1.\"
2.\" Copyright (c) 1996 Joerg Wunsch
3.\"
4.\" All rights reserved.
5.\"
6.\" This program is free software.
7.\"
8.\" Redistribution and use in source and binary forms, with or without
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20.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
21.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27.\"
28.\" $FreeBSD: head/share/man/man7/clocks.7 81622 2001-08-14 10:01:54Z ru $
29.\" "
30.Dd April 1, 1996
31.Os
32.Dt CLOCKS 7
33.Sh NAME
34.Nm clocks
35.Nd various system timers
36.Sh SYNOPSIS
37.Fd #include <time.h>
38.Sh DESCRIPTION
39.Ql HZ
40is not part of the application interface in
41.Bx .
42.Pp
43There are many different real and virtual (timekeeping) clocks with
44different frequencies:
45.Bl -bullet -offset XXX
46.It
47The scheduling clock. This is a real clock with frequency that
48happens to be 100. It isn't available to applications.
49.It
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103.Xr sysctl 3
104or by reading it from the header in the profiling data file.
105.It
106The mc14618a clock. This is a real clock with a nominal frequency of
10732768. It is divided down to give the statistic clock and the profiling
108clock. It isn't available to applications.
109.It
110The microseconds clock. This is a virtual clock with frequency
1111000000. It is used for most timekeeping in
112.Bx
113and is exported
114to applications in
115.Xr getrusage 2 ,
116.Xr gettimeofday 2 ,
117.Xr select 2 ,
118.Xr getitimer 2 ,
119etc... This is the clock that should normally be used
120by
121.Bx
122applications.
123.It
124The i8254 clock. This is a real clock/timer with a nominal frequency of
1251193182. It is divided down to give the scheduling clock. It isn't
126available to applications.
127.It
128The TSC clock (64-bit register) on fifth-generation or later x86 systems.
129This is a real clock with a frequency that is equivalent to the number of
130cycles per second of the CPU(s).
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2.\" Copyright (c) 1996 Joerg Wunsch
3.\"
4.\" All rights reserved.
5.\"
6.\" This program is free software.
7.\"
8.\" Redistribution and use in source and binary forms, with or without
--- 11 unchanged lines hidden (view full) ---
20.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
21.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27.\"
28.\" $FreeBSD: head/share/man/man7/clocks.7 81622 2001-08-14 10:01:54Z ru $
29.\" "
30.Dd April 1, 1996
31.Os
32.Dt CLOCKS 7
33.Sh NAME
34.Nm clocks
35.Nd various system timers
36.Sh SYNOPSIS
37.Fd #include <time.h>
38.Sh DESCRIPTION
39.Ql HZ
40is not part of the application interface in
41.Bx .
42.Pp
43There are many different real and virtual (timekeeping) clocks with
44different frequencies:
45.Bl -bullet -offset XXX
46.It
47The scheduling clock. This is a real clock with frequency that
48happens to be 100. It isn't available to applications.
49.It
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103.Xr sysctl 3
104or by reading it from the header in the profiling data file.
105.It
106The mc14618a clock. This is a real clock with a nominal frequency of
10732768. It is divided down to give the statistic clock and the profiling
108clock. It isn't available to applications.
109.It
110The microseconds clock. This is a virtual clock with frequency
1111000000. It is used for most timekeeping in
112.Bx
113and is exported
114to applications in
115.Xr getrusage 2 ,
116.Xr gettimeofday 2 ,
117.Xr select 2 ,
118.Xr getitimer 2 ,
119etc... This is the clock that should normally be used
120by
121.Bx
122applications.
123.It
124The i8254 clock. This is a real clock/timer with a nominal frequency of
1251193182. It is divided down to give the scheduling clock. It isn't
126available to applications.
127.It
128The TSC clock (64-bit register) on fifth-generation or later x86 systems.
129This is a real clock with a frequency that is equivalent to the number of
130cycles per second of the CPU(s).
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