[Bug 1314653] [NEW] sysvinit: default cpufreq governor to powersave for intel-pstate driver

[Colin King]

Public bug reported:

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.

** Affects: sysvinit (Ubuntu)
     Importance: Undecided
         Status: New

** Patch added: "95_ondemand_pstate.patch"
   https://bugs.launchpad.net/bugs/1314653/+attachment/4101463/+files/95_ondemand_pstate.patch

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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:
  New

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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