kernel-packages team mailing list archive

[Doug Smythies <1188647@xxxxxxxxxxxxxxxxxx>]

Kernel 3.15 contains some intel_pstate changes that should address the
issues I raised in post 16 above.

For Ubuntu one concern is: For the 250 Hz kernel the default sample rate
will result in an actual different sample rate, and thus the response
curve is a little different than for the 1000 Hz kernel. The desire is
to have the default sample rate be 12 milliseconds instead of 10 (3
jiffies for 250 Hertz and 10 jiffies for 1000 Hz). This change is on the
to-do list. This is probably a minor issue.

For this change:
"intel_pstate: add sample time scaling" I have a concern (and a ton of evidence to support it) that often, but very dependent on periodic workloads, the deferrable timer is delayed when it is not expected to be delayed, and sometimes by a huge amount (4 seconds). The result can be lower than expected CPU frequencies, because new the scale down code kicks in when it shouldn't.

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https://bugs.launchpad.net/bugs/1188647

Title:
  Please change intel_pstate default to disable

Status in “linux” package in Ubuntu:
  Fix Released

Bug description:
  3.9 introduced a new default governor on SandyBridge CPUs called
  INTEL_PSTATE which, when built in and enabled (the default), removes
  all other governors (like our usual default, ondemand). 3.10 extended
  this to Ivybridge generation CPUs.

  In theory, this isn't an awful thing, as the new Intel pstate governor
  should be higher performance and give better power savings.  In
  theory.

  In practice, it drives my CPUs to max frequency nearly constantly,
  spins my fans like mad and, somehow, does all of this while also
  eating enough CPU time in kernel threads to make my machine choppy,
  unresponsive, and unable to do simple things like play videos when I
  get off work.

  Therefore, I propose that we, for now, toggle intel_pstate to disable
  by default (I am using intel_pstate=disable on my command line right
  now, with great success), so it's still built in, and people can play
  with it, but it's off by default.

  ProblemType: Bug
  DistroRelease: Ubuntu 13.10
  Package: linux-image-3.9.0-4-generic 3.9.0-4.9
  ProcVersionSignature: Ubuntu 3.9.0-4.9-generic 3.9.4
  Uname: Linux 3.9.0-4-generic x86_64
  ApportVersion: 2.10.2-0ubuntu1
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  adconrad   2574 F.... pulseaudio
  CurrentDmesg:
   [   30.633035] init: plymouth-stop pre-start process (2079) terminated with status 1
   [   36.086916] br0: port 1(eth0) entered forwarding state
  Date: Fri Jun  7 08:48:56 2013
  HibernationDevice: RESUME=UUID=73040efa-baec-458a-8307-3bca07b26c3c
  InstallationDate: Installed on 2012-12-09 (179 days ago)
  InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Alpha amd64 (20121209)
  MachineType: LENOVO 4173LPB
  MarkForUpload: True
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.9.0-4-generic root=UUID=2222aad5-ef31-4428-973f-71740fc7cb6a ro intel_pstate=disable quiet splash vt.handoff=7
  RelatedPackageVersions:
   linux-restricted-modules-3.9.0-4-generic N/A
   linux-backports-modules-3.9.0-4-generic  N/A
   linux-firmware                           1.109
  SourcePackage: linux
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 09/13/2012
  dmi.bios.vendor: LENOVO
  dmi.bios.version: 8CET55WW (1.35 )
  dmi.board.asset.tag: Not Available
  dmi.board.name: 4173LPB
  dmi.board.vendor: LENOVO
  dmi.board.version: Not Available
  dmi.chassis.asset.tag: No Asset Information
  dmi.chassis.type: 10
  dmi.chassis.vendor: LENOVO
  dmi.chassis.version: Not Available
  dmi.modalias: dmi:bvnLENOVO:bvr8CET55WW(1.35):bd09/13/2012:svnLENOVO:pn4173LPB:pvrThinkPadT420s:rvnLENOVO:rn4173LPB:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
  dmi.product.name: 4173LPB
  dmi.product.version: ThinkPad T420s
  dmi.sys.vendor: LENOVO

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