[Bug 519142] Re: ThinkPad T43 CPU scaling (ondemand/fixed/..) not working correctly - Ubuntu 9.10/10.4 (stock & mainline)

[Eric Brasseur]

This is what worked for me, on an Intel-based HP Pavillon dv6000:

First of all, my puzzling started making sense only when I got rid of
the Gnome CPU Frequency Scaling Monitor. It does and displays nonsense.
For example, when the CPU is absolutely constantly at maximum speed, the
Gnome applet will show that the CPU is mostly at minimum speed and
sometimes rises at maximum speed.

I installed the sysfsutils package:

   sudo apt-get install sysfsutils

Which allowed to use this command line in a terminal window to monitor
the frequency:

   while : ; do sudo cat
/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq ; sleep 1 ; done

Alternatively, for example if you don't want sysfsutils installed or you
don't want to sudo, this command line should do the job:

   while : ; do cat /proc/cpuinfo | grep MHz ; sleep 1 ; done

Then, I had to install powernowd:

   sudo apt-get install powernowd

The presence of the powernowd package is what makes everything perform
properly. Actually the powernowd daemon does not run on my system... It
seems that it will not be started if the default governor is "ondemand".
But anyway the package needs to be installed.

I had some doubts about the gnome-power-manager package but simply it
seems to have no influence on this problem. I keep it so I can suspend
the machine without having to type "sudo pm-suspend" in a terminal
window. Some online texts made me believe that gnome-power-manager has
an influence on the CPU frequency but gconf-editor doesn't show that
there would be any related tuning. (The gnome-power-manager has a mostly
nonsensical behavior, for example using its graphical interface often
yields no or opposite results and the default behavior is very annoying.
I used gconf-editor to just shut down most of its features.)

With the powernowd package installed, my machine suddenly became fast as
craziness. The maximum speed is switched on instantaneously when
required. It's a delight. No more need to purchase a new laptop. I lack
an applet to monitor the frequency but actually this is not severe. I
simply know that when at least on of the cores is fully busy, the CPU
will be at maximum frequency. Also, I do no more need the applet to be
able to tune maximum frequency when needed, because powernowd does it
perfectly and automatically.

The only case when I need to tune the frequency is to impose a constant
low frequency to avoid the machine heating or making noise in some
occasions. I found no clean procedure to do that. Powernowd is unaware
of the need to sometimes keep the machine at low power consumption. The
commands below allow to do that but they have no effect on my system,
whether or not powernowd is installed.

   sudo su
   echo ondemand > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
   exit

or:

cpufreq-selector -g ondemand

Linux is a strange system. It has a whole set of different tools for one
purpose. Each tool is incomplete, has bugs and quite often the
configuration procedure is obfuscated beyond repair. A computer
scientist can often manage to assemble the working parts of some tools
to get something that works for an individual case. But no distro
maintainers ever managed to assemble something that would be general-
purpose and reliable. A few years ago I managed to tweak the kernel to
almost get a really multitasking multimedia system, with almost no
stuttering in operation. But the kernel changed and the work was to
begin again from zero so I abandoned. I also needed several months till
I found on the internet that to stop the X server from bleeding away all
the memory in a few hours time, you just need to disable Xinerama in
/etc/X11/xorg.conf. Some of those problems really need work to fix, yet
other ones are just a quick tuning that can be installed automatically
with the next package upgrade. But, even if plainly reported and
documented inside the distro's mailing lists since years, the fix will
never be implemented... When you complain, at best you get no reply, at
worst you get a flaming response from a developer (or from one of his
followers if he's already too deified to address common people)
explaining how repugnant you are for not seeing the brilliance of his
courageous choices. The best one I ever got is after simply reporting in
a forum that ext2 was the sole format that always allowed me to recover
my files after a severe crash and that ext3 was the only one that even
never crashed at all. I got a flaming reply stating that a file system
format *must not* be in charge of the integrity of the data and that
each individual software has to do the necessary work to restore its
files...

I believe that the human brain is capable to make a decent operating
system but mankind is not. The only way out of this is to impose a new
abstraction layer; that of hardware virtualization. It is already often
used but in a partial way or as a simplification at the behalf of
performance. It must become completely detached from the operating
system business and be a sector of its own, just like the operating
system business became detached from the application business.

-- 
ThinkPad T43 CPU scaling (ondemand/fixed/..) not working correctly - Ubuntu 9.10/10.4 (stock & mainline)
https://bugs.launchpad.net/bugs/519142
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