Re: Ondemand governor not working with kernel-2.6.12-12mdk

[Eric Piel <Eric.Piel@tremplin-utc.net>]

08.10.2005 19:30, Alex Simonov wrote/a écrit:
> Hello Eric,
:
> 
> Your patch did the trick, thanks! The only draw
> back is that the responsiveness is not 
> so good - it takes at least 2-3 seconds to 
> switch  to  the highest frequency and back, when
> thie high load is over. Is it supposed to be like
> that by design, or this latency could be changed?
> 
> 
That's strange, it's supposed to be faster (although it could be even 
faster). IIRC, on 2.6.12, it should be every 100 milliseconds. You can 
check the sampling frequency of the ondemand governor by doing a
cat /sys/devices/system/cpu/cpu0/cpufreq/ondemand/sampling_rate

It will give the period between each frequency update in microseconds. 
In general, it should change from low to high in a tenth of a second. 
You can check it with a stupid shell command like this (when nothing 
else is running), this is only one line:

# date +%T.%N; while test $(cat 
/sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq) != $(cat 
/sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq)  ; do true ; done 
; date +%T.%N

By doing the difference between the two times displayed you'll know how 
long it takes for the ondemand governor to change to the high frequency.

Here (pentium III), it takes about 0.08s .

Eric