Multi-core processors like the Core 2 Duo P8400 have an independent MSR for each core, but constrain all cores to operate at the same frequency. Basically, the hardware chooses to run all cores at the highest frequency and voltage requested for any individual core. cpufreq shows for the P8400: # cat /sys/devices/system/cpu/cpu0/cpufreq/affected_cpus 0 # cat /sys/devices/system/cpu/cpu0/cpufreq/related_cpus 0 1 For this processor, doing # cpufreq-set -g userspace # cpufreq-set -f 800MHz sets constant 800MHz only for cpu0. If cpu1 governor remains set to ondemand, both cpus will ramp up to cpuinfo_max_freq on demand, so the previous two commands do not have the desired effect of limiting cpu0 frequency. Doing that would require 4 cpufreq-set commands: # cpufreq-set -c 0 -g userspace # cpufreq-set -c 0 -f 800MHz # cpufreq-set -c 1 -g userspace # cpufreq-set -c 1 -f 800MHz which is rather cumbersome. It would be more convenient if cpufreq-set could be used to set properties on all related cpus in a single command. Some options for doing this: 1) If -c switch is not specified, then all related cores are modified. This differs from current behavior and so may break stuff. 2) Use some special value of -c switch to specify "all related cores" 3) Add a new -r switch to specify "all related cores" Thanks, Frank -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
