ba66454b69
that TSC is for any fifth-gneration of later x86 processor, not an i586, and document that it _is_ available to applications.
150 lines
4.6 KiB
Groff
150 lines
4.6 KiB
Groff
.\"
|
|
.\" Copyright (c) 1996 Joerg Wunsch
|
|
.\"
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" This program is free software.
|
|
.\"
|
|
.\" 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 DEVELOPERS ``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 DEVELOPERS 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 April 1, 1996
|
|
.Os
|
|
.Dt CLOCKS 7
|
|
.Sh NAME
|
|
.Nm clocks
|
|
.Nd various system timers
|
|
.Sh SYNOPSIS
|
|
.Fd #include <time.h>
|
|
.Sh DESCRIPTION
|
|
.Ql HZ
|
|
is not part of the application interface in BSD.
|
|
.Pp
|
|
There are many different real and virtual (timekeeping) clocks with
|
|
different frequencies:
|
|
.Bl -bullet -offset XXX
|
|
.It
|
|
The scheduling clock. This is a real clock with frequency that
|
|
happens to be 100. It isn't available to applications.
|
|
.It
|
|
The statistics clock. This is a real clock with frequency that
|
|
happens to be 128. It isn't directly available to applications.
|
|
.It
|
|
The clock reported by
|
|
.Xr clock 3 .
|
|
This is a virtual clock with a frequency that happens to be 128. Its
|
|
actual frequency is given by the macro
|
|
.Dv CLOCKS_PER_SEC .
|
|
Note that
|
|
.Dv CLOCKS_PER_SEC
|
|
may be floating point. Don't use
|
|
.Fn clock
|
|
in new programs under
|
|
.Tn FreeBSD .
|
|
It is feeble compared with
|
|
.Xr getrusage 2 .
|
|
It is provided for ANSI conformance. It is implemented by calling
|
|
.Fn getrusage
|
|
and throwing away information and resolution.
|
|
.It
|
|
The clock reported by
|
|
.Xr times 3 .
|
|
This is a virtual clock with a frequency that happens to be 128. Its
|
|
actual frequency is given by the macro
|
|
.Dv CLK_TCK
|
|
(deprecated; don't use) and by
|
|
.Fn sysconf SC_CLK_TCK
|
|
and by
|
|
.Xr sysctl 3 .
|
|
Note that its frequency may be different from
|
|
.Dv CLOCKS_PER_SEC .
|
|
Don't use
|
|
.Xr times 3
|
|
in new programs under
|
|
.Tn FreeBSD .
|
|
It is feeble compared with
|
|
.Xr gettimeofday 2
|
|
together with
|
|
.Fn getrusage .
|
|
It is provided for POSIX
|
|
conformance. It is implemented by calling
|
|
.Fn gettimeofday
|
|
and
|
|
.Fn getrusage
|
|
and throwing away information and resolution.
|
|
.It
|
|
The profiling clock. This is a real clock with frequency 1024.
|
|
It is used mainly by
|
|
.Xr moncontrol 3 ,
|
|
.Xr kgmon 8
|
|
and
|
|
.Xr gprof 1 .
|
|
Applications should determine its actual frequency using
|
|
.Xr sysctl 3
|
|
or by reading it from the header in the profiling data file.
|
|
.It
|
|
The mc14618a clock. This is a real clock with a nominal frequency of
|
|
32768. It is divided down to give the statistic clock and the profiling
|
|
clock. It isn't available to applications.
|
|
.It
|
|
The microseconds clock. This is a virtual clock with frequency
|
|
1000000. It is used for most timekeeping in BSD and is exported
|
|
to applications in
|
|
.Xr getrusage 2 ,
|
|
.Xr gettimeofday 2 ,
|
|
.Xr select 2 ,
|
|
.Xr getitimer 2 ,
|
|
etc... This is the clock that should normally be used
|
|
by BSD applications.
|
|
.It
|
|
The i8254 clock. This is a real clock/timer with a nominal frequency of
|
|
1193182. It is divided down to give the scheduling clock. It isn't
|
|
available to applications.
|
|
.It
|
|
The TSC clock (64-bit register) on fifth-generation or later x86 systems.
|
|
This is a real clock with a frequency that is equivalent to the number of
|
|
cycles per second of the CPU(s).
|
|
Its frequency can be found using the sysctl
|
|
.Sy machdep.tsc_freq .
|
|
It is used to interpolate between values of the scheduling clock.
|
|
It is only available to applications in a purely machine-dependant manner.
|
|
.El
|
|
.Pp
|
|
Summary: if
|
|
.Ql HZ
|
|
isn't 1000000 then the application is probably using the wrong clock.
|
|
.Sh SEE ALSO
|
|
.Xr gprof 1 ,
|
|
.Xr getitimer 2 ,
|
|
.Xr getrusage 2 ,
|
|
.Xr gettimeofday 2 ,
|
|
.Xr select 2 ,
|
|
.Xr clock 3 ,
|
|
.Xr moncontrol 3 ,
|
|
.Xr times 3
|
|
.Sh AUTHORS
|
|
This man page has been written by
|
|
.ie t J\(:org Wunsch
|
|
.el Joerg Wunsch
|
|
after a description posted by
|
|
.An Bruce Evans .
|