Add eventtimers(7) man page, briefly describing event timers subsystem
functionality and configuration options.
This commit is contained in:
mav
parent
da4ad90d63
commit
97cba22b58
@ -95,7 +95,7 @@ group is bound to specific CPU core. This is possible only when each
|
||||
of these comparators has own unsharable IRQ.
|
||||
.Sh SEE ALSO
|
||||
.Xr acpi 4 ,
|
||||
.Xr eventtimer 4
|
||||
.Xr eventtimers 7
|
||||
.Sh HISTORY
|
||||
The
|
||||
.Nm
|
||||
|
||||
@ -10,6 +10,7 @@ MAN= adding_user.7 \
|
||||
c99.7 \
|
||||
development.7 \
|
||||
environ.7 \
|
||||
eventtimers.7 \
|
||||
ffs.7 \
|
||||
firewall.7 \
|
||||
hier.7 \
|
||||
|
||||
131
share/man/man7/eventtimers.7
Normal file
131
share/man/man7/eventtimers.7
Normal file
@ -0,0 +1,131 @@
|
||||
.\" Copyright (c) 2010 Alexander Motin <mav@FreeBSD.org>
|
||||
.\" 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 September 15, 2010
|
||||
.Dt eventtimers 4
|
||||
.Os
|
||||
.Sh NAME
|
||||
.Nm eventtimers
|
||||
.Nd kernel event timers subsystem
|
||||
.Sh SYNOPSIS
|
||||
Kernel uses several types of time-related devices, such as: real time clocks,
|
||||
time counters and event timers.
|
||||
Real time clocks responsible for tracking real world time, mostly when system
|
||||
is down.
|
||||
Time counters are responsible for generation of monotonically increasing
|
||||
timestamps for precise uptime tracking purposes, when system is running.
|
||||
Event timers are responsible for generating interrupts at specified time or
|
||||
periodically, to run different time-based events.
|
||||
This page is about the last.
|
||||
.Sh DESCRIPTION
|
||||
Kernel uses time-based events for many different purposes: scheduling,
|
||||
statistics, time keeping, profiling and many other things, based on
|
||||
.Xr callout 9
|
||||
mechanism.
|
||||
These purposes now grouped into three main callbacks:
|
||||
.Bl -tag
|
||||
.It hardclock()
|
||||
.Xr callout 9
|
||||
and timekeeping events entry. Called with frequency defined by hz variable,
|
||||
usually 1000Hz.
|
||||
.It statclock()
|
||||
statistics and scheduler events entry. Called with frequency about 128Hz.
|
||||
.It profclock()
|
||||
profiler events entry. When enabled, called with frequency about 8KHz.
|
||||
.El
|
||||
Different platforms provide different kinds of timer hardware.
|
||||
The goal of the event timers subsystem is to provide unified way to control
|
||||
that hardware, and to use it, supplying kernel with all required time-based
|
||||
events.
|
||||
.Pp
|
||||
Each driver implementing event timers, registers them at the subsystem.
|
||||
It is possible to see the list of present event timers, like this, via
|
||||
.Va kern.eventtimer
|
||||
sysctl:
|
||||
.Bd -literal
|
||||
kern.eventtimer.choice: HPET(550) LAPIC(400) i8254(100) RTC(0)
|
||||
kern.eventtimer.et.LAPIC.flags: 15
|
||||
kern.eventtimer.et.LAPIC.frequency: 0
|
||||
kern.eventtimer.et.LAPIC.quality: 400
|
||||
kern.eventtimer.et.i8254.flags: 1
|
||||
kern.eventtimer.et.i8254.frequency: 1193182
|
||||
kern.eventtimer.et.i8254.quality: 100
|
||||
kern.eventtimer.et.RTC.flags: 17
|
||||
kern.eventtimer.et.RTC.frequency: 32768
|
||||
kern.eventtimer.et.RTC.quality: 0
|
||||
kern.eventtimer.et.HPET.flags: 7
|
||||
kern.eventtimer.et.HPET.frequency: 14318180
|
||||
kern.eventtimer.et.HPET.quality: 550
|
||||
.Ed
|
||||
, where:
|
||||
.Bl -tag
|
||||
.It Va kern.eventtimer.et. Ns Ar X Ns Va .flags
|
||||
bitmask, defining event timer capabilities:
|
||||
.Bl -tag -compact
|
||||
.It 1
|
||||
periodic mode supported,
|
||||
.It 2
|
||||
one-shot mode supported,
|
||||
.It 4
|
||||
timer is per-CPU,
|
||||
.It 8
|
||||
timer may stop when CPU goes to sleep state,
|
||||
.It 16
|
||||
timer supports only power-of-2 divisors.
|
||||
.El
|
||||
.It Va kern.eventtimer.et. Ns Ar X Ns Va .frequency
|
||||
timer base frequency,
|
||||
.It Va kern.eventtimer.et. Ns Ar X Ns Va .quality
|
||||
integral value, defining how good is this timer, comparing to others.
|
||||
.El
|
||||
.Pp
|
||||
Timers management code of the kernel chooses one timer from that list.
|
||||
Current choice can be read and affected via
|
||||
.Va kern.eventtimer.timer
|
||||
tunable/sysctl.
|
||||
Several other tunables/sysctls are affecting how exactly this timer is used:
|
||||
.Bl -tag
|
||||
.It Va kern.eventtimer.periodic
|
||||
allows to choose periodic and one-shot operation mode.
|
||||
In periodic mode, periodic interrupts from timer hardware are taken as the
|
||||
only source of time for time events.
|
||||
One-shot mode instead uses currently selected time counter to precisely
|
||||
schedule all needed events and programs event timer to generate interrupt
|
||||
exactly in specified time.
|
||||
Default value depends of chosen timer capabilities, but one-shot mode is
|
||||
preferred, until other is forced by user or hardware.
|
||||
.It Va kern.eventtimer.singlemul
|
||||
in periodic mode specifies how much times higher timer frequency should be,
|
||||
to not strictly alias hardclock() and statclock() events. Default values are
|
||||
1, 2 or 4, depending on configured HZ value.
|
||||
.It Va kern.eventtimer.idletick
|
||||
makes each CPU to receive every timer interrupt independently of whether they
|
||||
busy or not. By default this options is disabled. If chosen timer is per-CPU
|
||||
and runs in periodic mode, this option has no effect - all interrupts are
|
||||
always generating.
|
||||
.El
|
||||
.Sh SEE ALSO
|
||||
.Xr hpet 4
|
||||
@ -1019,6 +1019,7 @@ over services you export from your box (web services, email).
|
||||
.Xr rc.conf 5 ,
|
||||
.Xr sysctl.conf 5 ,
|
||||
.Xr firewall 7 ,
|
||||
.Xr eventtimers 7 ,
|
||||
.Xr hier 7 ,
|
||||
.Xr ports 7 ,
|
||||
.Xr boot 8 ,
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user