[Bug 1885730] Re: Bring back ondemand.service or switch kernel default governor for pstate - pstate now defaults to performance governor

[Balint Reczey]

The commit message removing ondemand.service has several bug references, too:
https://git.launchpad.net/~ubuntu-core-dev/ubuntu/+source/systemd/commit/?id=65f46a7d14b335e5743350dbbc5b5ef1e72826f7

remove Ubuntu-specific ondemand.service
New processors handle scaling/throttling in internal firmware
(e.g. intel_pstate), and do not require OS config.

Additionally, nobody else does this, not even Debian.

And finally, this has caused problems for years, e.g.:

https://bugs.launchpad.net/ubuntu/+source/sysvinit/+bug/1497375
https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1503773
https://bugs.launchpad.net/ubuntu/+source/sysvinit/+bug/1480320
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1579278
https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1806012
https://bugs.launchpad.net/charm-sysconfig/+bug/1873028


IMO the kernel is a better place for setting the default governor properly and can even set different governors in cloud-specific kernels.
If the decision is to control the governor in user space in Ubuntu I'd prefer a solution shipped in an other package because systemd does too many things already.

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to systemd in Ubuntu.
https://bugs.launchpad.net/bugs/1885730

Title:
  Bring back ondemand.service or switch kernel default governor for
  pstate - pstate now defaults to performance governor

Status in linux package in Ubuntu:
  Incomplete
Status in systemd package in Ubuntu:
  New

Bug description:
  In a recent merge from Debian we lost ondemand.service, meaning all
  CPUs now run in Turbo all the time when idle, which is clearly
  suboptimal.

  The discussion in bug 1806012 seems misleading, focusing on p-state vs
  other drivers, when in fact, the script actually set the default
  governor for the pstate driver on platforms that use pstate.
  Everything below only looks at systems that use pstate.

  pstate has two governors: performance and powerstate. performance runs
  CPU at maximum frequency constantly, and powersave can be configured
  using various energy profiles energy profiles:

  - performance
  - balanced performance
  - balanced power
  - power

  It defaults to balanced performance, I think, but I'm not sure.

  Whether performance governor is faster than powersave governor is not
  even clear.
  https://www.phoronix.com/scan.php?page=article&item=linux50-pstate-
  cpufreq&num=5 benchmarked them, but did not benchmark the individual
  energy profiles.

  For a desktop/laptop, the expected behavior is the powersave governor
  with balanced_performance on AC and balanced_power on battery.

  I don't know about servers or VMs, but the benchmark series seems to
  indicate it does not really matter much performance wise.

  I think most other distributions configure their kernels to use the
  powersave governor by default, whereas we configure it to use the
  performance governor and then switch it later in the boot to get the
  maximum performance during bootup. It's not clear to me that's
  actually useful.

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1885730/+subscriptions