Re: ondemand cpufreq ineffective in 2.6.12 ?

[Eric Piel <Eric.Piel@lifl.fr>]

11.07.2005 23:55, Con Kolivas wrote/a écrit:
> On Tue, 12 Jul 2005 05:45, Ken Moffat wrote:
>
> > On Mon, 11 Jul 2005, 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 ?
> >
> > And just for the record, it's still not working in 2.6.13-rc2.  Oh
> > well, back to 2.6.11 for this box.
>
>
> I noticed a change in ondemand on pentiumM, where it would not ramp up if the 
> task using cpu was +niced. It does ramp up if the task is not niced. This 
> seems to have been considered all round better but at my end it is not - if 
> it takes the same number of cycles to complete a task it does not save any 
> battery running it at 600Mhz vs 1700Mhz, it just takes longer. Yes I know 
> during the initial ramp up the 1700Mhz one will waste more battery, but that 
> is miniscule compared to something that burns cpu constantly for 10 mins. Now 
> I'm forced to run my background tasks at nice 0 and not get the benefit of 
> nicing the tasks, _or_ I have to go diddling with settings in /sys to disable 
> this feature or temporarily move to the performance governor.
echo 1 > /sys/devices/system/cpu/cpu0/cpufreq/ondemand/ignore_nice
Put it once for all in your initscript :-)

> Although I 
> complained lightly initially when this change was suggested, I didn't realise 
> it was actually going to become standard. 
I like it because it avoids that any background task which is ran makes 
the fans turning like hell. It's also very advantageous with tasks like 
screensavers or a la seti@home (but few people have this on their laptop).

> To me the ondemand governor was supposed to not delay you at all, but cause as 
> much battery saving as possible without noticeable slowdown...
>
> Oh well you can't please everyone all the time.
It's a tradeoff :-)

Ken, does this solve your problems (but that seems strange that all your 
tasks are nice'd) ?

Eric
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