[mythtv-users] Cool'n'Quiet setup help

Allen Edwards allen.p.edwards at gmail.com
Mon Feb 9 22:43:38 UTC 2009


On Mon, Feb 9, 2009 at 1:35 AM, John Finlay <finlay at moeraki.com> wrote:

> Allen Edwards wrote:
>
>>
>>
>> On Mon, Feb 9, 2009 at 12:44 AM, John Finlay <finlay at moeraki.com <mailto:
>> finlay at moeraki.com>> wrote:
>>
>>    Allen Edwards wrote:
>>
>>
>>
>>        On Sun, Feb 8, 2009 at 5:03 PM, John Finlay
>>        <finlay at moeraki.com <mailto:finlay at moeraki.com>
>>        <mailto:finlay at moeraki.com <mailto:finlay at moeraki.com>>> wrote:
>>
>>           Allen Edwards wrote:
>>
>>               I have an AMD 5400+ running Mythbuntu 8.10.  I would
>>        like to
>>               run cool'n'quiet to cut the cpu temp and power.  I
>>        enabled it
>>               in the BIOS and the results were unsatisfactory.  The
>>        program
>>               would stutter.  I could see that the cpu was running at
>>        1GHz
>>               during program mode and that wasn't enough.
>>
>>               What I want to do is have the CPU at a low clock
>>        frequency but
>>               when there is basically any activity at all, have it go to
>>               100% clock.  For example, right now the CPU is at .6%.  It
>>               would be nice if the clock was at a minimum.  But if
>>        the cpu
>>               goes above, say 2%?, I want the CPU to go to max clock
>>        so it
>>               wont stutter.
>>
>>               I see instructions on the net how to do this but they are 3
>>               years old and experience has thought me that following
>>               instructions like this causes a half day work getting the
>>               system working again because the instructions were for an
>>               older system.
>>
>>               So, can anyone with a system like mine who has enabled
>>               cool'n'quiet and understands what I am saying help me out?
>>
>>               Allen
>>
>>           This uses the cpufreq module which uses the threshold (%
>>        cpu) in:
>>
>>           /sys/devices/system/cpu/cpu0/cpufreq/ondemand/up_threshold
>>
>>           As root you can change this e.g.:
>>
>>           echo -n 10 >
>>           /sys/devices/system/cpu/cpu0/cpufreq/ondemand/up_threshold
>>
>>           Other params in /sys/devices/system/cpu/cpu0/cpufreq can be
>>           changed as well:
>>
>>           scaling_max_freq
>>           scaling_min_freq
>>           ondemand/ignore_nice_load
>>
>>           If using Ubuntu you can set params on boot in the
>>           /etc/init.d/powernowd file. Add in the use_ondemand() function
>>           something like:
>>
>>                     if [ -f $x"cpufreq/ondemand/up_threshold" ]; then
>>                         echo -n 20 > $x"cpufreq/ondemand/up_threshold"
>>                     fi
>>
>>
>>           If using Fedora the /etc/sysconfig/cpuspeed file allows you to
>>           tweak things.
>>
>>           John
>>
>>
>>        I apologize if this is a stupid question but I don't have a
>>        file called up_threshold on my system.  I do have powernowd
>>        but not cpufreq.  I can find online docs for powernowd  but
>>        again they are many years old and I have to assume out of date.
>>
>>        Allen
>>
>>
>>    Sounds like you are not loading the kernel module that provides
>>    cpufreq.
>>
>>    Install the powernowd package if it isn't already there (I think
>>    it's there by default). On my systems the powernowd rc links load
>>    the required modules but don't start the powernowd daemon. Check
>>    to see that both the powernod and powernod.early rc links are setup.
>>
>>    Here's the way to do it without the powernowd package:
>>
>>    http://ubuntuforums.org/showthread.php?t=248867)
>>
>>    A quick test is to:
>>
>>    lsmod | grep powernow-k8
>>    lsmod|grep cpufreq
>>
>>    to check if the modules are loaded. If not you can :
>>
>>    modprobe powernow-k8
>>    modprobe cpufreq_ondemand
>>
>>    to load them. Then the /sys/devices/system/cpu/cpu0/cpufreq
>>    directory should exist.
>>
>>    John
>>
>>
>>
>> Here is what I got (although cool'n'quiet is not presently enabled in the
>> bios if that makes a difference):
>>
>> dad at myth_desktop:~$ lsmod | grep powernow-k8
>> dad at myth_desktop:~$ lsmod|grep cpufreq
>> cpufreq_ondemand        9740  0
>> cpufreq_conservative     8712  0
>> cpufreq_stats           7104  0
>> freq_table              5536  2 cpufreq_ondemand,cpufreq_stats
>> cpufreq_powersave       2688  0
>> cpufreq_userspace       5284  0
>> dad at myth_desktop:~$
>>
>> As far as what is loaded, it is stock Mythbuntu so whatever gets loaded
>> with that is what I have.
>>
>> cool'n'quiet works when I enable it in the bios.  I just don't like the
>> set points and it doesn't seem to be ondemand in that there are 3 levels of
>> frequency selected vs cpu load.  Does that fact give a clue as to what my
>> correct setup should be?
>>
>> Allen
>>
>>
>>  You need to have C&Q enabled in the BIOS. Then cd to the
> /sys/devices/system/cpu/cpu0/cpufreq directory and cat the scaling_governor
> - it should be ondemand. The levels available are listed by
>
> cat scaling_available_frequencies
>
> John
>


Thanks for this help.  I enabled C&Q and like you said things started to
show up.  Here are some things  you expect:

dad at myth_desktop:~$ cat
/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
ondemand

dad at myth_desktop:~$ cat
/sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
2800000 2600000 2400000 2200000 2000000 1800000 1000000

dad at myth_desktop:~$ cat
 /sys/devices/system/cpu/cpu0/cpufreq/ondemand/up_threshold
80

and one you may not have:
dad at myth_desktop:~$ sudo echo -n 10 >
/sys/devices/system/cpu/cpu0/cpufreq/ondemand/up_threshold
-bash: /sys/devices/system/cpu/cpu0/cpufreq/ondemand/up_threshold:
Permission denied

I used nano to write "10" into this file and it still reads 80 when read.
The file time stamp changes but not the content.  Strange.

I looked at what the system is doing under different loads and it is giving
me three levels that I noticed, 1.0, 1.8, and 2.8.  It goes to 1.0 even
while decoding HD content, which is not what I want.

Interesting, the power in normal without C&Q enabled is 95 watts and when
running at 1GHz it is 85 Watts.  I guess I am dong this for $13 a year.
 More important, I would like to get the CPU temperature down and that has
gone from 55 degrees C to 45 degrees C and that should double the life of
the CPU.

So, I have C&Q working and can see all the files you said I should but I
still don't know how to change the settings yet.

Allen
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