1a978be6b6
- All now include maxscale/cdefs.h as the very first file. - MXS_[BEGIN|END]_DECLS added to all C-headers. Strictly speaking not necessary for private headers, but does not hurt either. - Include guards moved to the very top of the file. - #pragma once added.
65 lines
1.7 KiB
C
65 lines
1.7 KiB
C
#pragma once
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#ifndef _MAXSCALE_RDTSC_H
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#define _MAXSCALE_RDTSC_H
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/*
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* Copyright (c) 2016 MariaDB Corporation Ab
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*
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* Use of this software is governed by the Business Source License included
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* in the LICENSE.TXT file and at www.mariadb.com/bsl.
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*
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* Change Date: 2019-07-01
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*
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* On the date above, in accordance with the Business Source License, use
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* of this software will be governed by version 2 or later of the General
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* Public License.
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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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#include <maxscale/cdefs.h>
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MXS_BEGIN_DECLS
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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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MXS_END_DECLS
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#endif
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