[cpufreq] ondemand works, conservative doesn't

[cpufreq] ondemand works, conservative doesn't

[Sven Köhler]

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Hi,

currently, i'm using the ondemand governor. My CPU supports the
frequencies 800, 1800 and 2000 MHz (AMD Athlon64 Desktop with
Cool&Quiet). The simple bash commands

  while true
  do
    true
  done

cause 100% CPU usage, and the CPU immediatly switched from 800 to 2000MHz.

Using the conservative govenor, nothing happens. I would expect, that
the cpu switches to 1800 and than to 2000 Mhz after some seconds of full
CPU usage.

What's wrong?

My guess is, that the conservative govenor would need more frequencies
between 800 and 1800MHz to work properly.

Thx
  Sven

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Re: [cpufreq] ondemand works, conservative doesn't

[Alejandro Bonilla]

Sven Köhler wrote:

>Hi,
>
>currently, i'm using the ondemand governor. My CPU supports the
>frequencies 800, 1800 and 2000 MHz (AMD Athlon64 Desktop with
>Cool&Quiet). The simple bash commands
>
>  
>
In my case, I have a Pentium M 1.8ghz 400 FSB. In powersave, it goes to 
1.19ghz, in conservative, it goes to 1.20GHZ and of course performance 
goes to 1.8ghz if plugged.

Conservative works well here, and so far, lt moved slowly from 
frequencies, 1.2 then in 5 seconds 1.4, 2 seconds 1.8. Then it took the 
CPU like 10 seconds to move back from 1.8ghz to 1.2..

Mine did reach the full cpu in a moment, yours looks like it not going 
over 2.0ghz. Maybe is not needing that much CPU?

If it only supports 800, 1800 and 2000 MHz, then it will only jump to 
those frequencies. I use the CPU Frequency Scaling Monitor included in 
gnome to switch between these options a lot. Maybe you could play with 
this a bit more and see how it behaves. It does look like it might need 
more frequencies, but you would need to check what does you CPU support.

.Alejandro

Re: [cpufreq] ondemand works, conservative doesn't

[Sven Köhler]

>> currently, i'm using the ondemand governor. My CPU supports the
>> frequencies 800, 1800 and 2000 MHz (AMD Athlon64 Desktop with
>> Cool&Quiet). The simple bash commands
>>
>  
> In my case, I have a Pentium M 1.8ghz 400 FSB. In powersave, it goes to
> 1.19ghz, in conservative, it goes to 1.20GHZ and of course performance
> goes to 1.8ghz if plugged.
> 
> Conservative works well here, and so far, lt moved slowly from
> frequencies, 1.2 then in 5 seconds 1.4, 2 seconds 1.8. Then it took the
> CPU like 10 seconds to move back from 1.8ghz to 1.2..

Yes. Pentium M CPUs offer frequencies is 200MHz steps. And I was pretty
sure, that the conservative govenor works in that case.

> Mine did reach the full cpu in a moment, yours looks like it not going
> over 2.0ghz. Maybe is not needing that much CPU?

Running an "while true; do true; done" will result in process named
"bash" that uses 100% of the cpu. The problem i see is, that the
conservative govenor never considers to switch from 800MHz to 1800MHz
because it's a 1000MHz jump! (i'd consider that as a bug, since the
govenor is non-functional in such an environment)

> If it only supports 800, 1800 and 2000 MHz, then it will only jump to
> those frequencies. I use the CPU Frequency Scaling Monitor included in
> gnome to switch between these options a lot. Maybe you could play with
> this a bit more and see how it behaves. It does look like it might need
> more frequencies, but you would need to check what does you CPU support.

I would be very glad, if the conservative-govenor would switch to the
three frequencies i listet. The problem is: it doesn't.

AFAIK, AMD Desktop CPUs really support 3 frequencies only :-(