[RESOLVED]cpufreq-set conservative governor tweaking problem

Dheart · 2012-02-19 21:17:54

Hello,
Just installed arch on my old Dell Inspiron 1525 and I have a strange problem when I try to tweak the conservative governor using the methods described here.
For some reason when I try:

echo -n 100 > /sys/devices/system/cpu/cpufreq/conservative/sampling_down_factor

I get

echo: write error: invalid argument

.
I tried manually opening nano to edit the file but again it refuses to save.
This however happens only with this file, I can tweak fine the ondemand governor's files, but not this one. Does anyone know what seems to be the problem?

Could it be faulty filesystem? This computer is 4 years old and hadn't been turned on for an year and a half (broken screen). When I fixed it and turned it on yesterday, but my reiserfs was broken beyond rapair. I managed to rescue the majority of my files and then reinstalled putting btrfs with lzo2 compression and so far it has been working fine, except that tiny quirk.

Resolved, use lower values.

Last edited by Dheart (2012-02-20 13:06:20)

NSB-fr · 2012-02-19 23:35:18

Hello,

Files under /sys are not real files but virtual files allowing access to various kernel/module variables.

Last time I got this kind of "invalid argument" error I was trying to write a value out of the range of the variable I was modifying.

KingX · 2012-02-20 00:12:52

You can't set the sampling_down factor to 100 for conservative governor. It makes no sense! If you want your cpu to run at max speed possible then don't run cpufreq. OTOH if you are trying your cpu to stay at lower limit permanently you want the "powersave" governor.

Dheart · 2012-02-20 13:05:50

Yeah, figured it out. Misunderstood the problem, I just don't want the processor to downclock and reclock multiple times while doing something. Like changing the current dir while compiling. Actually during loading KDE the clock changes about 15 times...

Gusar · 2012-02-20 13:28:51

Dheart wrote:

Yeah, figured it out. Misunderstood the problem, I just don't want the processor to downclock and reclock multiple times while doing something. Like changing the current dir while compiling. Actually during loading KDE the clock changes about 15 times...

Err, that's *good*. The cpu clocks up to do the job as fast as possible, so that it can go to sleep as soon as possible. Don't think you're smarter than the power management of your CPU, which makes decisions in milliseconds.

The conservative governor was created to workaround buggy AMD processors that couldn't do fast switching. It should not be used except on those processors (early Athlons, I think).

Dheart · 2012-02-21 13:54:22

Gusar wrote:

Dheart wrote:
Yeah, figured it out. Misunderstood the problem, I just don't want the processor to downclock and reclock multiple times while doing something. Like changing the current dir while compiling. Actually during loading KDE the clock changes about 15 times...
Err, that's *good*. The cpu clocks up to do the job as fast as possible, so that it can go to sleep as soon as possible. Don't think you're smarter than the power management of your CPU, which makes decisions in milliseconds.
The conservative governor was created to workaround buggy AMD processors that couldn't do fast switching. It should not be used except on those processors (early Athlons, I think).

Isn't it not very efficient that you have to reclock several times between short cpu intensive tasks?
Wouldn't it be better to keep the cpu clock high untill you finish the task?

Gusar · 2012-02-21 14:07:17

Dheart wrote:

Isn't it not very efficient that you have to reclock several times between short cpu intensive tasks?

Like I said, CPU operations are measured in milliseconds. CPUs were *designed* to reclock in such intervals.

Dheart wrote:

Wouldn't it be better to keep the cpu clock high untill you finish the task?

That's exactly what the ondemand governor does. Clocks up so the task can be finished as fast as possible, then clocks down. The conservative governor does as well, but it's slower at both upclocking and donwclocking. So the task takes longer to complete and then it takes longer for the CPU to go back to sleep. You lose at both ends.

Arch Linux

#1 2012-02-19 21:17:54

[RESOLVED]cpufreq-set conservative governor tweaking problem

#2 2012-02-19 23:35:18

Re: [RESOLVED]cpufreq-set conservative governor tweaking problem

#3 2012-02-20 00:12:52

Re: [RESOLVED]cpufreq-set conservative governor tweaking problem

#4 2012-02-20 13:05:50

Re: [RESOLVED]cpufreq-set conservative governor tweaking problem

#5 2012-02-20 13:28:51

Re: [RESOLVED]cpufreq-set conservative governor tweaking problem

#6 2012-02-21 13:54:22

Re: [RESOLVED]cpufreq-set conservative governor tweaking problem

#7 2012-02-21 14:07:17

Re: [RESOLVED]cpufreq-set conservative governor tweaking problem

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