Why are the CPU frequency timing statistics all zeros?

Question

The cpufreq timing statistics are all zeros:

$ sort --unique /sys/devices/system/cpu/cpu*/cpufreq/stats/time_in_state | column
1600000 0       2100000 0       2600000 0       3100000 0
1700000 0       2200000 0       2800000 0       3300000 0
1900000 0       2400000 0       2900000 0       3400000 0
2000000 0       2500000 0       3000000 0       3401000 0

How is this possible? Is there really no time spent in any state?

Details

• /proc/cpuinfo

• The CPUs are clearly transitioning between frequency states:

  $ grep --perl-regexp --only-matching '(?<=cpu MHz\t\t: )[\d.]+' /proc/cpuinfo | column
  1600.000        1600.000        3401.000        1600.000
  2900.000        1600.000        2100.000        1600.000
  $ while sleep 10; do column /sys/devices/system/cpu/cpu*/cpufreq/stats/total_trans; done
  17839   17278   17497   17336   12332   14358   14054   17647
  17885   17313   17545   17384   12359   14394   14082   17691
  17888   17323   17556   17391   12359   14399   14085   17693
  17904   17336   17576   17417   12374   14402   14091   17696
  

• Someone else asked about this on a forum but never received a reply.

Answer 1

There is a problem regarding this in the Linux kernel 3.11. The bug was fixed with the following patch:

http://permalink.gmane.org/gmane.linux.kernel.cpufreq/11672%3E

https://lkml.org/lkml/2013/9/7/126

Upgrading your kernel (to 3.12-rc1 or higher) should fix the problem.