The
utility monitors the system state and sets various power control options
accordingly.
It offers three modes (maximum, minimum, and adaptive) that can be
individually selected while on AC power or batteries.
The modes maximum, minimum, and adaptive may be abbreviated max, min, adp.
Maximum mode chooses the highest performance values.
Minimum mode selects the lowest performance values to get the most power
savings.
Adaptive mode attempts to strike a balance by degrading performance when
the system appears idle and increasing it when the system is busy.
It offers a good balance between a small performance loss for greatly
increased power savings.
The default mode is
adaptive.
The
utility recognizes the following runtime options:
-a mode
Selects the
mode
to use while on AC power.
-b mode
Selects the
mode
to use while on battery power.
-i percent
Specifies the CPU idle percent level when
adaptive
mode should begin to degrade performance to save power.
The default is 90% or higher.
-n mode
Selects the
mode
to use normally when the AC line state is unknown.
-p ival
Specifies a different polling interval (in milliseconds) for AC line state
and system idle levels.
The default is 500 ms.
-P pidfile
Specifies an alternative file in which the process ID should be stored.
The default is
/var/run/powerd.pid
-r percent
Specifies the CPU idle percent level where
adaptive
mode should consider the CPU running and increase performance.
The default is 65% or lower.
-v
Verbose mode.
Messages about power changes will be printed to stdout and
will operate in the foreground.
An -nosplit
An Colin Percival
first wrote
estctrl
the utility that
is based on.
An Nate Lawson
then updated it for
cpufreq(4),
added features, and wrote this manual page.
BUGS
The
utility should also power down idle disks and other components besides the CPU.
If
is used with
power_profile
they may override each other.
The
utility
should probably use the
devctl(4)
interface instead of polling for AC line state.
