Enabling CPU Frequency Scaling November 4, 2005
Posted by Carthik in administration, applications, guides, ubuntu.trackback
I use the CPU Frequency Scaling Monitor on my panel to see the speed of my CPU. I have a centrino laptop. Ubuntu automatically increases the speed (frequency) of my laptop when the demand is more, and manages things very well.
However, when I am plugged in, I want to run my laptop at the maximum possible frequency at certain times. It turns out that the CPU Frequency Scaling Monitor can also have the functionality to change the Frequency, by “Governing” the CPU frequency. However, by default, on my laptop, left-clicking on the Monitor in the Panel did not give me the option to change the frequency.
In order to be able to change the operating frequency, your processor should support changing it. You can find out if your processor has scaling support by seeing the contents of files in the /sys/devices/system/cpu/cpu0/cpufreq/
For example, on my system:
$cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
gives:
1300000 1200000 1000000 800000 600000
Which means that the above frequencies (in Hz) are supported by my CPU.
and…
$cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors
gives:
userspace powersave ondemand conservative performance
All those are the different “modes” I can operate the CPU at. Userspace, for example, regulates the frequency according to demand. Performance runs the CPU at max-frequency, etc…
On the Ubuntu Forums, I read that one can manually change the frequency by executing commands like:
$ cpufreq-selector -f 1300000
which will set the frequency to 1.3 GHz.
Now, I was interested in being able to change the power mode (between the different values listed in the “governors” above, manually by using the Cpu Frequency Panel Monitor.
I found out from the Forums, again, that changing the permissions of the cpufreq-selector binary by doing a:
$sudo chmod +s /usr/bin/cpufreq-selector
will allow me to acheive this. However, I was curious as to why Ubuntu does not, by default, allow me to choose the frequency using the CPU Frequency Panel Monitor, and what the “right” or “correct” way of enabling this is.
With a little bit of detective work, I found the reason why things are the way they are in Bug #17604 :
Oh, please, not another setuid root application if we can avoid it. Which file does cpufreq-selector need access to to change the CPU speed? And why should a normal user be able to change the CPU speed in the first place? The automatic CPU speed works well enough for the majority of users, and control freaks can always use sudo to manually set the speed, or deliberately shoot themselves in the foot by making the binary suid root (as explained in README.Debian).
Anyways, since I really want to “shoot my self in the foot” using my CPU ;), so I read the readme:
$cat /usr/share/doc/gnome-applets-data/README.Debian
and as suggested in it, I did a
$ sudo dpkg-reconfigure gnome-applets
and answered “Yes” to the question regarding setting the suid of the cpufreq-selector executable. Now, by left-clicking on the CPU Frequency Monitor Applet, I can choose the frequency for my processor, and things couldn’t be better!!
P.S.: A lot of my detective work could have been avoided had I read the README in the first place. Stupid me.
I did this and got it working, but it seems like the CPU frequency will frequently revert back to computer control–it’ll stay where I set it for a bit, and then start auto-adjusting again. Have you experienced this?
Thanks for this — I just installed Ubuntu on my Centrino laptop, and was curious why I couldn’t change the CPU speed. No matter what I did, my 1.7 GHz CPU was always being reported at 800Mhz by the panel applet!
Alex, If you check the preferences for the applet, you can enable “Governors” and “Frequencies” for control. Try setting the frequency using the frequency menu after you enable it. It will then sta y at one frequencies. Each of the “governors” modify the frequency at various times.
Thank You, your hint worked perfectly for me (IBM Thinkpad T42)
It doesn’t look like Ubuntu, by default, twiddles the governors or the frequencies when you switch between battery and AC. When I’m on AC, I want the performance governor at full speed. When I/m on battery, I want the userspace governor, so the frequency will scale according to usage.
I poked around /etc/acpi/, /etc/defaults/laptop_mode, and /usr/sbin/laptop_mode and finally came up with the following, that works:
Edit /etc/defaults/laptop_mode and add the following:
Then move down to find
$LAPTOP_MODE stop(line 58 in the unmodified file) and add:Save the file. Yank your power cord. Note that the governor has switched to userspace:
cat /sys/device/system/cpu/CPU0/cpufreq/scaling_governorRestore AC power, and run the command above, to make sure that the “performance” governor is in use. Make sure the CPU frequency is at its max.
