CPU frequency scaling on Intel Core 2

Tony Houghton · External Since: Jul 22, 2006 Posts: 88

I can't get Linux to support CPU frequency scaling on my Core 2 Duo.
I've enabled the relevant drivers but the cpufreq directories aren't
appearing in sysfs. In the kernel options you can set the default
governor to "performance" (highest frequency all the time) or
"userspace" (which I've chosen). How are you supposed to enable
"ondemand" or "conservative"?

--
TH * http://www.realh.co.uk

Ian Rawlings · External Since: Oct 07, 2006 Posts: 238

On 2007-06-29, Tony Houghton <h.DeleteThis@realh.co.uk> wrote:

> I can't get Linux to support CPU frequency scaling on my Core 2 Duo.
> I've enabled the relevant drivers but the cpufreq directories aren't
> appearing in sysfs. In the kernel options you can set the default
> governor to "performance" (highest frequency all the time) or
> "userspace" (which I've chosen). How are you supposed to enable
> "ondemand" or "conservative"?

--------------------
# Set ondemand CPU frequency changing on both processors
echo ondemand > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
echo ondemand > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor
--------------------

In the same directories, you can see other files that list the
avialable governers, the speeds the CPU will run at, the current speed
etc etc etc.

Or at least you should! Is it the above directories that you can't
see, or have you just forgotten the path like I do every time Wink

--
Blast off and strike the evil Bydo empire!

Tony Houghton · External Since: Jul 22, 2006 Posts: 88

In <slrnf8atva.dbn.news06.RemoveThis@desktop.tarcus.org.uk>,
Ian Rawlings <news06.RemoveThis@tarcus.org.uk> wrote:

> On 2007-06-29, Tony Houghton <h.RemoveThis@realh.co.uk> wrote:
>
>> I can't get Linux to support CPU frequency scaling on my Core 2 Duo.
>> I've enabled the relevant drivers but the cpufreq directories aren't
>> appearing in sysfs. In the kernel options you can set the default
>> governor to "performance" (highest frequency all the time) or
>> "userspace" (which I've chosen). How are you supposed to enable
>> "ondemand" or "conservative"?
>
> --------------------
> # Set ondemand CPU frequency changing on both processors
> echo ondemand > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
> echo ondemand > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor
> --------------------
>
> In the same directories, you can see other files that list the
> avialable governers, the speeds the CPU will run at, the current speed
> etc etc etc.
>
> Or at least you should! Is it the above directories that you can't
> see, or have you just forgotten the path like I do every time Wink

The directories don't exist. I can follow the path as far as
/sys/devices/system/cpu/cpu0 and cpu1, but they each contain just
"cache" and "topology", not "cpufreq".

It worked before on my AMD64. Obviously I've had to change a lot of
settings for the Intel, and I did remember to change from
X86_POWERNOW_K8 to X86_ACPI_CPUFREQ. X86_ACPI_CPUFREQ replaces the
deprecated X86_SPEEDSTEP_CENTRINO and it says it uses the ACPI
Processor Performance States. Perhaps that means it has a completely
different sysfs interface. They haven't bothered to tell us if so.

--
TH * http://www.realh.co.uk

Ian Rawlings · External Since: Oct 07, 2006 Posts: 238

On 2007-06-29, Tony Houghton <h.DeleteThis@realh.co.uk> wrote:

> The directories don't exist. I can follow the path as far as
> /sys/devices/system/cpu/cpu0 and cpu1, but they each contain just
> "cache" and "topology", not "cpufreq".

My settings on this core 2 duo laptop are;

Processor family -> Pentium-4
ACPI (all on)

In CPU frequency scaling, everything that mentions Intel is compiled
into the kernel, and "Use ACPI tables to decode valid
frequency/voltage pairs" is on as is "Built-in tables for Banias
CPUs". All the governers are compiled in and "CPU frequency
translation statistics" is compiled in too.

If you want I'll email you my entire .config file.

--
Blast off and strike the evil Bydo empire!

Tony Houghton · External Since: Jul 22, 2006 Posts: 88

In <slrnf8bs71.dbn.news06 DeleteThis @desktop.tarcus.org.uk>,
Ian Rawlings <news06 DeleteThis @tarcus.org.uk> wrote:

> On 2007-06-29, Tony Houghton <h DeleteThis @realh.co.uk> wrote:
>
>> The directories don't exist. I can follow the path as far as
>> /sys/devices/system/cpu/cpu0 and cpu1, but they each contain just
>> "cache" and "topology", not "cpufreq".
>
> My settings on this core 2 duo laptop are;
>
> Processor family -> Pentium-4
> ACPI (all on)
>
> In CPU frequency scaling, everything that mentions Intel is compiled
> into the kernel, and "Use ACPI tables to decode valid
> frequency/voltage pairs" is on as is "Built-in tables for Banias
> CPUs". All the governers are compiled in and "CPU frequency
> translation statistics" is compiled in too.

I can't find "Use ACPI tables..." or the Banias one, but I'm sure I've
seen the latter somewhere. It may have been on my laptop which I noticed
has a considerably different set of frequency scaling options,
presumably because it's 32-bit and my desktop is 64-bit. Are you using a
32-bit kernel?

--
TH * http://www.realh.co.uk

Tony Houghton · External Since: Jul 22, 2006 Posts: 88

In <slrnf8at52.743.h RemoveThis @realh.co.uk>,
Tony Houghton <h RemoveThis @realh.co.uk> wrote:

> I can't get Linux to support CPU frequency scaling on my Core 2 Duo.
> I've enabled the relevant drivers but the cpufreq directories aren't
> appearing in sysfs.

I fiddled around a bit and loaded the acpi-cpufreq module manually and
then it worked. Maybe I had the driver built into the kernel before and
switched to modules when I recompiled for the Intel.

--
TH * http://www.realh.co.uk

Ian Rawlings · External Since: Oct 07, 2006 Posts: 238

On 2007-06-30, Tony Houghton <h.TakeThisOut@realh.co.uk> wrote:

> I can't find "Use ACPI tables..." or the Banias one, but I'm sure I've
> seen the latter somewhere. It may have been on my laptop which I noticed
> has a considerably different set of frequency scaling options,
> presumably because it's 32-bit and my desktop is 64-bit. Are you using a
> 32-bit kernel?

I'm using a 32-bit kernel, latest version as of a month ago, can't
remember version number right now and not near laptop.

--
Blast off and strike the evil Bydo empire!