Default CPU frequency scaling issue

[Ralf]

Hi :)

today I installed Ardour3, perhaps Paul Davis recommendation is more
important than mine [1].

My Kernel is set to use 'performance' as default setting for the CPU
frequency scaling [2]. If I start a GNOME session it's set to "ondemand"
automatically.

I'm starting sessions by a script, unfortunately some Ubuntu installs
need a "sudo" before "cpufreq-selector -g performance", while others are
not fine with the "sudo", some other installs, e.g. Suse do need a
different command, ok, Suse keeps "performance" ;). Older Ubuntu
installs needs a SUID bit set ;).

So I need to write a script checking for the distro + distro version or
I need to set it by the panel each time after starting a GNOME session,
or I need to add aliases to the shells. At the moment I'm doing it by
the panel.

The right way should be, that Ubuntu Studio GNOME does use the kernel's
default. This needs a fix. The DE shouldn't try to be smarter than the
user!

Btw. using "ondemand" might safe 1W on modern 40/50W CPUs. This isn't
much pollution projected onto Linux audio users. I'm using "ondemand"
when not making music, but the default should be "peformance". Note that
some people are working on a Jack frequency scaling!

Cheers!

Ralf




[1]
$ ./install.sh

Welcome to the Ardour installer

Sat May 21 10:32:35 CEST 2011
Architecture is x86
[snip]

System failed the quick sanity check... Looking for the cause

!!! WARNING !!! - Your system seems to use frequency scaling.
This can have a serious impact on audio latency. You have two choices:
(1) turn it off, e.g. by chosing the 'performance' governor.
(2) Use the HPET clocksource by passing "-c h" to JACK
(this second option only works on relatively recent computers)

Press ENTER to continue:^C
$ ./install.sh

Welcome to the Ardour installer

Sat May 21 10:36:01 CEST 2011
Architecture is x86
Unpacking bundle for x86

Checking system libs to see if they are compatible with Ardour.


Found existing Ardour installation.
Do you want to run the
uninstaller /opt/Ardour-3.0alpha3_9210-dbg.uninstall.sh ? [y/n]: n

Installing Ardour 3.0alpha3 built from 9210 in /opt

mkdir: cannot create directory `/opt/Ardour-3.0alpha3_9210-dbg': File
exists
Adding Ardour to the applications menu

Creating a desktop link for Ardour

Copying uninstall script to /opt


Checking to see if Jack is installed

Jack OK

Cleaning up

!!! Install Complete !!!

Press ENTER to exit installer:

[2]
$ cat config-2.6.33.9-rt31 | grep CONFIG_CPU_FREQ_DEFAULT_GOV
CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE=y
# CONFIG_CPU_FREQ_DEFAULT_GOV_POWERSAVE is not set
# CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE is not set
# CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND is not set
# CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE is not set