Tested — works for me. Enjoy!
Thanks, ubuntunista. That worked fine.
Now I can’t get Skippy’s idea working; I’ll have to tinker with that a bit more.
tnx for the tip, just what i needed!
your trouble shooting was definetly not a waste of time.
[...] e rispondete “Yes” alla domanda relativa al suid di cpufreq-selector. Fatto questo, andate nelle preferenze della vostra applet.. et-voilà! Per ulteriori informazioni leggetevi i commenti di questo post. [...]
Very nice. Thanks for the tip.
Hello there,
I am using Dapper with power manager 2.14.3 on Dell latitude 640. I inserted the lines in my conf but can’t see any changes. My sudo cat cpuinfo_cur_freq shows the max cpu speed regardless of the script. With the gnome cpu fre scaling monitor the changes seem to work, but not automated as I would hoped to. I suspect some other rights issue. What script is triggered when I unplug the AC cable?
Thanks
Cheers
Mike
I used both Ubuntu and SUSE Linux. In the latter, changing the governor is pretty easy and quick. I guess Ubuntu has set too much constraint on the security of the OS, such that it makes a big hassle to go through all the way just to enable a different frequency selection.
Hi . Im a total linux noob - how do U start CPU Frequency Scaling Monitor ? I seem to have downloaded the package in Ubuntu 6.06 - but I don t understand how to stat the application ? Can someone help me ?
Thanks, it seems I’m not the only one wondering why the applet doesn’t support frequency scaling in the first place.
Roger: in Gnome, right-click the menu panel on the top of the screen and select “Add to panel”. There you should find “CPU Frequency Scaling Monitor”
Is it safe to say that some cpus don’t support frequency scaling? Because, I don’t have a cpufreq directory in …/system/cpu.
Erik
Yes, some CPUs don’t have frequency scaling
What if you seem to be missing cpufreq in the …/system/cpu/ path, but your system does in fact support scaling? (Does it in Windows) (Pentium-M 733 1.1ghz ULV)
Has anyone seen this behavior?
[...] Debian (and ergo Ubuntu) has some of the best documentation in the world. The best thing about the documentation is that it is on your machine, not on the internet. However not many realize this, and many a problem that can be solved just by reading the documentation remains unsolved, and many a user resorts to forums, mailing lists etc when the answer is right there on their own computer. I am guilty too, having realized the power of RTFM-ing before. [...]
I also got a problem kind of like PodMonkeys.
I have a Dell Inspiron XPS Gen 2 Intel Centrino 2.0 Ghz (supports 800, 1.06, 1.3, 1.6 and 2.0)
isma@SoulFire:/$ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
2000000 1600000 1333000 1067000 800000
However I can’t seem to be able to use any of the frequencies other than 800 Mhz due to this:
isma@SoulFire:/$ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
800000
How can i fix this ???
This should be integrated into gnome-power-manager soon.
See my blog for updates.
[...] Handy applets for notebooks: wifi strength and CPU speed control I like to see the strength of my wifi connection, and also when any data is being transmitted, so I use the Network Monitor applet. Right-click a blank spot on the taskbar and select Add to Panel. Scroll down the window to the System & Hardware heading and click Network Monitor. Select it and click Add. A new icon should appear near the system tray. The four bars on the right indicate wifi signal strength. If you’ve got a compatible notebook, such as one containing an AMD chip or an Intel Mobile Pentium 4 chip, you might also be interested in the CPU Frequency Scaling Monitor, under the same heading in the Add to Panel dialog box. However, out of the box this isn’t configured to work properly. To make it work, open a shell and type sudo dpkg-reconfigure gnome-applets. Read and evaluate the warning about security and hit Enter and then agree to install cpufreq-selector with SUID root. Reboot the system. From then on, you can right-click the CPU-freq applet and select the speed you want the chip to run at. The Ubuntu Blog has an excellent write-up about this, which I advise you to read: http://ubuntu.wordpress.com/2005/11/04/enabling-cpu-frequency-scaling/. [...]
