[Bug 1806012] Re: set-cpufreq: 'powersave' governor configuration sanity on ubuntu server

[Trent Lloyd]

On the previously mentioned HP server today I was able to get closer to
reproducing the situation by testing with bionic (4.15.0-47-generic)
instead of xenial (4.4)

On bionic, unlike xenial, even with the BIOS set to "BIOS controlled
dynamic" mode, the intel_pstate driver is loaded instead of pcc-cpufreq

Found this kernel commit:
https://github.com/torvalds/linux/commit/bfa54a3a00e2f7ff051a50f3957e4fca3d73f6e7

Pull power management fix from Rafael Wysocki:
 "Fix a relatively old initialization issue in intel_pstate causing the
  pcc-cpufreq driver to be used instead of it on some HP Proliant
  systems.

  This turned into a functional regression during the 4.17 cycle,
  because pcc-cpufreq is a scalability disaster and that was amplified
  by the idle loop rework done at that time (Rafael Wysocki).

This suggests there has definitely been some related change in this area
that sound very much similar to this which is worth further research.

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https://bugs.launchpad.net/bugs/1806012

Title:
  set-cpufreq: 'powersave' governor configuration sanity on ubuntu
  server

Status in systemd package in Ubuntu:
  In Progress
Status in systemd source package in Xenial:
  In Progress
Status in systemd source package in Bionic:
  In Progress
Status in systemd source package in Cosmic:
  In Progress
Status in systemd source package in Disco:
  In Progress

Bug description:
  Whilst debugging 'slow instance performance' on a Ubuntu Bionic based
  cloud, I observed that the default cpu governor configuration was set
  to 'powersave'; toggling this to 'performance' (while in not anyway a
  particularly green thing todo) resulted in the instance slowness
  disappearing and the cloud performance being as expected (based on a
  prior version of the deploy on Ubuntu Xenial).

  AFAICT Xenial does the same thing albeit in a slight different way,
  but we definitely did not see the same performance laggy-ness under a
  Xenial based cloud.

  Raising against systemd (as this package sets the governor to
  'powersave') - I feel that the switch to 'performance' although
  appropriate then obscures what might be a performance/behavioural
  difference in the underlying kernel when a machine is under load.

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: systemd 237-3ubuntu10.9
  ProcVersionSignature: Ubuntu 4.15.0-39.42-generic 4.15.18
  Uname: Linux 4.15.0-39-generic x86_64
  ApportVersion: 2.20.9-0ubuntu7.5
  Architecture: amd64
  Date: Fri Nov 30 10:05:46 2018
  Lsusb:
   Bus 002 Device 002: ID 8087:8002 Intel Corp. 
   Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
   Bus 001 Device 003: ID 413c:a001 Dell Computer Corp. Hub
   Bus 001 Device 002: ID 8087:800a Intel Corp. 
   Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
  MachineType: Dell Inc. PowerEdge R630
  ProcEnviron:
   TERM=xterm-256color
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=C.UTF-8
   SHELL=/bin/bash
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.15.0-39-generic root=UUID=a361a524-47eb-46c3-8a04-e5eaa65188c9 ro hugepages=103117 iommu=pt intel_iommu=on
  SourcePackage: systemd
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 11/08/2016
  dmi.bios.vendor: Dell Inc.
  dmi.bios.version: 2.3.4
  dmi.board.name: 02C2CP
  dmi.board.vendor: Dell Inc.
  dmi.board.version: A03
  dmi.chassis.type: 23
  dmi.chassis.vendor: Dell Inc.
  dmi.modalias: dmi:bvnDellInc.:bvr2.3.4:bd11/08/2016:svnDellInc.:pnPowerEdgeR630:pvr:rvnDellInc.:rn02C2CP:rvrA03:cvnDellInc.:ct23:cvr:
  dmi.product.name: PowerEdge R630
  dmi.sys.vendor: Dell Inc.

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