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

[Balint Reczey]

I have a freshly installed 20.10 system running on a 2012 MacBook Air
(MBA 5,2) and it is completely silent and cold when being idle:

rbalint at chaos:~$ sudo cpupower frequency-info
analyzing CPU 0:
  driver: intel_pstate
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency:  Cannot determine or is not supported.
  hardware limits: 800 MHz - 2.80 GHz
  available cpufreq governors: performance powersave
  current policy: frequency should be within 800 MHz and 2.80 GHz.
                  The governor "performance" may decide which speed to use
                  within this range.
  current CPU frequency: Unable to call hardware
  current CPU frequency: 915 MHz (asserted by call to kernel)
  boost state support:
    Supported: yes
    Active: yes
    2600 MHz max turbo 4 active cores
    2600 MHz max turbo 3 active cores
    2600 MHz max turbo 2 active cores
    2800 MHz max turbo 1 active cores


@seb128, @juliank I'm not sure if there is anything to fix in the user space, but please report which laptops you experienced issues with. Those may need firmware/kernel fixes.


** Changed in: systemd (Ubuntu Groovy)
       Status: New => Invalid

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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:
  Confirmed
Status in systemd package in Ubuntu:
  Invalid
Status in linux source package in Groovy:
  Confirmed
Status in systemd source package in Groovy:
  Invalid

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.

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