[...] 2006-08-22: as suggested, I looked into cpufreq. Here’s a guide that explains what it is and how you can use it. Iusually set the “governor” to “conservative” and switch to a fixed frequency (e.g. 800 MHz) when playing a movie or watching a YouTube video. Works great so far — the temperature is still higher than on XP, but no extreme jumps anymore. [...]
In response to message 16 from PodMonkeys:
Try this: “modprobe speedstep-centrino”.
[...] CPU frequency scaling had, by default, its behaviour locked to automatic choosing of CPU frequency. All regarding setting unnecessary superuser powers to yet another application. Quoting: “And why should a normal user be able to change the CPU speed in the first place? The automatic CPU speed works well enough for the majority of users, and control freaks can always use sudo to manually set the speed, or deliberately shoot themselves in the foot by making the binary suid root”. And that’s the trick. Issue a sudo dpkg-reconfigure gnome-applets and answer “Yes” to the question regarding setting the suid of the cpufreq-selector executable. Now, when I left click the CPU Frequency Monitor Applet, I’m able to choose the behaviour (powersave, max. performance, etc) and/or the processor speed. Yay. [...]
Help. Ok I set up http://ubuntuforums.org/showthread.php?t=248867 and then added this utility to see it work. I’ve noticed only one processor changes and the other stays full out. Even if I put two icons up top and change them. One stays in Performance and the other changes.
[...] read more | digg story [...]
[...] Enabling CPU Frequency Scaling « Ubuntu Blog [...]
Is KDE better on this with the “Laptop configuration” system applet??
Perfect, this is exactly what I was looking for.
[...] http://ubuntu.wordpress.com/2005/11/04/enabling-cpu-frequency-scaling/ [...]
Hi,
thank you guys for this howto. I followed everything here on my Asus F3JA and i do have the Scaling Monitor. I can set the according CPU speed but i still have the problem that my fan won’t spin down, no matter to what speed i set the CPU (Core 2 Duo 2200) and no matter if its under full load or idling. Could you give me a hint where to start debugging?
Thanks in advance!
Jan
I have the same laptop as you and still trying to find a way to solve the fan problem…
News?
Thank’s a lot, this is my very first blog comment and I only post it because without this post I would have searched for another 2 hours
Thanks for the wonderful guide. You let me save energy! I was ready to turn off the scaling feature completely.
Great guide.
One thing:
The correct way is not to touch the /etc/default/laptop…..
It is the best if you create corresponding scripts in /etc/acpi/ac.d and
/etc/acpi/battery.d
Like:
/etc/acpi/ac.d/cpufreq.sh:
#!/bin/sh
/usr/bin/cpufreq-selector -g performance
/etc/acpi/battery.d/cpufreq.sh:
#!/bin/sh
/usr/bin/cpufreq-selector -g ondemand
Why isn’t it there by default? There is no suid problem because the whole acpi is running by root.
if userspace controls the speed according to demand, then what is ondemand for?
Thanks for that, it was a great help
Ondemand reacts a little faster at my acer travelmate 8003, userspace waits a bit to long before switching for my taste.
today I came over your blog searcing for the same problem and got it working. Thanks a lot . I now know where to come for my problem…
The ondemand mode changes speed based on usage, and is built in to the kernel. The userspace mode allows a user-mode program to tell the kernel where to set CPU speed at any given time.
hello, i wanna install ubuntu in intel core duo 2. this fileserver in small office. have i any problem with it?
Nice tutorial, thanks. Why is there only one cpu state, C1, in /proc/acpi/processor/CPU1/power ? I have the core 2 duo 2.13 ghz and a debian 2.6.18-4-amd64 kernel
oh yes, by the way, scaling with the tools you mention functions perfectly .. the cpu frequency is reported to be 1.6 GHz when using the powersave governor.
thank you very much, it works great for me…
I have a Thinkpad Z60t, and inserted the two scripts into “ac.d” and “battery.d” This works great when the laptop is on and I plug and unplug the power, however when booting up the laptop on AC power it still resorts to “ondemand” which is annoying. I would think that linux would read those scripts during boot time, but evidently not. Is there a workaround for this, or am I the only one having this problem?
yepp, worked perfectly in Debian as well. This guide allowed me to use the ondemand governor (which I couldn’t do manually, with sudo cpufreq-set -g ondemand)
Strange behaviour for the console mode, yesterday i could do it today I cannot ..
