All righty then... I was in a hacking mood tonight, so I decided to go DIY on this. Rather than picking one of the stock CPU power management governors and tuning it, I concluded that what I
really want is a meta-governor, which switches between governors based on system activity and load.
I wrote a simple daemon (as a bash script), which watches the desktop environment for keyboard and mouse activity. Any input device activity causes the "ondemand" governor (which favors responsiveness over power saving) to be used. After a certain number of seconds of inactivity, we fall back to the "conservative" governor, and eventually to the "powersave" governor (which pins clocks to their minimum frequency). But wait... if we have a resource intensive background job (e.g. media encode) running, we don't want the "powersave" governor to kick in, since that would slow things down. So we also watch system load, and if it exceeds a certain threshold, we hold off on enabling the "powersave" governor.
I've initially got the thresholds set to 15 seconds (for the drop to "conservative"), 15 minutes (to drop to "powersave"), and a system load load of 2.00 to keep the system out of "powersave"). The daemon polls every 0.5 second, so that's the maximum latency for switching out of the lower-power governor states back to "ondemand".
Gonna run with this for a while, and see if I experience any issues.
The script runs in a "debug" mode if executed as a non-root user, where it merely logs what changes it
would make to the CPU power management state if it could.
Here's the script... releasing it under GPL:
#!/bin/bash
#
# cpugovmon - change CPU governor based on inactivity time and system load
# Copyright (C) 2016 Michael Uchima
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# See <http://www.gnu.org/licenses/> for a copy of the GNU General
# Public License.
# Tunable parameters
SECS_CONSERVATIVE=15 # secs of DE inactivity for conservative governor
SECS_POWERSAVE=900 # secs of DE inactivity for powersave governor
LOAD_NOSAVE=200 # sys load (x100) that bumps us up from powersave to conservative
# Need the xprintidle tool; if not installed, bail
if [[ "`which xprintidle`" == "" ]]; then
echo "+++ xprintidle not installed, cpugovmon exiting +++"
exit 1
fi
# Let 'em know we're running
if [[ "`whoami`" != "root" ]]; then
echo "`date` - +++ cpugovmon started (non-root) +++"
else
echo "`date` - +++ cpugovmon started +++"
fi
NEWGOV=""
PREVGOV=""
NEWLOAD=0
PREVLOAD=0
while true; do
# Gather current system state
TIME_NOW=`date`
IDLE=$((`xprintidle`/1000))
NEWLOAD=`cat /proc/loadavg | sed -e 's/ .*$//;s/\.//;s/^0*//'`
# Log transitions above/below the "no powersave" threshold
if [[ $NEWLOAD -ge $LOAD_NOSAVE && $PREVLOAD -lt $LOAD_NOSAVE ]]; then
echo "$TIME_NOW - load above threshold"
fi
if [[ $NEWLOAD -lt $LOAD_NOSAVE && $PREVLOAD -ge $LOAD_NOSAVE ]]; then
echo "$TIME_NOW - load below threshold"
fi
# Decide which governor we want
if [[ $IDLE -ge $SECS_POWERSAVE && $NEWLOAD -lt $LOAD_NOSAVE ]]; then
NEWGOV=powersave
elif [[ $IDLE -gt $SECS_CONSERVATIVE ]]; then
NEWGOV=conservative
else
NEWGOV=ondemand
fi
# If desired governor changed, set it
if [[ "$NEWGOV" != "$PREVGOV" ]]; then
if [[ "`whoami`" == "root" ]]; then
echo "$TIME_NOW - setting CPU governor to $NEWGOV"
for CPU in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor; do
echo $NEWGOV >$CPU
done
else
echo "$TIME_NOW - would set CPU governor to $NEWGOV if running as root"
fi
PREVGOV=$NEWGOV
fi
PREVLOAD=$NEWLOAD
# Wait a half second so we're not hammering the system
sleep 0.5
done
