[Bug 524281] Re: Tens of wakes per second in "[kernel scheduler] Load balancing tick" on Core 2 Duo even with only 1 core enabled

Jan-Philipp Litza 524281 at bugs.launchpad.net
Thu Jul 15 15:37:26 UTC 2010

** Description changed:

- powertop reports above 70 wakes per second in "[kernel scheduler] Load balancing tick" task, and above 200 when there's any little load, running on a Core 2 Duo processor (T6500) with a single core enabled (multicore disabled in BIOS).
- Will still try noapic, nolapic, maxcpus and nosmp in the boot parameters and reproduce it with the mainline kernel.
+ powertop reports many wakes per second (quantity depending on system)
+ in "[kernel scheduler] Load balancing tick" task, rising with little
+ load, on many kinds of multi-core (?) systems (original report was on a
+ Core 2 Duo processor (T6500) with a single core enabled (multicore
+ disabled in BIOS)).
+ Cause of the problem:
+ With kernel 2.6.32, there came a patch to the scheduler that introduced this problem (that was backported to some other versions as well). Even though this problem occurred first in Lucid, it is NOT specific to Lucid or Ubuntu at all (Debian bug report at http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=521944, reproducable in Arch Linux as well). Work is ongoing to get things straight in kernel, but it will take a long time until this reaches Ubuntu (see http://lkml.org/lkml/2010/7/6/172).
+ Workarounds that DO NOT work (may improve situation but not solve it):
+ - maxcpus=1
+ - noapic
+ - nosmp
+ - nolapic
+ - use mainline kernel
+ Workarounds that DO (probably) work:
+ - tip version of kernel (git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git, from http://lkml.org/lkml/2010/7/8/75)
+ - use maverick's kernel with applied patches (https://launchpad.net/~brian-rogers/+archive/power, from comment #80)
  ProblemType: Bug
  AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.21.
  Architecture: i386
   **** List of CAPTURE Hardware Devices ****
   card 0: Intel [HDA Intel], device 0: ALC269 Analog [ALC269 Analog]
     Subdevices: 1/1
     Subdevice #0: subdevice #0
   /dev/snd/controlC0:  etrusco    1606 F.... pulseaudio
                        etrusco   15151 F.... foobar2000.exe
  CRDA: Error: [Errno 2] No such file or directory
   Card hw:0 'Intel'/'HDA Intel at 0xfddf8000 irq 22'
     Mixer name	: 'Realtek ALC269'
     Components	: 'HDA:10ec0269,1b0a4009,00100004 HDA:11c11040,1b0a4007,00100200'
     Controls      : 19
     Simple ctrls  : 11
   Card hw:1 'HDMI'/'HDA ATI HDMI at 0xfebec000 irq 17'
     Mixer name	: 'ATI R6xx HDMI'
     Components	: 'HDA:1002aa01,00aa0100,00100100'
     Controls      : 4
     Simple ctrls  : 1
   Simple mixer control 'IEC958',0
     Capabilities: pswitch pswitch-joined penum
     Playback channels: Mono
     Mono: Playback [on]
  Date: Fri Feb 19 05:25:42 2010
  DistroRelease: Ubuntu 10.04
  EcryptfsInUse: Yes
  MachineType: Philco PHN10XXX.
  Package: linux-image-2.6.32-13-generic 2.6.32-13.18
  ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.32-13-generic root=UUID=d482e94f-9370-4ad2-9536-986541003db5 ro acpi.power_nocheck=1 acpi_osi=linux radeon.blacklist=yes
  ProcVersionSignature: Ubuntu 2.6.32-13.18-generic
  Regression: No
  RelatedPackageVersions: linux-firmware 1.29
  Reproducible: Yes
   0: phy0: Wireless LAN
    Soft blocked: no
    Hard blocked: no
  SourcePackage: linux
  TestedUpstream: No
  Uname: Linux 2.6.32-13-generic i686
  dmi.bios.date: 06/01/2009
  dmi.bios.vendor: American Megatrends Inc.
  dmi.bios.version: 1.01
  dmi.board.asset.tag: To Be Filled By O.E.M.
  dmi.board.vendor: PEGATRON CORP.
  dmi.board.version: To be filled by O.E.M.
  dmi.chassis.asset.tag: To Be Filled By O.E.M.
  dmi.chassis.type: 10
  dmi.chassis.vendor: PEGATRON CORP.
  dmi.chassis.version: To Be Filled By O.E.M.
  dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr1.01:bd06/01/2009:svnPhilco:pnPHN10XXX.:pvr1.01:rvnPEGATRONCORP.:rn:rvrTobefilledbyO.E.M.:cvnPEGATRONCORP.:ct10:cvrToBeFilledByO.E.M.:
  dmi.product.name: PHN10XXX.
  dmi.product.version: 1.01
  dmi.sys.vendor: Philco

Tens of wakes per second in "[kernel scheduler] Load balancing tick" on Core 2 Duo even with only 1 core enabled
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