Tribblix: manual page: power.conf.5

POWER.CONF(5) File Formats and Configurations POWER.CONF(5)

NAME

power.conf - Power Management configuration information file

SYNOPSIS

/etc/power.conf

DESCRIPTION

The power.conf file is used by the Power Management configuration
program pmconfig(8), to initialize the settings for Power Management.
If you make changes to this file, you must run pmconfig(8) manually
for the changes to take effect.

Power Management addresses two specific management scenarios:
management of individual devices and management of the whole system.
An individual device is power managed if the device supports multiple
power levels and if the device driver uses Power Management
interfaces provided by the kernel to save device power when the
device is idle.

All entries in the power.conf file are processed in the order that
they occur in the file.

Automatic Device Power Management

Devices with drivers that use the automatic device Power Management
interfaces are automatically power managed if the autopm entry is
enabled. The autopm entry is described near the end of this section.
The pm-components property describes the Power Management model of a
device driver to the Power Management framework. See pm-
components(9P) for more information.

When a component has been idle at a given power level for its
threshold time, the power level of the component is reduced to the
next lower power level of that component, if any. For devices which
implement multiple components, each component is power-managed
independently.

Default thresholds for components of automatically power managed
devices are computed by the Power Management framework based on the
system idleness threshold. By default, all components of the device
are powered off if they have all been idle for the system's idleness
threshold. The default system idleness threshold is determined by the
applicable United States Environmental Protection Agency's (EPA)
Energy Star Memorandum of Understanding. See the NOTES section of
this manual page for more information.

To set the system idleness threshold, use one of the following
entries:

system-threshold threshold

system-threshold always-on

where threshold is the value of the system idleness threshold in
hours, minutes or seconds as indicated by a trailing h, m or s
(defaulting to seconds if only a number is given). If always-on is
specified, then by default, all devices are left at full power.

The system-threshold entry is applicable to CPU Power Management only
when CPU Power Management has been configured to operate in poll-
mode, which is expressed through the cpupm keyword.

If a system has power manageable CPUs, these can be managed
independently of the system idleness threshold by using one of the
following entries:

cpu-threshold threshold

cpu-threshold always-on

where threshold is the value of the CPU idleness threshold in hours,
minutes or seconds as indicated by a trailing h, m or s (defaulting
to seconds if only a number is given). If always-on is specified,
then by default, all CPUs are left at full power.

The cpu-threshold keyword is used only when CPU Power Management has
been configured to operate in poll-mode, which is expressed through
the cpupm keyword.

If no cpu-threshold entry is specified, then the system idleness
threshold is used.

To override the default device component thresholds assigned by the
Power Management framework, a device-thresholds entry can be used. A
device-thresholds entry sets thresholds for a specific automatically
power-managed device or disables automatic Power Management for the
specific device.

A device-thresholds entry has the form:

device-thresholds phys_path (threshold ...) ...

or

device-thresholds phys_path threshold

or

device-thresholds phys_path always-on

where phys_path specifies the physical path (libdevinfo(3LIB)) of a
specific device. For example,
/pci@8,600000/scsi@4/ssd@w210000203700c3ee,0 specifies the physical
path of a disk. A symbolic link into the /devices tree, for example
/dev/dsk/c1t1d0s0, is also accepted. The thresholds apply (or keeping
the device always on applies) to the specific device only.

In the first form above, each threshold value represents the number
of hours, minutes or seconds, depending on a trailing h, m or s with
a default to seconds, to spend idle at the corresponding power level
before power is reduced to the next lower level of that component.
Parentheses are used to group thresholds per component, with the
first (leftmost) group being applied to component 0, the next to
component 1, and the like. Within a group, the last (rightmost)
number represents the time to be idle in the highest power level of
the component before going to the next-to-highest level, while the
first (leftmost) number represents the time to be idle in the next-
to-lowest power level before going to the lowest power level.

If the number of groups does not match the number of components
exported by the device (by means of pm-components(9P) property), or
the number of thresholds in a group is not one less than the number
of power levels the corresponding component supports, then an error
message is printed and the entry is ignored.

