.Dd February 17, 2014
.Dt PERFBIAS 4
.Os
.Sh NAME
.Nm perfbias
.Nd device driver for Intel performance-energy bias support
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following line in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device perfbias"
.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
perfbias_load="YES"
.Ed
.Sh DESCRIPTION
The
.Nm
driver provides support for Intel performance-energy bias,
which allows OS to guide logical CPU heuristic of power management features
to favor increasing dynamic performance or conserve energy consumption.
Each logical CPU could has its own performance-energy bias setting.
.Sh MIB Variables
Each logical CPU's performance-energy bias is controlled through the
.Va machdep.perfbias Ns Em X
branch of the
.Xr sysctl 3
MIB.
.Em X
is the logical CPU id.
.Bl -tag -width "hint"
.It Va hint
Valid value ranges from 0 to 15, inclusive.
Set it to 0 to give the highest performance.
Set it to 15 to maximize energy saving.
.El
.Sh SEE ALSO
.Xr sysctl 3 ,
.Xr sysctl 8