groovy wrote:... I'm not convinced. Have you checked the *real* kernel settings available under /sys/devices/system/cpu/* ?? I'm a bit skeptical
I was skeptical too (I think it's good to be a little skeptical ), and am still a little wary of using the cpufrequtils bootup script in /etc/init.d
So I did check the settings in /sys/devices/system/cpu/* to try to convince myself that the cpufrequtils script, and the cpufreq-info command-line utility, were (or rather, are) giving accurate information.
In my Linux system (LinuxMint 17.3), there are directories for each CPU core located at--
/sys/devices/system/cpu/cpufreq/
The directories inside that location are--
policy0
policy1
policy2
policy3
policy4
policy5
--because my CPU (an Intel i7) has 6 cores, 0-5.
Inside each of those directories (/sys/devices/system/cpu/cpufreq/policy0/ for example) are text files, as follows--
affected_cpus
cpuinfo_cur_freq
cpuinfo_max_freq
cpuinfo_min_freq
cpuinfo_transition_latency
related_cpus
scaling_available_governors
scaling_cur_freq
scaling_driver
scaling_governor
scaling_max_freq
scaling_min_freq
scaling_setspeed
If, in a command-line terminal, inside /sys/devices/system/cpu/cpufreq/cpu0 (or cpu1, cpu2, etc.), I type the command--
sudo cat *
--the cat program prints out the contents of each of those files on a separate line, and in the case of cpu0, this is the output--
0
1580500
3800000
1200000
4294967295
0
performance powersave
1580500
intel_pstate
performance
3600000
2400000
<unsupported>
I'm a bit confused and worried by the last item, the contents of the file scaling_setspeed being <unsupported>, so I plan to do a little research about that. I think it means that using the intel_pstate frequency scaling kernel driver, a particular set and fixed frequency cannot be specified; the governor under the intel_pstate driver will always choose a range and never function at a specified fixed frequency.
Note: the path--
/sys/devices/system/cpu/cpufreq/policy0/
--is identical to--
/sys/devices/system/cpu/cpu0/cpufreq/
--because "cpufreq" in the path immediately above is a symlink to ../cpufreq/policy0
Last edited by Stephen_Doonan (25-05-2016 19:08)
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