touch-packages team mailing list archive

[Stefan Bader <stefan.bader@xxxxxxxxxxxxx>]

Not sure why this was initially rejected. It sounds reasonable to have
it now as there are (and will be HWE kernels with the intel_pstate
drive).

SRU justification:

Impact: When using HWE kernels in Trusty one can be using the
intel_pstate driver which will result in no other power saving governor
than powersave available. Given the choices (or lack of them) it is
better for power usage to fall back to that instead of keeping the
performance governor active.

Fix: Apply the same change we have for Utopic and add the powersave
governor as the last option to check and activate.

Testcase: See reproducer in description.

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https://bugs.launchpad.net/bugs/1314653

Title:
  sysvinit: default cpufreq governor to powersave for intel-pstate
  driver

Status in sysvinit package in Ubuntu:
  Fix Released
Status in sysvinit source package in Trusty:
  Confirmed
Status in sysvinit source package in Utopic:
  Fix Released

Bug description:
  When defaulting to the intel-pstate driver, there are only a couple of
  cpufreq governors available, none of which are handled in the
  /etc/init.d/ondemand script.

  Since this driver is meant to be used for power saving, it seems wrong
  to leave the system in the kernel default configured "performance"
  governor after boot, so I think it is pertinent to set this to
  "powersave" if it is the only suitable non-power hungry governor
  available.

  How to reproduce:

  1. enable the intel_pstate driver on a recent Intel machine
  (Sandybridge or above)

  edit /etc/default/grub, modify the following:

  GRUB_CMDLINE_LINUX_DEFAULT="quiet splash intel_pstate=enable"

  and run:

  sudo update-grub

  and reboot.

  2. login

  3. wait at least 60 seconds for /etc/init.d/ondemand to complete

  check out the default cpufreq governor, you will see it is still set
  to the boot default of "performance":

  cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

  With the attached fix the system will boot into a less aggressive
  cpufreq governor.

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