Perfect solution! This allows the CPU Frequency Monitor applet perform similarly to the power management setting in Windows (setting to always on sets top speed performance for laptops)
Having to configure a cpu speed applet to “Run As..Root” (In Windows terms) seems a little silly.
While I appreciate the security concern of having suid on a utility file. For a desktop based installation of ubuntu and functionality that this specific to laptops (speedstep), I do not agree that the applet should have been written to only allow root-level users access to speed adjusting functionality.
Oh well, got me to run “sudo dpkg-reconfigure gnome-applets” and now my little PIII laptop is pegged at its top speed of 1ghz vs 700mhz. I’m happy
Wonder how many other users of older laptops, hoping to leverage the efficiencies of Linux over XP to get more performance are slugging along at the slower speed and not even aware of it??
[...] http://ubuntu.wordpress.com/2005/11/04/enabling-cpu-frequency-scaling/ [...]
I gave up on frequency scaling. The power consumption is not notably lower.
My CPU (Spec#: SL4SH) is not fully supported by the p4-clockmod module. It reports wrong frequencies, but it works fine as the scaling is done as percent of the clock rate. It is just the reported clock rate which is wrong.
If you are using a P4 CPU you may need to manually modprobe the p4-clockmod module. At least I had to (6.10).
sudo modprobe p4-clockmod
sudo /etc/init.d/powernowd start
If you want to you can use the labtop_mode io scheduler to save some power/wear on your HDD. It takes a lot of power/wear to do spin ups on your HDD so it will only work if you find the balance that makes it worth it and doesn’t increase wear/power consumption.
sudo /usr/sbin/laptop_mode start
sudo hdparm -S 4 /dev/hda
The -S parameter is the spindown timeout in seconds divided by 5.
[...] though, I found out that I can still manually dim my laptop’s screen through the keyboard and this page showed me that I can manually switch my CPU to operate at lower speeds to conserve power. In [...]
I did what this guide says, now I have the selector for my scaling.
But if I click on any of the frequency, the speed on my laptop doesn’t change.
On another note, my laptop’s available governor only has one, the “performance” one. Doesn’t have a big list of them like yours, could that be why I can’t change it?
Lastly, I find if I start my laptop up without it being plugged in, the max speed will be at 1.4ghz, while if I start up my laptop with it plugged in, I get 1.5ghz. Any way to change this?
Very useful, Thanks a lot!!
The method works great with minimal configuration. Awesome work! Thank you.
[...] ACPI Support –> <> AC Adapter <> Battery (Note: For the next settings, I used this link and this Gentoo Wiki entry) CPU Frequency scaling –> <> ‘ondemand’ cpufreq policy [...]
Very informational
Searched via google, found this page, read it, fixed it. done.
Thumbs up.
[...] http://ubuntu.wordpress.com/2005/11/04/enabling-cpu-frequency-scaling/ [...]
I did the whole set suid bit (Ubuntu Feisty - $ sudo dpkg-reconfigure gnome-applets and answered “Yes” to the question regarding setting the suid of the cpufreq-selector executable) and it works fine *most of the time*.
From time to time, however, I click on the applet and it *won’t* change. Usually when I’m trying to get updates or using Synaptic or some other process where I’ve used sudo/entered my password to give a process root privileges.
Does anyone know if this is connected?
@ What you describe is the moment when your machine wants to power up Synaptic. Do you have the same problem with the governor “powersave”?
On my T60 (Core2Duo T7200) changing frequencies has no effect on battery wear.
The Frequency Scaling Applet shows the change in frequency. Well, at least when I change the frequency by hand.
But the remaining time on battery power remains unchanged and conky also shows full frequency all the time. And the fan is always running. Any clues anyone?
Thinkpad T60 Core2 Duo
Thankyou for this. : )
“sudo dpkg-reconfigure gnome-applets” seemed to work well.
