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.Dd July 11, 2015
.Dt APERF 4
.Os
.Sh NAME
.Nm aperf
.Nd driver measuring effective CPU frequency via APERF/MPERF MSRs
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following lines in your kernel configuration file:
.Bd -ragged -offset indent
.Cd "device aperf"
.Ed
.Pp
Alternatively, to load the driver as a
module at boot time, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
aperf_load="YES"
.Ed
.Sh DESCRIPTION
The
.Nm
driver provides support for measuring the effective CPU frequency, using the
APERF and MPERF MSRs.
The values are exposed through the
.Dv HW_SENSORS
.Xr sysctl 3
tree.
For example:
.Bd -literal -offset indent
% sysctl hw.sensors
hw.sensors.cpu0.freq0: 2684298000 Hz (cpu0 freq)
hw.sensors.cpu1.freq0: 1418960000 Hz (cpu1 freq)
hw.sensors.cpu2.freq0: 1234898000 Hz (cpu2 freq)
hw.sensors.cpu3.freq0: 1242533000 Hz (cpu3 freq)
.Ed
.Sh HARDWARE
The
.Nm
driver supports all AMD and Intel CPUs which provide the APERF and MPERF MSRs:
.Pp
.Bl -bullet -compact
.It
Most AMD CPUs starting at Family 10h
.It
Most Intel CPUs starting from Core series and Atom respectively.
.El
.Sh SEE ALSO
.Xr systat 1 ,
.Xr sysctl 3 ,
.Xr sensorsd 8 ,
.Xr sysctl 8
.Sh HISTORY
The
.Nm
driver first appeared in
.Dx 4.3 .
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was written by
.An Imre Vadasz Aq Mt imre@vdsz.com .