divenal
Posts: 4
Joined: Tue Jun 10, 2014 7:51 pm

scaling at 100% after upgrade

Tue Dec 29, 2015 6:01 pm

Hi,
I have a model B running wheezy. Have just updated the kernel from 3.12 to 4.1.15 and updated all packages. I now see from atop that it's running at 800MHz (100%) most of the time, even when 90% idle. Previously it was usually 700MHz with the occasional foray to 800MHz (100%) under load.

It's running as a tvheadend server with wifi and an external usb disk. tvheadend itself usually runs at about 10% cpu (since it's constantly scanning channels). Previously, I could be recording (20%) plus playing omxplayer (either locally or remotely via http), plus atop, and still be at 700MHz. It would jump to 800MHz if I was also doing a file transfer or something.

This is not necessarily a problem, but not what I expected. Has something changed in the way ondemand tunes itself ? Obviously, the very act of trying to read the frequency triggers activity which could be boosting it.

Apologies if this has already been discussed - I don't come here as often as I should.

Code: Select all

$ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_{governor,cur_freq}  /proc/loadavg 
ondemand
800000
0.17 0.28 0.26 1/109 10780

$ while sleep 1 ; do cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq /proc/loadavg ; done
800000
0.17 0.28 0.26 1/109 10782
800000
0.17 0.28 0.26 1/108 10784
800000
0.15 0.28 0.25 1/109 10787
800000
0.15 0.28 0.25 1/109 10789
800000
0.15 0.28 0.25 1/109 10791
700000
0.15 0.28 0.25 1/109 10793
800000
0.14 0.27 0.25 1/109 10795
800000
0.14 0.27 0.25 1/109 10797
^C

divenal
Posts: 4
Joined: Tue Jun 10, 2014 7:51 pm

Re: scaling at 100% after upgrade

Wed Dec 30, 2015 4:28 pm

I found a post which confirmed that the raspian 'ondemand' parameter defaults have been changed to make it a bit more aggressive, but putting them back didn't seem to help.

I discovered the cpufrequtils package which is useful, but still didn't solve the "problem".

In the end, I decided that the 'conservative' governor is perhaps closer to how I was expecting it to behave anyway, so I've changed over to use that, and will keep an eye on it.

I didn't mention that my other recently-updated model-b rpi really was totally idle (no desktop or anything), yet still showing more-than-expected time at the higher frequency.

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