As of now pretty much everyone has heard of
systemd, the next generation init system for Linux. Next to the fact that if provides a really fast boot (on different systems tested approximately 50% of the original boot time) and a clean solution for dependencies of services it also offers the capability to write services in a very simple manner. So today we are going to write a simple service to set your power profile (
as introduced last year). Note that you (obviously) need a systemd enabled system like
Fedora 15.
First of all we need to know how to set set power profile. This requires three things: a fairly recent kernel, a Radeon graphics card that supports power modes on Linux and sysfs enabled in your kernel. A simple way to test this is to execute the following command:
test -f /sys/class/drm/card0/device/power_profile && echo "power_profile supported" || echo "power_profile NOT supported"
Note: This assumes that your Radeon card is the "first card" (i.e. "card0"). This might vary from system to system.The will show you if the power modes are supported by your system. If your system is supported you need two files:
1.) The systemd service file in /etc/systemd/system/radeon-power_profile
[Unit]
Description=Radeon Power Profile
[Service]
Type=oneshot
ExecStart=/usr/local/sbin/radeon-power_profile low
[Install]
WantedBy=multi-user.target
2.) A small helper script to set the power mode in /usr/local/sbin/radeon-power_profile
#!/bin/sh
EXEC_NAME=`basename $0`;
TARGET="/sys/class/drm/card0/device/power_profile"
CURRENT_PROFILE=`cat ${TARGET}`
append_profile() {
local PROFILE=$1
echo -n " ${PROFILE}"
if [ "x${CURRENT_PROFILE}x" == "x${PROFILE}x" ]; then
echo -n " (current)"
fi
echo
}
if [ $# != 1 ]; then
echo "usage: ${EXEC_NAME} "
echo
echo "Valid profiles:"
for AVAILABLE_PROFILE in low high default auto; do
append_profile ${AVAILABLE_PROFILE}
done
exit 0
fi
PROFILE="$1"
if [ "x${PROFILE}x" == "xlowx" ] || [ "x${PROFILE}x" == "xhighx" ] || [ "x${PROFILE}x" == "xautox" ] || [ "x${PROFILE}x" == "xdefaultx" ]; then
echo "${PROFILE}" > ${TARGET}
else
logger "[${EXEC_NAME}] WARN: Invalid power_profile '${PROFILE}'"
exit 1
fi
exit 0
Note: If your card is not "card0" you need to change the value of TARGET to the proper value.After you create the scripts you should
test if this works for you. The service is meant to set your power mode to low which is the best for mobile devices running on battery or to cool down your system. To test the service call:
/usr/local/sbin/radeon-power_profile
This will print out which profile is currently active ("default" in most cases). Now you can start the service
systemctl start radeon-power_profile.service
This will most likely cause a single flicker of the display (this might be a
bug as it does not happen when GPU and memory clock changes happen on Microsoft Windows). After that a second call to /usr/local/sbin/radeon-power_profile should show your clock is now at "low". Verify that your system is running stable and smooth as before.
Note: Setting the power mode to low will obviously cause your 3D rendering to be slower. If everything works as expected you can enable the service by default using
systemctl enable radeon-power_profile.service
Now your system will set the power mode during boot. On my systems it really extended the battery life time and my passive (fan-less) card went from 70°C to 45°C.