For example, assume a device called xfb exports the components Frame
Buffer and Monitor. Component Frame Buffer has two power levels: Off
and On. Component Monitor has four power levels: Off, Suspend,
Standby, and On.

The following device-thresholds entry:

device-thresholds /pci@f0000/xfb@0 (0) (3m 5m 15m)

would set the threshold time for the Monitor component of the
specific xfb card to go from On to Standby in 15 minutes, the
threshold for Monitor to go from Standby to Suspend in 5 minutes, and
the threshold for Monitor to go from Suspend to Off in 3 minutes. The
threshold for Frame Buffer to go from On to Off is 0 seconds.

In the second form above, where a single threshold value is specified
without parentheses, the threshold value represents a maximum overall
time within which the entire device should be powered down if it is
idle. Because the system does not know about any internal
dependencies there can be among a device's components, the device can
actually be powered down sooner than the specified threshold, but
does take longer than the specified threshold, provided that all
device components are idle.

In the third form above, all components of the device are left at
full power.

Device Power Management entries are only effective if there is no
user process controlling the device directly. For example, X Windows
systems directly control frame buffers. The entries in the power.conf
file are effective only when X Windows is not running.

Dependencies among devices can also be defined. A device depends upon
another if none of its components might have their power levels
reduced unless all components of the other device are powered off. A
dependency can be indicated by an entry of the form:

device-dependency dependent_phys_path phys_path [ phys_path ... ]

where dependent_phys_path is the path name (as above) of the device
that is kept up by the others, and the phys_path entries specify the
devices that keep it up. A symbolic link into the /devices tree, such
as /dev/fb, is also accepted. This entry is needed only for logical
dependents for the device. A logical dependent is a device that is
not physically connected to the power managed device (for example,
the display and the keyboard). Physical dependents are automatically
considered and need not be included.

In addition to listing dependents by physical path, an arbitrary
group of devices can be made dependent upon another device by
specifying a property dependency using the following syntax:

device-dependency-property property phys_path [phys_path ...]

where each device that exports the property property is kept up by
the devices named by phys_path(s). A symbolic link into the /devices
tree (such as /dev/fb) is accepted as well as a pathname for
phys_path.

For example, the following entry ensures that every device that
exports the boolean property named removable-media is kept up when
the console framebuffer is up. See removable-media(9P).

# This entry keeps removable media from being powered down unless the
# console framebuffer and monitor are powered down
# (See removable-media(9P))
#
device-dependency-property removable-media /dev/fb

An autopm entry can be used to enable or disable automatic device
Power Management on a system-wide basis. The format of the autopm
entry is:

autopm behavior

Acceptable behavior values are described as follows:

default
The behavior of the system depends upon its model. Desktop
models that fall under the United States Environmental
Protection Agency's Energy Star Memorandum of
Understanding #3 have automatic device Power Management
enabled, and all others do not. See the NOTES section of
this manual page for more information.

enable
Automatic device Power Management is started when this
entry is encountered.

disable
Automatic device Power Management is stopped when this
entry is encountered.

A cpupm entry can be used to enable or disable Power Management of
CPUs on a system-wide basis, independent of autopm. The format of the
cpupm entry is:

cpupm behavior

Acceptable behavior values and their meanings are :

enable
CPU Power Management is started when this entry is
encountered.

Where the behavior is enable, an optional mode argument
can be specified:

cpupm enable mode

Acceptable mode values and their meanings are:

event-mode
CPU power state transitions is driven by
thread scheduler/dispatcher events. The
cpu-threshold, and system-threshold keywords
are not used for CPUs in this mode.

poll-mode
The Power Management framework polls the
idleness of the system's CPUs, and manages
their power once idle for the period of time
specified by either the system-threshold or
cpu-threshold.

disable
CPU Power Management is stopped when this entry is
encountered.

