Ubuntu
systemd package

  1. Bug #1806012
  2. Comment #5

Comment 5 for bug 1806012

Revision history for this message
Trent Lloyd (lathiat) wrote :

Something I was not previously aware of that informs this a bit more, is that in some BIOS modes (apparently HP uses this extensively, unsure about Dell and others) you get a "Collaborative Power Control" mode, which sets the scaling_driver to pcc-cpufreq (as opposed to cpufreq) and is some weird hybrid of OS+BIOS defined behavior.

In the case of these collaborative modes, the exact behavior is probably wildly different based on what the BIOS is doing and likely would explain why we get weird and inconsistent performance behavior. Unclear to me if such BIOS modes will still use intel_pstate or not.. something I'd have to look into. Or whether it's specific to pre-pstate.

Some more information about collaborative mode in this bug:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1447763