62 lines
2.0 KiB
C
62 lines
2.0 KiB
C
#ifndef _RDTSC_H
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#define _RDTSC_H
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/*
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* This file is distributed as part of the MariaDB Corporation MaxScale. It is free
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* software: you can redistribute it and/or modify it under the terms of the
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* GNU General Public License as published by the Free Software Foundation,
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* version 2.
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*
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* This program 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 FITNESS
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* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc., 51
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* Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Copyright MariaDB Corporation Ab 2014
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*/
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/**
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* @file rdtsc.h Access the process time-stamp counter
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*
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* This is an Intel only facilty that is used to access an accurate time
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* value, the granularity of which is related to the processor clock speed
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* and the overhead for access is much lower than using any system call
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* mechanism.
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*
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*
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* @verbatim
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* Revision History
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*
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* Date Who Description
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* 19/09/2014 Mark Riddoch Initial implementation
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*
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* @endverbatim
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*/
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typedef unsigned long long CYCLES;
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/**
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* Get the current time-stamp counter value from the processor. This is the
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* count of CPU cyceles as a 64 bit value.
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*
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* The value returned is related to the clock speed, to obtian a value in
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* seconds divide the returned value by the clock frequency for the processor.
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*
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* Note, on multi-processsor systems care much be taken to avoid the thread
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* moving to a different processor when taken succsive value of RDTSC to
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* obtian accurate timing. This may be done by setting pocessor affinity for
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* the thread. See sched_setaffinity/sched_getaffinity.
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*
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* @return CPU cycle count
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*/
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static __inline__ CYCLES rdtsc(void)
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{
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unsigned long long int x;
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__asm__ volatile (".byte 0x0f, 0x31" : "=A" (x));
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return x;
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}
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#endif
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