If supported by the platform, a cpu_deep_idle entry can be used to
enable or disable automatic use of power saving cpu idle states. The
format of the cpu_deep_idle entry is:

cpu_deep_idle behavior

Acceptable values for behavior are:

default
Advanced cpu idle power saving features are enabled on
hardware which supports it. On X86 systems this can
translate to the use of ACPI C-States beyond C1.

enable
Enables the system to automatically use idle cpu power
saving features.

disable
The system does not automatically use idle cpu power
saving features. This option can be used when maximum
performance is required at the expense of power.

absent
It the cpu_deep_idle keyword is absent from power.conf the
behavior is the same as the default case.

Once every device is at its lowest possible power state, additional
power savings can be obtained by putting the system into a sleep
state (if the platform hardware is capable of doing so).

S3 Support
Because of reliability problems encountered in BIOS implementations
of X86 systems not produced by Sun Microsystems, by default, only X86
workstation products produced by Sun are considered to support S3
(suspend to RAM). To override this default, an S3-support entry (of
the format S3-support behavior) can be used to indicate if the system
supports S3.

Acceptable behavior values are:

enable
The system supports entry into S3 state. If the BIOS of a
system enabled using an S3-support enable entry does not
support entry into S3, the attempt fails and the system
returns to normal operation. If support for S3 in the BIOS
of a system enabled via an S3-support entry contains bugs,
the system can be unable to enter S3 or resume
successfully, so use this entry with caution.

disable
The system does not support entry into S3 state.

Automatic Entry Into S3
If supported by your platform, an autoS3 entry can be used to enable
or disable automatic entry into the S3 state. When in the S3 state,
the power button, keyboard and mouse activity or network traffic
(depending upon the capabilities of the platform hardware) can wake
the system, returning it to the state it was in upon entry to the S3
state. If the platform doesn't support S3, the entry has no effect.

The format of the autoS3 entry is autoS3 behavior.

Acceptable behavior values are:

default
System behavior depends upon model. Sun X86 desktop and
workstation models that fall under the United States
Environmental Protection Agency's Energy Star Memorandum
of Understanding #3 have automatic entry into the S3 state
enabled. Non-Sun systems do not. See NOTES for more
information.

enable
Enables the system to automatically enter the S3 state if
autopm is enabled and every device is at its lowest power
state.

disable
The system does not automatically enter the S3 state.

System Power Management

The system Power Management entries control Power Management of the
entire system using the suspend-resume feature. When the system is
suspended, the complete current state is saved on the disk before
power is removed. On reboot, the system automatically starts a resume
operation and the system is restored to the state it was in prior to
suspend.

The system can be configured to do an automatic shutdown
(autoshutdown) using the suspend-resume feature by an entry of the
following form:

autoshutdown idle_time start_time finish_time behavior

idle_time specifies the time in minutes that system must have been
idle before it is automatically shutdown. System idleness is
determined by the inactivity of the system and can be configured as
discussed below.

start_time and finish_time (each in hh:mm) specify the time period
during which the system can be automatically shutdown. These times
are measured from the start of the day (12:00 a.m.). If the
finish_time is less than or equal to the start_time, the period span
from midnight to the finish_time and from the start_time to the
following midnight. To specify continuous operation, the finish_time
can be set equal to the start_time.

Acceptable behavior values are described as follows:

shutdown
The system is shut down automatically when it has
been idle for the number of minutes specified in the
idle_time value and the time of day falls between the
start_time and finish_time values.

noshutdown
The system is never shut down automatically.

autowakeup
If the hardware has the capability to do autowakeup,
the system is shut down as if the value were shutdown
and the system is restarted automatically the next
time the time of day equals finish_time.

default
The behavior of the system depends upon its model.
Desktop models that fall under the United States
Environmental Protection Agency's Energy Star
Memorandum of Understanding #2 have automatic
shutdown enabled, as if behavior field were set to
shutdown, and all others do not. See NOTES.

unconfigured
The system does not be shut down automatically. If
the system has just been installed or upgraded, the
value of this field is changed upon the next reboot.

