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