80 lines
3.1 KiB
C++
80 lines
3.1 KiB
C++
/*
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* Copyright (c) 2014, 2019, Red Hat, Inc. 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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#ifndef SHARE_GC_SHENANDOAH_SHENANDOAHMARKCOMPACT_HPP
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#define SHARE_GC_SHENANDOAH_SHENANDOAHMARKCOMPACT_HPP
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#include "gc/shared/gcTimer.hpp"
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#include "gc/shenandoah/shenandoahHeap.hpp"
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#include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
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/**
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* This implements Full GC (e.g. when invoking System.gc()) using a mark-compact algorithm.
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*
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* Current implementation is parallel sliding Lisp-2-style algorithm, based on
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* "Parallel Garbage Collection for Shared Memory Multiprocessors", by Christine Flood et al.
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* http://people.csail.mit.edu/shanir/publications/dfsz2001.pdf
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*
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* It is implemented in four phases:
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*
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* 1. Mark all live objects of the heap by traversing objects starting at GC roots.
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* 2. Calculate the new location of each live object. This is done by sequentially scanning
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* the heap, keeping track of a next-location-pointer, which is then written to each
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* object's fwdptr field.
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* 3. Update all references. This is implemented by another scan of the heap, and updates
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* all references in live objects by what's stored in the target object's fwdptr.
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* 4. Compact the heap by copying all live objects to their new location.
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*
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* Parallelization is handled by assigning each GC worker the slice of the heap (the set of regions)
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* where it does sliding compaction, without interfering with other threads.
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*/
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class PreservedMarksSet;
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class ShenandoahMarkCompact : public CHeapObj<mtGC> {
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friend class ShenandoahPrepareForCompactionObjectClosure;
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private:
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GCTimer* _gc_timer;
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PreservedMarksSet* _preserved_marks;
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public:
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ShenandoahMarkCompact();
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void initialize(GCTimer* gc_timer);
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void do_it(GCCause::Cause gc_cause);
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private:
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void phase1_mark_heap();
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void phase2_calculate_target_addresses(ShenandoahHeapRegionSet** worker_slices);
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void phase3_update_references();
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void phase4_compact_objects(ShenandoahHeapRegionSet** worker_slices);
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void distribute_slices(ShenandoahHeapRegionSet** worker_slices);
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void calculate_target_humongous_objects();
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void compact_humongous_objects();
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};
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#endif // SHARE_GC_SHENANDOAH_SHENANDOAHMARKCOMPACT_HPP
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