Unable to lower cpu frequency

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Unable to lower cpu frequency

jd1008
# /bin/cpupower --cpu all frequency-set -g performance 2G
# /bin/cpupower --cpu all frequency-info | grep "current CPU frequency is"
   current CPU frequency is 2.80 GHz (asserted by call to hardware).
   current CPU frequency is 2.80 GHz (asserted by call to hardware).

Cpu can accept frquencies as low as 800MHz.

So, does anyone have a more magical incantation to force the 2 cores
to run at 2.0 GHz?
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Re: Unable to lower cpu frequency

stan-3
On Tue, 15 May 2018 19:59:53 -0600
JD <[hidden email]> wrote:

> # /bin/cpupower --cpu all frequency-set -g performance 2G
> # /bin/cpupower --cpu all frequency-info | grep "current CPU
> frequency is" current CPU frequency is 2.80 GHz (asserted by call to
> hardware). current CPU frequency is 2.80 GHz (asserted by call to
> hardware).
>
> Cpu can accept frquencies as low as 800MHz.
>
> So, does anyone have a more magical incantation to force the 2 cores
> to run at 2.0 GHz?

You could try adding --max?  I'm not sure what the default is, might be
--min.

When governor is set to performance, the CPU runs full out all the time.
It is possible to change the governor on a running system, but I'm not
sure how.  You could change it to one of the below other than
performance, if it has been compiled into the kernel.  As you can see,
I have only the ondemand governor in my kernel.

These are the settings for my CPU, from boot/config-[]
# DEVFREQ Governors
CONFIG_DEVFREQ_GOV_SIMPLE_ONDEMAND=y
# CONFIG_DEVFREQ_GOV_PERFORMANCE is not set
# CONFIG_DEVFREQ_GOV_POWERSAVE is not set
# CONFIG_DEVFREQ_GOV_USERSPACE is not set
# CONFIG_DEVFREQ_GOV_PASSIVE is not set


Also, IIRC, the setting of CPU frequency is usually done directly in the
BIOS / firmware.  In the kernel docs they say that some CPUs can't be
set from the kernel (but don't give a list).  i.e. the BIOS would be
your only option if you have one of those, and it sounds like you
might.
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Re: Unable to lower cpu frequency

jd1008
You hit the nail on the head.
I found that the command line I was using contained the word performance.
Now, I am doing:
/bin/cpupower --cpu all frequency-set -u 2.00G

and cpu-info  is showing:
current CPU frequency is 1.60 GHz (asserted by call to hardware).
for both cpus.

This was necessary because of running ffmpeg alongside with
playing videos cause HW errors.
Even thought the kernel throttled the cpu, it did not help much.

Now, I do not get the HW errors and kernel ooops messages.


On Wed, May 16, 2018 at 10:00 AM, stan <[hidden email]> wrote:
On Tue, 15 May 2018 19:59:53 -0600
JD <[hidden email]> wrote:

> # /bin/cpupower --cpu all frequency-set -g performance 2G
> # /bin/cpupower --cpu all frequency-info | grep "current CPU
> frequency is" current CPU frequency is 2.80 GHz (asserted by call to
> hardware). current CPU frequency is 2.80 GHz (asserted by call to
> hardware).
>
> Cpu can accept frquencies as low as 800MHz.
>
> So, does anyone have a more magical incantation to force the 2 cores
> to run at 2.0 GHz?

You could try adding --max?  I'm not sure what the default is, might be
--min.

When governor is set to performance, the CPU runs full out all the time.
It is possible to change the governor on a running system, but I'm not
sure how.  You could change it to one of the below other than
performance, if it has been compiled into the kernel.  As you can see,
I have only the ondemand governor in my kernel.

These are the settings for my CPU, from boot/config-[]
# DEVFREQ Governors
CONFIG_DEVFREQ_GOV_SIMPLE_ONDEMAND=y
# CONFIG_DEVFREQ_GOV_PERFORMANCE is not set
# CONFIG_DEVFREQ_GOV_POWERSAVE is not set
# CONFIG_DEVFREQ_GOV_USERSPACE is not set
# CONFIG_DEVFREQ_GOV_PASSIVE is not set


Also, IIRC, the setting of CPU frequency is usually done directly in the
BIOS / firmware.  In the kernel docs they say that some CPUs can't be
set from the kernel (but don't give a list).  i.e. the BIOS would be
your only option if you have one of those, and it sounds like you
might.
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Re: Unable to lower cpu frequency

stan-3
On Thu, 17 May 2018 13:13:34 -0600
JD <[hidden email]> wrote:

> You hit the nail on the head.
> I found that the command line I was using contained the word
> performance. Now, I am doing:
> /bin/cpupower --cpu all frequency-set -u 2.00G
>
> and cpu-info  is showing:
> current CPU frequency is 1.60 GHz (asserted by call to hardware).
> for both cpus.
>
> This was necessary because of running ffmpeg alongside with
> playing videos cause HW errors.
> Even thought the kernel throttled the cpu, it did not help much.
>
> Now, I do not get the HW errors and kernel ooops messages.

Glad to hear it worked out for you.
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