Power saving

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Revision as of 23:51, 23 October 2012 by Thestinger (Talk | contribs) (writeback time)

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By default, audio power saving is turned off by most drivers. It can be enabled by setting the power_save parameter to a time (in seconds) to go in idle.

Note: Toggling the audio card's power state can cause a popping sound or noticeable latency on some broken hardware.
options snd_hda_intel power_save=1
options snd_ac97_codec power_save=1

Disabling NMI watchdog

The NMI watchdog is a debugging feature to catch hardware hangs and cause a kernel panic. On some systems it can generate a lot of interrupts, causing a noticeable increase in power usage.

kernel.nmi_watchdog = 0

or add nmi_watchdog as a kernel parameter.

Disabling Wake-on-LAN

Wake-on-LAN can be a useful feature, but if you're not making use of it then it's simply draining extra power waiting for a magic packet while in suspend.

Disabling for one interface:

ACTION=="add", SUBSYSTEM=="net", KERNEL=="eth0" RUN+="/usr/sbin/ethtool -s eth0 wol d"

Disabling for all interfaces:

ACTION=="add", SUBSYSTEM=="net", KERNEL=="eth*" RUN+="/usr/sbin/ethtool -s %k wol d"

Wireless power saving

Enabling for a specific interface:

ACTION=="add", SUBSYSTEM=="net", KERNEL=="wlan0" RUN+="/usr/sbin/iw dev wlan0 set power_save on"

Enabling for all interfaces:

ACTION=="add", SUBSYSTEM=="net", KERNEL=="wlan*" RUN+="/usr/sbin/iw dev %k set power_save on"

Writeback Time

Increasing the VM dirty writeback time can help to aggregate I/O together - reducing disk writes, and decreasing power usage:

vm.dirty_writeback_centisecs = 1500

To do the same for journal commits with ext4 and some other filesystems, use commit=15 as a parameter in fstab or with the rootflags kernel parameter.