Testing the intel_pstate CPU governor

28 Nov 2013

I’ve heard about the classical ondemand CPU scaling governor on Linux being no longer fit for modern intel CPUs, so I’ve tested the new intel_pstate governor. On Ubuntu 13.10, this is done by adding intel_pstate=enable to the GRUB_CMDLINE_LINUX_DEFAULT line on /etc/default/grub and running update-grub.

After reading some random posts about this new governor, I’ve found that, for some people, the CPU temperature increased up to 10°C, so I’ve became a little paranoid of my computer being too hot. In order to see if it was really hotter with intel_pstate enabled or if it was just my impression, I’ve wrote a little script to acquire the temperature of one core of my i7-3520M (both cores always had almost the same temperature) every 3 seconds, for 5 minutes. The script then outputs the mean temperature for this time interval.

I’ve evaluated the following governors, without workload: ‘acpi_ondemand’, ‘acpi_performance’, ‘acpi_powersave’, ‘pstate_performance’, and ‘pstate_powersave’. The results were quite interesting for me.

Results (no workload):

acpi_ondemand     : 55.25°C
acpi_performance  : 55.44°C
acpi_powersave    : 54.48°C
pstate_performance: 55.35°C
pstate_powersave  : 55.58°C

So, it really was only my imagination. The results are so close one can not say that one is better than another, or that the new governor is making my CPU hotter. So, for now, I’m sticking with intel_pstate.

Right now, it is raining outside and it is a little bit cold in here, and the CPU temperature is oscillating around 44°C.