Re: Ondemand governor by default in etch
Am Donnerstag 07 Dezember 2006 16:36 schrieb John Goerzen:
> I believe that we should enable CPU frequency scaling, and the ondemand
> governer, by default in etch.
Did you read the kernel help for it?:
"The support for this governor depends on CPU capability to do fast frequency
switching (i.e, very low latency frequency transitions)."
The most important word is "very".
> * Is compatible with almost all modern hardware, and just won't
> load on machines that don't support it
>
> * Requires only a 10K ondemand module and a 5-15K driver module to be
> loaded into the kernel
>
> Why should it be the default?
It shouldn't.
> Earlier this morning, I wrote up the procedure [1] to enable CPU
> frequency scaling and the ondemand governor. It's about 3 pages, and
> not even newbie friendly at that. So the first reason is that people
> that don't know about this feature aren't prone to find it, and even if
> they find it, they aren't prone to know how to enable it.
apt-get install cpufrequtils
cpufreq-set -g ondemand
Really hard ;)
> Secondly, the ondemand governor is very non-invasive. It requires no
> userspace daemon. It makes a negligible impact on performance. And if
> people do wish to run a userspace daemon, this default will not
> interfere with it. I've tried it all over the place. It is stable and
> reliable.
I already had a system go off with it. Ok, it didn't have low latency
switching.
> Thirdly, it is ethically the right thing to do. Think about all the
> thousands (millons?) of machines that are running Debian. If we save
> even an average of 10W per machine, we could be talking about huge
> energy savings worldwide. We save our users money on their power and
> cooling bills. We reduce air pollution, which has been shown to have
> negative health effects. And we reduce greenhouse gas emissions.
>
> I can't see any reason NOT to do it.
>
> How would we turn it on by default?
You REALLY should take a look at laptop-mode-tools.
They can do this for you including loading the proper modules when needed and
LOTS of other energy saving technics.
And you should take a look at the "conservative" governor, too.
And BTW, did you measure the power savings? My WLAN card and monitor backlight
eat _all_ the savings and the kernel usually knows how to put the processor
to a sleep state.
HS
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