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TIPS.txt
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=== Simple user tips for improving power usage === * Use a properly dimensioned system for the job (no need for overpowered systems for simple Desktop use e.g.). * For servers consolidate services on fewer systems to maximize efficiency of each system. * For a server farm consolidating all physical machines on one bigger server and then using Virtualization. * Enforce turning off machines that are not used (e.g. company policy). * Try to establish a company culture that is Green "aware", including but not limited to the above point. * Unplug and/or turn off peripherals that aren't used (e.g. external USB devices, monitors, printers, scanners). * Turn off unused hardware already in BIOS. * Disable power hungry features. * Enable CPU scaling if supported for ondemand CPU governor. DO NOT use powersave governor, typically uses more power than ondemand (race to idle). * Put network card to 100 mbit/10 mbit: ** 10 mbit: ethtool -s eth0 advertise 0x002 ** 100 mbit: ethtool -s eth0 advertise 0x008 ** Doesn't work for every card * Put harddisk to spindown fast and full power saving: ** hdparm -S240 /dev/sda (20m idle to spindown) ** hdparm -B1 /dev/sda (Max powersave mode) * Make sure writes to hd don't wake it up too quickly: ** Set flushing to once per 5 minutes ** echo "3000" > /proc/sys/vm/dirty_writeback_centisecs ** Enable laptop mode ** echo "5" > /proc/sys/vm/laptop_mode * Use relatime for your / partition ** mount -o remount,relatime / * Enable USB autosuspend by adding the following to the kernel boot commandline: ** usbcore.autosuspend=5 * Screensaver needs to dpms off the screen, not just make colors black. To turn off monitor after 120s when X is running: ** xset dpms 0 0 120 === Simple programmer tips for improving power usage === * Avoid unnecessary work/computation * Use efficient algorithms * Wake up only when necessary/real work is pending * Do not actively poll in programs or use short regular timeouts, rather react to events * If you wake up, do everything at once (race to idle) and as fast as possible * Use large buffers to avoid frequent disk access. Write one large block at a time * Don't use [f]sync() if not necessary * Group timers across applications if possible (even systems)