_state->iter_is_complete(region_idx)) {
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return false;
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}
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if (_scan_state->claim_iter(region_idx)) {
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// If we ever free the collection set concurrently, we should also
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// clear the card table concurrently therefore we won't need to
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// add regions of the collection set to the dirty cards region.
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_scan_state->add_dirty_region(region_idx);
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}
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// We claim cards in blocks so as to reduce the contention.
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size_t const block_size = G1RSetScanBlockSize;
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HeapRegionRemSetIterator iter(r->rem_set());
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size_t card_index;
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size_t claimed_card_block = _scan_state->iter_claimed_next(region_idx, block_size);
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for (size_t current_card = 0; iter.has_next(card_index); current_card++) {
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if (current_card >= claimed_card_block + block_size) {
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claimed_card_block = _scan_state->iter_claimed_next(region_idx, block_size);
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}
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if (current_card < claimed_card_block) {
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_cards_skipped++;
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continue;
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}
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_cards_claimed++;
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// If the card is dirty, then G1 will scan it during Update RS.
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if (_ct->is_card_claimed(card_index) || _ct->is_card_dirty(card_index)) {
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continue;
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}
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HeapWord* const card_start = _g1h->bot()->address_for_index(card_index);
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uint const region_idx_for_card = _g1h->addr_to_region(card_start);
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assert(_g1h->region_at(region_idx_for_card)->is_in_reserved(card_start),
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"Card start " PTR_FORMAT " to scan outside of region %u", p2i(card_start), _g1h->region_at(region_idx_for_card)->hrm_index());
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HeapWord* const top = _scan_state->scan_top(region_idx_for_card);
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if (card_start >= top) {
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continue;
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}
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// We claim lazily (so races are possible but they're benign), which reduces the
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// number of duplicate scans (the rsets of the regions in the cset can intersect).
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// Claim the card after checking bounds above: the remembered set may contain
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// random cards into current survivor, and we would then have an incorrectly
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// claimed card in survivor space. Card table clear does not reset the card table
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// of survivor space regions.
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claim_card(card_index, region_idx_for_card);
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MemRegion const mr(card_start, MIN2(card_start + BOTConstants::N_words, top));
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scan_card(mr, region_idx_for_card);
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}
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if (_scan_state->set_iter_complete(region_idx)) {
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// Scan the strong code root list attached to the current region
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scan_strong_code_roots(r);
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}
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return false;
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}
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void G1RemSet::scan_rem_set(G1ParScanThreadState* pss,
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CodeBlobClosure* heap_region_codeblobs,
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uint worker_i) {
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double rs_time_start = os::elapsedTime();
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G1ScanObjsDuringScanRSClosure scan_cl(_g1, pss);
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G1ScanRSForRegionClosure cl(_scan_state, &scan_cl, heap_region_codeblobs, worker_i);
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_g1->collection_set_iterate_from(&cl, worker_i);
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double scan_rs_time_sec = (os::elapsedTime() - rs_time_start) -
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cl.strong_code_root_scan_time_sec();
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G1GCPhaseTimes* p = _g1p->phase_times();
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p->record_time_secs(G1GCPhaseTimes::ScanRS, worker_i, scan_rs_time_sec);
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p->record_thread_work_item(G1GCPhaseTimes::ScanRS, worker_i, cl.cards_scanned(), G1GCPhaseTimes::ScanRSScannedCards);
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p->record_thread_work_item(G1GCPhaseTimes::ScanRS, worker_i, cl.cards_claimed(), G1GCPhaseTimes::ScanRSClaimedCards);
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p->record_thread_work_item(G1GCPhaseTimes::ScanRS, worker_i, cl.cards_skipped(), G1GCPhaseTimes::ScanRSSkippedCards);
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p->record_time_secs(G1GCPhaseTimes::CodeRoots, worker_i, cl.strong_code_root_scan_time_sec());
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}
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// Closure used for updating rem sets. Only called during an evacuation pause.
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class G1RefineCardClosure: public CardTableEntryClosure {
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G1RemSet* _g1rs;
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G1ScanObjsDuringUpdateRSClosure* _update_rs_cl;
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size_t _cards_scanned;
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size_t _cards_skipped;
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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 = G1BarrierSet::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);
|
|
}
|
|
|
|
inline void check_card_ptr(jbyte* card_ptr, G1CardTable* ct) {
|
|
#ifdef ASSERT
|
|
G1CollectedHeap* g1 = G1CollectedHeap::heap();
|
|
assert(g1->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)),
|
|
g1->addr_to_region(ct->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);
|
|
|
|
// 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 = _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;
|
|
}
|
|
|
|
// 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 = _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.
|
|
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(_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 != 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(_g1->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 = _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 + 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 = _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);
|
|
}
|
|
}
|
|
|
|
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,
|
|
TicksToTimeHelper::seconds(time) * 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);
|
|
}
|