84 lines
3.0 KiB
C++
84 lines
3.0 KiB
C++
/*
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* Copyright (c) 2014, 2019, 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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#ifndef SHARE_GC_G1_G1STRINGDEDUP_HPP
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#define SHARE_GC_G1_G1STRINGDEDUP_HPP
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//
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// G1 string deduplication candidate selection
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//
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// An object is considered a deduplication candidate if all of the following
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// statements are true:
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//
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// - The object is an instance of java.lang.String
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//
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// - The object is being evacuated from a young heap region
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//
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// - The object is being evacuated to a young/survivor heap region and the
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// object's age is equal to the deduplication age threshold
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//
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// or
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//
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// The object is being evacuated to an old heap region and the object's age is
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// less than the deduplication age threshold
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//
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// Once an string object has been promoted to an old region, or its age is higher
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// than the deduplication age threshold, is will never become a candidate again.
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// This approach avoids making the same object a candidate more than once.
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//
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#include "gc/shared/stringdedup/stringDedup.hpp"
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#include "memory/allocation.hpp"
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#include "oops/oop.hpp"
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class OopClosure;
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class BoolObjectClosure;
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class G1GCPhaseTimes;
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class G1StringDedupUnlinkOrOopsDoClosure;
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//
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// G1 interface for interacting with string deduplication.
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//
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class G1StringDedup : public StringDedup {
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private:
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// Candidate selection policies, returns true if the given object is
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// candidate for string deduplication.
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static bool is_candidate_from_mark(oop obj);
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static bool is_candidate_from_evacuation(bool from_young, bool to_young, oop obj);
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public:
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// Initialize string deduplication.
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static void initialize();
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// Enqueues a deduplication candidate for later processing by the deduplication
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// thread. Before enqueuing, these functions apply the appropriate candidate
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// selection policy to filters out non-candidates.
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static void enqueue_from_mark(oop java_string, uint worker_id);
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static void enqueue_from_evacuation(bool from_young, bool to_young,
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unsigned int queue, oop java_string);
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};
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#endif // SHARE_GC_G1_G1STRINGDEDUP_HPP
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