power use estimation

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fvolk
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power use estimation

Unread post by fvolk » Sun Jul 14, 2019 6:51 pm

So I measured again the power use of my H2,
to my surprise it idles at ~2.65W (no video, only network attached, 2x4GB, M2 SSD).
Last time I measured I got 3.xW, so something on the software side must have improved.

I suspect it's the docker daemon because I know from previous measurements that a started but idle docker daemon increased power use due to regular CPU wakeups (~0.5W), but now it doesn't seem to make a measureable difference any more whether docker daemon is not running or started and idle.

I think it would be nice if we compile a list of what components require how much power, for example just attaching a USB keyboard is about +0.3-0.4W.
What's the power change of
...attaching a SATA SSD, SATA mechanical 2.5" disk, SATA mechanical 3.5" disk?
Obviously this varies according to the manufacturer, but maybe it's still possible to give rough values and estimate the power required for a build before ordering the parts?

Just a Sunday idea.... :-)

fvolk
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Re: power use estimation

Unread post by fvolk » Mon Jul 15, 2019 5:42 am

Ok, I think I know what changes my power use:
Boot cold, either with DP video attached or not --> ~3.2W.
If DP video is attached AND then removed after boot -> drops to ~2.6W
If rebooted only warm, so by software, after reboot is complete -> still only 2.6W.

Question: If I cold boot without DP video attached and have the high power consumption, what must I do to get the same low power consumption as if I first attach video and then remove it?

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odroid
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Re: power use estimation

Unread post by odroid » Mon Jul 15, 2019 10:03 am

Seems to be a power management bug in the DisplayPort device driver.
Which OS and Kernel version do you use?

fvolk
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Re: power use estimation

Unread post by fvolk » Tue Jul 16, 2019 5:38 am

So I upgraded from 4.19.x to 4.19.59.
This latest LTS kernel consumes a little bit more than the previous - some defaults must have changed?

Bootup base usage is ~3.4W. Playing around with the tuneables in powertop,
the following 3 lines bring power down to lowest ~2.6W (docker is running, ~120 CPU wakeups/s):

# audio power save
echo '1' > '/sys/module/snd_hda_intel/parameters/power_save'
# network links power
echo 'auto' > '/sys/bus/pci/devices/0000:02:00.0/power/control'
echo 'auto' > '/sys/bus/pci/devices/0000:03:00.0/power/control'

Audio I don't care in a headless server, network links are probably slower to react(?), but I haven't measured.

Still impressed with ~2.6W for a x86 server - now I wish for a huge+cheap M2 SSD :-)

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