9a1487397b
microtime(9) nanotime(9) getmicrotime(9) getnanotime(9) microuptime(9) nanouptime(9) getmicrouptime(9) getnanouptime(9) tvtohz(9) Based on PR: docs/15889 Submitted by: Kelly Yancey <kbyanc@posi.net>
111 lines
3.1 KiB
Groff
111 lines
3.1 KiB
Groff
.\" Copyright (c) 2000 Kelly Yancey
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd January 3, 2000
|
|
.Dt MICROTIME 9
|
|
.Os FreeBSD
|
|
.Sh NAME
|
|
.Nm microtime ,
|
|
.Nm getmicrotime ,
|
|
.Nm nanotime ,
|
|
.Nm getnanotime
|
|
.Nd get the current time
|
|
.Sh SYNOPSIS
|
|
.Fd #include <sys/time.h>
|
|
.Ft void
|
|
.Fn microtime "struct timeval *tv"
|
|
.Ft void
|
|
.Fn getmicrotime "struct timeval *tv"
|
|
.Ft void
|
|
.Fn nanotime "struct timespec *ts"
|
|
.Ft void
|
|
.Fn getnanotime "struct timespec *tsp"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn microtime
|
|
and
|
|
.Fn getmicrotime
|
|
functons stores the system time as a
|
|
.Ft struct timeval
|
|
at the address specified by
|
|
.Fa tv .
|
|
The
|
|
.Fn nanotime
|
|
and
|
|
.Fn getnanotime
|
|
functions perform the same utility, but record the time as a
|
|
.Ft struct timespec
|
|
instead.
|
|
.Pp
|
|
.Fn Microtime
|
|
and
|
|
.Fn nanotime
|
|
always query the timecounter to return the current time as precisely as
|
|
possible. Whereas
|
|
.Fn getmicrotime
|
|
and
|
|
.Fn getnanotime
|
|
functions are abstractions which can alternately return a less precise, but
|
|
faster to obtain, time. This behaviour can be toggled via the
|
|
kern.timecounter.method sysctl variable:
|
|
.Bl -tag -width ABC
|
|
.It Dv 0
|
|
sacrifice precision in favor of faster code execution
|
|
.It Dv 1
|
|
return the more precise time (the same as calling
|
|
.Fn microtime
|
|
or
|
|
.Fn nanotime ) .
|
|
.El
|
|
.Pp
|
|
The intent of the
|
|
.Fn getmicrotime
|
|
and
|
|
.Fn getnanotime
|
|
functions is to enforce the user's preference for timer accuracy versus
|
|
execution time.
|
|
.Sh SEE ALSO
|
|
.Xr getmicrouptime 9 ,
|
|
.Xr getnanouptime 9 ,
|
|
.Xr microuptime 9 ,
|
|
.Xr nanouptime 9 ,
|
|
.Xr tvtohz 9
|
|
.Sh DIAGNOSTICS
|
|
Buggy hardware can cause "calcru negative..." when kern.timecounter.method
|
|
is set to 0.
|
|
.Sh HISTORY
|
|
The
|
|
.Nm microtime
|
|
and
|
|
.Nm nanotime
|
|
functions first appeared in
|
|
.Fx 3.0
|
|
but existed in other incarnations since
|
|
.Bx 4.4
|
|
.Sh AUTHORS
|
|
This manual page was written by
|
|
.An Kelly Yancey Aq kbyanc@posi.net .
|