Questions about cpu frequency

nsp · 02-25-2014, 11:34 PM

In a nutshell, ubuntu 13.10 doesn't scale up any of my cpu frequencies when one of the threads is in 100% use. Is this normal?

My CPU: i5 4200u, 4 threads, @1.6GHz up to 2.6GHz.
My OS : Ubuntu 13.10 with kernel 3.11.0-17

Other infomation:

Code:

$ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies 
1601000 1600000 1500000 1400000 1300000 1200000 1100000 1000000 900000 800000 

$ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
ondemand

$ cat /sys/devices/system/cpu/cpufreq/ondemand/up_threshold 
95

Problem:
When the cpu is idle, /proc/cpuinfo says all 4 threads are at 800MHz, which is very cool. But when a process is using one thread 100%, all the cpu frequencies are still 800MHz. The OS doesn't scale up any of the cpu frequencies. Is this normal?

I think when one of the threads is 100% in use, this single thread should be scaled up. What should I do if I want this?

Thank you. Sorry for my English.

replica9000 · 02-26-2014, 09:43 AM

I don't know if this is exactly the issue I was having. I have a i7-2600k. I could see the normal frequency range, but not the turbo frequencies. Under load, I was using the turbo speeds (set at 4500MHz), but was only shown 3400MHz. I had to use a tool called i7z to show the turbo frequencies. When I upgraded to kernel 3.12, I no longer need i7z to see the turbo frequencies.

nsp · 02-26-2014, 11:44 PM

Quote:

Originally Posted by replica9000

I don't know if this is exactly the issue I was having. I have a i7-2600k. I could see the normal frequency range, but not the turbo frequencies. Under load, I was using the turbo speeds (set at 4500MHz), but was only shown 3400MHz. I had to use a tool called i7z to show the turbo frequencies. When I upgraded to kernel 3.12, I no longer need i7z to see the turbo frequencies.

Thank you, relica9000. I do have the same problem that turbo frequencies are not shown when using kernel 3.11. Today I updated to kernel 3.12 and the turbo frequencies are shown.

But the lowest frequencies, which are correct in:

Code:

$ cat /sys/devices/system/cpu/cpu?/cpufreq/scaling_min_freq 
800000
800000
800000
800000
$

seem not to be used when the system is idle:

Code:

$ grep MHz /proc/cpuinfo 
cpu MHz		: 1688.074
cpu MHz		: 1600.117
cpu MHz		: 1600.027
cpu MHz		: 1604.160

Frequencies in /proc/cpuinfo are always higher than 1.6GHz. (The governors are "powersave" mode.)

What are the real frequencies the cpu is running at? Is the file /proc/cpuinfo giving incorrect infomation?