Re: ondemand cpufreq ineffective in 2.6.12 ?

[Daniel J Blueman <daniel.blueman@gmail.com>]

I find the ondemand governor works as expected with 2.6.12 on my
Athlon64 Winchester [1]; as soon as I bzip2 a file, processor freq is
pinned at 1.8GHz and drops to 1GHz when idle.

--- [1]

$ cat /proc/cpuinfo 
processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 31
model name      : AMD Athlon(tm) 64 Processor 3000+
stepping        : 0
cpu MHz         : 1004.646
cache size      : 512 KB
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx mmxext
fxsr_opt lm 3dnowext 3dnow
bogomips        : 1988.83
TLB size        : 1024 4K pages
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management: ts fid vid ttp

Ken Moffat wrote:
> Hi,
> 
>  I've been using the ondemand governor on athlon64 winchesters for a few
> weeks.  I've just noticed that in 2.6.12 the frequency is not
> increasing under load, it remains at the lowest frequency.  This seems
> to be down to something in 2.6.12-rc6, but I've seen at least one report
> since then that ondemand works fine.  Anybody else seeing this problem ?
> 
>  Testcase: boot (my bootscripts set the governor to ondemand), set the
> governor to ondemand, performance, powersave and untar a nice big
> bzip2'd tarball (gcc-3.4.1) from an nfs mount. All using the config from
> 2.6.11.9 and defaults for new options.
> 
> kernel		2.6.11.9	2.6.12-rc5	2.6.12-rc6	2.6.12
> 
> ondemand	20.8 sec	21.3 sec	33.9 sec	34.1 sec
> performance	21.3 sec	22.0 sec	22.6 sec	20.1 sec
> powersave	32.4 sec	33.1 sec	33.6 sec	33.9 sec
> 
> I don't have confidence that the numbers are more repeatable than +/- 2
> seconds on this, they just illustrate that ondemand used to give a
> similar time to performance, but now doesn't.  Other intermediate and
> later tests have been omitted for clarity, but 2.6.12.2 does show the
> same problem.
> 
> Since 2.6.12-rc6, 'ondemand' appears to be still accepted (the echo to
> scaling_governor returns 0, and the displayed frequency drops back if
> I try going from performance to ondemand).
> 
> When ondemand appears to work properly, /proc/cpuinfo shows the speed
> jumping to 2 GHz, then falling back to 1.8 after the untar ends, then
> back to 1.0 GHz.  In the problem cases, the speed remains at 1GHz.
> 
> As far as I can see, nothing untoward shows in the logs.  Any
> suggestions, please ?
> 
> Ken
___
Daniel J Blueman