[...] Scaling the CPU Frequency in Ubuntu July 10th, 2007 I really like my laptop, Sony did a great job constructing this series with small size and good performance. The downside of of good performance on small size is noise! When running on full load with 1.7 GHz my VGN-S5 makes too much noise for my sensitive ears. The fan is working all the time and drives me mad! On Windows XP the CPU scaling works fine, Vista needs more performance and the noise level is higher than in XP (or the scaling is badly implemented). But within Ubuntu the CPU is running with 1.7 GHz all the time and no scale down happens by default. This seems to be a bug and today I wanted to solve this problem, with success. I found a nice description at the Ubuntu blog on WordPress.com. [...]
[...] ACPI Support –> <> AC Adapter <> Battery (Note: For the next settings, I used this link and this Gentoo Wiki entry) CPU Frequency scaling –> <> ‘ondemand’ cpufreq [...]
works!!!
toshiba a100 va9 (centrino dual core 1.67ghz)
thank you so much
Thank you so much. Thank god for google and kind hearted bloggers such as yourself for the help you give to the rest of us. Your very simple method works great on a brand new core2duo T7500 in a Thinkpad X61.
[...] zum Thema http://ubuntu.wordpress.com/2005/11/04/enabling-cpu-frequency-scaling/ http://wiki.ubuntuusers.de/Prozessorspannung_absenken http://wiki.ubuntuusers.de/Strom_sparen [...]
I have a Toshiba a100 also with us centrino dual core 1.67 GHz processor. It worked very well thank you very much
DUDE! I love you
That was a GREAT and to the point tutorial on this. Thanks for taking the time to post the info you found - much appreciated!!
peace,
Johann
Thanks work great for me
I also got a problem kind of like PodMonkeys.
I have a Dell Inspiron XPS Gen 2 Intel Centrino 2.0 Ghz (supports 800, 1.06, 1.3, 1.6 and 2.0)
http://soundproducer.blogspot.com/
[...] you might want to take a look at this page: http://ubuntu.wordpress.com/2005/11/04/enabling-cpu-frequency-scaling/ [...]
still works on ubuntu 7.10:
sudo chmod +s /usr/bin/cpufreq-selector
Works well for me too (Thinkpad R50e with Gutsy). Thanks
thanks!
Wish I had found this about 40hrs ago, no matter fixed now, thank you
Thanks - took me a day of searching for this. I had it working before in Feisty have done it before myself but forgotten how, maybe this time I will remember…
Frustratingly I found screen shots of the applet preferences with a “Show menu” option that would let it display the governor change menu, but mine didn’t even have that.
It is possible to make a manual change to the on AC and on BATT values from the Gnome configuration editor - under /apps/gnome-powermanager/cpufreq/{policy_ac, policy_battery} - but I like to change it depending on what I’m doing and how long I think I’ll be on battery…
works , thanks
To make the menu show up when you left-click on the CPU Frequency Scaling Monitor, simply run the following in a console:
sudo chmod +s /usr/bin/cpufreq-selector
That’s all you have to do. That will “setuid root” for that application, letting a regular user run it and thus letting the handy panel icon change your CPU scaling settings.
always when installing new compu with linux, always coming to this pages. i’m never ever installing the normal way that’s why.
kr
thanks! you just increased my battery life by 25% and cooled my lappy enough to stop it crashing
Hi guys
I have recently changed my laptop to ubuntu 7 but I have a problem with connecting to Internet. It’s working properly when I use DHCP but when I connect to router and set IP, DNS, … it doesn’t work. Can you help me with this thanks.
Alex,
I used to have that problem… I googled and looked all over the internet for an answer and did not find one. I finally installed Tomato on my Linksys router. Tomato supports static DHCP. Now I just assign static DHCP addreses.
With ubuntu 7.10, there’s an easier way, if you don’t mind tweaking with gconf-editor. Drop a console, type gconf-editor, then choose apps > gnome-power-manager. You’re looking for the cpufreq folder, and the parameters you want to change are policy_ac set to performance and policy_battery set to either ondemand or powersave.
[...] Enabling CPU Frequency Scaling « Ubuntu Blog (tags: battery thinkpad t42p ubuntu linux cpu frequency laptop howto tuning) [...]
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