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diff --git a/share/man/man7/clocks.7 b/share/man/man7/clocks.7 new file mode 100644 index 0000000..6927968 --- /dev/null +++ b/share/man/man7/clocks.7 @@ -0,0 +1,178 @@ +.\" +.\" 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 January 18, 2008 +.Dt CLOCKS 7 +.Os +.Sh NAME +.Nm clocks +.Nd various system timers +.Sh SYNOPSIS +.In time.h +.Sh DESCRIPTION +.Dv HZ +is not part of the application interface in +.Bx . +.Pp +There are many different real and virtual (timekeeping) clocks with +different frequencies: +.Bl -bullet +.It +The scheduling clock. +This is a real clock with frequency that happens to be 100. +It is not available to applications. +.It +The statistics clock. +This is a real clock with frequency that happens to be 128. +It is not 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. +Do not use +.Xr clock 3 +in new programs under +.Fx . +It is feeble compared with +.Xr getrusage 2 . +It is provided for +.Tn ANSI +conformance. +It is implemented by calling +.Xr getrusage 2 +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; do not 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 . +Do not use +.Xr times 3 +in new programs under +.Fx . +It is feeble compared with +.Xr gettimeofday 2 +together with +.Xr getrusage 2 . +It is provided for +.Tn POSIX +conformance. +It is implemented by calling +.Xr gettimeofday 2 +and +.Xr getrusage 2 +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 mc146818a 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 is not available to applications. +.It +The microseconds clock. +This is a virtual clock with frequency 1000000. +It is used for most timekeeping in +.Bx +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 +.Bx +applications. +.It +The i8254 clock. +This is a real clock/timer with a nominal frequency of 1193182. +It has three independent time counters to be used. +It is divided down to give the scheduling clock. +It is not 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 +.Va machdep.tsc_freq +sysctl, if it is available. +It is used to interpolate between values of the scheduling clock. +It can be accessed using the +.Dv PMIOTSTAMP +request of +.Xr perfmon 4 . +.It +The ACPI clock. +This is a real clock/timer with a nominal frequency of 3579545. +It is accessed via a 24 or 32 bit register. +Unlike the TSC clock, it maintains a constant tick rate even when the CPU +sleeps or its clock rate changes. +It is not available to applications. +.El +.Pp +Summary: if +.Dv HZ +is not 1000000 then the application is probably using the wrong clock. +.Sh SEE ALSO +.Xr gprof 1 , +.Xr clock_gettime 2 , +.Xr getitimer 2 , +.Xr getrusage 2 , +.Xr gettimeofday 2 , +.Xr select 2 , +.Xr clock 3 , +.Xr moncontrol 3 , +.Xr times 3 +.Sh AUTHORS +.An -nosplit +This manual page was written by +.An J\(:org Wunsch +after a description posted by +.An Bruce Evans . |
