Red Hat Bugzilla – Bug 977392
cpu frequency does not scale back all the way
Last modified: 2013-10-08 13:09:09 EDT
Description of problem:
On the most recent kernels cpu scaling does not not scale the frequency back to the lowest possible value.
While on previous kernels it would scale back to 800MHz, now I get only
> cat cpuinfo_cur_freq
Under the load the frequency does scale up (to 2.9GHz) and it does scale down
again, but again not to the lowest value.
Of course, I tested with a minimal load. Only lightdm and a console were running.
Version-Release number of selected component (if applicable):
FC19 with kernel 3.9.6-301.fc19.x86_64
cat scaling_governor : powersave
Steps to Reproduce:
2. cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq
1025000 ... 1525000
On previous kernels in FC18, the frequency would scale all the way back to
800Mhz (which is I think the minimum)
*** Bug 977389 has been marked as a duplicate of this bug. ***
Forgot to say: this is on a Lenovo X220 with
Intel(R) Core(TM) i5-2520M CPU @ 2.50GHz
I think this issue might have to do with the
change in powermanagement reported here:
I guess the real question is whether this new policy actually saves power.
This is hard to measure accurately, but I shall give it a shot.
I have now ran some power consumption test.
On my computer it does not make a difference in battery power consumption.
So it is not really a bug, just confusing.
FYI, I used the following script
for i in $(seq 1 100); do
cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_min_freq >/sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
cat /sys/class/power_supply/BAT0/power_now >> /tmp/batl.log
cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq >/sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
cat /sys/class/power_supply/BAT0/power_now >> /tmp/bath.log
Then compare the mean of bath.log to batl.log
*********** MASS BUG UPDATE **************
We apologize for the inconvenience. There is a large number of bugs to go through and several of them have gone stale. Due to this, we are doing a mass bug update across all of the Fedora 19 kernel bugs.
Fedora 19 has now been rebased to 3.11.1-200.fc19. Please test this kernel update and let us know if you issue has been resolved or if it is still present with the newer kernel.
If you experience different issues, please open a new bug report for those.
This bug is being closed with INSUFFICIENT_DATA as there has not been a response in 2 weeks. If you are still experiencing this issue, please reopen and attach the relevant data from the latest kernel you are running and any data that might have been requested previously.