Default CPU frequency scaling issue

[Mike Holstein]

On Sat, May 21, 2011 at 5:05 AM, Ralf <ralf.mardorf at alice-dsl.net> wrote:

> 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
>

hey Ralph,

the way im reading this email, you are experiencing ubuntustudio using the
"on demand" CPU scaling setting at startup, and you want it to be
"performance" by default. that is a very valid point. i encountered this
same issue, and i googled around a bit, found an easy fix, and now, when i
start my production machine, it starts in "performance" mode. the issue is
this... not all ubuntustudio users are doing audio production, and not all
ubuntustudio users doing audio production are using JACK. also, main ubuntu
uses the "on demand" setting by default. this is a bug report where CPU
scaling was defaulting to "performance" instead of "on demand"
https://bugs.launchpad.net/ubuntu/+source/cpufreqd/+bug/344252 . i would say
realistically, thats something that will not be changed, however that is
something easy for you to change on your machine, and i can help you with
that if needed. now would be a great time to address issues like this
though. since we are switching to XFCE, and im assuming most of the power
management tools will be changing. we could potentially put something in the
ubuntustudio controls that checks for CPU scaling and offers to set it
differently. this would be something you would need to personally be
proactive about though. this is an example of a bug report marked
"wishlist" https://bugs.launchpad.net/ubuntustudio/+bug/695892 . you could
start with that, and email the -dev list about the possibility of including
some kind of option in ubuntustudio-controls... or just set the CPU scaling
default on your machine and let it go... im sure paul davis has strong
opinions about ubuntustudio and our default settings. with much due respect
for paul davis, i totally agree, and i think a lot of us would like to have
an ubuntustudio that is tailored for running JACK and ardour out-of-the-box.
however, this is not what *every* user will want, and arguably, not what the
majority would want. i think the agrument is, if you are a power user using
JACK, you will know how to, and know that you need to tweak these things.
someone coming to ubuntustudio for arguably lighter needs might not care to
find out how to change the CPU governor settings. if you strongly disagree
with that, then this would be a good point for your upcoming wishlist bug
report.

>
>
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-- 
MH

http://opensourcemusician.libsyn.com/
http://wnclug.ourproject.org/
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