94 lines
2.5 KiB
Groff
94 lines
2.5 KiB
Groff
.\" Copyright (c) 2000 Mark R V Murray
|
|
.\" 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 October 24, 2009
|
|
.Dt GET_CYCLECOUNT 9
|
|
.Os
|
|
.Sh NAME
|
|
.Nm get_cyclecount
|
|
.Nd get the CPU's fast counter register contents
|
|
.Sh SYNOPSIS
|
|
.In sys/param.h
|
|
.In sys/systm.h
|
|
.In machine/cpu.h
|
|
.Ft u_int64_t
|
|
.Fn get_cyclecount "void"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn get_cyclecount
|
|
function uses a register
|
|
available in most modern CPUs
|
|
to return a value
|
|
that is monotonically increasing
|
|
inside each CPU.
|
|
.Pp
|
|
On SMP systems,
|
|
there will be a number of
|
|
separate monotonic sequences,
|
|
one for each CPU running.
|
|
The value in the SMP case is
|
|
selected from one of these sequences,
|
|
dependent on which CPU
|
|
was scheduled to service the request.
|
|
.Pp
|
|
The speed and the maximum value
|
|
of each counter
|
|
is CPU-dependent.
|
|
Some CPUs
|
|
(such as the
|
|
.Tn Intel
|
|
80486)
|
|
do not have such a register,
|
|
so
|
|
.Fn get_cyclecount
|
|
on these platforms
|
|
returns a (non-monotonic) combination of numbers
|
|
represented by the
|
|
structure returned by
|
|
.Xr binuptime 9 .
|
|
.Pp
|
|
The
|
|
.Tn Pentium
|
|
processors all use the
|
|
.Li TSC
|
|
register.
|
|
.Pp
|
|
The
|
|
.Tn IA64
|
|
processors use the
|
|
.Li AR.ITC
|
|
register.
|
|
.Sh SEE ALSO
|
|
.Xr binuptime 9
|
|
.Sh HISTORY
|
|
The
|
|
.Fn get_cyclecount
|
|
function first appeared in
|
|
.Fx 5.0 .
|
|
.Sh AUTHORS
|
|
This manual page was written by
|
|
.An Mark Murray Aq markm@FreeBSD.org .
|