75 lines
2.4 KiB
C++
75 lines
2.4 KiB
C++
/*
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* Copyright (c) 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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#ifndef SHARE_UTILITIES_SPINYIELD_HPP
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#define SHARE_UTILITIES_SPINYIELD_HPP
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#include "memory/allocation.hpp"
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#include "utilities/globalDefinitions.hpp"
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#include "utilities/ticks.hpp"
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class outputStream;
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extern "C" int SpinPause();
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class SpinYield : public StackObj {
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Tickspan _sleep_time;
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uint _spins;
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uint _yields;
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uint _spin_limit;
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uint _yield_limit;
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uint _sleep_ns;
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void yield_or_sleep();
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public:
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static const uint default_spin_limit = 4096;
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static const uint default_yield_limit = 64;
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static const uint default_sleep_ns = 1000;
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// spin_limit is ignored (treated as zero) when !os::is_MP().
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explicit SpinYield(uint spin_limit = default_spin_limit,
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uint yield_limit = default_yield_limit,
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uint sleep_ns = default_sleep_ns);
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// Perform next round of delay.
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void wait() {
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// Simple policy: return immediately (spinning) configured number
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// of times, then switch to yield/sleep. Future work might
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// provide other policies, such as (1) always spin if system is
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// not saturated, or (2) sleeping if yielding is ineffective.
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if (_spins < _spin_limit) {
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++_spins;
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SpinPause();
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} else {
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yield_or_sleep();
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}
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}
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// Write information about the wait duration to s.
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void report(outputStream* s) const;
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};
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#endif // SHARE_UTILITIES_SPINYIELD_HPP
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