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63 lines
2.1 KiB
63 lines
2.1 KiB
#ifndef MY_ATOMIC_INCLUDED
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#define MY_ATOMIC_INCLUDED
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/* Copyright (c) 2006, 2017, Oracle and/or its affiliates. All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License, version 2.0,
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as published by the Free Software Foundation.
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This program is also distributed with certain software (including
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but not limited to OpenSSL) that is licensed under separate terms,
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as designated in a particular file or component or in included license
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documentation. The authors of MySQL hereby grant you an additional
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permission to link the program and your derivative works with the
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separately licensed software that they have included with MySQL.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License, version 2.0, for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
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/**
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@file include/my_atomic.h
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*/
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#if defined(_MSC_VER)
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#include <windows.h>
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/*
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my_yield_processor (equivalent of x86 PAUSE instruction) should be used
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to improve performance on hyperthreaded CPUs. Intel recommends to use it in
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spin loops also on non-HT machines to reduce power consumption (see e.g
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http://softwarecommunity.intel.com/articles/eng/2004.htm)
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Running benchmarks for spinlocks implemented with InterlockedCompareExchange
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and YieldProcessor shows that much better performance is achieved by calling
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YieldProcessor in a loop - that is, yielding longer. On Intel boxes setting
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loop count in the range 200-300 brought best results.
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*/
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#define YIELD_LOOPS 200
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static inline int my_yield_processor() {
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int i;
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for (i = 0; i < YIELD_LOOPS; i++) {
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YieldProcessor();
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}
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return 1;
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}
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#define LF_BACKOFF my_yield_processor()
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#else // !defined(_MSC_VER)
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#define LF_BACKOFF (1)
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#endif
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#endif /* MY_ATOMIC_INCLUDED */
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