linux-kernel - cpufreq scaling appears not to work on overclocked systems

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Date:	Sun, 29 Jul 2007 15:16:45 -0600
From:	"Berck E. Nash" <flyboy@...il.com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: cpufreq scaling appears not to work on overclocked systems

This is not new, but exists as far back as 2.6.17.  I haven't reported
it before because I figured that surely someone else had noticed it, but
since it's still unfixed and I cannot find any mention of it on LKML,
here we go.

I'm running a Core2 Duo 1.86GHz overclocked to 2.56GHz.  Everything is
normal with cpufreq scaling disabled.  With cpufreq scaling enabled in
the kernel, using any governor, /proc/cpuinfo indicates a maximum of the
rated frequency rather than the actual frequency.

Here it is under 100% utilization, with userspace governor and powernowd:

berck@...a:~$ cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 15
model name      : Intel(R) Core(TM)2 CPU          6300  @ 1.86GHz
stepping        : 6
cpu MHz         : 1862.000
cache size      : 2048 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 2
fpu             : yes
fpu_exception   : yes
cpuid level     : 10
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 syscall
lm constant_tsc pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm
bogomips        : 5134.39
clflush size    : 64
cache_alignment : 64
address sizes   : 36 bits physical, 48 bits virtual
power management:

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 6
model           : 15
model name      : Intel(R) Core(TM)2 CPU          6300  @ 1.86GHz
stepping        : 6
cpu MHz         : 1862.000
cache size      : 2048 KB
physical id     : 0
siblings        : 2
core id         : 1
cpu cores       : 2
fpu             : yes
fpu_exception   : yes
cpuid level     : 10
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 syscall
lm constant_tsc pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm
bogomips        : 5131.64
clflush size    : 64
cache_alignment : 64
address sizes   : 36 bits physical, 48 bits virtual
power management:

At idle it drops down to 1596.000 MHz reported.  At boot the kernel
doest report the correct frequency (2564.907), which agrees with the
bogomips reported by /proc/cpuinfo as well.

I haven't done any benchmarking to try to determine if perhaps freq
scaling works as it should and just the reported frequency is incorrect.

Berck
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