Dual-core processor slow when laptop unplugged

[mfreeman]

I have a dual-core AMD Athlon M300 processor in my Laptop. When running the laptop plugged in, it runs very smooth and fast. When it's unplugged, it's jerky and slow. I loaded the CPU frequency scaling monitor panel applet, and it shows the normally 2GHz processor being scaled down to 800MHz. In addition, running the System Monitor, which shows two processors when plugged in, now shows only one processor running at a very high percentage when unplugged.

I can use the CPU frequency scaling monitor applet to bring it back to 2GHz when needed, but is there a way to bring back the missing processor core when the computer is unplugged?

I'm using Linux Mint 11 64-bit edition.

Thanks!

[xenopeek]

For those with multiple cores or processors who happen to be a bit needy in the info department (like myself) you can add an applet for each CPU. Just add as many applets as you have CPUs and then right click on them, choose Preferences and use the drop down to choose which CPU that particular applet is monitoring.

There is some more info here: http://1n73r.net/2008/10/16/ubuntu-cpu-scaling

[mfreeman]

Vincent,

Thank you for your reply! Unfortunately, this does not solve the root of my problem. I can control the speed of the processor(s) with the applet(s). That's fine. But what I'm having difficulty with is that when the power is unplugged, one of the processor cores becomes completely inactive, like it doesn't exist anymore. It's not recognized by the system at all. Once it becomes inactive, I can't turn it back on, even after plugging the computer back in. My computer becomes very slow, the one active processor core works very hard to make up for its missing twin, and video and visual effects become jerky. I have to completely restart the computer to bring everything back to normal.

I would like to know if there is a way to control the on/off states of the individual processor cores, so that when it won't come back on, or I just need a power boost when unplugged, I can manually activate it. This cannot be done with the applet. The applet only allows control of clock timing (MHz/GHz speed of each core), not its on/off state.

[xenopeek]

Okay, don't unplug your laptop Seriously, have you checked your BIOS for power save options that you might change? This sounds like something that might also be in the BIOS.

Other option, run the following commands before unplug and see if that makes a change:

Code: Select all

echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor 
echo performance > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor 

Basically that says, don't let the CPU cores go into idle state but keep them ready for work at all times. Edit: this change remains in effect until next reboot, or you change it.

Also, after your CPU 2nd core goes to sleep, investigate the sys filesystem. Here you can read information real-time from your system, and even configure some parts of CPU behaviour. Basically, have a look around the folder /sys/devices/system/cpu/cpu1/cpufreq/. For example:

Code: Select all

cat /sys/devices/system/cpu/cpu1/cpufreq/scaling_cur_freq

To see the current frequency in Khz (divide by 1 million to get to Ghz).

[mfreeman]

Haven't checked the BIOS yet. Will do that soon.

Wouldn't doing this:
echo performance > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor

simply result in the same thing the CPU Frequency Scaling Monitor applet does when I select Performance mode for that CPU?

Also, tried looking into my sys folder with the cat command, as you suggested.

Before unplugging the computer, I get:
mike@mike-laptop ~ $ cat /sys/devices/system/cpu/cpu1/cpufreq/scaling_cur_freq
2000000

After unplugging the computer:
mike@mike-laptop ~ $ cat /sys/devices/system/cpu/cpu1/cpufreq/scaling_cur_freq
cat: /sys/devices/system/cpu/cpu1/cpufreq/scaling_cur_freq: No such file or directory

After plugging the computer back in:
mike@mike-laptop ~ $ cat /sys/devices/system/cpu/cpu1/cpufreq/scaling_cur_freq
cat: /sys/devices/system/cpu/cpu1/cpufreq/scaling_cur_freq: No such file or directory

So it's like the CPU goes into power-save mode (thus shutting down the 2nd core), and can't get back out.

Just a side note, this did not happen with Mint 10, but does with Mint 11. So I'm not sure what changed between the two versions. Perhaps something in the newer kernel?

Like I said, I look through the BIOS, too, and get back to you.

[mfreeman]

Didn't find anything in the BIOS related to this issue.

[richyrich]

I wish I could suggest a solution . . . .

this did not happen with Mint 10

many have done just that . . gone back to 9 LTS or 10 . . .

[chefcale]

I have a similar buggy problem, I am running MInt 11 Katya on a Samsung NF210 , Dual Core 1.5 each , MInt runs very smooth and extremely fast when I start up on A/C , if I start up on battery power my screen brightness is dimmed with no noticable effects to speed , yet the display brightness is set to 100%. In order to get back to standard brightness I have to shut down , plug in and reboot. How can I correct this issue? Am I lacking a driver? or is it a setting issue? Please advise! THX!!