67 lines
2.4 KiB
C++
67 lines
2.4 KiB
C++
/*
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* Copyright (c) 2015, 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_G1YOUNGREMSETSAMPLINGTHREAD_HPP
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#define SHARE_GC_G1_G1YOUNGREMSETSAMPLINGTHREAD_HPP
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#include "gc/shared/concurrentGCThread.hpp"
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// The G1YoungRemSetSamplingThread is used to re-assess the validity of
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// the prediction for the remembered set lengths of the young generation.
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//
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// At the end of the GC G1 determines the length of the young gen based on
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// how much time the next GC can take, and when the next GC may occur
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// according to the MMU.
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//
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// The assumption is that a significant part of the GC is spent on scanning
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// the remembered sets (and many other components), so this thread constantly
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// reevaluates the prediction for the remembered set scanning costs, and potentially
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// G1Policy resizes the young gen. This may do a premature GC or even
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// increase the young gen size to keep pause time length goal.
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class G1YoungRemSetSamplingThread: public ConcurrentGCThread {
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private:
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Monitor _monitor;
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double _last_periodic_gc_attempt_s;
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double _vtime_accum; // Accumulated virtual time.
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void sample_young_list_rs_length();
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void run_service();
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void check_for_periodic_gc();
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void stop_service();
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void sleep_before_next_cycle();
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bool should_start_periodic_gc();
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public:
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G1YoungRemSetSamplingThread();
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double vtime_accum() { return _vtime_accum; }
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};
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#endif // SHARE_GC_G1_G1YOUNGREMSETSAMPLINGTHREAD_HPP
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