You can use the following format to configure the system's notion of
idleness:

idleness_parameter value

Where idleness_parameter can be:

ttychars
If the idleness_parameter is ttychars, the value field
is interpreted as the maximum number of tty characters
that can pass through the ldterm module while still
allowing the system to be considered idle. This value
defaults to 0 if no entry is provided.

loadaverage
If the idleness_parameter is loadaverage, the
(floating point) value field is interpreted as the
maximum load average that can be seen while still
allowing the system to be considered idle. This value
defaults to 0.04 if no entry is provided.

diskreads
If the idleness_parameter is diskreads, the value
field is interpreted as the maximum number of disk
reads that can be perform by the system while still
allowing the system to be considered idle. This value
defaults to 0 if no entry is provided.

nfsreqs
If the idleness_parameter is nfsreqs, the value field
is interpreted as the maximum number of NFS requests
that can be sent or received by the system while still
allowing the system to be considered idle. Null
requests, access requests, and getattr requests are
excluded from this count. This value defaults to 0 if
no entry is provided.

idlecheck
If the idleness_parameter is idlecheck, the value must
be pathname of a program to be executed to determine
if the system is idle. If autoshutdown is enabled and
the console keyboard, mouse, tty, CPU (as indicated by
load average), network (as measured by NFS requests)
and disk (as measured by read activity) have been idle
for the amount of time specified in the autoshutdown
entry specified above, and the time of day falls
between the start and finish times, then this program
is executed to check for other idleness criteria. The
value of the idle time specified in the above
autoshutdown entry is passed to the program in the
environment variable PM_IDLETIME. The process must
terminate with an exit code that represents the number
of minutes that the process considers the system to
have been idle.

There is no default idlecheck entry.

When the system is suspended, the current system state is saved on
the disk in a statefile. An entry of following form can be used to
change the location of statefile:

statefile pathname

where pathname identifies a block special file, for example,
/dev/dsk/c1t0d0s2, or is the absolute pathname of a local ufs file.
If the pathname specifies a block special file, it can be a symbolic
link as long as it does not have a file system mounted on it. If
pathname specifies a local ufs file, it cannot be a symbolic link. If
the file does not exist, it is created during the suspend operation.
All the directory components of the path must already exist.

The actual size of statefile depends on a variety of factors,
including the size of system memory, the number of loadable
drivers/modules in use, the number and type of processes running, and
the amount of user memory that has been locked down. It is
recommended that statefile be placed on a file system with at least
10 Mbytes of free space. In case there is no statefile entry at boot
time, an appropriate new entry is automatically created by the
system.

EXAMPLES

Example 1: Disabling Automatic Device Power Management

To disable automatic device Power Management, change the following
line in the /etc/power.conf file

autopm default

to read:

autopm disable

Then run pmconfig or reboot. See pmconfig(8) for more information.

ATTRIBUTES

NOTES

SPARC desktop models first shipped after October 1, 1995 and before
July 1, 1999 comply with the United States Environmental Protection
Agency's Energy Star Memorandum of Understanding #2 guidelines and
have autoshutdown enabled by default after 30 minutes of system
idleness. This is achieved by default keyword of autoshutdown entry
behave as shutdown for these machines. The user is prompted to
confirm this default behavior at system installation reboot.

SPARC desktop models first shipped after July 1, 1999 comply with the
United States Environmental Protection Agency's Energy Star
Memorandum of Understanding #3 guidelines and have autoshutdown
disabled by default, with autopm enabled after 30 minutes of
idleness. This is achieved by interpreting default keyword of autopm
entry behavior as enabled for these machines. User is not prompted to
confirm this default behavior.

To determine the version of the EPA's Energy Star Memorandum
applicable to your machine, use:

prtconf -pv | grep -i energystar

Absence of a property indicates no Energy Star guidelines are
applicable to your machine.

System Power Management (suspend-resume) is currently supported only
on a limited set of hardware platforms.

Sun X86 desktop models first shipped after July 1, 1999 fall within
United States Environmental Protection Agency's Energy Star
Memorandum of Understanding #3 guidelines and have autopm and autoS3
enabled by default, with entry into S3 after 30 minutes of idleness.
This is achieved by interpreting the default keyword of the autopm
and autoS3 behaviors as enabled for these machines. You are not
prompted to confirm the default behavior. On all other X86 systems,
the autopm and autoS3 default keywords are interpreted as disable.

June 20, 2021 POWER.CONF(5)