I am running plex on my unraid box, and using the powernow_k8 frequency scaling module. In order to prevent buffering while transcoding, I had to change the cpu frequency governor from "ondemand" to "performance". When using ondemand, the CPU frequency would increase, but not quickly enough to avoid buffering (I could see in the log file that the creation of some transcode segments would approach or exceed 10 sec). When using ondemand, the creation is staying below 6 seconds max.

 

The video I am transcoding is a 1080p movie (The American), and I am restricting the output stream to 1.5Mbit.

 

It would be better for heat/power if I didn't have to use the "performance" governor, since it seems to keep the cpu frequency at maximum all the time. If anyone else has had success with other governors, I would appreciate hearing about your experience.

 

My configuration: unRaid 5.0-rc8a, plex v0.9.7.7.339-5ec3b53, AMD Phenom X4 965 processor (4 cores, 3.4Ghz max), 2GB of memory.

You need to turn the up frequency setting to somewhere around 30% CPU usage, not the default 80 or 90.

 

Works perfectly here on a Core i3-3220 (3.3Ghz dual with HT).

 

Although anything that uses two or less cores the Core i3 is faster.

The ondemand sampling_rate and up_threshold options are not supported in unRAID 5.0-rc8a. I started another thread here to ask about these features being added in a future release:

http://lime-technology.com/forum/index.php?topic=25175.0

The ondemand sampling_rate and up_threshold options are not supported in unRAID 5.0-rc8a. I started another thread here to ask about these features being added in a future release:

http://lime-technology.com/forum/index.php?topic=25175.0

 

Why not?

 

They work for me!!

 

Mine are set at 20 and 400 respectively and yes, they do work.

 

My code:

 

#!/bin/bash

modprobe acpi-cpufreq
modprobe cpufreq_ondemand

echo ondemand > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
echo ondemand > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor
echo ondemand > /sys/devices/system/cpu/cpu2/cpufreq/scaling_governor
echo ondemand > /sys/devices/system/cpu/cpu3/cpufreq/scaling_governor

echo 400 > /sys/devices/system/cpu/cpufreq/ondemand/sampling_down_factor
echo 20 > /sys/devices/system/cpu/cpufreq/ondemand/up_threshold

Thanks, I was looking for the ondemand directory in /sys/devices/system/cpu/cpu?/, instead of /sys/devices/system/cpu/cpufreq/

 

This configuration is now working for me (avoids buffering when transcoding):

modprobe powernow-k8 

echo 50 > /sys/devices/system/cpu/cpufreq/ondemand/up_threshold

echo 400 > /sys/devices/system/cpu/cpufreq/ondemand/sampling_down_factor

 

My configuration: unRaid 5.0-rc9a, plex v0.9.7.10.382, AMD Phenom X4 965 processor (4 cores, 3.4Ghz max, 800Mhz min), 2GB of memory.

 

The ondemand sampling_rate and up_threshold options are not supported in unRAID 5.0-rc8a. I started another thread here to ask about these features being added in a future release:

http://lime-technology.com/forum/index.php?topic=25175.0

 

Why not?

 

They work for me!!

 

Mine are set at 20 and 400 respectively and yes, they do work.

 

My code:

 

#!/bin/bash

modprobe acpi-cpufreq
modprobe cpufreq_ondemand

echo ondemand > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
echo ondemand > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor
echo ondemand > /sys/devices/system/cpu/cpu2/cpufreq/scaling_governor
echo ondemand > /sys/devices/system/cpu/cpu3/cpufreq/scaling_governor

echo 400 > /sys/devices/system/cpu/cpufreq/ondemand/sampling_down_factor
echo 20 > /sys/devices/system/cpu/cpufreq/ondemand/up_threshold

Does this have to be reset every time unraid is rebooted?

Yes.  Put it in your go script.