3.2GHz cpus with cpufreq become 2.8GHz

3.2GHz cpus with cpufreq become 2.8GHz

[Krzysztof Oledzki]

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Hello,

I have just noticed that enabling cpufreq on my Dell PowerEdge 1425SC 
changes my secondary cpu clock to 2.8GHz.

# cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model           : 4
model name      : Intel(R) Xeon(TM) CPU 3.20GHz
stepping        : 3
cpu MHz         : 3200.000
cache size      : 2048 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 1
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 5
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc pni monitor ds_cpl cid cx16 xtpr
bogomips        : 6403.72

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 15
model           : 4
model name      : Intel(R) Xeon(TM) CPU 3.20GHz
stepping        : 3
cpu MHz         : 3200.000
cache size      : 2048 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 1
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 5
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc pni monitor ds_cpl cid cx16 xtpr
bogomips        : 6400.24

processor       : 2
vendor_id       : GenuineIntel
cpu family      : 15
model           : 4
model name      : Intel(R) Xeon(TM) CPU 3.20GHz
stepping        : 3
cpu MHz         : 2800.000
cache size      : 2048 KB
physical id     : 3
siblings        : 2
core id         : 0
cpu cores       : 1
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 5
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc pni monitor ds_cpl cid cx16 xtpr
bogomips        : 6400.30

processor       : 3
vendor_id       : GenuineIntel
cpu family      : 15
model           : 4
model name      : Intel(R) Xeon(TM) CPU 3.20GHz
stepping        : 3
cpu MHz         : 2800.000
cache size      : 2048 KB
physical id     : 3
siblings        : 2
core id         : 0
cpu cores       : 1
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 5
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc pni monitor ds_cpl cid cx16 xtpr
bogomips        : 6400.29

According to cpuinfo the primary CPU (two HT logical CPUs) works with 
3.2GHz clock but the secondary works with 2.8GHz.

What is also strange, this 3.2GHz freq is not listed on 
scaling_available_frequencies for both CPUs:

# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver
p4-clockmod

# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
350000 700000 1050000 1400000 1750000 2100000 2450000 2800000

# cat /sys/devices/system/cpu/cpu2/cpufreq/scaling_driver
p4-clockmod
# cat /sys/devices/system/cpu/cpu2/cpufreq/scaling_available_frequencies
350000 700000 1050000 1400000 1750000 2100000 2450000 2800000

I can confirm that this problem exists on 2.6.16/2.6.17/2.6.18 (just 
tested). Is it a problem with BIOS or p4-clockmod cpufreq driver?

Best regards,


 				Krzysztof Olędzki

Re: 3.2GHz cpus with cpufreq become 2.8GHz

[Krzysztof Oledzki]

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On Thu, 19 Oct 2006, Wes Felter wrote:

> Krzysztof Oledzki wrote:
>> Hello,
>> 
>> I have just noticed that enabling cpufreq on my Dell PowerEdge 1425SC 
>> changes my secondary cpu clock to 2.8GHz.
>
> [snip]
>
>> # cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver
>> p4-clockmod
>
> You shouldn't be using this driver. Use speedstep-centrino or

Hm... speedstep-centrino on Xeon? AFAIK speedstep-centrino requires "est" 
and /proc/cpuinfo does not mention this flag:
  fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc pni monitor ds_cpl cid cx16 xtpr

> acpi-cpufrreq.

I will check this, thank you. BTW: what wrong is with p4-clockmod? I was 
not able to find any information that it is broken and should not be 
used?

Best regards,


 				Krzysztof Olędzki

Re: 3.2GHz cpus with cpufreq become 2.8GHz

[Jarek Poplawski]

On 20-10-2006 00:25, Krzysztof Oledzki wrote:
...
> I will check this, thank you. BTW: what wrong is with p4-clockmod? I was 
> not able to find any information that it is broken and should not be used?

At least it is very suspected:

"Subject: Hardware bug or kernel bug?
On Mon, Oct 16, 2006 at 03:32:38PM +0100, David Johnson wrote:
..
> I've found the culprit - CPU Frequency Scaling.
> With it enabled I get the reboots, with it disabled I don't. That's the same
> with every kernel version I've tried (2.6.19-rc1+rc2, 2.6.17.13 & Centos'
> 2.6.9) The system was using the p4-clockmod driver and the ondemand governor.

> I'm still not sure exactly what the problem is - the reboots only happen in
> the circumstances I've mentioned and are not triggered by changes in clock
> speed alone - but disabling cpufreq seems to make it go away... "

Cheers,

Jarek P.

Re: 3.2GHz cpus with cpufreq become 2.8GHz

[Krzysztof Oledzki]

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On Thu, 19 Oct 2006, Wes Felter wrote:

> Krzysztof Oledzki wrote:
>
>> Hm... speedstep-centrino on Xeon? AFAIK speedstep-centrino requires "est" 
>> and /proc/cpuinfo does not mention this flag:
>>  fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 
>> clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc pni 
>> monitor ds_cpl cid cx16 xtpr
>
> Odd; I have a similar processor and it has est and uses the 
> speedstep-centrino driver. But I am using an old kernel (2.6.5) and the flag 
> detection has changed since then.

Anyway, I have just tested speedstep-centrino, but it does not work.

>> BTW: what wrong is with p4-clockmod? I was not able to find any information 
>> that it is broken and should not be used?
>
> It makes the processor slower but only reduces power consumption slightly, 
> making the processor less power-efficient. You probably don't want your 
> processor to be less efficient.

I also tested ACPI Processor P-States driver (X86_ACPI_CPUFREQ), but it 
does not work either.

Any other ideas?

Best regards,

 				Krzysztof Olędzki