Re: Overall picture of cpufreq..

[Tomasz Chmielewski <mangoo@wpkg.org>]

Thomas Renninger schrieb:

(...)

>>> could it be that you are using
>>> p4-clockmode driver which is doing throttling, not frequency scaling,
>>> better try with acpi-cpufreq then.
>> Indeed, I am using p4-clockmod.
> Sorry, but your bug report is invalid then.
> p4-clockmod is using throttling (means the CPU ignores cycles/ticks) and
> not CPU frequency/voltage reduction.
> There is another interface for that:
> /proc/acpi/processor/throttling

Umm, do I need to build/insert some additional modules here?

# cat /proc/acpi/processor/CPU0/throttling
<not supported>

(...)


>> acpi-cpufreq doesn't work for me on that machine (p4-clockmod not loaded 
>> when I try to insert acpi-cpufreq):
>>
>> # modprobe acpi-cpufreq
>> FATAL: Error inserting acpi_cpufreq 
>> (/lib/modules/2.6.23.12-pata-1/kernel/arch/i386/kernel/cpu/cpufreq/acpi-cpufreq.ko): 
>> No such device
> 
> Have you checked whether that the CPU is cpufreq capable at all?

According to Documentation/cpu-freq/user-guide.txt, Intel Xeon is 
supported by cpufreq. Are there exceptions to that (i.e., some Xeons are 
not supported)?

Anyway, "cat /dev/zero >/dev/null" scales the frequency up; reading from 
a dm-crypt device doesn't.


> If yes, you might want to upgrade the BIOS.
> 
> Still, it looks strange that frequency (in this case throttling) is not
> set to the highest state as measuring the idle time should be the same
> mechanism and low-level driver independent. So this may be a valid bug,
> but using p4-clockmode is not a good idea to work on it (p4-clockmode is
> not a good idea to work on in general, IMO it should vanish totally...).

In that case, it's not documented very clearly (in "make menuconfig"). 
Basically, a P4 user can pick either:

CONFIG_X86_ACPI_CPUFREQ:

This driver adds a CPUFreq driver which utilizes the ACPI 
 
     Processor Performance States. 
 


This driver also supports Intel Enhanced Speedstep.



or:


CONFIG_X86_P4_CLOCKMOD: 


This adds the CPUFreq driver for Intel Pentium 4 / XEON 
 
processors. 



CONFIG_X86_P4_CLOCKMOD is more explicit and implies that is the 
preferred module for a P4 CPU.



-- 
Tomasz Chmielewski
http://wpkg.org